What was found
(CAN) WHILE HOVERING IN FIRE SUPPRESSION ACTIVITY, THE PILOT REPORTED A COMPRESSOR STALL/SURGE FOLLOWED BY POWER LOSS FORCING AN UNSCHEDULED LANDING. SUBSEQUENT INVESTIGATION REVEALED POWER TURBINE FAILURE. CONTRIBUTING FACTORS TO THE STALL/SURGE MAY HAVE BEEN A DIRTY COMPRESSOR (SMOKE INGESTION) AND/OR THE FCU WAS SENT TO HONEYWELL AND REPORT NR 86304 FOUND THE FCU TO BE FAILING SEVERAL SCHEDULING PARAMETERS.