Experimental methods for determining dynamic characteristics of aircraft landing gear

DOI: 10.34759/vst-2019-4-66-80

Аuthors

Kolyshev E. S.^*, Krapivko A. V.^**

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia

*e-mail: eskolyshev@gmail.com
**e-mail: a_krapivko@tsagi.ru

Abstract

The article describes methods and algorithms for determining the fundamental eigen modes of landing gear, such as torsion, lateral and longitudinal bending of support, according to the amplitude-phase frequency characteristics measured at characteristic points of the structure. Resonant frequencies, shapes and decrements of vibrations are determined using transfer functions (dynamic compliance and dynamic stiffness). A typical accelerometers arrangement of a system for oscillations registering and arrangement of vibration exciters are given. The described methods for obtaining dynamic characteristics were developed based on the long experience in landing gears GVT of various aircraft.

The novelty in landing gear GVT is marked:

1. Moveable carriages with vibration exciter mounted on them, which are equipped with special connecting devices for attaching rods to the axis of wheels. The rods are equipped with forces sensors transmitted to the structure, in order to eliminate the excitation system effect.

2. The GVT is performed for the landing gear both in a free state and at various vertical loads on supports created from action of the aircraft mass by hydraulic lifts.

3. The applied shock method application on landing gear to obtain amplitude-phase frequency characteristics at the selected points of structure according to the results of response functions processing. This method allows giving an operational evaluation of the landing gear resonant characteristics and speed up the ground frequency testing procedure.

4. The GVT results processing is performed using transfer functions of dynamic compliance and dynamic stiffness of landing gear strut for bending and torsion and their cross links.

5. To determine hydraulic lifts effect on landing gear dynamic characteristics, the GVT in a free state is performed in cases when the aircraft is installed on the standard hydraulic lifts and when the aircraft is installed on pneumatic supports.

Keywords:

landing gear, shimmy, resonance characteristics, ground vibration testing, frequency response characteristics, transfer functions

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