Flight, September 1926

British Light ‘Plane Development & Lympne Meeting

THE 1926 MACHINES

No. 8. The Halton H.A.C. 1 "Mayfly" (Bristol "Cherub" Engine)

   IN some ways the Halton Aero Club is unique. Formed in December, 1925, as a service club among the staff and apprentices at Halton, the chief training centre for apprentices in the Royal Air Force, the club already has a membership of more than 1,100, and the funds of the club have been raised by 5s. and 2s. 6d. shares. The apprentices alone have raised in this way L170. The club was formed with the object of increasing the interest of both the staff and the boys in their work by designing and building machines of their own and entering them in such competitions as may occur. At the same time it was hoped that the carrying out of this work from the first ideas to the finished aeroplane might help to improve the liaison between the various branches of the staff. When the first machine has been completed it is intended to arrange for a series of lectures to be given to the apprentices by those responsible for the various branches of the design and construction.
   The H.A.C. 1, or "Mayfly," as it has been somewhat facetiously called by the apprentices, is the club's first effort. It has been designed by the school educational staff, and built in the workshops largely by the apprentices under the supervision, and with the assistance, of their officers, N.C.O's. and civilian instructors. Some of the work has been carried out as part of the regular training of the apprentices, but the majority has been voluntary spare time work on the part of all concerned, and one wishes the club every success in the future. It is obviously tackling the job in the right spirit. It is, therefore, all the more to be regretted that as far as can be seen at the moment the machine is unlikely to be finished in time for the Lympne meeting.
   But few particulars relating to the construction of the H.A.C. 1 are available, but the general arrangement drawings show the machine to be a biplane with "X" interplane struts and a total wing area of 195 square feet. The weight of the machine empty is 480 lbs., and the weight of fuel and oil is 60 lbs., while the useful load is 340 lbs., giving a total loaded weight of 880 lbs. and a wing loading of 4-5 lbs. per sq. ft. The estimated top speed is 76 m.p.h., and the landing speed 38 m.p.h. The wing section used is R.A.F.15. The engine is a Bristol "Cherub," which drives a Fairey-Reed duralumin propeller.

