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Aviation History
1924
1924 - 0207.PDF
APRIL 10, 1924 against angle at constant wind speed, the readings were taken of lift at varying wind speeds at selected angles. This method gave straight-line curves passing not through the origin but a known distance to one side. Thus two safeguards were introduced. If the first curves did not pass the origin at the known distance the wind-speed measurements alone must be at fault, provided the points formed a straight line. Any irregularity in the second curves could only be caused by faulty setting of model for angle, and this could easily be traced back and re-tested. A large number of models were tested, the first of which was No. 11, which did not, it will be seen, give very good results as regards efficiency. Other models, using different wing sections, gave better results. For instance, model No. 17, whose characteristic curves are published herewith, have a maximum L/D ratio of about 8-7 with fuselage. Considering that the tests were made with old-fashioned sections, this result is very good, and must have been considerably better than the average maximum L/D obtained with contem poraneous machines. As far as tested the lift went up to a maximum lift coefficient of 0 • 5 absolute, but as the tests did not go above 20° there is no means of telling what was really the maximum lift coefficient. A biplane model was tested, whose curves space does not permit of publishing. This model was tested up to 30°, and it was found that the lift reached a maximum value of 0-42 and then remained sensibly constant up to 30°, the lift curve over the last section being for all practical purposes a straight horizontal line. In other words, the circular biplane did not show any burble point. There is no reason to believe, and the flying experiments seemed to confirm the opinion, that the monoplane type would behave differently as regards stalling angle, and this appears to be one of the most interesting features of the annular 'plane. It has no stalling angle, or if it does have one the sudden drop found with ordinary wings is turned into a very gradual drop in the annular wing. In view of the fact that it is generally admitted that the majority of flying accidents are due to stalling, this feature of the annular 'plane alone seems to entitle it to attention for further development. The pressure plotting curves are of interest in showing the distribution of lift over the annular surface. Mr. Tilghman Richards is of the opinion that over the leading and trailing portions of the annular wing the lift reaction is of normal type, as found on the high aspect ratio " pterygoid " 'plane, while over the side portions, or " apteroid " sections, there is a vortex motion which gives rise to lift, a sort of " false lift," which contributes towards the lift of the entire surface. H H The centre of pressure can be kept stationary with the annular type of wing, or it can be made to move in a stable direction. On model No. 11 it was a stable movement, as will be seen from the curves of c.p. movement. In other models it was quite neutral, and on one power-driven machine built the c.p. was neutral. This, however, had the effect of rather frightening the pilot, as he could not " feel " the machine. From an aerodynamic point of view the annular plane may He summed up as follows : It gives a high lift, without violent stalling point; it develops the high lift at large angles ; its L/D curve is very rounded, with a not very high maximum value ; and it can be made stable to any desired degree. As regards efficiency it should be remembered that these model tests were carried out at a time when the best, or one of the best, wing sections known was the R.A.F.6. It seems reasonable to suppose that by employing ^modern sections, perhaps some of the good modern high-lift sections and others similar to R.A.F.15, considerably higher values of L/D may be obtained. Even granting, however, that on the score of efficiency the annular plane is somewhat inferior, does it not possess certain advantages which will largely offset any such inferiority ? Take, for example, the question of structure weight. The circular type of wing, with a fuselage resting on it at both its ends, should work out very light per unit of area, more especially so in the case of large machines. Then there is the question of overall size. A machine of the annular wing type, having a wing area of close an 1,500 sq. ft., would only have an overall span of 50 ft. This in monoplane form. If in biplane form the span would be reduced, for 1,500 sq. ft. of area, to about 35 ft. An ordinary monoplane of this area, if of normal proportions, would'have to have a span of approxi mately 100 ft., and a biplane about 70 ft. If one imagines a commercial passenger 'plane of the annular type, the cabin would occupy the central part of the fuselage, and the view would be practically unrestricted in all directions. The circular wing entirely surrounding the cabin should make for safety in a crash, as a great deal of structure would break before the cabin touched, and would thus considerably lessen the shock. Taking it all round, it would appear that there is quite good reason to give these early experiments of Mr. Tilghman Richards a close scrutiny with a view to seeing how far past experience justifies taking them up again where they were left off in 1914. Here, we think, is a case where the light 'plane would come in very usefully in allowing full-scale flying experiments to be carried out at relatively low cost m m PILOT'S LICENCE REGULATIONS Air Navigation Directions, 3 C 1. THE Air Navigation Directions, 1922 (A.N.D. 3), as amended by the Air Navigation Directions, 1923 (A.N.D. 3A), and by the Air Navigation Directions, 1924 (A.N.D. 3B), are hereby further amended as follows :— (1) After paragraph 53, the following new paragraph is inserted :— " 53A. A person applying for the grant or renewal of a pilot's licence to fly flying machines other than flying machines c'arrying passengers or goods for hire or reward (i.e., a ' Private Pilot's Licence ' as referred to in paragraph 55 hereof) will be required to undergo a medical examination by a duly qualified medical practitioner, who may be the applicant's usual medical attendant. Such examination shall be conducted in accord ance with C.A. Form 61, and a copy of that form, completed as required, shall be forwarded by the medical examiner to the Secretary (D.C.A.), Air Ministry, London, W.C. 2 (by whom copies will be supplied on application)." (2) For paragraphs 60 and 61 (including the heading "Flying Experience ") the following provisions are sub stituted :— " Flying Experience, etc. " 60. As regards Private Pilots' Licences' for flying machines :— " (a) A candidate for the issue of a licence will be required to produce satisfactory evidence that he has carried out not less than three hours solo flying during the twelve months preceding the date of the application. The evidence normally required for this purpose will consist of the production of a Pilot's Log Book recording such flying, or of a certificate issued by a responsible authority or person approved for the purpose by the Secretary of State. "(b) A candidate for the renewal of a licence will be required to produce in respect of the preceding twelve months the same evidence as is mentioned in sub-paragraph (a), or in default thereof to carry out satisfactorily the following practical flying tests under the observation of an official observer appointed by the Royal Aero Club, or of some person approved for the purpose by the Secretary of State. " (i) To execute three figure-of-eight turns, and " (ii) To carry out three landings, finally stopping the aircraft on each occasion within a distance of 50 yards from a point fixed by the candidate before starting. "61. As regards pilots' licences for passenger or goods flying machines :— " (a) The maximum period for which a candidate for the issue of a licence may not have flpwn but yet may be con sidered to have recent reasonable flying experience is six months. "(b) A licence «,will be granted only for such types of flying machines as the applicant can produce evidence of his ability to fly. A licence may, however, be extended to cover further types on production of evidence of the holder's ability to fly those types. " 61A. With reference to proviso (b) to Art. 3 (1) of the Order and proviso (c) to Art. 4 (1) thereof, a flying machine may be flown by a person not holding a Private Pilot's Licence for flying machines for the purpose of becoming eligible for the issue of such a licence, provided that the following conditions are complied with ;— " (i) The flight must start from, take place within three miles of, and finish at, a licensed aerodrome, a Royal Air Force aerodrome, or an aerodrome under the control of the Secretary of State. " (ii) Before the flight is commenced, notice that it is being undertaken for the purpose stated above must be given to the person in charge of the aerodrome from which the flight starts. " (iii) No passengers may be carried." 2. These Directions mav be cited as the Air Navigation Directions, 1924 (A.N.D. 3c). 3. These Directions shall come into operation forthwith. THOMSON, Secretary of State for Air 207
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