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Aviation History
1952
1952 - 0405.PDF
FLIGHT, 15 February 1952 181 Semi-submersible Seaplane A British " Water-walking" Design of 1912 By JOHN W. R. TAYLOR REFERENCES to the 1929 Piaggio P.7 Schneider Trophy seaplane, in Flight of February 1st, call to mind a most interesting series of aircraft on compar able lines. They were built by the British and Colonial (Bristol) Aeroplane Company some 17 years earlier than the time of the Italian experiment. These seaplanes, known simply, and mysteriously as the X.i, X.2 and X.3, were projected by Sir Dennistoun Burney, inventor of the paravane, and, as originally conceived, they foreshadowed not only the Piaggio P.7 but also the submarine-based ParnaU Peto and the Focke-Achgelis Fa330 rota-kite. In 1912, Sir Dennistoun (then Lt. C. D. Burney, R.N.) appreci ated the major role that submarines would play in any future war. Having made a number of oversea flights in a Bristol Box-kite fitted with flotation bags, he also realized that aeroplanes would one day be reliable and powerful enough to search out and destroy submarines and, conversely, to help them find their prey. So he set to work designing an aeroplane that could be carried aboard a submarine, assembled quickly and flown off the water to provide, in effect, an airborne periscope. Such requirements would be difficult enough to meet today, and it is not hard to imagine how insoluble they must have seemed in the stick-and- string pioneer days. Nevertheless, Sir Dennistoun completed his design, and approached Bristols on the question of getting it built. They must have been somewhat startled, for the original con cept was for a collapsible seaplane made entirely of rubberized fabric, which could be stowed in a small compartment on a sub marine and inflated only when required for action. Nor was that all, for instead of wheels, skids or floats, it was to have three stalky legs, carrying a marine propeller and series of hydrofoils. The idea was that, after being inflated, the aircraft would be lowered over the side into the water, like the later Piaggio P.7. Then, for take-off, the pilot would start his engine and engage the marine propeller only. This would cause the aircraft to move forward and, at the same time, begin to lift its hull clear of the water by "stepping up" from one hydrofoil to the next. When he reached high speed and the bottom step, the pilot was supposed to engage the airscrew and take off. It was wisely decided to try out one idea at a time, so the Bristol- Towed behind a destroyer, the X.2 takes the air—but not for long. built prototypes were intended to test the "hydroped" water undercarriage only, and were of normal construction. They were, in fact, the first Bristol designs by Frank Barnwell. The X.i was fitted with a Canton-Unne engine of either 80 or noh.p.; but it never left the water, as towing trials behind a destroyer showed that it was unstable at moderate speeds. In addition, the light streamline fairings behind the tubular hydroped legs were torn off by water drag. To put things right, the aircraft was provided next with a water elevator and stronger hydroped undercarriage, with reduced hydrovane area. At the same time, the engine was replaced by 500 lb of ballast, and the design was renamed the X.2. It achieved a measure of success on September 21st, 1912, for, while being towed dead into wind at 12 knots, it rose from the water and became airborne at the end of its-tow-rope like a kite. Unfortunately, it then proceeded to do what almost any other self-respecting kite would have done in the circumstances : it stalled, and side-slipped into the water. . Heartened by this moderate success, Bristols at once set to work on the X.3, an improved version with more powerful engine, ailerons instead of wing warping, and redesigned hydroped, with contra-rotating marine propellers mounted back to back on a cen tral strut to improve stability. This aircraft also achieved some success; but by then Short and Sopwith seaplanes and the Sopwith Bat Boat had demonstrated much simpler and more satisfactory approaches to the whole problem of sea-flying, and the Burney conception went the way of so many other ingenious designs. Like the Piaggio of 1929, the Bristol X.3 (upper right) looked oddly like a half-awash wreck when stationary. Above is a close-up view of the hydrofoils on the undercarriage, and at right, below, is Ve complete machine. Note the corresponding set of hydrofoils under the tail, and the marine propeller with its vertical-shaft drive.
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