Flight, April 1924

THE ARMSTRONG-WHITWORTH "AWANA" TROOP-CARRIER
Two Napier “Lion” Engines

   ON several occasions during the last year or two the general public has been promised an opportunity of seeing the "Awana" troop-carrier, designed and built by the Aircraft Section of Armstrong-Siddeley Motors, Ltd., of Coventry, but each time something has turned up to prevent the machine from putting in an appearance. If we recollect aright, the last occasion when the "Awana" was expected to appear in public was at last year's Aerial Pageant at Hendon. The machine did not, however, take part in the show for some reason or other, and it is not until now that it has become possible to publish a detailed description of the machine, illustrated by photographs and general arrangement drawings.
   The Armstrong-Whitworth "Awana" is a large twin-engined biplane designed to act as a troop-carrier. In general outline the machine is of orthodox design, and the feature which impresses most on first sight is the size. Measuring 105 ft. 6 ins. from tip to tip, and with an overall length of 68 ft., the "Awana" is one of the largest of modern land machines. The total loaded weight is 18,450 lbs., or nearly 8 1/4 tons. The upper and lower planes are of equal span, but unequal chord, that of the top plane being considerably the greater of the two.
   Structurally, the "Awana" is interesting on account of its composite construction, in which the fuselage is built entirely of steel tubing, while the wings are built of wood, with the exception, of course, of the usual metal fittings. One of the accompanying sketches illustrates a fairly typical fuselage clip. It will be observed that the clip surrounds the longeron, and is located by the diagonal bolt of the panel bracing. Wiring plates are welded into the space between the bent-over flanges of the clip, and the fork-ends of the vertical and horizontal struts are bolted to these plates. Bracing is by tie-rods, and it should be noted that the structure is unusual in that an auxiliary strut is used between two main struts, the bracing passing through the centre of the auxiliary strut, which latter serves to steady the longeron between main strut attachments. An arrangement similar in principle was, it may be remembered, used in the wing bracing of the earlier "Spad" machines.
   In the extreme nose there is accommodation for the crew (pilot and engineer), while the cabin extends from behind the pilot's cockpit to a point about 9 ft. aft of the trailing edge of the lower plane. The cabin has accommodation for 25 troops with their kit, the seats being arranged 'bus fashion along the sides of the cabin with an open gangway down the centre. Access to the cabin is through a trap-door in the floor of the fuselage.
   The wings are of more or less standard construction, with wooden spars and ribs. Some of the fittings, however, are of considerable interest, as, for instance, those occurring at the hinges of the folding wings. One such joint is shown in a sketch, in which the woodwork, such as ribs, etc., has been omitted in order to show more clearly the arrangement of the really interesting parts, i.e., the spar box and hinge-pin attachments. The sketch should make the arrangement clear. It will be realised that with an overhang of something like 42 ft. in length the stresses set up in the hinges when the wings are folded back are likely to be somewhat severe, and that, therefore, very substantial fittings and joints are called for.
   From the front elevation of the general arrangement drawings, it will be seen that there are four pairs of struts on each side, including the engine struts. The top plane is divided into five sections, and the bottom plane into six. The hinges for the folding occur just outside the engine struts. Ailerons are fitted to both top and bottom planes, and are of the type mounted on brackets from the rear spar, with their leading edge projecting forward of the hinge.
   The tail is of the biplane type, with a fairly small central fin and large central rudder, assisted by two side rudders pivotted on the rear struts of the biplane structure. Horn-balanced elevators are hinged to top and bottom tail planes.
   The Napier "Lion" engines are mounted on steel tube supports well ahead of the lower plane, and the cowling is continued aft for a considerable length, so as to form a good streamline shape. With the cowling in place and the spinner over the propeller boss, the engine nacelles are of very clean outline, broken to a small extent only by the sloping radiators just ahead of the undercarriages. The cooling can be varied by drawing up the trailing edge of the radiators until they lie nearly flush with the bottom of the nacelles, the radiators being hinged at their upper or forward end. Streamline water header tanks are mounted just behind the propeller spinners.
   The main petrol tanks are carried under the floor of the fuselage, and are in the form of three cylindrical tanks enclosed in an aluminium fairing. A small service tank is placed above each engine, slung from the top plane, and windmill-driven pumps force the petrol from the main tanks to the service tanks. The main tanks have a capacity of 192 gallons (64 gallons each) and the service tanks 50 gallons each, giving a total petrol capacity of 292 gallons. The oil tanks, carried in the engine nacelles, have a capacity of just over 9 gallons each.
   The undercarriages are of normal type, i.e., a two-wheeled chassis under each engine. They are, however, of the oleo-pneumatic type with the shock-absorbing gear incorporated in the front undercarriage struts. The diagonal bracing is in the rear panel, while cables run from the wheel hubs to the fuselage and to the second inter-plane strut respectively.
   The main dimensions of the Armstrong-Whitworth "Awana" are indicated on the general arrangement drawings. The empty weight of the machine is 10,000 lbs., and the total loaded weight is 18,450 lbs., so that the ratio of useful load to total weight is very good. The performance figures obtained at Martlesham include the following: Speed at 3,000 ft., 97 m.p.h.; at 6,000 ft., 93-5 m.p.h.; at 8,000 ft., 89 m.p.h. The climb to 3,000 ft. occupies 10 mins. 27 secs., and the corresponding rate of climb is 247 ft./min. at an indicated air speed of 76 m.p.h. For the climb to 6,000 ft. (in 25 mins. 30 secs.), the corresponding figures are 160 ft./min. and 71-5 m.p.h. respectively, while the service ceiling (height at which rate of climb is 100 ft./min.) of 8,000 ft. is reached in 41 mins. 30 secs, at a speed of 69 m.p.h. The estimated absolute ceiling is 11,350 ft.
   Although designed originally as a troop carrier, there does not appear to be any reason why the "Awana" should not be capable of useful work as a commercial passenger carrier. The accommodation would have to be a bit more comfortable, but the machine should carry 20 passengers in comfort at a cruising speed of somewhere around 80 m.p.h.