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Aviation History
1941
1941 - 2300.PDF
FLIGHT OCTOBER 2ND, 1941. THE IDEAL TRAINER Even though they have certain advantages, tail skids can play such havoc with an aerodrome surface that tail wheels are probably advisable. This rather entails the fitting of brakes, but although it is essential to keep an elementary trainer as simple as possible, brakes are desirable for several reasons; not so much to familiarise a pupil with their use at an early stage as to simplify taxying and park- ing, thus saving pre- and inter-flight time. A brake sys- tem, while itself able to cause accidents due to nosing over, is more likely to be instrumental in preventing taxy- ing accidents if well designed. Due to the rather wide fuselage and the deflection of airscrew slipstream from the rudder, light side-by-side aircraft without brakes are apt to be difficult to control on the ground, especially in a strong wind. Importance of Visibility Earlier it was stated that America had produced types similar to the ideal suggested here. In general this is true, . but several drawbacks exist, an important one from the training point of view being the almost universal use of radial engines except in ultra-light types. This at once sets a problem for forward visibility, quite apart from con- siderations of the engine type itself. One hardly dares to be in the least degree unorthodox in trainer design. Instructors are themselves a conservative lot. They are well used to a certain type and are rather prone to regard it as the only type possible. It has been said that our present trainers are quite adequate for the job and, at a time like the present, a change would involve trouble, expense, and a risk of shortage of machines. There is a good deal of truth in this, but it may be assumed that our production of trainers is sufficient to enable a reserve to be built up, thus eliminat- ing at least the last-mentioned objection; while the fore- going discussion will have failed if it does not give justi- fication for a certain initial expenditure of money--and effort to conserve just these two things in the long run. Providing one or two major problems could be satisfactorily overcome, a pusher engine has several good characteristics for application to a trainer. However, to mention in simple terms two considerations which come to mind at once: can a straightforward tail unit be designed, and what will happen to the engine—or, more important, the pupil and instructor—in the event of landing on the nose or being involved in a head-on collision? A possible alternative to the present orthodox arrange- ment or the pusher would be the mid-engine arrangement with a short shaft drive. This would be something of a compromise, permitting a simple single tail, good visibility, and no fear of an engine "in the back of one's neck" in the event of a collapsed undercarriage or nose-over. I he side-by-side cabin of the De Havilland Hornet Moth madeit a very popular machine and it conforms to some of our contributor's ideas. The time for a tricycle trainer has not yet arrived, in my opinion. Tricycle undercarriages in service are still few and far between, but, one hears, show excellent promise. It may be that in a year or two we shall have to discriminate at the elementary stage between bomber and fighter instruction. Recently the flying characteristics of these two types have diverged more and more. It is not suggested that, say, the Bulldog and the Virginia could have been very closely compared, but they were possibly more similar than the Spitfire and Whitley. It will, however, depend largely upon fighter development, whether big twin-engined escort fighters, with manoeuvra- bility to some extent sacrificed for speed and range, will completely oust the smaller single-engined fighter for attacking hostile as well as defending friendly bombers. The particular mention of a recently announced trainer as a trainer for night operation admittedly finds a strong pro-tricycle argument. Night flying is, however, part of the more advanced syllabus. Method of Construction Whatever type be chosen, the, construction most suit- able for the conditions of operation is the fabric-covered, welded-steel tube structure. This is reasonably light and inexpensive and lends itself readily to repair. The engine section should be metal covered. Stressed skin or any form of monocoque construction suffers the disadvantages of expense, difficulty of repair, complication of the very frequent ' inspections to which trainers are subjected, rather greater weight and, at the present time, un- necessary use of materials needed for service types. Wood is, of course, an alternative, but among other things, is not likely to weather too well if picketed out for long periods in all weathers. For the most conventional of the three designs illustrated, the type with engine ahead of cockpit, a horizontally opposed four-cylinder engine would perhaps be the most suitable. The, engine shape would fit into a side-by- The Ryan PT-21, with its Kinnerradial of 125 h.p., is one of the stan- dard trainers of the U.S. Army AirCorps. It is one of the very few braced monoplanes in existence.
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