Accident Air Tractor AT-302 N4441S, Thursday 15 November 1990

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Date:	Thursday 15 November 1990
Time:	21:30 LT
Type:	Air Tractor AT-302
Owner/operator:	Private
Registration:	N4441S
MSN:	302-0101
Year of manufacture:	1977
Total airframe hrs:	4950 hours
Engine model:	P&W R-1340 AN1
Fatalities:	Fatalities: 0 / Occupants: 1
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Somerton, AZ - United States of America
Phase:	Manoeuvring (airshow, firefighting, ag.ops.)
Nature:	Agricultural
Departure airport:
Destination airport:
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
THE PILOT EXPERIENCED A LOSS OF ENGINE POWER AND COLLIDED WITH THE TERRAIN DURING A SWATH RUN. EXAMINATION OF THE ENGINE REVEALED THE NUMBER 3 EXHAUST VALVE WAS CRACKED. THE ENGINE HAD 266 HOURS SINCE OVERHAUL AND HAD 20 HOURS SINCE THE LAST INSPECTION.

Probable Cause: THE FAILURE OF THE NUMBER 3 EXHAUST VALVE WHICH LED TO AN ENGINE FAILURE AND SUBSEQUENT CRASH LANDING.

Accident investigation: