Introduction to Volume 1

Written by Neil Williams, the following articles were originally published in 'Shell Aviation News' in the 1970s. They are reproduced by kind permission of his son David, who owns the copyrights. Neil is widely acknowledged to have been one of the world's most skilful aerobatic pilots. His aviation writings, including his books 'Airborne' and 'Aerobatics', have likewise earned universal acclaim.

The annotations below show SAN issue number and year.

Voyage of the Humming Bird (426, 1974)
An Introduction to the Jet Environment (427, 1975)
F28 Mk 6000 (428, 1975)
Like a Duck to Water - Lake Buccaneer (429, 1975)
From Caterpillar into Butterfly - Restoration of a Spitfire Mk Vc (431, 1975)
The Art of the Approach (432, 1975)




Last September a USAF Lockheed SR-71 strategic reconnaissance aircraft covered the 3490 st miles between New York and London, England, in just under 1 hour 56 minutes. During the early part of this year NEIL WILLIAMS, one of the select band of test pilots who demonstrate the veteran aeroplanes of the Shuttleworth Collection, accomplished a 60 mile delivery flight between two provincial English airfields in 5 months, 3 weeks, 5 days and 2 hours.


ABOVE: At the start of the voyage, Author taxies Humming Bird with wing-tip assistance

'THIS LITTLE MACHINE has shown itself to possess an excellent all-round performance, to be extremely easily handled, both on the ground and in the air, and to be capable of all forms of "stunting". It has been flown in the worst of weather and has demonstrated that either as a sporting single seater or as a training machine, it can take the place of much more expensive and powerful types.'

So runs a contemporary account of the de Havilland 53 Humming Bird light monoplane in the Flying Encyclopedia for 1923.

By the autumn of 1973, DH 53 G-EBHX had achieved the somewhat uninspiring record of 5 hours 30 minutes total flying and three major crashes since it was built 50 years earlier. Its last unpremeditated descent had been a particularly severe one. The engine had seized up after take-off; burning stubble fields ahead made the ensuing crash inevitable. The various components were collected and transported to White Waltham for restoration, while the offending engine was despatched to Rolls-Royce at Leavesden where its behaviour was investigated by Dr. Moult and his team of experts.

There was evidence enough from the twin pistons of the 42 horse-power ABC Scorpion, for they were heavily scored, as were the cylinder liners. Clearly the alloy pistons, already hot from ground running, could not stand the extra temperature and reduced cooling of the take-off and climb. A fix had to be found. The pistons were cleaned up and the cylinders honed out until there was approximately 0.020 inch clearance, the same as a Gipsy Major. Then the engine was thoroughly inspected, assembled and run.

Back at White Waltham, Jim Kelly and Pete Baston completed a mammoth rebuild of the airframe which had taken five years of spare time work. On 7 November 1973 the first flight was made by Air Commodore Allen Wheeler, Custodian of the Shuttleworth Collection to which the Humming Bird now belongs. He remarked that the characteristics coincided very accurately with his recollections of a similar machine some 40 years previously. Then I was invited to fly it, and if tests proved satisfactory, to arrange for it to be ferried back to Old Warden Aerodrome in Bedfordshire where the Shuttleworth Collection is based.

First impressions

Although the DH 53 was only a 'simple little aeroplane' the fact that it had averaged one hour every ten years, and had still contrived to come to grief in spectacular fashion three times, made me approach the project with some caution.

The cockpit, though cramped, was fairly comfortable. There was no real nose reference, the nose itself being practically non-existent. Instruments were minimal, with a solitary gleaming brass switch dominating the panel to control the single magneto. Fuel and oil tanks were immediately aft of the tiny engine, fuel capacity being a ridiculous two gallons.




The starting sequence, begun before the pilot boarded the aircraft, resembled some primitive rite. First the fuel was selected on, following which the tail was lifted at arm's length for half a minute or so, then it was shaken bodily for a few seconds before being lowered to the ground. This was the moment for the pilot to climb in. At the same time the exhaust pipes, each of which stood up like the twin smoke stacks of a Mississippi paddle steamer, were carefully dosed with one teaspoonful of neat gasoline. The brass magneto switch was turned on and the propeller spun vigorously. This was accompanied bv barks and wheezes, and on one terrifying occasion two yellow tongues of flame licked hungrily towards the cockpit. At last the engine shuddered into life, spitting and belching black smoke. Its behaviour grew less alarming at full power, with a loud exhaust crackle, as though it were trying to make up in noise for what it lacked in thrust.

Finally the great moment arrived. Very much aware of the lurid tales surrounding the aeroplane, I lined up into what little wind there was and opened the throttle wide.

Anticlimax reigned supreme - it refused to move! With the engine still at full power the stick was eased forward to take the weight off the skid and the rudder waggled vigorously. This unusual combination, learned many years ago from another ultra-light type, was the key to the problem and the little aeroplane reluctantly started forward.

Owing to the lack of nose reference it was difficult to find the correct attitude for the take-off run; I had to achieve a delicate balance between aerodynamic drag with the tail too low and undercarriage drag with the tail too high. An occasional backward glance gave a fairly good indication of pitch attitude at this stage. The tiny, narrow wheels sank into the soft grass and eventually the machine stabilised at about 35 mph. This would never do, especially as we were by now halfway across the aerodrome . . . However, there was still plenty of time, and sure enough, when the aircraft encountered a small bump it was neatly propelled into the air. Thereafter the speed built up reasonably well. On subsequent take-offs I found that by lifting the tail very much higher during the early stages the ground run, although still prolonged, was improved.

Appraisal

In the smooth air, just after take-off, I noticed that the ailerons were tramping very slightly. I determined to investigate this further. The phenomenon disappeared as speed was increased and the aircraft settled into the climb, the Scorpion flogging away for all it was worth. Still alert for any tricks it might play, I manoeuvred so that I could land on the airfield at any time should the engine stop. This performance must have driven ATC nearly to distraction as I wandered irregularly about. Finally I achieved a safe height and continued to climb in slow wide spirals. The engine, very underpowered it seemed, vibrated continuously but showed no particular signs of distress.

The aircraft responded briskly to control movements, the ailerons being particularly powerful. Maximum speed in level flight at 2400 rpm was 65 mph, and the aeroplane was slightly nose heavy, no trimmer being available. As speed was reduced towards the stall it was noticeable that when ailerons were used there was a tendency for them to trail in the direction of roll, and for such a little aeroplane there was considerable inertia in the aileron circuit. This obviously needed further investigation. A slow stall approach gave lateral rocking at 45 mph. followed by a g break at 42 mph. During the rocking the ailerons were trying to snatch towards the dropping wing. When the ailerons were held firmly the nose dropped gently and cleanly at the stall, but when held lightly they snatched to the right coincident with a sharp wing drop through 90 degrees. This behaviour was also apparent as the dynamic stall was approached, and during fast roll reversals. It was only at very high angles of attack just prior to the stall that it was noticeable, and could be corrected by a firm grip on the stick.

Part of the reason for the DH 53's bad reputation was now beginning to come to light. Sideslips were made to assess stability, and although the aircraft behaved normally at low sideslip values, as these were increased first the ailerons and then the rudder suffered a force reversal, and the ailerons had to be deflected in the opposite sense to maintain the sideslip, demonstrating marked lateral instability in this mode. This was perhaps the second link in the chain. I next carried out some general handling, and found that despite this interesting behaviour, provided the machine was flown with a firm hand it responded in a brisk and lively manner. These peculiarities, having once been sampled at a safe height, fell into their proper perspective; but at low level, just after take-off, with the additional complication of an engine failure, would be no place to discover them for the first time.

I was just beginning to sit back and enjoy myself when the oil pressure decided to fall. The engine showed no signs of ailing; I was even getting used to the vibration! It was obvious that the pressure was going to vanish before I could land so I removed the need for further decisions by switching off, whereupon the propeller stopped.

'Now I'm for it', I thought, with lurid tales of brick-like gliding angles springing to mind. Again, anticlimax! At 55 mph the little aeroplane glided at about the same angle as a throttled-back Tiger Moth. I even had to slip a little height off at the last moment, and there was plenty of control left to flare and settle on three points.

Adjustments were made to the oil pressure relief valve, and off we went again. This time the take-off run, with the tail a little higher initially, was more reasonable. ATC again suffered my wanderings around the circuit (for I was determined not to be caught out if the engine stopped) until eventually a safe height was reached. Again the oil pressure fell and the engine was switched off, and again the gliding angle was quite reasonable. During the ensuing sideslip it was noted that the control force reversal was not present with the propeller stopped.

Finally, after several adjustments, the oil pressure more or less behaved itself. During a normal approach to land it was slightly embarrassing to find that the aircraft had an extremely flat glide, which was not helped by the fact that the engine had to be set at a rather fast tick-over to keep it running at all. Once on the ground, however, the high drag of the undercarriage brought the machine to a halt in a very short distance indeed.


ABOVE: The DH 53 is walked to the hangar at Hatfield. Raising the machine to this attitude is part of the starting procedure, after the fuel has been turned on


ABOVE: Author displays the machine at a recent Old Warden flying day. Some caution is necessary until sufficient height has been gained to retrieve the situation should the engine stop; thereafter, provided the aircraft is flown with a firm hand, it responds in a brisk and lively manner

The voyage begins

We had decided that following a trouble-free flight of 30 minutes it would be possible to plan the ferry flight back to Old Warden. And so, on the 21 January 1974, the Humming Bird set out on its journey home. There was high cloud cover, but the visibility was excellent. It was also very cold. One large orbit of the field was made at 800 ft to give the engine its final option of quitting, but it crackled away as though it really meant business. 2200 rpm gave a cruising speed of 57 mph.

Eventually there was nothing for it but to forsake the safety of White Waltham and to point the nose at Booker, some 11 miles to the north. There I would fuel and would be met by Jim Kelly and Air Commodore Wheeler who, having seen me off, would make the journey by road to coincide with my arrival. There was no such refinement as a compass. However, on a clear winter's day I expected no problems so long as the engine kept running.

Slowly the countryside flowed beneath the wings, while I selected field after field against the possibility of a forced landing. But the engine had never sounded better, and soon I found myself gliding around the final turn, close in and with plenty of height in hand. At the pumps I asked for the tank to be topped up. The mechanic's face was a study when he found it would only take five pints! After lunch we returned to find the DH 53 surrounded by incredulous onlookers, whose ribaldry turned to thoughtfulness when they discovered the fuel consumption.

Now for the first time I was able to take off on a hard runway, and what a difference it made. Full control and reasonable acceleration from the start . . . I was able to unstick cleanly before I passed the Air Commodore, who was positioned 150 yards down the runway, armed with his camera to record the occasion.

Taking a bearing from the runway as I flew back overhead I settled down for the longest leg of the day - 18 miles to Leavesden, via Bovingdon. Eventually the hangars of Bovingdon appeared over the bows. I reflected on the last time I had flown from here, in a Mosquito. How different that powerful beast from its tiny predecessor. But now the airfield is deserted, and of no use to me except as an emergency landing ground . . . Wait, though, it can still help me, for here I must turn for Leavesden. The runways are still painted, so using this rudimentary compass, and estimating the angle of my track, I roll out on the new heading.

Now the Humming Bird is affected by a slight headwind which cuts down its already very low ground speed. I remember a tale of a DH 53 years ago in Belgium where to the pilot's disgust it was overtaken by a train. The engine chugs away steadily. Why was it called a Humming Bird, I wonder? We are so slow that we seem to hover; a speck in the distance materialises into a modern lightplane which flashes past a few hundred yards away, even its mediocre speed seeming alarming by contrast with our snail-like progress. He doesn't see me.

Cold sets in, and I begin to shiver. At last Leavesden appears ahead. I decide to land on the grass, uphill towards the north-east, and as I spiral lower a green light shines from the tower. A careful sideslip to get rid of height . . . as I straighten I switch off the engine. Now the glide is normal, and in the flare I 'blip' the engine just as if I were controlling a rotary. This gives no more than a short float and an early touchdown.




Third leg

The programme now called for a stay at Leavesden of about a week, so that the Rolls-Royce apprentices could see what sort of an aeroplane was propelled by the engine they had helped overhaul. To say that they were thunderstruck would be an understatement. From here the machine was to be flown to Hatfield, home of de Havillands before the merger with Hawker Siddeley Aviation, and it was fitting that an HSA test pilot should fly it for this leg.

