Percival. Самолеты семейства Gull
Эдгар У. Персиваль построил прототип своего трехместного туристического моноплана Type D.1 Gull в Мэйдстоуне в 1932 году. В том же году в гонке на Королевский кубок самолет показал среднюю скорость 229,7 км/ч. Аэродинамически чистый дизайн привлек внимание,
и новая компания "Percival Aircraft Со." выдала субподряд на постройку 24 Type D.2 Gull компании "George Parnall & Со.". На машины ставились двигатели Cirrus Hermes IV и de Havilland Gipsy Major мощностью 130 л. с., а также Napier Javelin III мощностью 160 л. с. Самолеты известны под общим обозначением Gull Four.
В 1934 году компания "Percival Aircraft" открыла в Грейвсенде свою собственную сборочную мастерскую и начала выпускать улучшенную модель Type D.3 Gull Six с двигателем de Havilland Gipsy Six мощностью 200 л.с. Самолет имел более изящное одноподкосное неубирающееся шасси с обтекателями и улучшенную кабину, но сохранил складывающиеся крылья модели Gull Four. В 1936 году компания переехала в Лутон, где был построен 48-й самолет D.3, поставленный компании "Shell" в Южную Африку в октябре 1937 года.
Flight, July 1932
The Percival "Gull”
130 h.p. "Hermes IV" Engine
THERE are those who maintain that practically all the progress made during the last ten years or so has been due to improvements in aero engines, and that of real advance in the aerodynamic design of aircraft there has been almost none. It is certainly true that the aero engine has been improved out of all recognition. A gradual decrease in specific weight has been accompanied by a pronounced increase in reliability. This was amply proved during the recent race for the King's Cup, when engine trouble was almost entirely absent in spite of the running of the engines at full throttle for a distance of 1,230 miles. That progress has been made in the aerodynamic design of aircraft becomes evident every so often, when a new type is produced which shows a very much better performance than previously existing machines of comparable type. There was an instance of this with the de Havilland "Fox Moth" flown by Hope in the King's Cup, which he won easily. That machine was very much faster than anyone had expected, and its aerodynamic design must be very clean indeed.
Another type which flew in the King's Cup Race, and one of the "dark horses," being quite a new machine, was the Percival "Gull," fitted with the new "Hermes IV" inverted engine. Although the "Gull" did not succeed in getting a place in the race, it was quite evident, from the fact that it averaged 142.75 m.p.h. around the whole course, that here was a new machine of more than average efficiency. An examination of the data relating to the machine shows that this impression is indeed well founded.
I t is our custom, when describing new aircraft, to endeavour to get an idea of their aerodynamic and structural efficiency by examining certain "figures of merit" which represent, in a general way, these two qualities. For the former the Everling "High-speed Figure" is useful, and a very fair indication of structural efficiency is provided by the ratio of gross to tare weight.
When using British units, but keeping the actual "Highspeed Figure" value the same as it would be in the units employed by Dr. Everling in his original article, the formula for the "High-speed Figure" is N/2Kd = V^3/147,000*S/HP., where V is the speed in m.p.h., S is the wing area in square feet, HP. the maximum horse-power of the engine, Kd the "absolute" drag coefficient, and N the propeller efficiency.
In the case of the Percival "Gull," the wing area is 169 sq. ft., the maximum engine power 130 b.h.p., and the maximum speed claimed is 145 m.p.h. These figures give to the Everling "High-speed Figure" a value of 27, which is the highest we have ever recorded. It is even slightly higher than that for the Schneider machines, and indicates that, assuming the same propeller efficiency, the "Gull" has a lower minimum drag coefficient! When it is remembered that the "Gull" is a three-seater, this is somewhat remarkable.
If the aerodynamic efficiency of the "Gull" is high, the structural efficiency also appears to be well above the average (again probably due to all-wood construction). The gross weight is 2,050 lb., and the tare weight 1,170 lb. This gives a ratio of gross to tare weight of 1.75, which although not the highest we have recorded, is well above the average. (The highest ratio of gross to tare weight of any recent British machine which we have described is that of the de Havilland "Fox Moth," which shows a ratio of 1.9.)
