Recent developments at the numerical simulation of landing gear dynamics

Abstract

Aircraft landing gears support the aircraft during ground operations, including take-off, landing impact, taxiing, gate handling and maintenance. Mostly for reasons of minimum mass and ground clearance, landing gears are slender structures which exhibit a considerable dynamic response to ground load excitations. As the landing gear is one of the few systems on the aircraft without redundancies, the knowledge of landing gear dynamics is crucial for aircraft design and aircraft safety. Simulation of landing gear dynamics is a cornerstone of aircraft loads analysis, as well for vertical loads resulting from touch-down as for longitudinal and lateral loads resulting from braking, steering and towing. Another important field of interest is landing gear vibrations like gear walk and shimmy. Those phenomena can be brake induced or result from tire spin-up at touchdown or simply from a coupling of dynamics of the running tire and structural mechanics of the landing gear leg. All those effects strongly depend on a number of parameters such as aircraft speed, landing gear vertical deflection, tire pressure and wear of the parts. Many of those parameters can only be estimated and might change during the operation of the aircraft. Numerical investigation is thus a challenging task. Analysis methods exist both in the frequency domain and in the time domain. As stability analysis is straight forward in frequency domain methods, this approach is still often used. However, in many cases nonlinearities are dominant which lead to limit-cycle characteristics of the vibrations. Here, multibody modelling or a mixture of multibody and finite element modelling including time domain simulation is used. In the article, a general outline is given of how vibration problems in landing gears can be treated by numerical analysis methods. The article will start with a classification of typical problems, give a short overview of classical papers, and explain typical approaches. In addition, alternative approaches for stability analysis and for the detection of limit-cycle oscillations as well as state-ofthe-art modelling approaches will be presented.

Efficient Driving Plan and Validation of Aircraft NLG Emergency Extension System via Mixture of Reliability Models and Test Bench

“…Landing gear is one of the key systems in aircrafts, which are used in take-off, landing and ground operation [1][2][3][4]. The landing gear of civil aircrafts includes both normal retractable system and emergency extension system.…”

Investigation on the effect of coulomb friction on nose landing gear shimmy

“…Analytical models, which are prevalent in the literature (Esmailzadeh and Farzaneh, 1999; Sura and Suryanarayan, 2007; Thota et al., 2008; Howcroft et al., 2013; Kewley et al., 2016), are frequently handled using numerical continuation or time integration. Multi-body dynamic (MBD) simulation (Khapane, 2003, 2006; Gualdi et al., 2008; Krüger and Morandini, 2011; Krason and Malachowski, 2015) is another versatile tactic to obtain the time response of dynamic systems. The MBD model is assembled in a modular manner and it can be modified without the necessity to manually update equations of motion.…”

“…The MBD model is assembled in a modular manner and it can be modified without the necessity to manually update equations of motion. Other methods also employed in shimmy studies include quasi-linear analysis (Krüger and Morandini, 2011), describing functions (Burton, 1981), multiple timescales (Gordon, 2002), and harmonic balance (Zhou and Zhang, 2005; Padmanabhan and Dowell, 2015).…”

Taxiing stability verification and airworthiness certification for amphibious aircraft

“…Previous studies on the overall layout and taxiing stability of amphibious aircraft landing gear are relatively rare. In [2][3][4], a numerical simulation is the main approach to taxiing stability.…”

“…If the nose wheels are completely free (or the steering system is inactive) and only a restoring torque of the main wheels occurs, the taxiing direction of the aircraft becomes stable. In contrast, when the damping of the nose wheels is too large, the aircraft becomes prone to losing its directional stability, as described in [3].…”