What was found
WHILE HOVERING FOR TAKEOFF A LOUD BANG CAME FOR THE ENGINE COMPARTMENT FOLLOWED BY A TORQUE FLUCTUATION AND A RIGHT YAW. CHECKED ALL THE SYSTEMS ALL IN GREEN AND THEN HOVERED TO PARKING. MAINTENANCE INSPECTED COMPRESSOR FOR FOD AND LEAKS, NO DEFECTED NOTED. REMOVED AND INSPECTED PC AIR FILTER, FOUND CLEAN REINSTALLED PC FILTER ASSY. REMOVED AND REPLACED COMPRESSOR BLEED VALVE, AIRCRAFT GROUND RAN LEAK AND OPS CHECK, ALL SYSTEMS GOOD. AIRCRAFT OPERATIONAL CHECK FLOWN AND RETURNED TO SERVICE. WORK DONE IAW THE MANUFACTURES MM. (M)