The Drag of Airplane Wheels, Wheel Fairings, and Landing Gears: III

The tests reported in this paper conclude the investigation of landing-gear drag that has been carried out in the N. A. C. A. 20-foot wind tunnel. They supplement earlier tests (reported in Technical Report No. 485) made with full-scale dummy wheels, wheel fairings, and landing gears intended for airplanes of 3,000 pounds gross weight and include tests of tail wheels and tail skids.

For airplanes of this weight classification the results indicate that the drag of a landing gear having slight wheel-strut interference will be materially less when equipped with the proper size of streamline wheels than when furnished with low-pressure wheels. The drag of a cantilever landing gear is as low when equipped with the proper size of streamline wheels as when equipped with low-pressure wheels and the best type of wheel fairing.

Two of the landing gears tested combine, to a high degree, the structural advantages of the tripod types with the low drag of the full cantilever types.

The drag of a conventional tripod landing gear with streamline wheels can be reduced about 39 percent by careful fairing of all strut intersections.

Expanding fillets are useful in reducing landing-gear drag, especially on landing gears that are attached to wings.

The drags of tail-wheel units and tail skids are, even in the worst case almost negligible.