ALL-METAI AIRCRAFT.

Hawera Star, Volume XLV, 2 May 1925, Page 14

ALL-METAI AIRCRAFT.

DEVELOPMENTS IN GREAT BRITAIN. The development of an all-metal aircraft —that is to say, aeroplanes and seaplanes made entirely of duralumin and other light alloys —is making steady progress in Great Britain. The leading European expert on this .subject, Dr. Rohrbaeh, recently gave the Royal Aeronautical Society in London a lecture- descriptive of his experiments with machines of this construction.

The type to which chief reference was made is a large twin-engined monoplane with a high, wing loading for which the designer claims many advantages. In addition to the usual living boat hull, side floats are fitted, these add considerably to the stability of the boat on the water; it will stand up to quite a rough sea and a high wind. With two Rolls-Royce Eagle engines, the maximum speed is about 120 m.p.h. In still air the machine takes off from the water in twentyseven seconds.

Duralumin, of which these aircraft are made throughout, is non-rusting alloy which combines much, of the lightness of aluminium with the strength and toughness of steel. Even for covering the wings and fuselage, thin duralumin plates are used in place of fabric. The metal needs no dope, paint or' other treatment, yet is proof against any climatic, conditions; in fact, the design of the machine would probably be obsolete before its structure showed any signs of wear or deterioration. Size for size, all-metal machines are lighter than the ordinary type, and, in quantities, cheaper to build. They have a higher wing loading, and consequently a better speed and general performance. In the discussion following the lecture, Flight-Lieut. Lucking, R.A.F., described tests with any ordinary wood-and-fabric seaplane to determine how far its structure was water-proof. An 18,000 lb. machine, after a day or two at anchor in harbour, was found to have gained no less than 600 lb. in weight, and this after all leaks had been accounted for and carefully drained out. That is a heavy handicap, and one which metal construction almost entirely eliminates. The wings of the’' monoplane described by Dr. Rohrbaeh are constructed on the cantilever principle, and the leading and trailing edges, i.e., the extreme front and rear poivtioii of the wings, are detachable. The strength of their .construction was well illustrated when, during trials at Copenhagen, sixteen men walked on them without doing any damage. The ingenuity of the danger is strikingly evidenced by the detail sVtShould one engine fail, the pilot can set the tail fin so as to counteract the uneven pull exercised by the remaining engine, and remain in the air.

At the lecture Dr. Rohrbaeh, who worked on the design of the earlier Zeppelins and was largely responsible for that of the famous Gotha bombers, showed slides and cinema films of his all-metal flying boats on test at Copenhagen." An interior view of the hull revealed the portholes and other accoutrements of a comfortable cabin cruiser. There was an excusable murmur of amusement at several views of the flying boat with masts and sails rigged, * and evidently making good headway in a rough sea. The lecturer stated "that she performed excellently as a yacht, even against the wind, and could* make over four knots with the gear shown, while a much larger area of canvas could be fitted. This is, of course, an important advantage in case of complete engine failure at sea.