Yet another indication of the efficiency or refinement of an aeroplane is provided by its speed range. The maximum speed of the "Gull" is 145 m.p.h. and the minimum speed approximately 42 m.p.h. This gives a speed range of nearly 3 1/2 to 1, which is a very unusual figure.
Thus, which ever way one looks at it, the Percival "Gull" appears to be an aeroplane with qualities well above the average. This is further borne out by other features of the machine. For example, the cruising speed is 125 m.p.h. with pilot and two passengers, luggage, and fuel for 700 miles on board. Cruising at more than two miles a minute, with three people "sharing" an engine of a maximum of 130 b.h.p. and a normal power of 120 b.h.p., is economical travelling indeed, and it is travelling in great comfort, as the staggered seats for the two passengers are so placed and spaced that each has sufficient, if not an abundance, of leg room. The pilot's seat, being in front, has very ample space around it, and the view over the inverted engine is excellent.
Structurally the Percival "Gull" is a very straightforward piece of work. The fuselage is a "box" composed of light spruce stringers and struts, the whole covered with a three-ply skin. The cantilever wing incorporates the Hendy Patent wing construction, which consists of two main spars braced in the planes of their upper and lower flanges by a series of lattice ties. This construction gives a wing which is particularly strong in torsion.
The undercarriage is of the divided type, and each wheel is carried on a short axle which rests at each end in a crosshead running in guides. Springing is by two springs on each side of the wheel, an oil ashpot between the two springs on each side serving to damp out bouncing.
The "Hermes IV" engine is very neatly installed, and the careful cowling to which the inverted engine lends itself has doubtless contributed materially to the clean lines and high aerodynamic efficiency of the machine. In the King's Cup Race the "Hermes IV" ran without a hitch, and remarkably smoothly. If the engine stood without trouble a distance of 1,230 miles at full throttle, there should be no likelihood of it being other than absolutely reliable when used in the ordinary way at cruising power. (The engine was described and illustrated in our issue of July 8, 1932.)
The petrol tanks are placed in the inner ends of the wings, each having a capacity of 20 gallons. At cruising speed this suffices for a range of about 700 miles. The oil tank is built into the leading edge of the port wing root, and has a capacity of 3 gallons. The tank acts at the same time as an oil cooler.
It is of interest to point out that if the two seats for passengers are removed, the machine can be used as a mail carrier, when it will carry approximately 400 lb. of mails at a cruising speed of 125 m.p.h. over a range of 700 miles. This should be a very useful mail plane on many routes.
Finally, it can be stated that Mr. E. W. Percival has arranged for the "Gull" to be put into production at once, and the first production machine should be ready in about 10 weeks. The price of the "Gull" will be ?1,250, completely equipped. Inquiries should be addressed to Mr. Percival at 81, St. George's Square, London, S.W.I.
Flight, November 1932
E. W. Percival
20, Grosvenor Place, London, S.W.I
A WELL-KNOWN firm is now building for Mr. E. W. Percival the very fast little "Gull" three-seater cabin monoplane, the first specimen of which put up such a splendid performance in the race for the King's Cup last summer, when the machine averaged 142.75 m.p.h. (230 km./h.) over the whole course.
The Percival "Gull" is a low-wing monoplane, mainly of wood construction, with a tapered cantilever wing faired into the fuselage, and a very simple type of undercarriage attached direct to the wing. That the design is very clean aerodynamically is proved by the high performance, which is unusually good in view of the fact that the machine is a three-seater and the engine a Hermes IV of 130 b.h.p. only.
The main data of the Percival ''Gull" are :-
Length o.a. 24 ft. 8 in. (7,52 m.)
Wing span 36 ft. 0 in. (10,8 m.)
Wing area 169 sq. ft. (15,7 m!.)
Tare weight 1,170 lb. (532 kg.)
Gross weight 2,050 lb. (932 kg.)
Maximum speed 145 m.p.h. (233 km./h.)
Cruising speed 125 m.p.h. (201 km./h.)
Range 700 miles (1 125 km.)
