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Aviation History
1945
1945 - 1631.PDF
i 8A FLIGHT AUGUST I6TH, 1945 CORRESPONDENCE The Editor does not hold himself responsible for the views expressed by correspondents. The names and addresses of the writers, not necessarily for publication, must in all cases accompany letters. WHAT DOES THE PRIVATE OWNER WANT? A Clean 3-4-seater for Less than £1,000 INDICATOR " asks in Flight of July 12th what the privateowner wants. 1 want a modern private aircraft of my own ; it must be small, economic, clean, reliable, pleasant to fly, easy to maintain and, preferabl ', be a four-seater, although I would be content with a three-seater. Further, I want to be able to buy it for less than £1,000, and I insist on it being British. Having set this down, I can now mull over the "musts" and adduce the sort of machine I should like. Initially, the size must be of the 30ft. to 35ft. span order which allows of. convenient parking and hangarage, including manhandling. Economic operation is bound up with the engine, and as I prefer to put my trust in a Gipsy or Cirrus, that is more or less taken care of; however, linked with the economic operation of the engine is the imposition placed upon the engine efficiency by the aircraft design, which is resolved as to what you get in terms of aircraft performance for given engine operating con- ditions. We are thus led to the precept that the aircraft must be aerodynamically clean and that the whole drag side of the design should receive very careful attention. Cleanliness is my next condition, and this I feel is quite important. I see no reason why one's personal aircraft should not be as cleanly as one's car, and there is every reason to insist that to go to the field, take out the machine, fly it for 150 miles and go to a meeting without the necessity of extensive ablution should be taken for granted. Reliability is probably the Achilles heel of all aircraft; never- theless, it would be pleasant to have an aircraft which needed no more attention to the airframe and bits and pieces than that required by its engine. Possibly this sort of reliability will one day eventuate—it will be a happy day. On the score of being pleasant to fly, I am particularly in- sistent. If the .seat, pedals and column are not adjustable, then I should probably want them modified to suit. In a light air- craft, control forces are usually negligible, and in many cases, unfortunately, so also is accuracy of response. Light, positive and accurate control is essential, likewise accurate trim control. Visibility must be first class, with as large a field of view in all directions—including upward and backward—as possible. Seats must be high backed and have the back nearly vertical— it reduces fatigue. Instruments must be clearly marked (if not of Service standard) and placed as nearly as possible directly facing the- pilot's seat. As to what flying instruments* should be provided, as distinct from the engine instruments, I should like an A.S.I., sensitive altimeter, turn and bank, and directional gyro.' In addition to these a P.6 or P.4 compass is a necessity, and I should also like a really accurate clock with a secondary trip dial. Ease of maintenance I have already touched upon, but a factor which has a most important bearing on this subject is the ease and cheapness with which spares can be obtained— not only from the maintenance angle, but also from considera- tions of insurance. Whether or not the machine is of wood or metal I do not really care. In the case of such a machine as I have in mind, there is not much to choose between the two, for what you gain on the swings you forfeit on the roundabouts. Finally, there is the question of accommodation. Three seats are essential; four are desirable. If a three-seater, the front seats should be side by side with a central rear seat; if a four-seater, the seats should be paired front and rear. Wide car-type doors hinged on their leading edges are also desirable, and if it is considered not worth while fitting doors on each side, then the door should be on the starboard side. Accommodation for light luggage should also be provided, and in this case probably the rear seats could be made easily removable, and, say, four or six lashing points be incorporated whereby a couple of suitcases could be secured. In general the type of private aircraft I should so much like to own would doubtless make a positive appeal to many people. It might also be a useful type for clubs to own for charter by members for week-ends. When one considers the potential market for such a machine as this, not only here, but in other countries, then one is a little bewildered by the seeming lack of incentive or market appreciation by the British manufac- turers. • If I wanted, and the import tax permitted, there are Ameri- can machines that would fulfil my requirements—after all ^1,000 is a fair amount of money—but, like many others, I have a fondness lor the products of my own country. «How- ever, I would point out to the British aircraft industry or that section of it interested in light, private aircraft that although forbearing and wishing to buy British, I am not immune from foreign attraction in offering me what I want at a price I can afford, and if Britain cannot, or will not, trouble to make available that which I want to buy, then I shall have to buy foreign. BARRIE HILERY. CENTRIFUGAL FORCE A Mathematical Query from " Seac " CAN anyone help me? I have worked out a perfectly validformula foi the calculation of centrifugal force in a turn, but am unable to prove that it is correct. In fact I am per- fectly able to prove that it cannot possibly be right. It started in an attempt to provide a formula which would angle \— • ^. ) for radius of turn in the i substitute rate of turn .1 xlffiG /v2 conventional lormula of — commonly used. This*on given farts relating to a turning aircraft, would make the calcula- tion easier, eliminating the need to calculate the radius of turn. After a lot of woolly-headed working, it seemed that the centrifugal force (horizontal component) bore relationship to the speed in unit time as follows (see diagram): TT- = tan - GIVEN: AB=AC=V; and AC tangential at A PROVABLE: (1) <BAC=i<a (2) H =H where <B,CA (3) OBC = iSo° S where H= horizontal component (centrifugal force) V=speed, i.e., distance in unit time a=angular change of direction in degrees in unit time. However, this is wrong and gives about half the required IT answer. By "inspiration," I tried using ^ = tan a (the whole% of a) and obtained results which were nearly right. I found that they varied from the correct answer by a definite constant for any given rate of turn (a). Thus I got H=tm aVKa. Ka proved to be .9996 for a = 2°; .9991 for a=3°l .9984 for a = 4°; etc. (i.e., 1.0000—.0004 ; 1.0000 — .0009; and 1.0000—.0016, etc). In other words, Ka = i—- 10,000 This formula, then, gave correct answers: H = tanaVK,. Where H = horizontal component (centrifugal force) deea—rate of turn, V = speed, unit time distance unit time and K = 1 10,000 Can somebody help a tormented South-East Asian soul bf proving that this is right. As I say, all I can do is to prove it wrong. J. COHEN (Fit. Lt.).
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