On the appointed day, after some initial difficulty in starting, the ground run was satisfactory and so a telephone call was made to Hatfield. This produced Des Penrose, complete with flat hat (to be worn backwards) and Mk 8 goggles. Thus attired he was soon installed in the DH 53 and pointed in the direction of the runway. Well content with our efforts, I returned home.

Later that day the telephone rang. It was Des. Apparently as he was passing Radlett Aerodrome the Scorpion came out in sympathy with the now sadly defunct Handley-Page company, and quietly died.
 
With more than 7000 ft of runway under him it seemed the obvious place to go, so down he went. 'Couldn't happen to a nicer chap', I said, totally lacking in concern. A ground run seemed OK so he launched off once again, but although Hatfield was only four miles away the Scorpion was determined to remain at Radlett, where eventually the Humming Bird was wheeled into a hangar, now practically empty save for the ghosts of Hastings, Herald, Victor and Jetstream.

An inspection failed to reveal anything significant. With some misgivings, therefore, the machine was wheeled out a day or so later and had its minute tank topped up. Inexplicably the engine behaved normally, and after orbiting Radlett for some time Des Penrose set out across country. It was with some relief that he finally dropped the Humming Bird on to the grass beside the control tower at Hatfield.

Now all that remained was to embark on the final leg of the journey to Old Warden, 20 miles away to the north. It was clear that so long a flight couldn't be attempted without a more thorough look at the engine, so over the next few months the experts delved into the mystery of the reluctant Scorpion. During this period Des Penrose left the company to become a commercial pilot. I personally think that he fled rather than embark on another epic in the DH 53. All in fun, Des!

Evidently the pistons had again been scored; it was apparent that the clearances were still not sufficient. The cylinders were honed out, and a Ki-gass priming pump was fitted, as it was thought that by priming through the exhaust system the oil had been washed off the liners. Most important, the little engine appeared to need all of its two gallon head of fuel to ensure safe operation during the take-off and climb.

Finale

So it was that on a July morning I received a telephone call from Ron Clear, who had been in charge of these modifications, to inform me that the aeroplane was ready for collection. I turned up at the flight sheds to find the DH 53 nestling between a Mosquito and a Cirrus Moth. Obviously it would be a pity to disturb it. I peered into the cockpit; yes, there was the Ki-gass pump modification. I scowled suspiciously at the engine - it looked just the same as it always did.

With a rumble the hangar doors opened and willing hands pushed the machine out. A crowd of onlookers materialised from nowhere, looking expectant. I climbed aboard and gave the engine a shot via the Ki-gass. 'Contact' said the mechanic, and spun the propeller. Nothing happened. Just as I was beginning to think I was reprieved, the engine gave a mighty snort and burst into life. At first it wouldn't run below 1800 rpm, which gave so much vibration that I could hardly focus on the instruments. It had a monumental flat spot between slow running and half throttle and from the twin exhaust slacks there issued a veritable cacophony of bangs, splutters and coughs.

It's difficult to do a magneto check when there is only one, so I thought I had better get going before something melted. With assistants on the wing tips I was finally aligned into wind. I opened the throttle and was horrified by the cloud of black smoke that was hurled skywards; however, this soon cleared, and the tiny machine started to move. I didn't really care what sort of noises came from the front end just so long as they kept coming.


It was a day of large cumulus clouds and good visibility. The last leg of the journey had begun! Slowly we climbed to 2000 ft, where I let the speed increase to 57 mph at 2200 rpm. The engine, by comparison with a modern power unit, rattled and vibrated in a shocking manner, but I had now come to accept this vibro-massage as normal Scorpion operation. Perched at the front of the machine, I had time to see every detail on the ground and to note the overtaking speed of the traffic on the A1 Motorway below - all the more evident because of the north wind.

Slowly we crawl across the vast dome of the sky, giving Luton and its airport a very wide berth. In the distance a jet flashes across and I am alarmed in case it comes my way - I cannot get out of its path if it does. But it turns away. I note that the oil pressure is falling slowly and wish I had an oil temperature gauge. Navigation is no problem; I know this part of the country well, though I had not realised how many golf courses there are near Stevenage.

Now Baldock is in sight as I swing back towards the north west. My ground distance will be more like 25 miles, but I make sure that I can always reach a safe landing area. I relax a little as I reach Henlow, an RAF base - only five more miles to go, with the oil pressure still within limits though dropping slowly. Here I can land without difficulty should the engine stop, but no, it seems determined to keep going. We rattle on northwards for several minutes when I glance down and notice a jet aeroplane on the ground. I am at a loss to know what an aircraft could be doing there; then it dawns on me, I am still over Henlow!

And at last, Old Warden - always hard to detect from the air among the woodlands of Bedfordshire. There is the familiar copse of trees on the south side of the aerodrome. As I get within gliding distance I inform the engine that it may now quit if it wants to. It refuses to do so, and clatters away merrily. The oil pressure has stabilised at 18 psi. I turn over the hangars, the DH 53 pivoting exuberantly on a wing tip, for she has completed a flight of more than 60 miles in less than six months.

The Voyage of the Humming Bird is over.







NEIL WILLIAMS, a military and civil test pilot who has held command on many commercial types, evaluates the BAC Strikemaster as an airline pilot trainer. He argues that exposure to the performance capabilities of a docile, aerobatic jet aircraft should become an integral part of the instructional syllabus.


ABOVE: Strikemaster's side-by-side seating makes sense for both instructor and two-student missions. If necessary, flight plan data could be presented as a head-up display, making use of the existing gunsight equipment

TODAY'S large commercial flying schools do everything in their power to ensure that their students have an excellent command of all the requirements of the syllabus, and the high standard of instrument flying they demand ensures a very high level of competence. Yet there is still one area where a potential deficiency exists. A student will perhaps learn to fly on a Cessna or Cherokee, and will gain the necessary twin engine time on a larger piston powered type such as the Cessna 410, Baron or Navajo. All very well, and excellent training to boot, one might say. However, the next step may well be the right hand seat of a big commercial jet, with no prior jet experience.

We know that the system does work, and that simulators play a large part in such training. But how can a student pilot hope to get experience of the complete envelope of any jet or high performance aeroplane? He certainly will not do so from his conversion flying. Must he then wait until a 'jet upset' or a disconnected autopilot sends him earthward in an ever tightening spiral descent? Must he wait until a series of errors leads him into pre-stall bullet with engines surging, in a heavily laden high performance aeroplane? This is hardly the time or the place to gain such experience. Remember that the current generation of airline captains probably flew the early jets operationally, to say nothing of the remainder of their military backgrounds.

It becomes apparent, then, that some form of jet training is highly desirable for the trainee airline pilot. Indeed, perhaps the day is not far off when civil pilots will follow the lead of their military counterparts, at least in the government run schools, and go over to all-through jet training. The British Royal Air Force instituted all-through jet training as long ago as 1955, using the Jet Provost, and this system has proved its worth over the years. Even if the expense of all-jet training is unacceptable, more and more thought is being given to the possibility of allocating a certain section of a civil course to jet conversion. The Italians for example are contemplating using the Macchi 326 in this role.

One runs up against the cost question here. Yet it would seem reasonable to mount an experiment using existing service aircraft and instructors, and attaching a course of civilian cadets to a military unit for jet conversion. Ultimately, should this prove successful, a civilian conversion unit could be formed, which all students could attend on completion of their piston engined course. The cost would be borne by the airlines concerned, who at present finance their piston trained students.

Equipment selection

The choice of a suitable training aircraft has to be made with some care. It is not necessary to go to the expense of a corporate jet; indeed, this would largely defeat the object of the exercise when it comes to letting the student get into some degree of trouble without at the same time hazarding the aeroplane. The Italians corroborate this line of thought by their choice of the Macchi 326, so it seems that it is to this sort of aeroplane that we must look.

Considerations governing the choice between a tandem seating and a side-by-side layout are many and varied. It may be argued that, especially in ab initio instruction - where it is important for the instructor to watch his student - the side-by-side trainer offers most advantages. With an eye to crew co-operation, where two students could fly an airways instrument detail, again the side-by-side layout makes sense.

The long line of success of British Aircraft Corporation's Jet Provost with the R.A.F. prompted me to look in this direction in the development of this paper. In the event it was an aircraft of similar shape emanating from a completely new design that was finally assessed as a potential airline trainer. This new aircraft was developed from the accumulated background experience of half a million training hours flown by the Jet Provost. With good pressurisation and temperature control, crew efficiency is improved,  and the increased performance allows a marked extension of the normal training syllabus. Designed in its basic form as a training ground attack aeroplane, it consequently possesses increased resistance to fatigue, resulting in a life in normal service of more than 18 years. This is the BAC 167 Strikemaster.


Introduction

My first acquaintance with the Strikemaster came when I was invited by BAC Military Aircraft Division, Warton, Lancashire, to participate in the fourth flight of a production aeroplane. R. T. Stock, whose long association with the type goes back as far as Luton in the early days of the Jet Provost, had kindly arranged for me to fly with him. I elected to sit in the left seat, although the aircraft could easily be operated from either seat.

It was seven years since I had last flown a single engine jet. As I refamiliarised myself with the various connections and strapping systems on the ejection seat, it occurred to me that this was likely to be the facet of the operation most likely to prove a stumbling block to students accustomed to flying in blazer and flannels, with their Jeppesen bag dumped in the back seat! Nevertheless, once installed, I was not conscious of being constricted in any way. At least one could assume that no pilot graduating from the Strikemaster would consider the standard working area of an airliner restrictive.

There are many combinations of instrument layout available, depending on customer requirements. It would be quite feasible to produce an instrument panel representative of current airline thinking, without compromising the view and accessibility currently afforded by the Strikemaster. The panel was placed at a sufficient distance from the eyes to allow comfortable focus and rapid translation to exterior objects, without effort. Additionally, the large perspex areas and raked nose gave a remarkably good view, both on the ground and in the air. Such a situation encourages the student to keep a good lookout, a discipline very much lacking in our present day 'head in the cockpit, radar will provide' attitude.

Conventional fighter controls were provided for each pilot - throttle operated by the left hand, stick by the right. There is no practical reason why the pilot in the left seat could not hold the control column with his left hand and operate the 'co-pilot's' throttle with his right hand, since all his previous training would have orientated him to this layout.

Although the aeroplane is capable of being started from internal power, it is usual to provide external power. A standard three pin socket is provided on the port fuselage aft of the wing, which keeps both power source and ground crew well clear of intakes and exhaust.

Starting the engine was simplicity itself. With LP and HP cocks ON the starter button was pressed for two seconds and released, whereupon the Viper lit up and stabilised at 40% rpm in 40 seconds. A rain shower conveniently allowed a demonstration of the rain repellent system, which consists of hot air ducted from the final stages of the compressor onto a section of both windscreens, and which effectively and instantly disperses the raindrops. Its use is not necessary at high speeds, rain clearance being effected by the curve of the windshield.

The canopy can be declutched and manoeuvred manually, or operated as is usual by electrical power, both from inside and outside the cockpit. Pressurisation and conditioning air, including the canopy seal, is also tapped from the final stage of the compressor. Throughout the flight, one had to make a conscious effort to assess environmental conditions as both pressure and temperature, especially the latter, were very well controlled. Pressurisation instrumentation consisted of a cabin altimeter, and as a rule of thumb, cabin altitude should read half aircraft altitude + 5000 ft, except that up to 8000 ft the cockpit is unpressurised, and reaches a maximum differential of 3 psi at 38,000 ft.

The aircraft was quite easy to manoeuvre on the ground, requiring about 60% rpm to start rolling, after which around 50% gave enough power to compensate for the small usage of brake to taxi. Brakes were toe operated, there being no nosewheel steering; they had short travel and relatively high resistance. This meant that pressure, rather than movement, was necessary to steer, and one very quickly became accustomed to the system. It became obvious that very precise control of the aircraft was possible on the ground. When rolling absolutely straight the idling rpm of 40% was enough to maintain normal taxying speed, and of course at least one hand, and often both, were free to carry out other checks without compromising directional control. In a crosswind the aircraft had a slight tendency to turn down wind at these slow speeds. Engine response was very smooth, and throttle gearing was especially good. Rapid slams were possible, with all parameters well controlled.


ABOVE: 'unstick occurred 18 seconds after brake release at 102 kt'. (Aircraft assessed by the Author carried no armament)

Take-off

Take-off was initiated using 30 degrees flap, at an AUW of 9000 lb, with just under 2800 lb of fuel, having started with full mains and tip tanks.