Flight, April 1934
AN IMPROVED "GULL"
Increased comfort with no sacrifice of performance
SINCE 1932, when the Percival "Gull" appeared, machines of this type have put up some quite astounding performances for aircraft of such low power. Four "Gulls," fitted with Napier "Javelin" engines, completed the King's Cup course in 1933 at average speeds of about 150 m.p.h., and another carried Sir Charles Kingsford Smith to Australia in the record time of seven days. Others have been doing hard, if less spectacular, work in the service of private owners and air operating companies. The machine has proved itself particularly useful for fast air taxi work and for the transport of Press photographers and films.
When last week, the 1934 model "Gull" was announced and was demonstrated by Capt. Percival at Heston, we found that the few respects in which the machine differs from its forerunner are mostly in the nature of improvements made for the comfort of the occupants and are not mere "modifications" in the accepted aeronautical sense of the word.
An exterior view of the new type shows few differences. Entrance to the cabin of the older "Gull" was made through a hinged roof. This arrangement, although necessitating less acrobatic skill than is needed to enter some aircraft, was by no means ideal, and the two wide doors which have now been fitted to the cabin make a great improvement. The cabin itself has been slightly enlarged and has been thoroughly sound-proofed by Rumbold & Co., Ltd. This must be considered a real improvement over the old "Gull," especially the "Javelin"-engined version, which is a rather noisy aircraft. To the rear of the cabin windows is the door of the luggage locker. Access to the locker may also be gained from the cabin itself. Both the interior and exterior finish are above the average of most aircraft.
A new wing-folding arrangement which is simple, safe and easily operated is now fitted.
Much comment has been aroused regarding the undercarriage of the "Gull," which is of Percival design and construction. The original design was so clean that the complications of a retractable version were not considered worth while. It was, however, generally considered a little harsh, and has now been redesigned. Longer travel is provided for in the shock absorbers. The tail skid fitted to the early "Gulls" has been superseded by a swivelling tail wheel.
The "Gull" which was demonstrated by Capt. Percival at Heston last Friday was fitted with a Napier "Javelin" engine, but "Gipsy Major" and "Hermes IV" engined versions are available, and the de Havilland "Gipsy Six" engine of about 200 h.p. is soon to be fitted as an alternative power plant. At present Capt. Percival is waiting to make the first "Gipsy Six" installation in a "Gull," and this version should be flying in about four or five weeks' time. Capt. Percival expects that the top speed, with the "Gipsy Six," will be about 170 m.p.h. and the cruising speed 160 m.p.h. It should be remembered in this connection that the normal power of the "Gipsy Six" is more than the maximum power of the "Javelin," with which engine the top speed of a "Gull" is about 160 m.p.h. With a "Gipsy Major" or "Hermes IV" engine the maximum speed is about 145 m.p.h. and the cruising speed 125 m.p.h. The machine may be supplied with tankage for a range of either 550 miles or 750 miles.
For a thick-winged cantilever monoplane the "Gull" must be considered a very manoeuvrable aeroplane. We have not yet done any aerobatics in it, but in the hands of Capt. Percival it appears to loop beautifully.
Capt. Percival expects that the price of the "Gipsy Six" model will be between ?1,575 and ?1,580.
Flight, March 1935
THE 1935 MODEL "GULL"
Comfortable Touring for Three at 150 m.p.h.: a Speed Range of 3.6 to 1
AT Gravesend aerodrome last Thursday, Captain E. W. Percival introduced his 1935 model "Gull." Generally speaking, the new machine retains the main features of last year's model, but a few modifications have been made and certain features added which together render the "Gull" thoroughly up to date in the private-owner's class. Split trailing-edge flaps reduce the landing speed and steepen the approach, while differentially operated wheel brakes reduce the landing run, so that the machine can be brought into a reasonably small field. At the same time, the aerodynamic design is such that a high maximum speed and a cruising speed of 150 m.p.h. are attained when the power plant is a 200 h.p. D.H. "Gipsy Six" six-cylinder-in-line air-cooled engine. With engines of lower power the performance is, of course, correspondingly reduced, but is still quite good. For example, with the Napier "Javelin" the cruising speed is 140 m.p.h., and with the "Gipsy Major" or "Hermes IV" it is 130 m.p.h. These figures apply when carrying pilot and two passengers.
