Quiet, Please

Almost every U.S. town wants an airfield of its own. But when the local Chamber of Commerce or the American Legion post tries to establish one, prospective neighbors complain bitterly and point to some other part of town. Better no airport at all than one so close that plane noises will panic the chickens and disturb folks' sleep.

Well aware of this understandable resistance to progress, NACA (National Advisory Committee for Aeronautics) regards it as a serious obstacle to the development of aviation, and in particular of amateur flying. Last week NACA offered a solution: a comparatively silent airplane. As it went through its muffled paces at Langley Field, Va., 170 assorted airmen listened with nods of approval.

First a conventional Army liaison plane flew across the field at 300 feet, roaring like an elevated train. Then followed the same type of plane, with an improvement. The sound it made was like wind in the willows. A muffler and a special propeller had reduced the plane's "noise pressure" 90%.

Only a small part of a plane's noise comes from the engine exhaust. Up to 95% comes from the propeller, whose fast-moving tips stir up racketing sound waves. To eliminate the waves, NACA designed a five-bladed prop, which looks like a five-petaled flower. It gives plenty of push when driven (through reduction gears) at a comparatively slow 1,000 r.p.m. The broad, leisurely blades do their work in near silence.

NACA says that its quiet prop is more efficient than faster, noisy propellers. (The plane equipped with it flew 5 m.p.h. faster.) NACA hopes that airplane manufacturers will adopt the design, and thus make small airfields acceptable in nicer and fussier neighborhoods. It even hints darkly of legislation making the quiet prop mandatory.

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