FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1926
1926 - 0306.PDF
decided as an afterthought to turn the machine into a two- seater, by adding a second seat between the pilot and the engine. Under the tail end of the nacelle is fitted a small wheel supported by an arrangement not unlike that of the front forks of a bicycle, so as to allow the wheel to swivel. For steering on the ground the wheel is geared to the rudder bar. Capt. Hill first tested the machine as a glider and found that even at very low speeds the controls were effective, and having ascertained this, he proceeded to instal the engine so as to test the machine as a power-driven light 'plane. Up to this point Capt. Hill had been doing all the work of designing, and most of the construction himself, but the results were so encouraging that when he approached the Aeronautical Research Committee it was recommended that wind tunnel tests be carried out, and also that encouragement in the form of financial assistance and helpers, not to mention shed space, be given. Consequently, Capt. Hill was able to transfer the scene of his activities to the Royal Aircraft Establishment at Famboroiigh, where the installation of the engine and certain minor modifications to the machine were carried out. The Hill tailless machine does not merely consist in what might be termed a modern version of the pre-war Dunne machines, but incorporates a number of features which were not to be found in -the original Dunne. Chief among these should perhaps be placed what Capt. Hill calls the " con- APRIL 29, 1926 left-hand rudder is still left trailing, and thus offers no extra resistance. It might have been thought that by now Capt. Hill had done all that could be expected or was neces- sary. He had secured adequate lateral and longitudinal control for all attitudes of the machine, and he had provided rudders which were equally effective for the work which they had to do. The inventor of the " Pterodactyl " was not, however, content with this, but decided that by providing a separate control for the rudders he could operate them in such a way that they would form air brakes. This was attained by setting the two rudders over at a large angle to the flight path, the rudders, of course, swinging out symmetrically—that is to say, the trailing edge of the right- hand rudder moving outwards to the right and that of the left-hand rudder to the left. As the centres of pressure of the rudders are approximately on a level with the centre of resistance of the whole aeroplane, the trim should not be appreciably altered by the use of the rudders as air brakes, and in actual flying tests this was found to be the case. Moreover, it was found that by moving the two rudders simultaneously to their full extent the resistance of the machine was approximately doubled. In other words, the gliding angle was halved. With the Hill " Pterodactyl " it is thus possible for a pilot, if he realises that he is likely to overshoot the mark, to put on his air brake, thus making the gliding angle steeper, without any necessity for side-slip or any [R.A.F. Official Photograph. Crown Copyright. THE BOOMERANG: Plan view, from below, of the Hill tailless aeroplane " Pterodactyl." This view was secured with the camera pointing almost vertically upward. trailers." These are pivotted wing tips, so arranged that no matter at what angle of incidence the main wing is flying the •controllers are always lying along wind, that is to say they may be described as " floating." The advantage of this type of control over ordinary ailerons is that when the main wing approaches the stall the controllers are still neutral and thus have their full range of movement up or down available for control. As expected this was found to give adequate lateral control at angles which would be beyond the stall in an ordinary aeroplane. In point of fact Capt. Hill stated that the " Pterodactyl " did not show a decided stalling point, as does an ordinary normal aeroplane, and when following a flight path inclined approximately 45 deg., the machine itself is almost on a level keel. Actual flight tests had demonstrated that the " controllers " in the first machine were rather unnecessarily large (no less than one quarter of the total wing area) and in future machines it seems likely that the area of these controllers can safely be considerably reduced, while still retaining ample controllability. While on the subject of the " controllers " it should be pointed out that these serve, when operated separately, as ailerons, while when worked together up and down, being placed aft of the centre of gravity of the machine, their function is that of elevators. The rudders of the Hill " Pterodactyl " are vertical surfaces, one on each side, placed below the wing and some con- siderable distance out. Normally these rudders are free to trail, and for turning to the right, for instance, the right rudder is turned so as to form an angle with the flight path of the machine. The resistance or drag thus set up on the right-hand side swings the machine to the right, since the similar stunt landings. A most valuable feature of the " Pterodactyl " has been found to be that it is possible to change from the stalled to the unstalled state without diving. The enormous advantage of this is that if the machine is accidentally brought into the stalled condition (in so far as a machine without any definite stalling-point can be said to be stalled in the ordinary sense of the word) when close to the ground, the pilot can bring it back to the unstalled condition without any appreciable loss of height. It would almost appear that if the " Pterodactyl " possessed no other advantage than that, this alone would be sufficient to make it worth while developing it further. The designer of the " Pterodactyl " is, however, of the opinion that the tailless machine can be built with a smaller percentage structure weight than the normal machine. Another advantage is that it is possible to revert to the pusher type of aeroplane without loss of performance, while it is thought that an improvement can be made in the general arrangement of the flying-boat by employing the tailless design. An appendix to Capt. Hill's paper contained the main data relating to the "Pterodactyl," and, as the figures are of considerable interest, they are given below. The machine has an overall span of 45 ft. The area of the main plane is 223 sq. ft., and the area of the controllers 55 sq. ft. The area of the rudders is 13 sq. ft. The weight empty varies slightly, according to whether large or small wheels are fitted to the undercarriage. With large wheels the empty weight is 458 lbs., and with small wheels 444 lbs. The weight of petrol and oil is 30 lbs., and of pilot 170 lbs. The total loaded weight of the machine as a single-seater is 658 lbs., and as a two- 262
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