Full power was held easily by the brakes, whose pressure was shown on an indicator. Brakes were released and the aircraft rolled straight. The rudder became effective at 40 kt and at 65 kt the elevator was capable of moving the nose up and down appreciably. The nosewheel was a little reluctant to leave the runway with a gentle back pressure, so a firm pull was made at 90 kt whereupon a sprightly rotation followed. Elevator authority increased with the nosewheel off the ground and some of the back pressure could be released. Unstick occurred 18 seconds after brake release at 102 kt.

The undercarriage retracted quickly with no significant trim change, although the flaps caused a nose-up attitude change and noticeable sink as they retracted.

As the Strikemaster accelerated, a slight amount of nose-down trim was required. Ailerons were very powerful, and the high rolling inertia due to the full tip tanks, plus a detectable amount of aileron circuit friction, produced a slight wing rocking tendency as speed was increased to the 220 kt climbing speed, later to convert to Mach 0.5. The power could be left at 100%, this setting being restricted to 20 minutes in any hour. This resulted in a climb performance which conformed to the book figures, as follows:
Sea Level  . . .   0 min   0 sec
      5000 ft  . . .   1 min 18 sec
   10,000 ft  . . .   2 min 36 sec
   15,000 ft  . . .   4 min 12 sec
   20,000 ft  . . .   6 min   6 sec
   25,000 ft  . . .   8 min 12 sec
   30,000 ft  . . . 10 min 42 sec

It was noticeable that the climb performance dropped off more rapidly above 30,000 feet.

General handling

Speed was increased in a shallow dive from 34,000 ft with full power. At Mach 0.7, slight snaking was noticeable. This snaking appeared in other modes, but was so slight that it was really of academic interest. Passing 30,000 ft in the dive, at Mach 0.73, slight buffet was detectable, and at 0.75 (limiting Mach number) buffeting increased and the left wing became slightly heavy. At the same time the trim curve started to flatten and the aircraft no longer resisted the forward stick pressure which had held the dive angle until this time.

At Mach 0.75 the throttle was closed and airbrakes selected out by means of the rocker switch on the throttle. There was a slight nose-up trim change coincident with very good deceleration.

In the cruise at 25,000 ft, rudder kicks showed positive if slow damping in yaw oscillation, while aileron inputs resulted in the aircraft continuing to roll slowly, partly owing to the high roll inertia and partly to the slight circuit friction. Longitudinal stability was very good, with very powerful and precise elevator trimming via a trim wheel. The ease of trimming was indicative of the stability in pitch, while manoeuvring stability was later shown to be high by the rate of increase of stick force with speed and g.

Much thought has gone into the aeroplane with regard to the possibilities of overstressing. When the stick was released in an out-of-trim dive (trim set in the cruise condition) the g increment resulting was very small. No directional trimming was possible in flight and the aileron trim did not have to be used on this occasion, proving fairly symmetric automatic supply of tip tank fuel. Elevator trim wheel movement from the 9 o'clock (nose-up) to 5 o'clock (nose-down) positions gave a sufficient trim range to trim the aeroplane throughout the speed range tested. At the same time the trim curve (outside Mach effects) was steep enough to ensure that a student would pay constant attention to retrimming, something that too many aeroplanes fail to teach.

A maximum rate descent is really an experience that no budding airline pilot should be without! With throttle closed and airbrakes out, the speed was allowed to increase to 350 kt in a dive of about 65 degrees. During this period the aircraft descended from 15,000 ft to 10,000 ft in 15 seconds. Buffet was noticeable but not severe, and the pressurisation system coped very well.

A dive to maximum speed was required as part of the test programme and this was accomplished at low altitude, reaching 450 kt at 3,000 ft. Above 400 kt the ailerons heavied up appreciably, and simultaneously the elevators became very heavy indeed. It would require a lot of strength to overstress a Strikemaster at these speeds. The use of airbrakes resulted in very harsh deceleration, accompanied by strong buffet, and also by a recurrence of the snaking noted earlier, especially in a shallow turn. 5 g was pulled in the recovery. The application of the higher levels of g for relatively protracted periods is something that is probably completely foreign to 'straight through' airline pilot students. While one hopes that they would never encounter such loadings in their working careers, they should at least be aware of what it feels like. This is something that a simulator cannot teach!
 


ABOVE: 'The large perspex areas . . . encourage the student to keep a good lookout'


ABOVE: 'The application of higher g levels for relatively protracted periods is probably completely foreign to "straight through" airline pilot students . . . They should at least be aware of what it feels like'

Stalling and spinning

Trading speed for height on the completion of the high speed dive, it did not take long to reach the recommended height to investigate stalling and spinning - namely 18,000 ft. The Strikemaster is limited in service to four turns of a spin, but the tests on this flight demanded six full turns prior to initiating recovery. Accordingly I added another 10,000 ft to the minimum required altitude. On reaching 28,000 ft at an AUW of 8300 lb, stalls were made in clean, approach, and landing configurations, power off.

In the clean case slight airframe and elevator buffet gave about 10 kt warning of the stall, which actually occurred at 98 kt and was marked by right wing heaviness followed immediately by a mild g break. With undercarriage and take-off flap lowered the warning buffet was slightly masked by flap buffet, but still gave 5 kt warning of the stall, which occurred at 85 kt with the left wing lowering in a g break. With full flap the behaviour was identical, except that there was only about 2 kt warning, and the stall occurred at 83 kt.

In all cases recovery was immediate upon releasing the back pressure. There was no control lightening or tendency to spin, although no attempt was made to provoke the aircraft by pulling the stick fully back at the stall.

During the stalling exercise the trim changes with flaps and undercarriage were assessed. In the case of the undercarriage trim, changes were negligible, and the operation was extremely quick. The flap positions were infinitely variable; flap movement was just as quick, or as slow, as the rate at which the pilot chose to move the selector. In addition, a gate was provided to enable 30 degrees of flap to be selected with ease. From the flaps up position to 30 degrees there was a nose-down attitude change as opposed to a trim change, and the aircraft ballooned upwards slightly, the rate depending on IAS and rate of flap lowering. As noted on take-off, retraction produced a noticeable sink and nose-up pitch. From 30 degrees to 50 degrees (fully down) there was a distinct nose-down trim change. Limiting speeds were 145 kt for undercarriage, 175 kt for take-off flap and 150 kt for full flap.

Six-turn spins were assessed as part of the test programme at both high and low weight during the sortie. Although this manoeuvre would be of little value as such to the potential airline pilot there is no doubt that as a confidence manoeuvre it is without parallel!

Among many civilian trainee pilots there is to be found a great deal of apprehension and lack of understanding of the principles and practicalities of spinning. With an aeroplane such as the Strikemaster, fully cleared for spinning, we have the means of instilling, if not confidence, at least the awareness of the physical and physiological parameters involved. If for no other reasons than these, the manoeuvre is worth doing, and in this machine can be demonstrated with safety.

The spin was entered from straight flight, power off. It was noticed that if the entry was too quick, the aircraft rolled to the inverted position before beginning the spin proper. There was no difficulty in establishing the direction and type of spin; yaw, roll, pitch and bank attitudes were easily identified. The aircraft had to be held firmly into the spin, which took up to four turns to stabilise. The IAS steadied eventually at speeds of between 130 and 155 kt, and there was airframe and control buffet present. Elevator buffet and snatching were most noticeable during the incipient stages, with rising IAS. Pitch attitude was about 60 degrees, and the ailerons tended to trail in-spin. Although I was holding the stick back with considerable force, it is likely that this was a direct result of seeing the speed increasing, because during the subsequent recovery it was necessary to use about a 20 lb push to get the stick forward. It is very likely that I was holding the stick back unnecessarily hard against the stop in the spin.

All the six turn spins stopped within 1½, turns, although if there was insufficient pause between applying opposite rudder and pushing the stick forward, the built up rotational energy made itself manifest in the rolling plane as the spinning couple was broken, with the attendant fierce acceleration in roll before the spin stopped. This did not occur when a two second pause was made between application of rudder and stick. Total height consumed in seven and a half turns plus pullout was 9000 ft.

With 700 lb of fuel still remaining, I accepted Reg Stock's invitation to try a few aerobatics. With plenty of power available, 3410 lb static, at an AUW of 7100 lb, the aircraft was very pleasant to manoeuvre through a loop and a vertical roll and at 100% power it continued to accelerate in a constant height band during these aerobatics.

Resisting the temptation to continue, we returned to the airfield, where I was invited to explore the relighting capabilities of the Viper Series 20 (Mk 535). Although the relighting envelope extends to 30,000 ft it was deemed prudent to first set up a practice forced landing pattern at 4000 ft - test pilots are cautious by nature! The engine was stopcocked and speed reduced to 140 kt in the glide (optimum relighting range 120-140 kt). The relight drill was quite straightforward; I pressed the relight button for 5 seconds and then opened the HP cock. Lightup was immediate and 40% rpm was achieved in 15 seconds - an impressive demonstration.


Circuit and landing

Entering the circuit the general impression was of an aeroplane that had no vices, but which flew around fast enough for a student to need to stay alert in order to keep up with events.

The circuit itself presented no problems, the trim and attitude changes noted previously being in evidence once again. Pilot view remained good throughout the landing and go-around, even during a flapless landing. With full flap there was good speed control available, although if the speed was allowed to increase appreciably above the 95 kt threshold speed required there was noticeable float in the ground effect.

The overshoot from the runway was again straightforward. Slight engine hunting following a full power slam was due to slight over-controlling by the overspeed governor. This was detectable but not significant in terms of thrust. Undercarriage was selected up and flaps to take-off, and power reduced to 90%. The flaps were left at take-off in the circuit, which resulted in very good speed control. Airbrakes could be used in conjunction with flaps, but this resulted in a noticeable degree of buffet and slight snaking. Landing with airbrakes extended tends to mask the stall warning bullet. However, airbrakes could be used to good effect to help stabilise speed and glide path in the event of a flapless landing. While of no real significance on this aircraft, it could be considered a useful exercise in preparation for certain heavier types.

The landings themselves, with and without flap, were completely straightforward, with no tendency to swing or bounce. Since the brakes were not equipped with anti-skid devices, some care was necessary, as they are quite powerful. Normal braking was used, and the stopping distance was quite acceptable, although it was not measured. After I hour 25 minutes airborne, we still had 400 lb of fuel remaining.

In short, there is no doubt that the Strikemaster is already an admirable training aeroplane. In the airline instructional role projected here it would seem to have good potential. It could add a new dimension to the training of students in the sense that they could gain actual experience of high level airways operation. Admittedly the same thing can be achieved in a simulator - with the one exception that there is no substitute for the psychological boost of having actually done it.

Exposure to the Strikemaster will expand the speed and height band to which the student has become accustomed. It will bring home to him the requirement for exact fuel planning, together with jet engine handling. The amount of anticipation demanded by both the aircraft and the engine will stand him in very good stead later. Here the results of wake turbulence and autopilot disconnect can be explored in safety, and the lessons really appreciated, for example, when up to 5 g has to be pulled in a recovery. It doesn't take a lot of imagination to appreciate what could happen to a big jet in similar circumstances. Safe in the knowledge of the Strikemaster's strength, these and other abnormal situations can be explored without danger. It should be always remembered that today's young civil pilots have never had the advantage of military training, where they would have experienced all these things.


A new capability

Two disadvantages that spring to mind when contemplating an approach such as this to airline pilot training are the lack of space in the cockpit for maps and charts, and the self-evident fact that one cannot simulate an engine failure, as it would affect a multi-engined layout.

The first problem can be largely overcome at present by careful and specific flight planning; let's face it, many Service single seat aeroplanes are able to operate to civil standards. Also, one doesn't actually need to cart about the travelling libraries with which most of us encumber ourselves (charter pilots who may get diverted to Timbuctoo excepted!). For the future, it is not beyond the bounds of possibility that a computer index type of card could be utilised to present the required information on a head-up display, utilising the existing gunsight equipment.
 
The other problem area is the requirement to simulate asymmetric flight. Of course a ground simulator can teach the fundamental principles of coping with an engine failure; and such simulators can be electronically 'doctored' to represent a wide cross-section of the types of airliner in service today. All well and good, but however sophisticated the simulator, there is nothing like experiencing the real thing.

