This paper describes the phenomenon of stall and surge in an axial flow aeroengine using fast response static pressure measurements from the compressor of a Rolls-Royce VIPER engine. It details the growth of flow instability at various speeds, from a small zone of stalled fluid involving only a few blades into the violent surge motion of the entire machine.

Various observations from earlier theoretical and compressor rig results are confirmed by these new engine measurements. The main findings are as follows:

1. The point of stall inception moves rearwards as engine speed increases, and is shown to be simply related to the axial matching of the compressor.

2. The final unstable operation of the machine can be divided into rotating stall at low speed and surge or multiple surge at high speed.

3. The inception process is independent of whether the final unstable operation is rotating stall or multiple surge.

4. Stall/surge always starts as a circumferentially small flow disturbance, rotating around the annulus at some fraction of rotor speed.

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