DIVING AT 400M.P.H.

Otago Daily Times, Issue 22068, 26 September 1933, Page 14

DIVING AT 400M.P.H.

AN" UNUSUAL ENGINE TEST ! (From Our Own Correspondent.) LONDON, August 18. Modern British fighting aeroplanes go through, in the course of flying trials, what is known as the terminal velocity dive. In this evolution, which imposes extremely high stresses on the structure and is not yet included in the routine testing of the war planes of any other nation, the machine is dived vertically until it reaches its ultimate diving velocity—the speed at which the resistance offered by the falling body makes further acceleration impossible. Some of the newer types of British single-seater fighter have attained speeds much in excess of. 400 miles an hour in terminal velocity dives. . „ .

During the dive the engine speed increases far beyond the normal rates of revolution, up to. as much as 30 per cent, higher than the rate officially approved in level flight. The dynamic loadings and other stresses on vital components go up by approximately 70 per cent. Plainly, ample margin of strength is needed in an engine which may be asked to withstand the strain of terminal velocity diving. And because the safety margin can be satisfactorily tested only in actual running, the Bristol company put their latest fighter type engine; the " Mercury ■""V-5.2 unit, through trials simulating the conditions met'in the dive. On completion of the usual official type tests the engine was submitted to supplementary high-speed tests consisting in one hour's running at a speed 20 per cent, higher than the normal rate, followed by a 10 minutes' burst at 30 per cent, excess. The test went through without incident; when the motor was subsequently taken to pieces and examined, no appreciable detrimental effect of the abnormally high-speed running was revealed.