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Aviation History
1923
1923 - 0208.PDF
'MSas APRIL 1&, 1923 promise of being useful when fitted in light 'planes. We still have to demonstrate by actual experience that these engines have the reliability required, and certain other features of greater importance in aircraft than on a motor-cycle. For instance, the question of vibration enters into the problem to a greater extent than on the road. The flat twin will probably be chosen for preference, owing to its good mechanical balance. The Vee type is something of an unknown quantity in two-cylinder units as far as the air is concerned, although there is reason to believe that the somewhat imperfect balance need not seriously interfere with its use in a light 'plane. If the Vee type be found sufficiently smooth, the choice afforded the designer of light 'planes will be considerably increased, as a large number of Vee twin-cylinder engines is on the market. The chief consideration at the moment is that we shall have to utilise existing cycle engines, for our preliminary experiments at any rate. Consequently we commence this week a series of articles dealing with cycle engines of a capacity in the neighbourhood of, but not exceeding, 750 c.c. capacity, and which appear to be suitable for experimental purposes. The limited capacity of 750 has been adopted owing to considerations of the Sutherland Prize, but other- wise we are not at all certain that the light 'plane of the future will necessarily be limited to this capacity. For a machine to be of any practical use, it should be able to make reasonably good headway against winds of average strength, and it has not yet been demonstrated that engines of 750 c.c. capacity are powerful enough to do this. We are quite prepared to find that with efficient aerodynamic design this size of engine is sufficient, but this still remains to be proved. For cruising around in the neighbourhood of an aerodrome the smaller cycle engines would probably be powerful enough, but for cross-country work a reasonable reserve will probably be necessary. There can, however, be no doubt that several types of motor-cycle engines are capable of giving us the initial practical experience required, and enable us to form a very sound basis upon which to judge the capabilities of light 'planes. Let us assume, for the moment, that it has been proved that light engines of suitable power are available, and are sufficiently reliable to make cross- country flying a practical proposition. Is there then likefy to be a demand for such machines ? We are convinced that there is every probability that the demand will be very large. It should be possible to design these machines with a great amount of inherent stability, so that a minimum of skill is required to fly them. Landing, as they will, at only slightly over 30 m.p.h. the danger in case of a crash should be relatively small. If anything goes wrong in a machine landing at 60 m.p.h., or more—if the pilot makes a slight error, the consequences are likely to be serious. At 30 m.p.h. not only will the shock be comparatively gentle, but the low speed gives the pilot more time to think and act. Thus it seems that probably the greatest difficulty will be, not economy, nor performance as regards cruising speed, but the question of taking off. These light 'planes will have a relatively high power loading, and consequently the rate of climb will be somewhat indifferent. At the same time, it will occur at a very low speed, and it would seem probable that a pilot would have a very good chance of turning back into the aerodrome, should his engine fail just as he is taking off. If a 208 sufficiently good take-off can be attained, we see no great difficulty in providing the other desiderata. If machines are designed—as they certainly ought to be—with folding or easily dismantled wings, they will take up very little space in a shed, and a number of machines could be accommodated in an ordinary hangar. Thus at the London aerodromes (to take the case of the London district) there should be ample and relatively cheap accommodation at Croydon, Cricklewood, Stag Lane and Hendon, the choice depending on which part of London the owners resided. At all these places, too, there would be facilities for repairs and overhaul, and it might be expected that clubs would be formed. The natural sequel would be the holding of races for light 'planes, and it seems likely that a very great number of enthusiasts would be attracted who could not otherwise afford to take up practical flying. Thus from the sporting point of view, the light 'plane will almost certainly become popular. Other ^e Possit>ilities of the light 'plane are Uses n°t> however, confined to sporting aviation. One purpose which immedi- ately suggests itself is instruction in flying. These light 'planes will cost, when produced in large quanti- ties, something between £100 and £200, according to type. Consequently, it .will be possible to train a pilot for very much less than it now costs, not to mention the greater security resulting from using slow machines. This points to a large field of usefulness for the light 'planes, not only in civil life, but also in the R.A.F., where a preliminary, or elementary, course in flying might well be instituted, starting with gliders and then proceeding to light 'planes, and then, by easy stages, to the high-speed scout. In this way the R.A.F. should save a great deal of money on crashes, as the preliminary training should suffice to find out the pupils who were likely to become good pilots, and those never likely to have the necessary " hands." Apart from school work, it appears likely that the light 'plane will form a very useful step between wind tunnel work and full scale experiments. Thus one can imagine certain research work—for instance on a new type of wing—instituted in the wind channel. The results are promising, but there is still some doubt as to " scale effect." The wing is tested in free flight on a light 'plane, and the scale effect is determined. Not only this, but a number of other characteristics about which the channel tests have still left some doubt. Another field for free flight research, and one which cannot very well be carried out in the wind tunnel, is controllability at or even beyond the stalling angle. At present this is a very costly business, and there does not seem to be any reason to doubt that the necessary information could be obtained by the use of light 'planes. Free flight tests on slotted wings of the Handley Page type, or wing flaps of the Fairey type, might also be carried out in this manner, and altogether it would appear that the light 'plane might form the " missing link " between the channel and the large machine—providing information which the former cannot give, and at a cost not very much higher than the cost of a series of tests in the channel. One fuselage and engine could probably be used for testing a great number of wings, and it is not incon- ceivable that firms who do not at present run their own wind channel would do better to build a light 'plane for their experiments. TT ! .. : -.^.
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