The Drag of Airplane Wheels, Wheel Fairings, and Landing Gears II: Nonretractable and Partly Retractable Landing Gears

This is the second paper giving the results obtained in the N. A. C. A. 20-foot wind tunnel on the drag due to landing gears. The first paper presented the results of tests made with full-scale models of wheels, wheel fairings, and landing gears intended for airplanes of approximately 8,000 pounds weight. The present report gives the results of tests of nonretractable and partly retractable landing gears intended for heavier low-wing monoplanes of the transport and bomber type.

The tests were made on 1|2.8-scale models of gears with a capacity of 16,000 pounds total weight. The landing gears were mounted on a wing of a 5-foot chord, 15-foot span, and thickness of 20 percent of the chord. The effect of a radical-engine nacelle mounted in the leading edge of the wing on the drag of the landing gears was also investigated. Propeller tests were made in conjunction with several types of landing gears in order to ascertain the effect of the landing gears on the propeller characteristics.

The tests indicated that in general, the presence of the engine nacelle did not appreciably affect the drag due to the landing gears. The retractable landing gears were at least one-half retracted into the wing or fairing before the drag became less than that due to the best nonretractable landing gears. Landing gears that were partly retracted into a nacelle near the maximum section or into the wing near the leading edge had a much higher drag than landing gears that were partly retracted farther aft on the wing. The drag due to the streamline wheels used on partly retracted landing gears was less than that for low-pressure wheels. Landing gears that were partly or fully retracted into streamline fairings below the wing had only slightly greater drag than those that were partly retracted in the wing or nacelle. The propulsive efficiency was reduced from 1 to 3 percent by the presence of landing gears tested in conjunction with the propeller.