Flight, February 1927

AIRCRAFT CONSTRUCTION UNDER DIFFICULTIES
Halton H.A.C.1 in Commission

   AIRCRAFT apprentices all over the country will be glad to learn that the little machine which many of them helped to build, and for which more of them helped to pay, has at last been completed and tested in flight at the Bicester aerodrome, as recorded in FLIGHT recently. They will also hear with satisfaction that the H.A.C.1, or "Mayfly," does not, as far as the somewhat brief flight tests carried out up to the present indicate, show any signs of possessing any vices likely to detract from the amusement and instruction to be derived from flying the machine at Halton and elsewhere during the coming summer. In fact, the machine has been found to be handy on the controls, to have a low landing speed and a good take-off, while the top speed seems sufficient for all purposes for which the machine is likely to be used.
   In trying to form an opinion of the merits of the Halton H.A.C.1, several points should be kept in mind. To begin with, the machine is entirely an amateur production. It was designed by officials and civilian instructors at Halton Camp. The necessary funds were raised by voluntary subscriptions among the officers, instructors and boys, contributions being mostly of the order of half-a-crown or so. The work of constructing the machine was carried out in spare time, with the exception that some of the boys were permitted to make certain parts for it as part of their manual training, i.e., instead of making the usual test specimens of various joints in wood, window frames, etc., they were allowed to make certain structural parts for the "Mayfly." And, finally, the machine was originally intended for the light 'plane competition held at Lympne last year for the Daily Mail prize. Bearing in mind the conditions under which the machine was produced, and the fact that it was found impossible to finish it in time for that competition, the determination required to carry on and finish the machine shows an extremely fine spirit among the Halton boys and instructors, the more so as by the time the machine was finished most, if not all, of the boys who took a part in building and/or financing it had completed their courses at Halton and had been sent elsewhere, with but small chance of ever seeing the result of their efforts and sacrifice in the air. We had hoped to be able to show them, this week, photographs of the "Mayfly" in flight, but, owing to circumstances this has not been possible. When we paid a visit to Halton last week, the machine was still at Bicester aerodrome, where the initial test flights were carried out, and, owing to the fact that the Air Ministry's test pilot had not yet arrived to fly it, the machine did not possess its airworthiness certificate, and was not, therefore, permitted to be flown the 20 miles or so across to Halton! However, we hope later on to be able to obtain some good flying pictures of the "Mayfly," when Halton boys now with various squadrons in different parts of the country will have, at any rate, the satisfaction of seeing the photographs of their machine. In the meantime the "ground views" and sketches published this week will have to suffice.
   In designing the H.A.C.1 a number of conflicting requirements had to be met, due chiefly to the fact that the machine was, as already mentioned, intended for the Lympne competition of 1926. The machine is a tractor biplane with high gap/chord and span/chord ratios and a very pronounced stagger. An endeavour was made to provide as good a view as possible from both cockpits, and the illustrations show that this object has certainly been attained, particularly as regards the front seat. Accessibility to the cockpits was another consideration, and again the front has scored, although the aft cockpit is rendered slightly difficult of access owing to the overhanging trailing edge of the top centre section.
   It will be noticed that the "Mayfly" is a single-bay biplane, and thus is of orthodox design. The wing struts, however, are somewhat unusual, being in the form of an unsymmetrical letter X. We do not envy the man whose task it was to draw out these struts. Owing to the difference in chord (or rather distance between spars), forward stagger, angle of incidence, and outward rake, the struts must have presented a very pretty problem in projection drawing. The wing bracing, apart from the struts, started life as a normal type. During construction, however, and after the wings had been completed, it was discovered that an error had crept in while "stressing" the wings, and that the load factors for the drag bracing were inadequate. Rather than wait for another set of wings to be got out, it was decided to bring the existing wings up to strength by adding external drag wires to nose and tail. This will explain the presence of these wires, which may be seen in the photographs, and which are not actually to be regarded as part of the design.
   One point about the wings that attracts attention at once is the placing of the rear spar of the bottom wing. This is situated rather less than halfway from the leading edge along the chord. This position was chosen in order to bring the upper and lower rear spars vertically in line, since it would otherwise have been difficult to design hinges for folding the wings. Large wing flaps are fitted to the top wing only, and so arranged as to act as camber flaps, as well as ailerons. They are held up by rubber cords on top of the wing, and all aileron cables and pulleys have been mounted externally for the sake of simplicity, although the original intention was to place them inside the wings. The wing section used, by the way, is R.A.F. 15.
   The fuselage is of the flat-sided box type, with a light skeleton of spruce covered with ply-wood. The longerons are stop-chambered between struts to approximately triangular section. There are no metal fittings in the main fuselage structure, the struts simply butting on to the longerons as in the De Havilland "Moth." The deck of the fuselage is cambered in the ordinary way, but owing to the fact that it curves slightly in side view, some difficulty was experienced in applying the plywood panels, due to the fact that flat sheet can be bent over a cylinder but not over a barrel.
   The tail of the "Mayfly" is of fairly orthodox design, except for the fact that the rudder is placed wholly above the elevator, the latter being undivided. The rudder is of large area, and provided with a large horn balance. All control cables pass inside the fuselage, those from the elevator cranks straight into the stern, while the rudder cables run from the rudder cranks to other cranks on a vertical lay shaft placed inside the fin. From cranks on the lower end of this shaft the cables are taken to the rudder bar in the cockpits.
   The cockpits are roomy, and provided with dual controls, one of the "sticks" being removable.
   The Bristol "Cherub" is mounted on light sheet-steel brackets, built up to form four pyramids, one on each corner of the fuselage. The engine is very accessible, and further cowling may be added at a later date. The propeller is a Fairey-Reed of Duralumin, and was presented to the club by the Fairey Aviation Company. The petrol tanks are situated in the top centre-section.
   A simple undercarriage of steel tubing with built-on fairings is fitted with rubber cord shock absorbers.
   Altogether, the Halton H.A.C.1 is a very creditable piece of work, and it is to be hoped that the machine may be able to take part in meetings and races during the coming summer, so that the boys who have helped to produce it may have at any rate that satisfaction.