It can be argued that the majority of asymmetric accidents in the past have occurred as a direct or indirect result of simulated engine failures during flight training. Clearly, what is required is the potential to teach, in the air, the effects of an engine failure (including during the take-off), without the increased expense and risk of actually throttling back an engine on a student. This was a wild Utopian dream until recently. But now a research team at RR Bristol have put forward a novel idea. Basically it provides for an aircraft such as the Strikemaster to serve the dual role of a single engined basic trainer and a twin engined intermediate trainer! It also offers the ability to reproduce the general handling characteristics of a wide variety of types of multi engined aeroplanes. It permits simulated engine failures to be practised in a much more realistic attitude than hitherto, where the instructor pulled back the throttle in full view of the student.

The principle of this invention is quite simple. The student is provided with two throttle levers as in a twin engined aeroplane. Operation of these levers in various angular relationships produces, via a thrust deflector in the jet pipe, variations in power and yawing moment similar to the same throttle movements on a twin engined machine. The rates of yaw and thrust decay can be preset to simulate any aircraft. Cockpit instrumentation can simulate the visual results of all this, while for basic flying instruction the two throttles can be linked together, and the 'second' engine's instruments covered over by a flap.


With this 'twin engined' system installed an engine 'failure', as well as causing a yaw, would also involve an overall thrust reduction to between 50% and 70% of normal full power, thus representing fairly accurately what would happen if one engine of a real twin type failed. Since there would be no sideslip in the stabilised condition following an engine 'failure', there would be no fuselage side force, as is the case with the real thing. To correct this it is suggested to bleed off some engine air and to supply small 'puffer' jets on one side or the other of the nose. In this way engine failures may be simulated in flight with much more safety than before. The instructor has at his disposal a 'master' throttle, which restores full and symmetric thrust in the event of an unsafe condition being approached.

In addition to this, the system can be modified to safely demonstrate 'negative excess thrust' situations, i.e. simulation of a modern high performance aircraft on the wrong side of the drag curve on asymmetric power, a situation which on a conventional aircraft would be exceedingly dangerous. Similarly, afterburner light up procedures can be demonstrated.


Another great advantage is that a student would not have to re-learn a new aeroplane for his twin conversion, and for the operator there would be dramatic reductions in costs, servicing and spares.

The invention is simple, relatively cheap, extremely light - only 45 lb extra weight - and was designed with the Jet Provost/ Strikemaster specifically in mind. It can also be easily fitted as a retrospective modification. If there were any doubts about the civil potential of a single jet aeroplane in the airline pilot training role, the incorporation of this new device must surely dispel them.





WHEN considering today's jet travel, we tend to think of airports in terms of those larger facilities with which we are all familiar: New York, Chicago, London. It may therefore come as something of a surprise to realise that more than half the world's commercial airports have runways 6000 ft long, or less, and many are several thousands of feet above sea level. For years they have been faithfully served by a fleet of wide variety, mostly piston and turboprop types. These, in their turn, have had to make way for the age of the pure jet, for as soon as the novelty of propeller driven air transport had worn off, customers for the most regional routes succumbed to the need to cut down their travelling time.

Obviously the moment was ripe for operators who had started out with propeller types to invest in new equipment, and it was inevitable that manufacturers specialising in the field of short haul schedule and charter operation should have anticipated this demand. One of the leading companies in this field is the Fokker-VFW consortium, and the aeroplane they put forward was the twin jet F.28 Fellowship.

To enable this aircraft to take over from the older machines with any degree of success, the requirements for the short haul task were considered in detail. High take-off and landing performance was demanded, with good handling, and a high structural fatigue resistance to cope both with the associated frequency of operation and with flight at low altitude. In addition the aircraft needed to use unprepared runway surfaces, and to have good self-support and quick turnround capabilities. Finally it had to be efficient and economical in order to be competitive with the types it was designed to replace.

The 65 seat F.28 Mk 1000 has fulfilled all these qualifications and is now in service with no less than 53 airlines throughout the world. With a range fully laden of 1100 nautical miles, it has a break-even load factor as low as 25 seats, so that it can economically replace aircraft from the DC-3 to the Viscount and DC-6. It has achieved a regular continuous operation pattern of more than 10 hours per day and a despatch reliability of 99% with maintenance schedules adapted to suit the customer's requirements.

Development history

In the original design, the size was decided upon because it represented the smallest rear engined twin jet in the required payload and performance class, with regard not only to economy, but also to any passenger and baggage loading combination without either compromising the permitted CG range, or requiring specific loading restrictions. The problem is that any such aircraft, owing to the weight of the engines, becomes tail heavy when scaled down without reducing the fuselage diameter. As a result, engines must be less aft with respect to the wing in the smaller sizes.

In fact, the aircraft had not been long in service when it was realised that far from being too big, there was actually a need for a stretched version. This resulted in the Mk 2000, with 79 seats but otherwise similar to the Mk 1000. Owing to the increased weight there was naturally a loss in performance, which could have compromised operation from some of the smaller high altitude airports in tropical locations. It was therefore decided to evolve another mark of F.28 with the performance of the Mk 1000 and the capacity of the Mk 2000.

This has resulted in the Mk 6000. It differs from the Mk 2000 only in having full span leading edge slats and a modified Rolls-Royce Spey engine (555-15H) with developed flat rating and silencing. To complete the family, the Mk 1000 was similarly modified to Mk 5000 standard, using the same slatted leading edge and engine silencing fit, thereby conferring on the 65 seat model exceptional short field characteristics and enabling it to use special short runways at major airports.

Both Mk 5000 and Mk 6000 aircraft incorporate strengthened wings with a span extension of 5 ft.

The development prototype of the Mk 6000 series is actually the rebuilt Mk 2000 prototype which has seen a considerable amount of development flying. Last year it completed an intensive performance programme with the high lift wing, designed in close collaboration with Shorts (Belfast) who are main contractors for this item. With the increased weight there has been a requirement to design and fit a heavy duty undercarriage, and this can also be fitted retrospectively to any of the previous models. The first production models of the slatted wing F.28 are scheduled for delivery in the early part of 1975, so it was with keen anticipation that I recently visited the Fokker works at Schiphol, having been invited to evaluate the prototype Mk 6000. I was fortunate in being able to fly with Jaap Hofstra, who was project pilot assigned to the Mk 6000 and who gave me every assistance during my assessment.


Prototype cockpit layout as sampled by Author (above) has been greatly improved and simplified in the production aircraft (below). Of note are the IPECO crew seats, medically designed to achieve the best pilot posture





ABOVE: Prototype Mk 6000 was a Mk 2000 fitted with the new slatted wing and hush kit. In effect, these changes have restored to the Mk 2000 the performance of the smaller, lighter original

Airframe and systems

As if to make the point that the F.28 is completely self contained, the aircraft had been parked on an apron that was completely devoid of any form of ground power unit. The APU was running as I approached; it was noticeable that the unit was quiet in operation, and that the exhaust was sufficiently high so as not to affect a crew member carrying out a pre-flight check. A look around the aircraft impressed me particularly with the very high standard of workmanship involved. I was reminded of my visit to the production line, where the experience with the F.27 had been utilised to good effect in the F.28. Cold bonding has been extensively used in addition to riveting to give a stable and long-life structure with excellent crack-stopping properties.

Accessibility to the pressurised baggage hold was excellent. There was a very neat single point pressure fuelling installation which could be pre-set for required contents. Large main undercarriage doors remain retracted on the ground and prevent water and debris from being thrown into the undercarriage wells. APU access was also very easy through a ventral hatch.

Of particular interest was the cleanliness of the slat installation, which is split into three sections. The slats themselves are deiced with engine air tapped from the compressor and piped through a telescopic tube. The air exhausts into the slot and helps to deice the main leading edge, which is not in itself specifically protected. The large double slotted Fowler flaps are also a neat installation, being equipped with a cutout device so that if any flap asymmetry is detected, all flap operation is automatically stopped.

Because the aircraft is geometry limited in the rotation, production models will have a telescopic tail bumper to prevent any damage should the tail touch the runway. The main door is equipped with steps and handrail, and is electrically operated from outside as well as inside. It is locked and unlocked manually, requires two completely different techniques when opening and closing, while in emergency the electrics can be disconnected and the door opened manually. In its open position it rests on the ground and is protected by a small bumper. Inside, the Mk 6000 was very definitely a test aircraft, with banks of instrumentation, an escape chute, and a very useful ballast system containing water which could be pumped forward or aft to alter the CG through the full range in ten minutes.

On this very early prototype, cockpit layout was not really representative of the production aeroplane, although all primary controls corresponded to production. An assessment of the production cockpit confirmed the impression of space, both vertically and horizontally, while the layout of instruments was so neat that one was left with the impression that some of them were missing!

In fact, everything was there. An addition to the basic panel was an angle of attack indicator, and there was a good reason for this, as I was to discover. Panel lighting was particularly good, everything being very clear with no bright or dark areas. External lights were neatly installed, in particular the way in which the landing lights were fitted into the flap track shroud, since the slats precluded the mounting of any lights in the leading edge. The IPECO crew seats, which had their origins at Farnborough, could be adjusted to suit any shape of pilot and in conjunction with the adjustable rudder pedals resulted in a good sitting position with excellent access to all controls. Not so the long suffering prototype with its non-adjustable rudder pedals, where I had to use cushions to make sure I could reach full rudder!

The cockpit of the prototype had one or two interesting additions installed for flight test work, including a battery of switches controlling tail-mounted rockets to allow the aircraft to be pitched nose down during tests involving penetration into the stall. There was also provision for roll spoilers to assist the ailerons, but these have been found unnecessary, and will not appear on the production aircraft.

It can be fairly stated that the application of jet aircraft to the short haul case has been made possible by the development of the turbofan engine. The early F.28s were fitted with Rolls-Royce Spey 555-15 engines, delivering 9850 lb of thrust each, and having a typical cruise sfc of 0.8. The engine is made up of HP and LP sections, has a bypass ratio of 1:1, and a compression ratio of 15.4 : 1. It contains conditioning monitoring features, including magnetic chip detectors, which facilitate in-service inspection. It has proven itself to be exceptionally reliable, and the current life of 8000 hours is being extended.

A modified version known as the Spey 555-15H has been planned for the production Mk 6000 aircraft. This will result in a further reduction of noise level over the standard F.28, which is already one of the quietest airliners in service, and which complies easily with FAR 36. The reduction will permit the aircraft to comply with the most rigorous future requirements; it is achieved by means of noise attenuating devices, and in addition the new engine is flat rated to give some 5% extra thrust at ISA + 10C.


Start-up and taxi

The Spey is started by bleed air supplied by the APU, or by a ground power unit. With one engine running, the other can be started by cross feeding HP bleed air, and finally there is provision for a 'buddy' start where both engines can be started from a second F.28 by means of connecting pipes. One airline in Australia requires each of its aircraft to carry such a pipe in the event of a rescue operation.

On the tarmac at Schiphol the APU was utilised in the normal manner, and engine starting was perfectly straightforward. The engine is selected, and as soon as there is a reading on the LP spool (some 12 seconds later), the START position is selected on the HP cock, which is then selected to open when either 50% HP rpm or 400C TGT is achieved. Total time from initiating the start to a stabilised idling rpm of 50% is 30 seconds. The engine note is low and not unpleasant, while from the cockpit the noise of the APU is barely discernible.

The throttles are low geared and are extremely pleasant and smooth in operation. Some 70% to 75% HP rpm is required to start the F.28 rolling, depending upon aircraft weight, after which 55% to 60% rpm on both engines permits a comfortable taxying speed.

The hydraulically powered nosewheel steering has a range of 76 degrees each way. In the event of this being exceeded - during towing, for example - the steering is automatically disconnected. The steering wheel is located on the left console, and the straight ahead position is shown by an arrow. Nosewheel steering is also provided for the copilot. The system is pleasantly geared, has no tendency to oversteer, and is rather heavy in operation, which perhaps accounts for the 'big aircraft' feel.

Toe brakes are excellent, with anti-skid. They are light in feel and have a very pleasant balance between movement and pressure in operation. Extremely smooth and controlled braking is therefore possible, symmetric or differential. Emergency brakes are available, operated via two levers aft of the nosewheel steering wheel.

Proportional and differential braking are available hydraulically but there is no anti-skid protection in the emergency case. This system, too, is very smooth in operation. The parking brake catch on the left hand secondary instrument panel is released when the toe brakes are depressed.

