Abstract
This paper deals with current design and production practice in regard to aeroplane undercarriages, in particular the shock absorber element. While there are numerous types of shock absorber (steel or rubber springs., compressed air, etc.), disposed on aircraft in numerous ways (twin-leg undercarriages, undercarriages with two or more wheels, articulated units, nose wheels, tail wheels, etc.), the paper deals specifically with the more or less “classic” solution—a single telescopic leg with a single wheel mounted in cantilever.
The methods of determining the capacity of the shock absorber and the required stroke are given, as well as details of methods of calculating telescopic friction, and the determination of “overlap”. Sufficient information is given on methods of stressing to enable a competent engineer to produce a design of adequate strength.
The various main known types of shock absorber are illustrated, and the relative advantages of each discussed from the points of view of length, rebound control, orifice control, and methods of mounting the shock absorber in the actual undercarriage.
The paper also gives: load deflexion curves with details of good practice on compression ratios, etc.; curves of performance obtained on actual drop test, illustrating what can be achieved in the way of energy absorption efficiency; and methods of effecting orifice regulation and the calculation of the size of the various orifices by an approximate formula.
Current practice in relation to glands or seals is discussed, and the paper concludes with a description of a modern undercarriage assembly, and its testing.
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