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

Abstract

The emergence extension system (a mechanical system) of nose landing gear (NLG) seriously influences the reliability, safety and airworthiness of civil aircrafts. To efficiently realize the NLG emergence extension, a promising driving plan of emergence extension is proposed in respect of the reliability sensitivity analyses with a mixture of models. The working principle, fault tree analysis and four reliability models are firstly discussed for NLG emergence extension. In respect of the mixture of models, the reliability sensitivity analyses of emergence extension are then performed under different flight speeds (270 Kts, 250 Kts, 220 Kts, and 180 Kts). We find dimpling torque and aerodynamic torques of forward and after doors are the top three failure factors and the start reliability is the most in emergence extension failures. Regarding the results, feasible driving plans of NLG emergence extension are developed by adjusting the aerodynamic torque of NLG forward door, and are validated by the aerodynamic torque experiment of forward door with regard to strut rotational angle under the flight speed 270 Kts. It is indicated that (1) the adverse torque generated by the new driving mechanism obviously reduces by about 24.8% from 1462.8 N·m to 1099.6 N·m, and the transmission ratio of aerodynamic torque (force) is greatly improved when the NLG strut is lowered near to 100 • ; (2) under different flight speeds (180 Kts, 220 Kts, 250 Kts, and 270 Kts), the new driving mechanism realizes the lower tasks of emergence extension which cannot be completed by the initial driving mechanism; and (3) the lowering time of the new driving mechanism shortens with the increasing flight speed. The proposed new driving mechanism is verified to be reliable for emergence extension of aircraft NLG besides normal extension and to be a promising feasible driving plan with high lowering reliability. The efforts of the paper provide an efficient driving mechanism for the design of NLG in civil and military aircrafts.

Research on the Performance of an Aircraft Landing Gear Hook Lock Based on Bifurcation Analysis

“…Subsequently, as M decreases, the system moves to position 4 instead of returning by the original path. This suggests that position 4 is the stable equilibrium point of the locked state. The value of θ 1 corresponding to this position is denoted by θ c 1 representing the locking ability of the hook lock mechanism.…”

“…Then, as F Unlock decreases, the system moves back to position 1 . Notably, each component of the lock will suffer interference in positions 1 and 4 . Actually, in the abrupt locking and unlocking processes, the lock will be limited by a stop block to prevent interference.…”

“…The main failure modes include the locking failure, unlocking failure, and automatic unlocking of landing gear. Thus, the rational design of landing gear lock mechanisms and the analysis of locking performance are critical to the safe and reliable operation of the landing gear retraction system [4].…”

Decomposed-Coordinated Framework With Enhanced Extremum Kriging for Multicomponent Dynamic Probabilistic Failure Analyses

“…and distribution types, are determined by the extremum selection method [44]. In respect of engineering practices [19], the random variables are considered to be normal distribution, for reducing the complexity of analysis [45], [46]. The distribution features of all random inputs are listed in Table 1.…”

Advances in Mechanical Systems Dynamics

“…The third paper [34] addresses the problem of the emergency extension of nose landing gear. An interesting combination of mechanism analysis methods and statistical methods for reliability analysis is presented.…”