Background
Flight 476 was a scheduled operation on August 4, departing Tulsa, Oklahoma, for La Guardia Field, New York, with intermediate stops at Joplin, Springfield, and St. Louis, Missouri. The crew consisted of Captain Hugh C. Barren, First Officer William G. Gates, and Stewardess Thelma R. Ballard. The flight departed Tulsa at 1006, one minute behind schedule, and made en route stops at Joplin and Springfield without any reported discrepancies. However, a traffic delay in the Joplin area caused the flight to arrive and depart Springfield 21 minutes behind schedule. Two passengers deplaned at Springfield, and 21 new passengers boarded. The aircraft's gross weight at takeoff was 38,663 pounds, 2,302 pounds below the allowable maximum, and the center of gravity was within limits.
Flight Progress and Emergency
Flight 476 departed Springfield under visual flight rules (VFR) for St. Louis at 1153 via Victor Airway 14, cruising at 7,000 feet. It was off the ground at 1156. At 1217, 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 near Springfield at 7,000 feet and another 30 miles north-northeast of St. Louis—heard a transmission from Flight 476 indicating that the No. 2 engine was on fire. This message was also received by American's ground station at St. Louis. Three minutes later, the American flight in the Springfield area intercepted another message: "Springfield, are you reading 476? We have bad engine fire." This was the last communication from the flight. All transmissions were on the company frequency.
Witnesses and Radar Tracking
During this period, numerous witnesses on the ground along the flight path observed the aircraft with smoke and flame emanating from the right engine. The aircraft was tracked by a military radar installation near Springfield until it disappeared from the scope in the vicinity of Fort Leonard Wood.
Crash and Response
At approximately 1222, the operations officer on duty at Forney Field, Fort Leonard Wood, received a radio message from an Army pilot flying nearby that a two-engine aircraft with a fire in the right engine was on final approach to runway 14. The tower operator at Forney Field saw the approaching aircraft and cleared it to land. Before the operations officer could alert the crash crew, another call from the Army pilot informed him that the airplane had crashed short of the runway, at 1223. Army personnel with portable fire-fighting equipment reached the wreckage on foot. There were no survivors. Heavy fire-fighting equipment and ambulances could not reach the scene until Army engineers bulldozed a road through the densely wooded crash area.
Investigation Findings
The official investigation determined that the probable cause of the accident was the installation of an unairworthy cylinder, the failure of which resulted in an uncontrollable fire and subsequent loss of a wing in flight. Specific findings included: weather was not a factor; the No. 12 cylinder of the right engine was unairworthy and failed near its base after less than six hours of operation, causing a fire that the crew could not control; visual inspection procedures used by the carrier did not reveal the unairworthy condition; the right main tank fuel shutoff valve was open, greatly increasing the fire's intensity and duration; fire damage prevented closing this valve; and procedures recommended by the manufacturer and specified in the carrier's overhaul manual had been countermanded by verbal instructions approved by the carrier's engineering department, and were not being followed by inspectors regarding cylinder handling.