Landing gear design in an automated design environment

Landing gear design in an automated design environment

Heerens, N.C.

Voskuijl, M. (mentor)
Vos, R. (mentor)

Aerospace Engineering

Aerospace Design, Integration & Operations

2014-03-07

The design of the landing gear is one of the prime aspects of aircraft design. Literature describes the design process thoroughly, however the integration of these design methods within an automated design framework has had little focus in literature. Landing gear design includes different engineering disciplines including structures, weights, kinematics, economics and runway design. Interaction between these different disciplines makes the landing gear a complex system. Automating the design process has shown to have the advantage of increased productivity, better support for design decisions and can provide the capability of collaborative and distributed design. The automation tools improve performance of current designs and simplify the development of new aircraft configurations. In this thesis a systematic and automated landing gear design procedure is proposed. Positioning the landing gear on the aircraft is limited by several requirements. Requirements include take-off stability, touchdown stability, wing-tip and engine clearance, ground handling and stability while taxiing. Evaluation of all these limits results in a feasible design space from which the shortest possible landing gear is found. From the resulting landing gear position, loads on the landing gear struts are calculated. Tyres and wheels are selected and brakes and shock absorbers are designed. The assembly of landing gear components can then be used to make an analytical weight estimation. This analytical weight estimation is based on maximum stresses occurring within the structure due to extreme load cases prescribed in certification specifications. Preventing yielding and buckling within the structure then results in required component thicknesses. A multi-body model is then made, where structural parts are seen as rigid bodies. The multi-body model evaluates and visualises the system dynamics. The oleo-pneumatic shock absorber forces and motion are modelled using an analytical relation. An empirical tyre model models tyre motion and forces at the contact point. These two models can accurately describe forces within the tyres and shocks due to externally applied forces, which then allows for the evaluation of extreme landing load cases. This is done to verify empirically estimated dynamic landing loads used in the weight estimation. And this is done to identify loading peaks that could occur during a landing. In addition to the landing simulation a simulation of the landing gear retraction mechanism is done to check the kinematic feasibility and compliance to certification requirements. Verification of results of the implemented landing gear with reference aircraft shows that landing gear positions closely match with actual landing gear positions. The analytical weight estimation of the landing gear assembly estimates the total gear weight with an error of 15 percent. This is comparable to the result of an empirical weight estimation that has an error of 17 percent. Multi-body simulation results show that dynamic loads during an extreme landing are similar to empirically estimated dynamic loads. For landing gears with multiple rows of tyres it is especially important to look at landing loads, since a hard landing then creates peaks at high frequency in the shock loads. These peaks originate from the interaction between front and rear axle tyres hitting the ground at different times. A kinematic simulation of retraction and extension then verifies the kinematic feasibility. This simulation also shows that the retraction and locking mechanisms work and that it can be stowed within the available space. The resulting landing gear design and analysis tools complete the existing aircraft design tools, which then forms the basis for the future improvement of automated transport aircraft design.

landing gear
aircraft design
structural analysis
class 2.5 weight estimation
component weight estimation
mdo
novel aircraft
initiator
automated design

http://resolver.tudelft.nl/uuid:d3239c8e-a423-4aa1-8752-c977d03d58e1

2014-03-26

Student theses

master thesis

(c) 2014 Heerens, N.C.