PT6A surging

[islandguy]

Compressor stall?

There were no audible sounds coming from the engine like those you hear with compressor stalls. Is it possible to have a compressor stall with virtually no noticable sound?

You reckon the bleed valve at the P2.5 station is sticking closed at the high power settings of cruise, then failing to open properly at reduced power settings like this occasion on approach?

Thanks for the info!