A Critical Study of Spin-Up Drag Loads on Aircraft Landing Gears

Author: Brown, John R.

Year: 1949

Degree: Engineer's thesis

Advisors: Sechler, Ernest Edwin; Hudson, Donald E.

Committee Member: Unknown, Unknown

Option: Aeronautics

DOI: 10.7907/PDPG-ET80

Abstract

This report attempts to analyze in detail the spin-up drag loads imposed upon an aircraft main landing gear. Other factors in the landing gear problem are ignored except insofar as they affect this one type of loading. As an instrument for study, one model of aircraft was chosen for which extensive flight test and drop test data were available.

The main parameters which enter into the spin-up drag load are the landing weight of the aircraft, the rate of descent at contact, the ground speed, the time interval from initial contact to attainment of maximum vertical load, and the coefficient of friction between the tire and the runway surface. Minor parameters which may affect the drag load are the tire pressure, moment of inertia of the rolling stock, oleo pressure, and quantity of oil in the hydraulic shock absorber.

The results of this study indicate that the maximum gear drag load is primarily a function of the time required to reach maximum vertical load, and that further study of this parameter, using drop test data for several types of aircraft, might well lead to some valuable empirical information essential to landing gear design. The value of the coefficient of friction was seen to vary widely in test landings but a maximum value of 0.55 appears to be satisfactory for limit design calculations.

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