Steady state and dynamic data were acquired in a T55-L-712 compressor rig. In addition, a T55-L-712 engine was instrumented and similar data were acquired. Rig and engine stall/surge data were analyzed using modal techniques. This paper compares rig and engine preliminary results for the ground idle (approximately 60% of design speed) point. The results of these analyses indicate both rig and engine dynamic events are preceded by indications of traveling wave energy in front of the compressor face. For both rig and engine, the traveling wave energy contains broad band energy with some prominent narrow peaks and, white the events are similar in many ways, some noticeable differences exist between the results of the analyses of rig data and engine data.

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