AS FAST AS SOUND

Gisborne Herald, Volume LXVI, Issue 20016, 15 August 1939, Page 3

AS FAST AS SOUND

TESTS IN WIND TUNNEL SECIJET. I-'KIIITEKS LONDON, July 1. Air Ministry tests to be made in the wind tunnel now under construction at the National Physical Laboratory, Teddington, may result in R.A.F. fighter planes capable of 700 miles an hour, or nearly as fast as sound. The R.A.F.'s Spitfire lighters have reached 3G7 miles an hour in official service trials and between 520 and 550 miles an hour in dives.

An official at the laboratory said -to n press representative:—

“Engine improvements have made possible aircraft speeds of more than 000 miles an hour, if we can reduce air drag.

“I may not disclose the Air Ministry’s secret of the fastest R.A.F. planets speed, but it is far more than the published figure of about *SOO an hour.

“The super-fast planes of the future will be of metal specially treated to prevent skin friction. With tests in the new air tunnel we hope to reduce this friction by 00 to 70 per cent. Air Compression “Speeds approaching 700 miles an hour will then be within practical reach. The speed of sound is 750 miles an hour at sea-level and 700 at higher altitudes. ; “When approaching the speed of sound we meet the difficulty of air compression. “Up to 500 miles an hour the air is pushed aside by the moving object, but as the 700 miles an hour mark is approached air compression and air shocks take place.

“The air is compressed by the wings and body of the plane. The resisting pressure is suddenly increased as much as 20 limes.

“In the new tunnel wc shall have a rectangular model, plane 20in. by Bin., equipped with special photographic apparatus. We shall study from the exposed plates exactly what happens at this speed.”