The aircraft gives a well damped ride on the ground, and when one hears oleo noises as the aircraft traverses undulating taxiways one is reminded that the undercarriage is designed to accept a vertical descent of 10 fps. The view during taxying is excellent, which coupled with the well matched idling thrust and excellent brakes gives a feeling of confidence.

Take-off

For this flight, the all-up weight was 71,558 lb, with a CG of 30.7% MAC (effectively a fully aft CG). The take-off configuration was with slats extended, zero flaps, and a horizontal stabiliser setting of 2½ divisions nose up. If the stabiliser is set outside the safe range there is an audio and visual warning. V1 equalled VR at 120 kt, and V2 was 127 kt.

Although a thrust indicator was installed, I used full power for take-off. The thrust indicator compared P1, (set manually from a graph of temperature against pressure) with P7 air from the compressor. In Europe during winter the ensuing thrust datum is a figure of 162, which permits a gauge reading of better than 100%, this being the minimum figure for take-off. There is a detent in the left throttle gate which determines climb power setting.

The brakes are capable of holding the aircraft against full power, and one can release them gradually to permit a gentle start. In fact I released quickly, enabling the time to unstick to be measured at 30 seconds. Directional control was easy via the nosewheel steering, and the rudder became effective at 60 kt. The elevator showed signs of life at 80 kt, and the nosewheel tended to lift slightly before VR. Rotation at 120 kt resulted in the F.28 literally leaping into the air. The low geared trimmer had to be wound forward quickly to trim out.

Wheel braking was automatic on gear retraction, any nose-up trim change being due to acceleration rather than undercarriage even at a pitch attitude of 15 degrees. Slat retraction was made at 180 kt, with again no trim change. The slats, which are cable controlled from a single jack, have a movement of 15 degrees and out of phase indicators are placed in the cockpit. The slats must be extended before flap can be lowered.

The aircraft is pleasantly harmonised, with ailerons and rudder fully powered hydraulically, and having spring feel, while the elevator is boosted hydraulically in the ratio of 4 : 1, which results in a 'q' feedback to the control column. Pitch trim is via the variable incidence tailplane, while roll and yaw  trimming is achieved by spring datum trim. All primary controls are served by two separate and independent hydraulic systems. A yaw damper is also fitted. An anti-upfloat cable connects the ailerons, ensuring correct operation. In the event of a malfunction of an aileron control unit, the failed aileron can be driven partly via the upfloat cable, and partly by its own servo tab which is released from its previously locked neutral position by a hydraulic system pressure sensor.

En route to the test area, the F.28 cruised easily in the slight turbulence at 270 kt indicated and 6000 ft. A power setting of 85% HP rpm resulted in a fuel flow of 2200 lb/hour/engine. Most of this transit was in cloud under Amsterdam radar, and I found the F.28 remarkably easy to fly on instruments with no tendency to overcontrol on the powered ailerons.

A climb was made from 5000 ft to 28,000 ft. by setting the left throttle to the detent, aligning the right throttle, and using the top temperature control, which held the engine temperature at 470C TGT.

It was necessary to keep reminding myself that the aircraft was in fact loaded at aft CG because it felt remarkably stable and dead-beat. During the climb the throttles were not adjusted, and in spite of this I could not detect any out-of-synchronisation beat from the engines. Times and fuel flows were noted as follows, using a climbing speed of 270 kt, changing to Mach 0.65 at 23,000 ft.
   Height      Time    RPM    RPM   Fuel flow per
    (feet)  (min, sec)     left    right   engine (lb/hr)
     5,000              0      95      95         4900
   10,000       1   59      95      95         4200
   15,000       4   24      95      95         3700
   20,000       7   20      95      97         3280
   25,000     11   05      95      97         2850
   28,000     14   02      95      97         2600

Height was then reduced to 25,000 ft and the aircraft was set up at max. cruise, which resulted in an IAS of 298 kt, Mach 0.72, with a power setting of 95%. This gave a fuel consumption of 2800 lb/hr/engine.


ABOVE: Take-off at excessive angle of attack. Part of the performance testing for certification established that the aircraft would continue the take-off when rotated to a speed, V mu (velocity minimum unstick) derived from the normal take-off parameters

General handling

During an assessment of longitudinal stability in the cruise, the aircraft showed itself to be well damped, and was reluctant to be disturbed, even at aft CG. Yet in spite of this it remained pleasantly light on the controls for normal flying and responded well to small control movements. Trimming was also quite easy, the need to make occasional small adjustments being the only indication that the CG was in fact aft. Dynamic stability was excellent, being dead beat in the SPO (short period oscillation) mode, and damping steadily in a gentle LPO of 70 seconds cycle. A qualitative assessment of stick force per g in the cruise at 300 kt IAS showed that the stick force increased rapidly with increasing g, and I estimated the force at 40 lb per g, with airframe buffet just detectable at 2 g indicated (limit 2.5 g). Subsequent readings from the graphs confirmed this figure at aft CG and indicated that the figure could be as high as 90 lb per g at 200 kt with a fully forward CG.

During these tests the noise level on the flight deck was low, permitting normal conversation. Most of the extraneous noise appeared to be around the windscreen, and this increased marginally with sideslip.

Still at 25,000 ft, 300 kt, 66,800 lb all-up weight, the harmonisation was changed a little as compared with the low altitude case at 270 kt. It seemed to me that with the higher speed the feedback from elevator inputs had markedly increased, while of course the spring feel ailerons and rudder gave constant force feedback. In spite of the slightly heavy elevator, the aircraft was still pleasant to fly. Lateral and directional stabilities were assessed with the yaw damper engaged, and it was noticeable that the rudder breakout force was a little higher, perhaps a function of the lower temperature at height. This resulted in a slightly 'sticky' feel to the rudder, which would not be significant in normal operation. Ailerons remained light and pleasant in response.

Stability sideslips showed very low but positive lateral stability, while directional stability was good. This balance was thought to be satisfactory when one considers the role of the F.28 in short haul and VFR operation; it feels like a pilot's aeroplane. With the yaw damper out, dutch roll oscillation was slow to damp in a 4 second cycle, but selection of the yaw damper stopped the oscillation instantly. While the aeroplane can obviously be flown without need for the yaw damper, the device will certainly ensure a very smooth passenger carrying platform.

A shallow dive was made at 95% power, and at Mach 0.76 (310 kt IAS) the Mach horn sounded. There were no other indications of Mach effects, and the elevator trimmer was smooth in operation and pleasantly geared. No Mach trimming device was fitted, nor was one needed. In fact cruising speed at high altitude need not be pushed to a high value for this type of aircraft, as it is more important to design for a high Vmo than for a high Mach number, for short haul operations. At Mmo the F.28 does not exhibit any appreciable drag rise, although this does increase rapidly above the critical drag Mach number.

Because of the high set tailplane position, downwash effects on the tail are minimised during local transonic losses of lift on the wing. This results in no appreciable trim change up to Mach 0.76.

Again because of the design philosophy, the cabin differential pressure is quite low at a value of 7.45 lb, giving a cabin height of 8000 ft at an aircraft altitude of 35,000 ft.

This is instrumental in increasing the in-service life of the airframe, which is currently being certificated for no less than 60,000 flight cycles. The pressurisation system was quite adequate in coping with sudden and severe changes of altitude during the tests, especially since I often reduced power to full idle quite suddenly.


During the high speed dive, the cabin descended at 700 fpm as compared with the actual aircraft rate of 2500 fpm. Vibration was practically non-existent, and a sudden reduction of power caused no appreciable trim change. Selection of full airbrake achieved an extension of between 40  and 45 degrees: an automatic restriction permits the full 60 degrees extension at 180 kt and below. Again there was no trim change with airbrake, and no buffeting either - just a smooth, steady deceleration. The airbrakes are petal bifurcated type on the rear fuselage and can be used without compromising the normal flight controls. Infinitely variable, with a cockpit indicator showing instantaneous position, they can be used in preference to throttles to control speed, which also has the advantage that the pressurisation system is not liable to fluctuation. As they opened fully below 180 kt, the rate of deceleration increased. They retracted smoothly with the barest hint of a nose-down trim change, and at the lower speeds below 180 kt it was noticeable that the aileron controls heavied up slightly as a result of increased deflection of the spring feel system in normal manoeuvres.

Low speed handling

I had been looking forward with some interest to carrying out stalls on the F.28, with especial regard to the high set tailplane and full span leading edge slats.

One naturally tends to look askance at the combination of leading edge slats and a high set tailplane in the light of previous problem areas on some other types in the deep stall case. Wind tunnel tests on the basic F.28 had indicated that prompt recovery could be expected by elevator only, except possibly with the CG at the extreme aft limit when recovery might be a little slower. The tunnel investigations suggested that airbrake extension might be instrumental in promoting a nose-down pitch, but rather than take any chances, the prototype was fitted with recovery rockets for these tests.

With the advent of the Mk 6000 and its full span slats, this area was again investigated. Tests showed that at about 30 degrees angle of attack the stick force showed signs of a reversal tendency. It was therefore decided that a stick pusher should be fitted to give positive protection when the flaps were lowered, and since the slats offer a very high CL it is possible to provide a good margin of safety between stick push and aerodynamic stall. This margin is about 8 degrees in the landing flap case. It is achieved without compromising runway and climb performance, as one could not realistically utilise the exaggerated angle of attack which the slats could permit. Since a deep stall cannot be achieved with the pusher operating, the use of airbrake in the stall recovery was not assessed.

Angle of attack is measured by fuselage mounted vanes, with gust filtering. Stick pusher activation depends not only upon angle of attack and position of slats and flaps, but also on rate of increase of angle of attack: it does not operate in the clean configuration.

The stalling tests were made from a slow approach in straight flight, power off, airbrakes in, at a weight of 64,300 lb. In the clean configuration the stick shaker operated at 142 kt (11 degrees angle of attack), and at 130 kt slight natural airframe buffet could also be felt. The aircraft was descending at 1000 fpm, with a pitch attitude of 10 degrees nose-up, when the g break occurred at 122 kt (16 degrees angle of attack), and the right wing lowered. There was no nose-down pitch at the stall although the aircraft was still controllable.

Since the stick pusher was not operating I experimented by pulling back on the control column to determine the ease or otherwise of penetrating further. However, as I did so the airframe warning increased to heavy, pounding cyclic buffet, and I was effectively forced to recover. Nobody could possibly pull into the stall through that buffet: small wonder that a pusher was not considered necessary!

When 18 degrees of flap (plus slats) were extended, it was noticeable that the aircraft responded in a much more positive manner to elevator inputs. At 1200 fpm rate of descent, the stick force lightened very slightly before airframe buffet appeared at 100 kt (19 degrees angle of attack), with the nose 12 degrees pitched up. At 95 kt (21 degrees angle of attack) there was a slight self pitch-up tendency, and at the same time the stick shaker operated. The aircraft was still easily controllable. As the speed fell towards 80 kt there was an increase in buffet which precipitated the g break, and coincided with a slight right wing down tendency, all at 23 degrees angle of attack. This was followed immediately at 23½ degrees angle of attack by the activation of the stick pusher, which fired with a hiss of air and thrust the nose down smoothly and powerfully. The aircraft recovered instantly, and as the control column passed the neutral point the force reduced from 80 to 30 lb push.

For the full flap case, wheels were also lowered, and the rate of descent stabilised at 2000 fpm. As speed was reduced, the stick force lightened marginally, until at 90 kt (18 degrees angle of attack) the onset of stick shake coincided with the right wing becoming heavy. The pusher operated at 83 kt (21½ degrees angle of attack) and did not feel so severe on this occasion, although recovery was still instantaneous.

During these tests it became obvious that the most constant cockpit indication during the stall approaches was angle of attack. Since this would be very important during, for example, performance take-offs, it is an excellent feature to incorporate in the production cockpit, as Fokker-VFW have done. The stall protection system on the F.28 is certainly most effective in ensuring that the aeroplane is kept well clear of any potentially hazardous condition. Its angle of attack sensing vanes are in addition provided with anti-icing heaters. Although the aerodynamic stall can be achieved in the 18 degree flap configuration prior to stick push, the resulting behaviour is innocuous. In the full flap case the pusher is activated early in relation to the aerodynamic stall, which is in fact not achieved. The angle of attack indicator is able to provide the crew not only with the stall margin, but also in the dynamic case with the rate of approach. In combination with the mechanical stall protection it should give F.28 crews complete confidence, especially during low level manoeuvres in perhaps bad visibility, for let us not forget that this aeroplane has a VFR role where it will operate in and out of rough airstrips.

