HIGH-SPEED BRAKING OF AN AIRCRAFT TIRE ON GROOVED SURFACES.

The Federal Aviation Administration is engaged in an experimental program to determine the effectiveness of grooves and other low-cost surface treatments that alleviate hydroplaning. A ground test facility provides speeds of up to 150 knots by the use of a jet-powered pusher car that also supports a tire-wheel assembly. The tires of a Boeing 727 aircraft are inflated to 140 psi and loaded vertically to 35,000 lb. The tire-runway braking is measured by the use of proper instrumentation. High-speed braking tests show that low-cost surface treatment can be provided in two ways: 1) by increasing the spacing of the square saw-cut grooves beyond 1 1/4 in. , and 2) by installing V-shaped grooves using a reflex-percussive cutting process. In both cases, the braking effectiveness of an aircraft tire was found to be 'acceptable' and hydroplaning was not experienced at speeds of up to 150 knots.