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Author Greenwood, Fredric H. Schmitz Eric ♦ Gopalan, Richard D. Sickenberger Gaurav ♦ Conner, David ♦ Decker, William A.
Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword U.s. Army Aeroflightdynamics Directorate ♦ Noise Source ♦ Linear Ground Array ♦ Special Acoustic Flight Test Program ♦ Special Instrumentation ♦ Helicopter Performance State ♦ Helicopter Longitudinal Tip-path-plane ♦ Direct Measurement ♦ Dynamic Maneuver ♦ Differential Global Positioning System ♦ Acoustic Benefit ♦ Specific Noise Source ♦ Inertial Navigation Unit ♦ High Quality ♦ Acoustic Data ♦ Important Noise ♦ In-flight Microphone Boom Array ♦ Special Care ♦ Flight Path ♦ Flight Track Easier ♦ Simultaneous Acoustic Measurement ♦ Low Wind ♦ Accelerated Segment ♦ Precise Operating Condition ♦ First Time ♦ Pursuit Guidance Display ♦ Ground Noise Measurement ♦ Flight Segment ♦ Descending Segment
Abstract A special acoustic flight test program was performed on the Bell 206B helicopter outfitted with an in-flight microphone boom/array attached to the helicopter while simultaneous acoustic measurements were made using a linear ground array of microphones arranged to be perpendicular to the flight path. Air and ground noise measurements were made in steady-state longitudinal and steady turning flight, and during selected dynamic maneuvers. Special instrumentation, including direct measurement of the helicopter’s longitudinal tip-path-plane (TPP) angle, Differential Global Positioning System (DGPS) and Inertial Navigation Unit (INU) measurements, and a pursuit guidance display were used to measure important noise controlling parameters and to make the task of flying precise operating conditions and flight track easier for the pilot. Special care was also made to test only in very low winds. The resulting acoustic data is of relatively high quality and shows the value of carefully monitoring and controlling the helicopter’s performance state. This paper has shown experimentally, that microphones close to the helicopter can be used to estimate the specific noise sources that radiate to the far field – if the microphones are positioned correctly relative to the noise source. Directivity patterns for steady, turning flight were also developed, for the first time, and connected to the turning performance of the helicopter. Some of the acoustic benefits of combining normally separated flight segments (i.e. an accelerated segment and a descending segment) were also demonstrated.
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study
Learning Resource Type Article