The engines behaved impeccably throughout, their only restriction being on fast throttle opening above 10 degrees angle of attack. Normal throttle openings at high incidence resulted in perfect behaviour, and at no time did the engines show any signs of distress.

In the event of an engine shutdown, a relight can be made at up to 25,000 ft between 200 and 330 kt. One may use either a windmilling start, or air starter assistance at the lower airspeeds. In this case I relit the port engine using the windmilling method, following a shutdown at 11,500 ft and 200 kt. Igniters were selected on, and the HP cock set to START. The engine lit up in three seconds and stabilised in a total of 14 seconds at 55% rpm. It was as simple as that.

With the weight down to 63,000 lb, I lowered the undercarriage and 18 degrees flap (including slats). Some general handling was carried out in this configuration at 150 kt at 10,000 ft. Longitudinally the stability was very good and again it did not feel as though the CG was fully aft. The response of the aircraft was naturally much lower in pitch, and it was very reluctant to depart from its trimmed condition. Stick force per g was estimated at 20 to 25 lb at 150 kt, which meant that the aircraft was light enough to be easy and pleasant to fly, yet sufficiently heavy to eliminate any over-controlling tendency. Lateral and directional stability remained good, with well harmonised controls, the aircraft being quite stiff directionally, especially with the yaw damper in. The difference produced by the yaw damper, though, was much less noticeable than at high altitude.

With the yaw damper out, a deliberate dutch roll input damped out in one cycle. The overall result indicated an aircraft that can be manoeuvred easily and safely.

Systems timings were then made, the most noticeable feature being the extended time during undercarriage lowering - 26 seconds - against 5 seconds during retraction; however, short lowering times are not a certification requirement. On the production aeroplane warning lights will be provided for the undercarriage doors as well as for the gear itself. There was no trim change with undercarriage, nor indeed with slats and flaps up to 18 degrees extension. The flap timings were 12 seconds in both directions, while slats took 3 seconds to extend and 3½ seconds to retract. The drag of the slats seemed to be quite high, and there was a slight nose-up trim change as they retracted which was thought to be due entirely to aircraft acceleration. The only significant trim change resulted when the flaps were lowered from 18 to 42 degrees as the double slotted section came into operation; this was gently nose-down, taking 7 seconds. From 42 to 18 degrees the time was 8 seconds.

The aircraft was cleaned up and accelerated at low level to 330 kt, at a weight of 62,000 lb. There was moderate turbulence but the aircraft remained very stable, with only a slight lateral shake. The Vmo warning horn sounded at 330 kt and there was plenty of reserve power available at this speed, which was achieved with 90% rpm. Throttles were slammed down and up with no trim change. Airbrakes were extended, and gave very smooth deceleration without any buffet. They are without doubt the smoothest airbrakes I have ever encountered.


ABOVE: Deceleration phase. The airbrakes are infinitely variable, can be used in preference to throttles to control speed

The undercarriage and 18 flap, including slats, were lowered, and the left engine throttled fully back at 1500 ft. Full power was applied on the right engine, and speed was steadily reduced, at a weight of 61,500 lb, until at 21 degrees angle of attack the stick pusher operated. This resulted in a Vmca of 85 kt, with the wings level and slip ball centred, although I had just reached full rudder as the stick pusher fired.

Gear was retracted and a V2 climb was continued at 109 kt, which resulted in a 500 fpm rate of climb, still with full power on the right engine. There were 3 inches of rudder travel still available.

Approach and landing

An instrument approach was then made to Schiphol, during which it was interesting to note the 10 degree nose-up attitude change at constant airspeed and altitude as the slats extended. Normal speed and height reductions would be made using airbrakes, thus allowing 80% rpm to be left set up, which in turn would provide for passenger comfort as regards pressurisation changes.

During the initial approach the aircraft flew level with a nose-up attitude of 5 degrees. However, this was not specially significant from the pilot's viewpoint owing to the excellent field of vision afforded by the big windscreens. VREF was 113 kt using 42 degrees flap, and the final approach was flown at VREF + 5 kt, using full airbrake at 100 ft to reduce speed to 113 kt.

The attitude change to flare completely is quite noticeable, and at first one is reluctant to make the relatively large input needed. One soon realises, however, that the F.28 handles more like a straight wing piston or turboprop in the landing flare, rather than a swept wing jet. There is in fact a very good flare capability, although the undercarriage can accept a relatively high descent rate on touchdown without problem. There is no tendency to bounce, and unless the nosewheels are deliberately held off they tend to drop as soon as lift dump is deployed.

These lift dumpers take the form of spoilers which extend above the wings, five on each side. They act as aerodynamic brakes, as well as fulfilling their primary function of destroying all wing lift and allowing the powerful wheel brakes to be used to full effect. The airflow over the high T tail remains unaffected, and elevator control remains good.

The lift dumper actuation and protection system is rather complex. This arises from the demand that they shall never extend in flight, while acceptance of their use in the certificated landing distances requires that their correct operation during landing must be guaranteed. The automatic extension of lift dump is effected with the system armed, both throttles at idle, and mainwheel spin-up equivalent to a ground speed of 50 kt. 'Touch and go' landings may be carried out, as the action of opening the throttles initially retracts 'lift dump', and as full power is selected, the airbrakes - if used - also retract automatically. Also the captain's right-hand throttle is provided with a manual lift dump actuation lever, allowing lift dump to be selected in the event, for example, of aquaplaning after landing.

The stopping power of the Mk 6000 is such that reverse thrust is not envisaged. This results in a considerable saving in engine installed weight (important in a relatively small rear engined aeroplane), and a longer engine life generally.

In the circuit

Since visual circuit work promises to feature extensively in the service life of the Mk 6000, I was fortunate in having the opportunity to assess the aircraft during a circuit detail at Ypenburg, which is used by Fokker as a satellite airfield. For this second flight the aircraft was again at aft CG (30.5% MAC) at 65,000 lb AUW.

On this occasion 6 degrees flap was used for take-off, with VR 113 kt and V2 120 kt. Again the aircraft rotated and flew off in a sprightly manner; in service, because the aircraft is geometry limited, it will be necessary to rotate at about 4 degrees per second to 15 degrees pitch attitude until unstick, and then to make a second rotation to up to 20 degrees. In practice it seems likely that an easier technique would be to rotate a little more slowly to avoid the need for a two-stage rotation, and this could perhaps be facilitated by using a more nose-down trim setting than the 2½ divisions nose-up currently called for. Should 15.7 degrees pitch attitude be achieved with the aircraft still on the ground, the tail bumper will touch, but Vmu tests have proved that the aircraft will still get airborne in this extreme attitude.

The selection of flaps for take-off will be dictated by the WAT limit prevailing, and may be up to 18 degrees. Under extreme conditions it may be necessary to use zero flap and 1.3 or even 1.4 Vs for V2. The prototype carried performance cards for easy reference detailing speeds for rotation, V2 climb, slat retraction, clean climb and immediate threshold speed for a wide range of aircraft weights, thus allowing rapid access to these parameters.

In the circuit at Ypenburg, the nose-up attitude downwind was again noticeable, and at a circuit speed of 150 kt and below, the ailerons were slightly heavy in feel. The view from the cockpit was at all times excellent: I had no occasion to utilise the 'eyebrow' windows during a series of visual circuits.

The exercise was made more interesting by a 70 degree crosswind from the right of 20 kt, which caused very little problem. With an engine throttled back, the standard circuit was flown using a final flap setting of 25 degrees and a VREF of 122 kt. The technique was again to fly at VREF + 5 kt, and to use airbrakes at 100 ft to reduce to VREF. The approach and landing was just as simple as the normal two engine case, and the amount of control over both attitude and flight path was surprising. There was certainly no problem in landing the F.28 on one engine.

For the next take-off, 18 degrees flap was selected, for a simulated engine failure. The aircraft was rotated at 104 kt and the left throttle was closed. The yaw was easily contained by rudder application, and rotation was continued to 16 degrees (optimum at this weight). I was rather reluctant to achieve what looked like a very steep attitude, but it did allow the speed to stabilise at 111 kt (V2). In the slightly gusty conditions it would have been only too easy to start trying to chase the slightly fluctuating airspeed, and I found it much simpler to fly a steady angle of attack, this technique resulting in a much steadier climbout. Care was necessary in levelling out at 400 ft for flap retraction, as the nose attitude remained rather high, and it would be easy to let the aircraft descend.

Flap retraction was made at 122 kt with no trim change and the aircraft gently accelerated to slat retraction speed of 143 kt. It was obvious that drag was increasing rapidly with slats extended at the higher speeds, but it was necessary to achieve at least the exact figure before retraction to avoid a momentary stick shake input. There was no noticeable trim change with slat retraction, and the aircraft then accelerated quickly into the clean single engine climb.

Although the technique might appear slightly complicated, it is in fact fairly straightforward, the most important area being the need to fly the V2 climb to close limits if one is to achieve the performance chart rate of climb. This can be facilitated by reference to angle of attack indication, which is easier to fly, and by the knowledge that the steep pitch attitude is a function of extended slat; which ought not to be compared with a similar pitch attitude on an unslatted aeroplane. The acceleration phase at 400 ft is not a rapid process, and the height needs to be monitored, as there could be a temptation to descend a little to gain speed.

A single engined overshoot was then made. From an approach using 25 degrees flap, full power was applied, gear retracted, and flaps raised to 18 degrees. Using a V2 of 107 kt a rate of climb of 1000 fpm was achieved.

The final landing at Schiphol coincided with a heavy rainstorm, which enabled the windscreen wipers to be used, and they were most effective.

Throttles were closed at 50 ft at 113 kt (1.3 Vs), and full airbrake selected. There was ample lift available in the flare, although at first one is reluctant to rotate the aircraft, owing to the fact that most other types would be on the wrong side of the drag curve. The Mk 6000, however, remains as controllable as a straight wing aeroplane. Touchdown was about 900 ft from the threshold after a comfortable float, and the nose was lowered immediately. I then applied full brake. Although there was slight snaking the aircraft remained fully controllable, stopping in about 900 ft, and this on a very wet runway! It was a tribute to the lift dump and wheel brake systems.


ABOVE: 'The Fellowship enjoys . . . high structural fatigue resistance to cope with the low altitudes associated with the short haul task'. Good cockpit view greatly facilitates VFR operation at these heights

In summary

The general overall impression was of a docile, easy aeroplane with simple handling characteristics. The slatted wing has effectively restored to the 79 seater the performance of the 65 seater, particularly in the high altitude high temperature cases, maximum operating temperature being ISA + 35C; however, it does demand a slightly different technique in the single engine take-off case.

Structurally, great emphasis has been placed on integrity and reliability throughout, and extensive fatigue and pressure tests have been completed. Flaps and exposed surfaces have been treated to prevent damage when operating from unprepared runways. Additionally, great care has been taken during manufacture to achieve a superior standard of durability and corrosion resistance under the most severe conditions of humidity. In the design of the F.28, special emphasis was placed on good accessibility and simplicity of maintenance. Maximum use has been made of 'non-handed' components, allowing interchangeability of left hand and right hand items.

Fokker-VFW run English speaking courses on the F.28, for which all manuals, drawings, and associated technical literature are produced in English. Alternatively, instruction can be given in German, Spanish and French, as well as Dutch. The Product Support Organisation extends throughout the world and has extensive experience with F.27 and earlier Marks of F.28. Operators can rely on a very efficient AOG service 24 hours per day. Service experience, reliability and maintenance costs are continuously monitored, this information being analysed and made available to all operators.

The Mk 6000 is a natural follow-up to the F.27 and the earlier versions of the F.28. Thanks to its built-in versatility, from unprepared strip operation to night operation in built-up areas with a noise reduction of some 5 EPNdB below FAR Part 36 requirements, potential operators can rest assured that they are getting something more than 'just a replacement aeroplane'.







 
By CAPTAIN NEIL WILLIAMS; photos by TOM HAMILL, Flight International


DURING the course of March I was offered a chance to fly the Lake Buccaneer four-seat amphibian, and I jumped at it, never having sampled a marine aircraft nor indeed any kind of small seagoing craft before. The moving spirit in this enterprise was Pete Young, Chief Pilot of Medburn Air Services Ltd, who distribute the Lake in the UK, Europe and Africa. On a calm, clear Sunday morning I was installed in the left hand seat, preparatory to a flight across to the Essex coast for a new experience.

