Noise Characterization of a Full-Scale Nose Landing Gear

Abstract

This paper presents experimental results from a nose landing-gear test campaign. A highly detailed model of the nose section of a 90-seat configuration green regional aircraft concept was built and tested in an aeroacoustic open-jet wind tunnel at full scale. All of the landing-gear components, fixtures, and small details and associated structures such as the complete wheel bay, bay doors, and hydraulic dressings were included at full scale. This paper focuses on one element of the testing: that of component noise assessment. The dressings, wheels, torque link, steering pinion, bay doors, and then the main strut and drag stay were removed in succession, and an acoustic evaluation was performed at a range of velocities from M 0.12 to M 0.19. In addition, hub caps were installed on the wheels, and their performance as a low-noise treatment is presented and assessed for efficacy. The landing gear, doors, and bay generated most noise in the frequency range between 120 and 400 Hz, but appreciable noise above the baseline was measured up to 10 kHz. The low-to midfrequency aerodynamic noise was found to scale with V 6 , as usual; however, the spectra at high frequencies collapsed perfectly when scaled to V 7 , confirming the fact that high-frequency noise is radiated from the turbulent flow surrounding small features. The total noise output of the landing-gear assembly differs from that of the sum of the components in isolation due to installation effects. The research in this paper studied these effects and the influence of the components on each other.

Multi-Approach Study of Nose Landing Gear Noise

“…All the spectra are mostly broadband above 600 Hz. The low frequency tonal content of these spectra does not scale, and is the subject of different studies [19,28] which examine the tonal contribution of the wheel bay and LG components in that frequency range. Referring again to Fig.…”

“…Curle's theory only holds true when the sound sources are compact, i.e., the relationship is true only when the geometric size of the sound source is small when compared to the acoustic wavelength. Guo et al [81] and Bennett et al [28] demonstrated that this assumption is no longer valid for the small details in the landing gear, such as dressings, small details, rods, fixtures, etc.…”

“…A detailed representation is especially essential for cavity noise, which can be a dominant noise source, like in the case of the Airbus A320 fuel overpressure vents [5]. In this paper, wind tunnel measurements [24,28] of the full-scale, high fidelity NLG model within the ALLEGRA project are considered. The model includes the wheel bay, doors, fairings and a large portion of the nose fuselage all of which set the campaign apart compared to previous tests.…”

Implementation of tonal cavity noise estimations in landing gear noise prediction models

“…Several studies have investigated the noise levels generated by the LG system using wind-tunnel experiments [24,27,[31][32][33][34][35], aircraft flyover measurements [13,21,[36][37][38] and computational simulations [39][40][41][42]. Multi-approach studies [30,43] showed that all these three methods have their respective benefits and disadvantages, and that hybrid investigations combining two or more approaches can offer an improved solution.…”

Landing gear interwheel tonal noise characterization with the Boundary Element Method

“…These tones can be due to the landing gear bay itself [7,8], vortex shedding from cylindrical subcomponents of the landing gear, or resonances in the wheels cavities. The latter case is illustrated by the LAGOON experimental campaign led by Manoha et al in 2008 [9] who showed that two strong tones took place due to the excitation of the facing wheels cavities, and later by Bennett et al [10] on the ALLEGRA nose landing gear. This phenomenon has been thoroughly investigated with a dedicated LBM study by Casalino et al [11] in the case of the LAGOON geometry.…”