Landing gear

About: Landing gear is a research topic. Over the lifetime, 3403 publications have been published within this topic receiving 25370 citations. The topic is also known as: landing gear & gear.

An Empirical Model for Landing Gear Noise Prediction

Abstract: *† ‡ This paper presents an experimental investigation on aircraft landing gear noise. The study consists of systematic testing and data analysis, using the full-scale Boeing 737 landing gear. The database covers a range of mean flow Mach numbers typical of landing conditions for commercial aircraft and various landing gear configurations, ranging from a fully dressed, complete gear to cleaner configurations involving only parts of the complete gear. This enables us to reveal contributions from various groups of the gear assembly and to derive functional dependencies of the radiated noise on the flow Mach number at various far field directivity angles and on various gear geometry parameters. It is shown that the noise spectrum can be decomposed into three frequency components, namely, the low, mid and high frequency components, respectively representing contributions from the wheels, the main struts and the small details such as hoses, wires, cutouts and steps. It is found that these different frequency components have different dependencies on flow parameters and gear geometry. For example, while the low and mid frequency noise scale on the sixth power law with flow Mach number, the high frequency noise follows the eighth power Mach number scaling and has a spectral shape proportional to the inverse square of frequency, indicating the turbulent wake, instead of the unsteady forces on the gear, as the sources of the noise. This is confirmed by phased microphone array measurements, identifying a source distribution in the wake region at high frequencies. Based on the spectral decomposition in the three frequency domains, normalized spectra are derived for all three components in terms of the Strouhal numbers. A model for the Overall Sound Pressure Level (OASPL) is also developed as a function of flow and geometry parameters. For the high frequency noise generated by small features in the landing gear, a detailed description of their numbers, sizes, shapes, locations and orientations is apparently not practical so that a complexity factor is introduced to account for the aggregate effects of all the small details. This complexity factor can be empirically related to aircraft design parameters such as the maximum takeoff or landing weight. Some examples are given to show the accuracy of the empirical model and comparisons with data show very satisfactory results.

An Analysis of a Civil Aircraft Main Gear Shimmy Failure

Abstract: A dynamical model is presented to analyse the stability of motion of the two-wheeled ‘Fokker F.28-like’ landing gear including tyres. The model is equally applicable to similar landing gears. The influence of the introduction of a specially designed torsional damper on the dynamical behaviour of the landing gear-tyre combination is investigated. Results of the stability calculations are supported by test results.

Aircraft landing gear kinetic energy monitor

Abstract: A system for use in monitoring, measuring, computing and displaying the Kinetic Energy generated and experienced while aircraft are executing either normal, overweight or hard landing events. Pressure sensors and motion sensors are mounted in relation to each of the landing gear struts to monitor, measure and record the impact loads and aircraft touch-down vertical velocities experienced by landing gear struts, as the aircraft landing gear initially comes into contact with the ground. Velocity adjustments are made to correct for errors caused by landing gear per-charge pressure and landing gear strut seal friction. The system also measures the landing loads experienced by each landing gear strut during the landing event and determines if aircraft limitations have been exceeded.

Two-stage aircraft landing gear

Abstract: A two-stage aircraft gear. The landing gear includes a cantilever landing gear whose lower end is attached to a trailing arm (or articulated) landing gear. The cantilever gear is a collapsible piston-cylinder assembly, and the trailing arm gear also has a shock absorber connected between a fixed portion of the trailing arm gear and the movable wheel support arm. When landing, the load imposed is first absorbed by the trailing arm landing gear. After the trailing arm gear has been fully compressed, the cantilever gear begins to compress. The cantilever and trailing arm landing gear can be combined to provide the desired performance. The landing gear static position can be designed to be in the static load curve of the first component, allowing the aircraft to be stably supported and yet difficult to overturn.

Control of Noise Sources on Aircraft Landing Gear Bogies

Abstract: The main landing gears of large commercial aircraft are an important contributor to the total aircraft noise during landing approach. Within a European financed research project called SILENCER (“Significantly Lower Community Exposure to Aircraft Noise”) a study in “advanced low noise landing gear design” was performed to develop operational landing gears that take into account aeroacoustic constraints early in the design stage. In full scale tests a good level of noise reductions was achieved relative to the equivalent conventional landing gears. For the main landing gear however, there was evidence that further noise reductions might be achievable by refining the design of the bogie. This paper describes a follow- on study at 0.25 model scale to investigate in detail some of the design parameters that affect the noise of the bogie. The test results show that the distribution of sources on the bogie is sensitive to the detailed design, but that achieving reductions in total noise is not straightforward. Analysis of flow patterns indicated by the noise data and flow visualization does however lead to a number of ways of adapting the design of the gear to provide significant noise control.