Controls for the 200 hp Lycoming IO-360 pusher engine, in true aero 'nautical' sense, are in the roof. It was some time before I could persuade my right hand to reach up for the throttle, instead of forward. The fuel cock, well out of the way but still within reach, is on the rear cockpit wall. Unusually, the elevator trimmer comprises 'mini' elevators outboard of the conventional surfaces, much like the trim flaps on some of the early experimental deltas. The trimmer is electrically selected but hydraulically powered as a precaution against the ingress of water; although a cockpit indicator is provided, its position can be confirmed visually, such is the view from the cockpit. The single slotted flaps have two positions only - 'up', and 20 degrees. Under normal conditions flap is always used for take-off and landing.

Our runway take-off presented no problems, the only point being the need to keep straight in the early stages by judicious use of brake. The initial climb was made at 70 mph until the gear had retracted. This operation could be confirmed visually from the cockpit, directly in the case of the main gear, and via a mirror on the port float in the case of the nosewheel, it being rather important to ensure full retraction before water operation.

In flight the aeroplane handled like a much bigger machine. This feeling was caused by positive stability all round, with pleasant control gearing. In general, I found the controls 'over harmonised' in that the ailerons were very light and the rudder very heavy, especially power on.

Over the medium speed band, such as one would encounter when operating in the circuit with flaps down, trim changes are small, but towards the top of the speed range the trimmer really has to be used to take the load off the stick - probably owing to the drag build-up on the engine pylon. In normal flight it feels very much like a DC-3 and one is continually surprised to look out and realise that it really is only a small aeroplane.

The power off stall (clean) was very mild, with the horn sounding at 70 mph, and a slight pitching oscillation at 60 mph. The stall itself was marked by a slight left wing drop at 55 mph, with instantaneous recovery.

With gear up and flaps 20, still power off, the horn sounded at 53 mph, and the stall occurred with no further warning at 42 mph, with the right wing dropping gently. Recovery was again immediate.


ABOVE LEFT:  Access to the bow walkway for mooring purposes is straightforward when the engine is running thanks to the pusher propeller.   ABOVE RIGHT: Curved halves of the windshield also serve as doors, hinged at the central support strut. They open upwards and forwards

Into a new environment

The normal cruising speed of 130 mph was achieved at 2000 ft with 24 inches MP and 2400 rpm. This soon brought us to an estuary suitable for marine aircraft. Following several passes over the water to check for obstructions we were ready to begin.

Pete first demonstrated a circuit. In spite of the briefing I was not prepared for the noise as we touched down. It seemed hard to believe that the hull could take such a pounding from the small wavelets as we scuttled across them. In fact the aeroplane is incredibly strong, with seven water tight compartments.

Then I tried it for myself. With flap selected, the optimum approach speed was 70 mph, a power setting of 12 inches MP in fine pitch giving a nice shallow approach. The only problem here was to get low enough early enough, otherwise we would have used up half the estuary. We were able to determine the wind direction not only from the wind lanes, which stood out better when seen downwind, but also from the smoke from some chimneys. I found the best technique was to glide at 80 mph throttled back, which gave a good descent rate and then to flare, reducing to 70 mph and resetting 12 inches MP.

It seemed that the old adage 'a good approach means a good landing' also applied here. As demonstrated by Pete, I made a slow flare very similar to a 'wheeler' landing, with a very slow power reduction as the speed dropped. It was here that the trim change due to the high thrust line was of most consequence. I had to be careful not to let the aircraft 'balloon' as I throttled back, with the inevitable loss of speed and drop on to the water.

As speed gently fell, the aircraft skittered across the water to the accompaniment of various thumpings and bangs from below. It dawned on me that there was no tendency to swing, and as the speed fell I instinctively eased the stick back. This produced quite considerable drag and a great deal of spray as she squashed nose-high into the water and stopped in a remarkably short distance.

As I got more proficient, I found that after the initial touchdown I could ease the stick slightly forward to keep the aircraft planing on the step while the throttle was eased closed. This gave a very smooth and steady deceleration with no pitch-up and hardly any spray. It became obvious that the way to stop in a hurry was to throttle back and ease the stick back, whereupon the machine came to a spectacular stop in a cloud of spray. Having found out how to stop, I began to gain confidence. Pete showed me that the Lake could operate easily in waves up to 12 inches high. As a rule of thumb, if one feels unhappy in an open boat of the same size, then the swell is probably too high for amphibian operation.

It is important to realise how susceptible these craft are to wind and tide in the taxying mode. One has to select the predominant parameter when it comes to mooring. As it happened we were able to approach the buoy into both wind and tide, so with the port windscreen fully open I was able to steer the Lake so that the buoy scraped gently against the hull, whereupon I grabbed it and switched off the engine simultaneously. During later mooring attempts I found it advantageous to 'blip' the ignition on and off, thus slowing the Lake almost to a dead stop alongside the buoy.

There is a small locker in the bows for the mooring line. It is easy to climb out there with the engine running because the propeller is well out of harm's way. Furthermore, the wing can be used as a walk-way. To beach the machine, one should ideally pace the area first to make sure it is hard enough; where this isn't possible, however, one can - after an airborne reconnaissance - gently ground the keel on the bottom to check its suitability, then back off and lower the undercarriage before driving up the beach.


ABOVE: A useful load of 1135 lb makes the Buccaneer a good workhorse as well as pleasure craft

BELOW: Tricycle gear with wide track makes land handling simple. In aircraft's other element the water rudder (seen lowered, right aft) is essential to low speed manoeuvring


Getaway

Now it was time to try a take-off. There was plenty of open space ahead so I retracted the water rudder, whereupon the Lake weathercocked smartly into wind. It became apparent that this control was essential to low speed manoeuvring on the surface.

With the stick held hard back, the throttle was opened wide and the Lake surged forward, rising heavily out of the water. I steadily released the back pressure as she gathered speed, and she lifted lightly onto the step and planed happily across the estuary. In the early stages it was necessary to use coarse aileron in the same way as one does in a glider to keep the wings level, as the floats are clear of the water. With 55 mph on the ASI, a gentle backward pressure persuaded the aircraft, with some reluctance, to leave the water, and as the drag on the keel disappeared, the ensuing mild pitch-up helped to propel the aeroplane clear of the surface.

At a height of about 5 ft there was another, and more noticeable, mild pitch-up as the downwash over the tail unit ceased to impinge on the water, and the elevator authority increased. Although this last effect is also present on land, it is an indication of the smoothness of the whole operation that it is only detectable during a water take-off.

Yet there are problems for the unwary during water take-offs. Initially if the stick is not held fully back, the nose immediately digs in, and the windscreen is awash in no time. Later, once on the step, if the stick is pushed too far forward, the nose again tends to dig in, and this results in the notorious 'porpoising', which if left unchecked can cause structural problems or even an accident. Any attempt by inexperienced pilots to damp out a 'porpoise' usually results in getting out of phase which makes the whole situation worse. The only thing to do is to throttle back, ease the stick back, and stop, whereupon one can have another attempt. When planing on calm water, if the stick is held slightly too far forward, flow separation can be heard behind the step. The remedy is simple - release the forward pressure.

Familiarity with the normal take-off brought us naturally to the next stage of the proceedings, step-taxying. This is used when one has some distance to go on the surface, without taking all day about it. It is begun as a normal take-off with the water rudder up, and can be in any direction, even down wind, although one may have to start the run in this latter case with the water rudder lowered, and retract it as speed is gathered. Once on the step the throttle is eased back to hold a speed of about 30 mph, relative to the water, so one has either to keep in mind the wind direction and speed and carry out a running 'ground speed' computation, or better, get used to the appearance of 30 mph with one's seat only an inch or so above sea level.

This phase of the operation feels very much like water ski-ing and is incredibly good fun. The enjoyment increases when one finds that one can bank the aeroplane and use rudder to give a fair imitation of a hydroplane as one roars around in crazy, but fully controlled circles. There is an element of outward skid involved, but the turning radius is remarkably small, and although one may lean heavily on the inboard float, there seems to be no tendency for it to dig in. One can jink left and right with wonderful agility for such a sedate looking machine, and on rolling out of a tight 360 degree turn, I had merely to open the throttle and we were airborne. There behind us, as we banked, was our wake on the surface of the sea - a perfect circle, slowly expanding.

Constant attitude approach

By now the sun was producing an awkward glare on the water, effectively prohibiting good depth perception. This was a good opportunity to try the glassy water landing technique, which demands a slow shallow descent of 100 fpm, on instruments at 60 mph, until the aircraft flies itself onto the water.

As on the normal approach, but more pronounced, was the difficulty of getting low enough early enough, especially if distance was at a premium. I found it best to approach over any easily visible obstacle as low as possible on finals, and then, with only water ahead, to transfer to instruments and hold the 'glidepath' steadily. This is a most eerie sensation, head in the cockpit and only a few feet up, waiting for it to touch. Drift, if present, is ignored, as the Lake straightens itself on the rollout. All one needs is confidence; the technique is extremely simple and touchdown very gentle, after which one throttles back easily and planes into a normal deceleration.

When operating in narrow channels one would be very fortunate to always have a head wind. So, having selected a channel 90 degrees out of wind, with the only advantage that it was also out of sun, we next had a look at some crosswind circuits. As was the case when beginning to step-taxi downwind, the water rudder was lowered initially but was retracted as soon as the aerodynamic controls became effective. The stick was held hard back and full aileron into wind was applied as the throttle was opened.

As the machine started to move there was an absolute deluge of water over the bows, obliterating all forward visibility. I found that by looking out sideways, down sun, I could get an idea of pitch and roll attitude, in much the same way as one does from a big radial-engined tail dragger. Once the Lake started to plane, life became very much easier as the water drained away from the windscreen and forward visibility returned. From this point the take-off was normal except that the controls were slightly crossed (aileron still held into wind) until the aircraft unstuck. This also removed any tendency to drift.

On one occasion the wind freshened and caused not only the lee float to go under but the wing tip too! The only solution was to close the throttle and let the machine right itself, as power was only driving the wing tip deeper into the water. In this case we compromised by angling slightly into wind until we were on the step, after which we could step-taxi and turn to any desired heading. One had to be careful in these enclosed spaces and I found it difficult to assess just how far away was the bank, and how fast I was approaching it.

The crosswind landing was simplicity itself; in fact it was just a normal landing, ignoring the crosswind completely, and letting the aircraft straighten itself after touchdown. One merely had to drop the water rudder just before the aircraft stopped to prevent a sudden weathercock into wind.

I asked Pete to show me a forced landing without power, following which he gave me a practice engine failure after take-off. The nose has to be pushed well down to maintain speed, as the engine failure causes a pitch-up which does not help the already high drag condition. From 60 mph the aircraft is flared, in much the same way as one flares a tail-wheel lightplane, then dropped onto the water with the nose high. Contact is made with a great swoosh of water and spray and with the stick held hard back the aircraft stops in a very short distance. It all looks slightly terrifying at first but in fact is quite easy.

Since one is not operating in a regulated environment like an airfield, one has to keep one's eyes very much open. One has to be continuously on the lookout for debris, other craft, and any changes in the wind or weather, to say nothing of the tide. It would be only too easy to finish up in very shallow water, though here one can look out for groups of wading birds as a warning. Small boat operators and yachtsmen seem much more friendly towards water borne aircraft than do their land counterparts; this too can bring its problems in that they may not appreciate the room you need to manoeuvre, especially at slow speed and when mooring. The faster you go, in general, the better control you have from an aerodynamic point of view, but when taxying the answer is minimum speed, with the engine idling. There is an area of no-man's-land in between where trouble lies! Constantly anticipating wind and tide is essential if one is really to enjoy an amphibian.

Landing the Lake on an airfield presents no problems. One can approach at 65 mph, the wide track and good aileron control allow a strong crosswind to be accepted, and there is no real danger of touching a float, even when the wing-down technique is used. All in all it feels a friendly sort of aeroplane.


ABOVE: Take-off under ideal conditions - plenty of sea room and a light lop on the surface. The Lake cultivates pilotage skills never normally used and is extremely rewarding to operate

Versatility

With a useful load of 1135 lb, the Lake can prove very handy as a communications and light freight transport. It can operate in dirty weather conditions, it is protected against corrosion and is simple and robust. The capability of beaching or tiedown at an airstrip has obvious advantages over a pure seaplane, which must either be dragged up a slipway or left to ride out any rough weather.