The cabin is airy and well lighted by large windows. Fresh air is drawn in from a point on the wing sufficiently far outboard to preclude engine fumes entering the cabin, and for really hot weather some of the windows can be opened, although this admits a certain amount of engine noise. With the windows closed, the noise level is by no means high. The seats are arranged one behind the other and slightly staggered. In spite of the relatively small width of the cabin there is sufficient room, and the controls have been so arranged as to leave the floor space completely free. Behind the cabin there is a luggage compartment, closed by a separate door.
Cabin doors of large area are fitted, and an arrangement of spring-loaded cables ensures that the doors remain open while passengers are getting in and out. The doors impress one as being particularly solid and rigid, in distinct contrast on the flimsy contraptions found on some machines. The stout member which runs lengthwise over the central roof inspires confidence, not only in its ability to transmit the loads in spite of the large doors, but also in its effectiveness as a skid in the unlikely event of the machine turning over on the ground.
The split trailing-edge flap gear is very ingenious, and Capt. Percival has managed to evolve a system which will appeal to the pilot by reason of its mode of operation. The flaps, which do not extend across the bottom of the fuselage, are worked by a plain lever placed on the left-hand side of the pilot. When the flaps are in the "up" position, the lever lies flat on the floor. As it is raised the flaps come down until, when the flaps are fully down, the lever is self-locked in the uppermost position. The arrangement is logical, being exactly the equivalent of the hand-brake lever on a motor car, and the pilot has the "feel" of the flaps throughout the whole range. The load on the lever, by the way, does not exceed about eight pounds, a weight which is well within the capacity of even a woman pilot, and which has been attained by an ingenious system of levers, toggles and springs. Ball bearings ensure easy and smooth working.
A "trousered" undercarriage is fitted, similar to that of the 1934 "Gull," but the fairings have been redesigned and are now of pleasing appearance and very low drag. A castering tail wheel in conjunction with Dunlop main wheels fitted with Bendix brakes makes manoeuvring on the ground very easy. The wheel brakes are applied by a small lever placed next to the air brake lever. Differential braking is effected via the rudder pedals.
A controllable-pitch airscrew is not fitted as standard, but can be supplied at extra cost if desired. Doubtless it would shorten the take-off time somewhat.
As in the earlier model, the wings are designed to fold, a hinged flap in the trailing edge on each side making this possible. The split flaps have to be divided to make folding possible, but an ingenious arrangement of the controls avoids any complications as far as the actual folding operation is concerned.
The maximum permissible weight of the "Gull" is 2,300 lb., the tare weight is 1,450 lb., 1,400 lb., and 1,240 lb. with the "Gipsy Six," Napier "Javelin" and "Gipsy Major" or "Hermes IV" respectively. The normal tankage is 31.5 gallons, which gives a range of 500 miles with the first two engines, and 575 miles with the last two. An optional alternative tankage of 40 gallons can be provided, also in the wings, which increases the ranges to 640 miles, 620 miles and 730 miles respectively. With the four alternative power plants the maximum speeds are 172 m.p.h., 160 m.p.h., and 148 m.p.h. respectively, the corresponding cruising speeds being 152 m.p.h., 140 m.p.h. and 130 m.p.h.
The efficiency of the aerodynamic design may be judged from the fact that the Everling "High-speed Figure" reaches a value as high as 29.25 for the "Gipsy Six" version. Structurally, also, the "Gull" is commendably efficient, the ratio of gross to tare weight being 1.586 for the machine with "Gipsy Six" engine, and 1.855 for the "Gipsy Major" and "Hermes IV" versions.
The finish of the new "Gull" is excellent. Capt. Percival informs us that one of the secrets is the application of a layer of nainsook over the plywood covering of the fuselage. This not only prevents splitting and raising of the grain, but forms an excellent foundation for the Titanine finish. The standard finish is turquoise blue for the fuselage and silver finish for the wing.
With "Gipsy Six," Napier "Javelin" and "Gipsy Major” engines the prices are ?1,575, ?1,475, and ?1,275 respectively.
These prices include, as standard equipment, compass, airspeed indicator, altimeter, revolution counter, oil-pressure gauge, petrol and oil contents gauges, oil thermometer, watch, wheel brakes, and split trailing-edge flaps. A controllable pitch airscrew can be supplied as an extra.