Date:	Thursday 4 August 1955
Time:	12:23
Type:	Convair CV-240-0
Owner/operator:	American Airlines
Registration:	N94221
MSN:	40
Year of manufacture:	1948
Total airframe hrs:	14865 hours
Engine model:	Pratt & Whitney R-2800-83AM4A
Fatalities:	Fatalities: 30 / Occupants: 30
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	1 km NW of Fort Leonard Wood-Forney AAF, MO (TBN) -   United States of America
Phase:	Approach
Nature:	Passenger - Scheduled
Departure airport:	Springfield Municipal Airport, MO (SGF/KSGF)
Destination airport:	Saint Louis (unknown airport), MO
Investigating agency:	CAB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
American Airlines Flight 476 was a scheduled operation between Tulsa Municipal Airport, OK (TUL) and New York-La Guardia Airport, NY (LGA), with several intermediate stops including Joplin Airport, MO (JLN), Springfield Airport, MO (SGF), and St. Louis, MO. The Convair CV-240 aircraft departed Tulsa at 10:06. En route stops were made at Joplin and Springfield, and no discrepancies were reported or noted at either point.
Two of the eight passengers deplaned at Springfield; 21 passengers boarded the flight there. Gross weight of the aircraft at takeoff was 38,663 pounds, 2,302 pounds under that allowable, and the center of gravity was located within prescribed limits.
Flight 476 departed Springfield VFR for St. Louis at 11:53 via Victor Airway 14 to cruise at 7,000 feet. It was off the ground at 11:56. Twenty-one minutes later (12:17) the crew initiated a general call asking, "Does anyone read 476?" Springfield company radio acknowledged but received no reply. Two other American Airlines flights, one cruising in the vicinity of Springfield at 7,000 feet, the other 30 miles north-northeast of St. Louis, heard a transmission from Flight 476 that No. 2 engine was on fire. This message was also heard by American's ground station at St. Louis.
Three minutes later the American flight in the Springfield area intercepted the following message, "Springfield, are you reading 476? We have bad engine fire." This was the last message heard from the flight.
Numerous witnesses on the ground back along the flight path saw the aircraft with smoke and flames coming from the right engine. the pilot diverted to Fort Leonard Wood-Forney AAF, MO (TBN) for an emergency landing on runway 14. However the airplane crashed and burned in a wooded area just short of the runway.
Investigation revealed that the no. 12 cylinder of the right hand engine failed. This was accompanied by the release of combustibles consisting of a fuel-air mixture from the disrupted intake pipe and oil from the crankcase section. The exhaust manifold probably caused the ignition. The crew feathered the propeller immediately and fired the CO2 bottles. The fire was not put out. The main fuel tank shutoff valve was not closed, feeding the fire. Probably the electrical wiring of the valve had been so damaged by fire that it was no longer operable. This situation greatly increased the intensity and duration of the fire. The right wing ultimately failed on finals to Forney Field.

PROBABLE CAUSE: "Installation of an unairworthy cylinder, the failure of which resulted in an uncontrollable fire and subsequent loss of a wing in flight."

ICAO Accident Digest Circular 50-AN/45 (160-165)
CAB Report File No. 1-0110

Other occurrences involving this aircraft

10 June 1973	N999JZ	Air Cambodge	0	Phnom Penh-Pochentong Airport (PNH)		w/o
Damaged on the ground

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