So the Lake can justify its existence commercially, not only as a hard working transport, but also for touring, fishing, and as a fun machine for renting, and this is where it really is in a class of its own. It combines almost everything that boating and flying can offer, and lends a completely new dimension to the experience of the land based pilot.

I spent nearly four hours in the Lake on my first introduction. It felt like a quarter of that time, so much did I enjoy myself. And I didn't get my feet wet!










I SETTLED myself into the cockpit, savouring that smell of petrol, leather, dope. An indefinable awareness that this, indeed, was a real aeroplane. There was no parachute; looking at the proud faces round me I could not bring myself to ask for one. I primed the engine and locked the Ki-gass pump.

'Contact!'

With starter and booster coil pressed, the propeller kicked once and exploded into a blur as the Merlin caught. A puff of blue smoke was snatched away by the slipstream. I could not linger long on the ground - already the radiator temperature was rising fast. As I increased power, four men flung themselves on the tail. The roar of the Merlin rose to a solid wall of noise, beating against the hangars. I throttled back and waved away the chocks.

Slowly, delicately, the Spitfire picked her way round the narrow perimeter track, the Merlin grumbling contentedly, the brakes hissing spasmodically. I taxied onto the runway and slid the hood shut.

Now I was in a different world. I slowly opened the throttle, and as she started to move, gave her full power. Instantly the tail lifted as she accelerated, poised on tiptoe like a ballet dancer. With a light rudder pressure she leapt down the runway, black smoke arcing outwards past the cockpit. I pressed back on the stick, and immediately responsive, she was airborne. The undercarriage retracted with a solid thump.

I was surprised at her stability. Unlike other Spitfires I did not need a firm grip on the quivering stick . . . she was light on the controls, yet perfectly stable. She wanted speed, and I had to restrain her, to lift the nose skywards: then, as if she had remembered after thirty-four summers, she climbed effortlessly at 3000 feet a minute.

Almost, it seemed, she revelled at being once again in the air. I could scarcely believe the combination of stability and manoeuvrability. I brought myself to the task in hand, my test card recording low damping in roll, high aileron power, low control inertia, precise control, instant response. Yet all the while I sensed the unbounded joy of flight that I was sharing with this wonderful aeroplane.

From low speed to high speed we flew together. She was reluctant to stall, and quick to recover - the test card showed 59 mph. In the dive she was in her element, the controls iron hard under my hand, even the roar of the Merlin muted in that headlong rush. Faster and faster, but she was an old and precious aeroplane: I eased her out at 350 mph. As she pointed her long nose to the sky again the temptation was too much, and with the merest hint of pressure on the stick she rolled effortlessly in the climb.

At last, reluctantly, I took her home. We levelled low over the hurtling runway, arcing up and round in a fighter break while the Merlin crackled its approval. A curving approach, radiator flap open wide to cool that great engine, undercarriage light green, a hiss of air as the flaps came down, and as the broad expanse of asphalt disappeared under the nose I throttled back fully and eased the stick back, flying now with fingertips. Gentle as a thistledown she touched, running straight and true, the wheels taking the weight as she slowed.

She turned into dispersal, and as I pulled the cutout ring the Merlin gave a final growl, then stopped. I sat there, savouring every detail, the silence heavy and oppressive. People crowded round, their eager faces all posing the same question - How did she fly? And in their expressions one could read an awareness that their relationship with this machine could never be the same again. Like the transition from caterpillar into butterfly, they had worked for two long years on a restoration project - but tonight they would be servicing an aeroplane.





   


The wild goose came out of the north, the wind sighing through his pinions, and circled the pool, assessing its length. It was a little on the small side, but there was no other, and darkness was approaching.

The boy, breathless with excitement, froze into immobility, hoping that the majestic bird would not fly on. Wings far outstretched, the goose glided the length of the pool, his head turning, his bright eyes missing nothing. He flew a wide circle, coming in low, tail spread, wings held high and arched in a hard curve, leading edge feathers lifting intermittently, showing the narrow margin above loss of control. Lower he came, with head held forward, all attention, for instinct told him that he was too big and heavy to be careless at such low speed. His feet, trailing, gave him not only retardation but directional control, and as he started to flare, they came suddenly forward to act as shock absorbers and planing surfaces.

With hereditary knowledge the bird flew into the water in a cloud of spray, aware that he must not waste valuable distance in a smooth and pretty landing. Twisting his wings upwards for maximum braking he surged to a stop in a shower of flying droplets. He turned, as if to assess his landing distance, and, satisfied, with a flick of his tail swam off into the gloom.

It was the sight of a young lifetime, and I still remember the attention with which I watched that superb demonstration of control. No human pilot could emulate the fine limits of skill and precision I saw that evening: for if they could, there would rarely be a landing accident. What the goose knows by instinct, we must learn by application and experience, though still we remain inefficient by comparison.

Touchdown optima

Yet we have learned something of the art, for if the goose is prepared to sacrifice a smooth landing in favour of accuracy, consider the case of a naval aircraft landing on a carrier. In stabilised flight with some distance to go, with wheels, flaps, hook, airbrakes and boundary layer control deployed and working, with audio signals from the ADD indicating by its steady tone that the angle of attack is correct for the configuration and that datum speed has therefore been achieved for the actual weight, the pilot follows the mirror signals to keep him on glidepath. Here there will be no flare - the aircraft is aimed at the deck. The touchdown when it comes will be hard, three to four g, and the hook engages in the arrester wire.

This is probably the most consistently accurate method of touchdown yet devised. Unfortunately, though, it cannot be applied exactly to civil passenger operation. The aircraft is close to the wrong side of the drag curve in this condition, and with the inertia of present day jetliners there would be no margin for error; indeed it would be a classic example of the old instructors' quip 'To go up, pull the stick back: to come down, pull the stick back further'.

With many naval aeroplanes, by increasing drag as much as possible (for example by airbrake extension on the approach) the minimum drag speed is reduced, although the total drag is higher, involving a higher power setting, more air for boundary layer control, and better and faster engine acceleration. This is all very well until one considers the possibility of an engine failure on the approach, which in the case of one naval twin engined aeroplane requires a configuration change and a speed increase of 19 kt to achieve the new single engined datum speed: hardly suitable for a civil airliner. Also, the slower the approach is flown, the more thrust, and therefore the greater the noise, and in these noise conscious days this is not acceptable. One is caught between the need to avoid speed instability, which can result from an attempt to achieve the glidepath from above, and the fact that a small increase in threshold speed can enormously increase the landing run. As a rough rule of thumb, 5 kt extra at the threshold means 10% extra landing run.

Touchdown technique is important. A great deal of distance can be wasted in floating just above the runway instead of getting the aircraft on the ground and utilising lift dump, reverse thrust, and wheel brakes. On a wet runway, tyres can be scalded badly by a silky smooth touchdown, and how many pilots know that the square root of the tyre pressure (in psi) multiplied by a factor of 8.6 gives the aquaplaning speed in knots? It can sometimes be advantageous to pull back on the control column while braking in order to increase the weight on the mainwheels, but one has to remember to release the back pressure before releasing brakes on some types if one still wishes to retain nosewheel steering.


ABOVE: Navajo with CAVU, Adelaide's West Beach Airport


ABOVE: Concorde to Fairford, UK


ABOVE: Queen Air to Wichita, USA

Threshold accuracy

It is often said that a good approach means a good landing, and while this may not always be true, it is fairly certain that a poor approach will result in an interesting landing.

When a jet aeroplane is certificated, the landing schedule requires that it shall be flown down to 50 ft above the ground at a glideslope determined by the manufacturer, after which all throttles are closed, and the aircraft is flared, landed and stopped as quickly as possible. The minimum speed at the 50 ft point is 1.3Vs, and the resulting distance is factored to give the required field length. The manufacturer has to demonstrate a spread of speeds around this 'throttle closure' point, usually minus 5 kt and plus 15 kt, to allow for errors in pilotage and extra speed used, for example, in turbulence. It follows that if the speed at threshold is above the 15 kt margin, an overshoot should be initiated, otherwise the usual result is a long, fast touchdown, often followed by lamentation and recriminations.

Normally, the aids to approach should be used, even when the aircraft is in good visual contact with the runway. This is because after a long time at high altitude, a pilot needs time at low level in order to re-adjust his depth perception. In the old days, when one could fly a visual circuit, this was no problem. But when one joins for a straight-in approach, VASIS, ILS or GCA should be used to ensure adherence to the glidepath. The conventional glidepath is 3 degrees, and most aircraft are happy to operate on this approach slope, although in some cases the very clean, high performance type may be more suited to a different slope, e.g. 2½ degrees.

High altitude airports and/or high temperatures also have a marked effect on glideslope. For example, when landing at Nairobi, which is more than 5000 ft above sea level, the TAS is appreciably higher on the approach, with the result that the aircraft wants to approach on a shallower glidepath, if it is to retain sufficient engine rpm to ensure rapid engine response. In this case, too, it is more important than ever to achieve the correct threshold speed, because a small increase in IAS means a lot of TAS and groundspeed for the brakes to get rid of.


ABOVE: Crew training with Baron
ABOVE: Navajo to a grass strip, Eire

One often reads of unresolved arguments between pundits as to whether one uses power to control the glidepath and elevator to control airspeed, or the other way round. Indeed, it is often considered that the former is a piston engined technique, and that jet operation requires the reverse. It is perhaps worthwhile recalling that initially this argument evolved because of the slow acceleration of the jet engine, at least in the lower rpm regime. Early jet aircraft like the Canberra were very clean in terms of drag in the approach configuration, and were reluctant to alter speed in response to elevator, as compared with the alteration that could be made to the glidepath. Of course this was only true during the initial control movement, because if one reached the wrong side of the drag curve the behaviour was more in line with a swept or delta type. Indeed, there is a certain delta winged research aeroplane which is still able to fly at 140 kt, except that it is going downhill at this speed, and even the use of full reheat will not accelerate it. The only recovery is to lower the nose to increase speed.

It seems that the answer to this problem depends on where the aircraft happens to be on the drag curve, and how much excess thrust it has. In practice, most pilots blend their actions together, to retain the glidepath, and while one might generally accept that one adjusts the flight path with elevator when using a flight director and controls the airspeed with power, this applies when the IAS is in the order of 1.4V s, and the aircraft is therefore on the front side of the drag curve. If the speed were to go around the corner on the approach (heaven forbid) then full power could be necessary to regain the flight path.

There is a good case for retro-fitting civil aeroplanes with a form of audio ADD which could be brought into operation when the first stage of flap is lowered. This would at least give a continuous presentation of angle of attack, which is, after all, the one parameter we are most concerned with in terms of a landing approach. It would make the calculation of threshold speeds, and the possibility of mistakes, a thing of the past, although runway distances would still be required. It would also give an early indication of a trend, such as a rapid pitch manoeuvre to regain the glidepath, and it could even be tied in to the stall warning systems, given enough redundancy.



ABOVE: King Air with companion


ABOVE: Navy Phantom with angled deck

Analysing the flare

Of all the visual approaches, perhaps the easiest to fly is the steady speed, steady angle of attack, no-flare type used in carrier operations. Here one is concerned with establishing the landing configuration and speed early in the approach and holding everything steady until contact is made.

As we depart from this basic method, the next step is to reduce speed steadily during a straight approach, which requires a slow increase in angle of attack to hold the runway perspective constant. As the aeroplane rotates slowly, the pilot is still flying a straight line approach, which will continue until 50 ft or so when the pilot selects a new approach line, looking further up the runway. This procedure is repeated in increasingly small and more rapid increments until the approach line is asymptotic with the runway, and the speed has reduced to that required for landing. We call this manoeuvre the flare. Add to this combination the problems of interception during a turning approach with its built-in problems of changing drag, wind shear, crosswind, and inertia, and we are faced with a problem which is suitable for solving by computer.

The human brain is an excellent computer for this sort of operation, equipped as it is with a good learning curve based on experience and powerful memory banks. Yet it is not only the conscious mind that plays a part here; it is the information derived from the sub-conscious which we have carefully placed there, by constant practice and training. This brain of which we are so proud is the largest and most active of any living animal, many times bigger and more logical than that of the wild goose. So why should we feel admiration when we see a goose slanting in to land on a sheet of glassy water, the setting sun glinting on his outstretched wings? Perhaps because here the science and art of flight are blended in perfection.


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