FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1929
1929 - 0216.PDF
SUPPLEMENT TO FLIGHT JANUARY 31, 1929 THE AIRCRAFT ENGINEER can be estimated some value of kg must be adopted. To be on the safe side, the lecturer suggested for the present the use of an overall value of k? of 0 • 002, which he thought would leave a little in hand to allow for using moderately thick wing sections, say, up to 12 per cent, of the chord. Using this figure for k$, the value of F becomes: F=0 -002 pV3E foot pounds when V is in feet per second, and F = (27ffV3mE)/W horse-power per 1,000 lbs. weight, where Vm is in hundreds of miles per hour units, E is the exposed surface in square feet, and W is the weight of the aeroplane in pounds. Finally, the climb power C is given by C = 0 • 030 Ve, where V,. is the rate of climb in feet per minute. Finally, Professor Melvill Jones showed some slides giving curves of power required for the streamline aeroplane and for existing commercial types. For the purpose of calculating the former he had taken E = 3 -2S, where S is the conventional wing area, so that F = 86aV:im/a>, where «is the wing loading in lbs. per sq. ft. This value of 3-2 represented an average E/S from machines ranging between 3 • 0 and 3-5. In drawing the curves a was taken to be unity and rj 75 per cent, for level flight, and 70 per cent, for climbing. The curves gave b.h.p. per 1,000 lbs. weight for wing loading a>) of 10 and 15 lbs. per sq. ft., and span loading (u,) 2 and 2-5 Ib3. per sq. ft. Large commercial aeroplanes such as the " Argosy," W.10 and " Hercules," would, were they ideally streamline, either fly at the present top speed for one-third the present power, or, alternatively, travel some 60 m.-p.h. faster for the same power. Two-thirds of the power used by these aeroplanes was being expended on the generation of turbulence which, from the aerodynamic viewpoint, was unnecessary. The improvement in power consumption for climbing was not so great as for top spesd, but was still appreciable. THE AUTOMATIC SLOT. In view of the fact that successful experiments with the Handley Page Automatic Slot have been carried out on the Westland Wapiti, the address given to members of the Westland Aircraft Society, the Yeovil branch of the Royal Aeronautical Society, on January 17, by Mr. G. C. D. Russell, A.F.R.Ae.S., of Messrs. Handley Page, Ltd., was of parti- cular interest. Mr. Russell, in the course of a highly technical paper, illustrated with diagrams and lantern slides, said the appli- cation of the automatic slot to any given aircraft had in the past necessitated the carrying out of a large amount of experimental work in the wind tunnel, but data would be accumulated in the near future, from which it would be possible to prophesy with fair accuracy, the slot character- istics of almost any type of wing section. Dealing first with the method of obtaining, and the nature of the data which the wind tunnel was called upon to provide, for any aircraft to which it was proposed to fit automatic slots, Mr. Ru?seU said that the experimental data required actually fell under two headings : " The Slot, its shape and effect," and " Characteristics of the Auxiliary Aerofoil, Resultant Forces, etc.," but a third heading might be added which could appropriately be termed " Improvements," into which could go all the data referring to improvements in the slot control due to factors quite distinct from the actual working of the slot itself. The Handley Page slot as at first used on aircraft, was intended solely to provide wider speed range to the machine so fitted, by enabling the machine to be brought to a much higher angle of incidence before the stall occurred, accompanied by a very high percentage increase in the value of the maximum lift co-efficient which resulted in it being possible to fly the machine with safety at far lower speeds than was possible without the slots. From the point of view of automatic slots when applied to the wing tips of a. machine for the purpose of improving its lateral stability and control the position was rather different. The latferal stability of a machine near or at its stalling point is dependent upon many factors, one of the most important Being its ability to resist the autorotative couple which sets in immediately the stalling angle is ex- ceeded, and which is in most cases the primary cause of the incipient spin. The automatic slots when applied to the wing tips definitely delay this autorotative couple to a much higher angle of incidence, thus allowing the righting couple to reassert itself. • With regard to " Improvements," the lecturer remarked that in the past very many experiments had been carried out with the interconnected slot and aileron control, in which a direct connection was made between the ailerons and the slots in front of them, in such a way that the downward moving aileron opens the control slot in front of it, whilst for the upward moving aileron the slot remains closed— this resulting in a large righting couple occurring at angles of incidence, at or past, the stall of the aircraft in question. The reason for this was that one side of the machine was completely stalled while the other side, being slotted was still developing increased lift. In order to obtain the same effect, and at the same time to allow the slots to function automatically, a lost motion link can be devised, by which either of the slots can be pulled back a little (or completely) when their corresponding ailerons are moved upwards. Alternatively, the pivot points of either front links may be mounted adjustably by eccentric sliding or other means, so that when in the open position the slot may be swivelled by a link connection operated by the aileron. These methods might, however, entail extra loads on the pilot's control column and in order to overcome this some tests were recently made with another device which gave extremely good results and at the same time caused practically no extra loads on the controls. The device is in the form of an interceptor or plate which is situated on the top surface of the wing, and to the rear of the front slot. It is connected to the aileron control, in such a way that for aileron normal it is held flush with the top surface of the wing, but on moving the aileron upwards, it is caused to project above the surface and destroy the effect of the front slot. For front slot closed it can be arranged that the inter- ceptor is entirely olit of action. Some full scale tests were recentlv earned out in order to definitely find out the effect produced on stability and control with various positions of the slots along the wing span. The results c"learly indicated that for improvement in stability, the best slot position is undoubtedly at the wing tips of the machine. Similar tests are now proceeding with the slot and interceptor control and the results would appear to be promising. Concluding, Mr. Russell said it gave him great pleasure to read his paper to that branch of the Royal Aeronautical Society, as he believed it was supported almost entirely by members of the Westland Aircraft Company, to whom his firm owed so much for their full co-operation and consider- able effort to make the slot a success. He believed he was right in saying the slot had been a great success on the Wapiti. Mr. A. Davenport, Chief Designer of the Westland Air- craft Works, who presided, referred to the fact that not only was Mr. Russell an authority on the automatic slot, but he had been connected with a great many research problems in wind tunnel work, and it was, therefore, a good opportunity for them to air their "pet" theories. Many interesting points were raised during the discussion which followed. " Have you slotted the slot yet ? " gained an affirmative answer,the lecturer adding that experiments had been carried out, and there was no reason why they should not do to the slot what they had already done to the wing. In response to a query as to whether there were any means of locking automatic slots, Mr. Russell said that it would be quite an easy matter, but rather dangerous for the simple reason that the slots would be locked when needed. A question was asked as to what would be the effects of the slot on a swept-back wing, and in reply, Mr. Russell said that the Virginia had a swept-back wing, and with slots had given very good results. They had not, however, tried out any wind tunnel tests with the Virginia. Generalising, Mr. Russell said he was interested in the effects of the slots on the Widgeon, as they had not yet done any tests on a monoplane, although they hoped to do so. S2h
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
