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Aviation History
1953
1953 - 0427.PDF
3 April 1953 425 THOUGHTS ON THE GNAT An Introduction to the New Light Fighter The small aircraft in this drawing is purely hypothetical. The illustration has been prepared to show the general proportions of the Folland Gnat in comparison with a Sabre. That the Gnat will have at least as much power as the early Sabres gives some idea of the possible performance. THE Gnat is a light fighter project under development by Folland Aircraft, Ltd., of Hamble, Hants. Before going on to discuss this most interesting aircraft—in the greatest detail permitted by security considerations—it will be as well if the term "light fighter" is clarified, if not defined. This can best be done by stating what a light fighter is not. It is not a normal fighter stripped down to the bare airframe in order to save weight. Again, it is not a target-defence intercepter capable of doing no more than climbing rapidly to altitude, making a single firing pass, and descending again in a glide with fuel exhausted—neither is it a conventional fighter stressed to a lower load factor in order to permit lighter construction. The true light fighter is a design in its own right, built to its own set of requirements, and making, if anything, less compromises than usual. Readers wishing to pursue the genesis of the light fighter in greater detail are referred to our issue of November 7th last. Additional information which has become available since that date reveals that light fighter projects are under development in a number of western countries. In Italy, for example, Dpi. Eng. Casiraghi is collaborating with the Piaggio Company on such work, and in France the newly-formed S.F.E.C.M.A.S. group is reported to be developing a small fighter with a delta wing. Of greater importance than these projects is the fact that the United States Air Force is reported to be very interested in the possibilities offered by light fighters, and development and prototype contracts are likely to be issued within a few weeks. Reports have it that North American Aviation is the company most likely to succeed in filling such a specification, and it is known that stripped-down versions of the Sabre have been under consideration by North American for a considerable time. It is appropriate to recall that a similar version of the Mustang was developed by the same company in 1944. Whether a drastically simplified Sabre would be an efficient aircraft is doubtful. The Gnat, on the other hand, is entirely a private venture, and largely the work of one man. It may be remembered that Mr. W. E. W. Petter, after becoming famed as chief designer of Westland Aircraft, went to the English Electric Company where he produced the Canberra, undoubtedly his magnum opus to date. In October, 1950, he went to Follands where he is now managing director. After taking over at Hamble, Mr. Petter made a thorough study of the economics of modern fighter production, and came to the conclusion that all present fighter aircraft represented far too great an expenditure in manhours and material. Further, some disinterested persons have expressed the view that, were a shooting war to break out, this country could not produce aircraft such as the Swift, Hunter, and Javelin in anything like the numbers essential for survival. Admittedly, the Air Staff are favouring a "quality not quantity" doctrine at present, and the world-beating quality of the three types just mentioned has never been questioned, but whether this country is economically in a position to mass-produce such aircraft is questionable, to say the least. Air Chief Marshal Sir Basil Embry, at present C.-in-C, Fighter Command, has also been examining the fighter-defence picture with an eye on what might happen were heavy daylight air attacks to be launched against these shores. His conclusion was that defending fighters should, for acceptable results, out number the attacking force. Those who, remembering the Battle of Britain, challenge this conclusion are reminded that not only is the modern bomber capable of flying almost as high and as fast as the best fighters, but in the realm of atomic bombing 100 per -ent of the attacking force must be killed before it reaches the arget. In any case, whatever the quality of the defending fighters, t would seem that numbers must be answered by numbers. Mr. Petter studied the range of engines available and came to he conclusion that one or two turbojets then under development might prove suitable for such an aircraft. It is not thought that he visualizes the use of ramjets or rockets, either as main or auxiliary power units. Assuming an engine thrust of 5,000 lb, it appears quite possible to produce a fighter grossing less than this, so permitting sustained vertical climb and an order of per formance exceeding that of any fighter now being built. During the past 18 months, the Folland design staff have pushed steadily forward with the development of the aircraft which has now received the company name of Gnat. So far, official backing has been conspicuously absent, but no time has been lost on this account. Work on a prototype is progressing to schedule. Little can be said of the type of engine likely to be used in production Gnats. According to Aviation Week. Rolls-Royce, Bristol and Armstrong Siddeley all have suitable axial engines under development, but for our part we can say nothing beyond the fact that the engine will be an axial turbojet built to normal standards and in no sense a short-life engine. For a fighter of this nature it might be imagined that Durestos or a similar resin-bonded fibre plastic might profitably be used in the structure. In the event, this is not so, for the Gnat will have a normal metal stressed-skin structure, flush-riveted. Machined members are gratifyingly absent and, in particular, there is an almost complete lack of forgings and large castings. The airframe is capable of manufacture in jigs of the simplest geometry and, according to the company, no special skill or tooling is required. Mr. Petter was also faced with the choice of fitting a normal undercarriage, or adopting the catapult and flexible-deck tech nique, using belly skids. It can be said that the Gnat under carriage will be quite normal and, due to the light weight of the aircraft, operation from good grass fields should be entirely possible. The landing speed is bound to be high—as it is on all modern fighters—but deceleration should be rapid enough to permit operation from spaces far more confined than could be used by larger fighters. With a good power/weight ratio, angle and rate of climb should be very great. A Gnat wing has already been made and it appears that, on a production basis, this wing could be produced at a quarter of the cost and less than one-fifth of the manhours of a wing for a conventional fighter. Having seen this prototype wing—currently undergoing severe static testing—we can say that it impresses both by its simplicity and by the standard of its finish. Follands express themselves well pleased with its performance under load, which exceeds all calculated estimates. The pilot of the Gnat need have no fear that he will be subjected to conditions more uncomfortable or dangerous than are experi enced in the cockpit of, for example, a Meteor. Full cabin pressure and temperature control will be provided, and also an ejection seat. Xhe latter feature is particularly interesting in view of difficulties experienced in accommodating such a device in much larger air craft; and it also underlines the "conventional" nature of the new fighter. The question of armour cannot be stated definitely, but it would be surprising if the pilot were left unprotected; in any case, the Gnat should qualify as the world's smallest and most elusive military aircraft. Other choices facing Mr. Petter were the adoption of complete electrics or hydraulics throughout the aircraft as opposed to a simplified circuit operated by a ground-charged accumulator. Again, the question of primary flying controls is one of absorbing interest; it will be interesting to find out whether Mr. Petter and his team have adopted the all-flying tail, and equally, whether the control circuits are powered or if they rely on spring-tabs. On the question of armament, of course, little specific informa tion may be divulged. If cannon are to be used, it is unlikely that they will be placed in the bottom of the fuselage for, on a small and light aircraft, their recoil would produce very severe nose- down change of trim. Spin-stabilized unguided rockets of the type now carried by so many American fighters offer a possible alternative, while one must not rule out the possibility of larger,
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