Full-scale noise testing on Airbus landing gears in the German Dutch Wind tunnel

Abstract

The acoustic flyover signature of modern aircraft in their approach configuration -i.e. with slats, flaps and gears deployed -are often dominated by airframe noise contributions. To study relevant source and radiation characteristics, airframe noise tests were performed in the German-Dutch Wind Tunnel employing -for the first time ever -full-scale landing gears of an A320 aircraft. Farfield noise characteristics were determined for different gear configurations (starting from the base configuration and subsequently covering ever more gear elements with streamlined fairings) at wind speeds ranging from 40 to 78 m/s. Aerodynamically generated noise from landing gears turnes out to be of broadband nature with constant levels (in 1/3-oct. bands) up to several kHz. One most essential result therefore is that landing gear noise is not at all a "low-frequency phenomenon". Moreover, levels increase with the 6th power of flow velocity. The study indicates that a technically feasible landing gear noise reduction potential of up to 5 EPNdB could be realized through localized component streamlining with fairings and/or by means of appropriate flow spoilers.

ANOPP Landing Gear Noise Prediction Comparisons to Model-Scale Data

“…The levels decrease by about 5-6 dB between the upstream and downstream polar angles for basically all azimuthal angles. This is consistent with the full-scale landing gear measurements of Dobrzynski et al 6 . Both the Fink and Guo methods predict this trend along the flight path ( ! "…”

“…Interest in landing gear noise subsided in the 1980's, but has gained increased interest since the late 1990's with the experimental work of Dobrzynski et al 6,7,8 , Michel et al 9 , Jaeger, et al 10 , Horne et al 11 , Stoker et al 12 , Humphreys et al 13 and the advanced modeling work of Smith et al 14 , Molin et al 15 , Guo 16,17,18 and computational aeraocoustic methods of Hedges et al 19 , Seror et al 20 , and Lockard et al 21 The experimental work has provided much needed data to advance the understanding of the noise generation mechanisms and to characterize the directivity of the radiated noise leading to the improvement and validation of prediction capabilities. The computational aeroacoustic methods are still too inefficient (although much progress has been made) to be included in a system capability such as ANOPP.…”

Comparing flyover noise measurements to full-scale nose landing gear wind tunnel experiments for regional aircraft

“…To obtain a better understanding of the actual noise emissions of LG systems, wind-tunnel [12,[14][15][16][17] and aircraft flyover experiments [4,9] are typically performed. Whereas the first case offers more controlled flow conditions, it requires the LG model being tested to have a high level of geometric detail to represent the small-scale sound generating mechanisms of the gear [4,5] and it is difficult to replicate the exact conditions present at an aircraft in flight.…”

Noise Characterization of a Full-Scale Nose Landing Gear

“…As noted repeatedly in previous test campaigns, although the actual flow velocity just upstream of the MLG can be 20% lower than the freestream velocity due to installation effects and circulation resulting from lift and its location under the wing [7,27], the NLG is exposed to higher velocities than that of the freestream due to the acceleration under the nose. A significant differentiator between this test campaign and previous ones is that the relative velocity and flowfield at the NLG is accurate relative to the freestream velocity.…”

“…Seminal studies in the 1970s provided initial insight [6], with later campaigns, enabled by the availability of larger test facilities, showing that full-scale and more detailed models are required to capture the high-frequency contribution of small components [7,8], which hitherto had been thought to be unimportant. Results from such tests indicate that landing gear, for the most part, generates broadband noise caused by the interaction of the landing gear with turbulent flow.…”