Rotorcraft Noise Abatement Procedures Development

Open Access
Author:
Villafana, Willca
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
August 31, 2016
Committee Members:
  • Kenneth S. Brentner, Thesis Advisor
  • Joseph F. Horn, Committee Member
  • George A. Lesieutre, Committee Member
Keywords:
  • aeroacoustics
  • helicopter
  • rotor noise
  • simulation
  • modeling
Abstract:
A rotorcraft noise prediction system has recently been developed as part of a project to develop and evaluate helicopter noise abatement procedures for a range of aircraft. The aim of this thesis is to demonstrate the noise prediction system capabilities and then consider simple noise abatement procedures for three different helicopters of varying technology levels and maximum gross weights. First, the codes that have been assembled into the noise prediction system are described. A brief presentation of acoustic theory on which the noise prediction is based is given as a reminder. Then, the noise prediction system has been validated with the Bell 430 helicopter flying in a level forward flight. The prediction system has also demonstrated its capacity to predict blade vortex interaction (BVI) noise and BVI noise reduction. Finally several abatement procedures have been examined. The two first ones underscored the benefits of flying higher and slower by using the S-76C+ as an example. Then, a S-76C+, Bell 430 and BK 117 helicopters were compared in a level forward flight. The comparison ended up with surprising results about loading and broadband noise since they do not appear correlated to the weight of the rotorcrafts. Yet, thickness noise results are expected since they are related to the rotor tip speeds. Finally, the effects of descent angle and speed on BVI noise have been demonstrated during approach. A Bell 430 helicopter was used for this study and the speed and angle of descent were varied separately while keeping all the other parameters constant.