1955 — Aug 4, American Air Flight 476 engine fire/crash, Fort Leonard Wood, MO–all 30

–30 AirDisaster.com. Accident Database. Accident Synopsis 08041955.
–30 Aviation Safety Network. American Airlines Flight 476, 04 Aug 1955.
–30 CAB. AIR. American Airlines, Inc. Convair 240, N 94221, Fort Leonard Wood, MO…
–30 Eckert. “Fatal commercial air transport crashes, 1924-1981.” AJFM&P, 3/1, Mar 1982, Table 1.
–30 NFPA. “Summary of Large Loss Aircraft Fires.” Quarterly…NFPA, 49/3, Apr 1956, p.394.

Narrative Information

Civil Aeronautics Board Accident Investigation Report: “American Airlines Flight 476, a Convair 240, N 94221, crashed at approximately 1223, August 4, 1955, about one-half mile northwest of runway 14, Forney Field, Fort Leonard Wood, Missouri. The three crew members and all 27 passengers were fatally injured; the aircraft was destroyed by impact and fire.

“Flight 476 of August 4 was a scheduled operation between Tulsa, Oklahoma, and La Guardia Field, New York, with several intermediate stops including Joplin, Springfield, and St. Louis, Missouri….

“Flight 476 departed Springfield VFR for St. Louis, its next scheduled stop, at 1153 via Victor Airway 14 to cruise at 7,000 feet. It was off the ground at 1156. Twenty-one minutes later (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 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. All transmissions were on company frequency.

“During this interval numerous witnesses on the ground back along the flight path saw the aircraft with smoke and flame coming from the right engine. The aircraft was also tracked by a military radar installation near Springfield until it disappeared from the scope in the vicinity of Fort Leonard Wood.

“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 gave it clearance 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. The time was 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 the Army engineers had bulldozed a road through the densely wooded area in which the crash occurred.

“Investigation at the scene revealed that the right wing, right engine, right landing gear, and associated parts had separated from the aircraft in flight, and that bits and pieces, including the right inboard landing gear door, had fallen from the aircraft before the wing came off. The remainder of the aircraft struck the ground approximately 300 feet beyond where the right wing fell. Ground fire and impact damage was extensive and much of the wreckage consisted of burned rubble only….

“Shortly after the accident American Airlines initiated a series of changes in overhaul procedures and in personnel assignments, all pointed toward more stringent supervisory control of work done. The change most directly concerned with this accident involves the handling of cylinders going through overhaul. Cylinders that had been operated with loose hold-down nuts or broken studs now have their barrels mutilated as soon as they are removed from an engine, thus making it impossible for them to be returned to service without first being re-barreled. Such mutilation is witnessed by at least one other person, Further, the cheek of all cylinder barrel flanges by means of the surface plate and feeler gauge has been resumed, and the warpage tolerance has been reduced from .005 to .003 inch in accordance with a recommendation issued by the manufacturer after the accident.

“Analysis: Failure of the cylinder 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 most likely source of ignition was the exhaust manifold which is routed rearward of the cylinders….

“The Board has given much consideration to the evidence in an effort to determine just how an unairworthy cylinder could have been put back in service at the carrier’s overhaul base. If, as testified, a wear pattern caused by operation of cylinders with broken studs or loose hold-down nuts would be evident to visual inspection, there seems no logical reason why this and other cylinders so operated were passed by inspection regardless of whether the alert tag was on the cylinder when it reached the inspection station. In addition, the reported long-existing difficulty with the metal alert tags should have emphasized the importance of rigid inspection to avoid the possibility of passing faulty cylinders. From the fact that cylinders which should have been rejected were returned to service instead, it is obvious that visual inspection alone, dependent on the judgment and evaluation of an individual, is inadequate. After the accident American Airlines was able from its records to locate these cylinders and remove them from service. However, prior to that time no use was made of the records as a crosscheck to prevent the installation of cylinder that should have been rejected by inspection….

“The Board determines that the probable cause of this accident was installation of an unairworthy cylinder, the failure of which resulted in an uncontrollable fire and subsequent loss of a wing in flight.” (CAB. American Airlines, Inc., Convair 240…Fort Leonard Wood, Missouri…1955.)

Sources

AirDisaster.Com. Accident Database. Accident Synopsis 08041955. Accessed at: http://www.airdisaster.com/cgi-bin/view_details.cgi?date=08041955&reg=N94211&airline=American+Airline

Aviation Safety Network. Accident Description. American Airlines Flight 476, 04 Aug 1955. Accessed 2/-21-2009 at: http://aviation-safety.net/database/record.php?id=19550804-0
Civil Aeronautics Board. Accident Investigation Report. American Airlines, Inc., Convair 240, N
94221, Fort Leonard Wood, Missouri, August 4, 1955. Washington, DC: CAB (File No. 1-0110), December 9, 1955, 10 pages. Accessed at: http://dotlibrary1.specialcollection.net/scripts/ws.dll?file&fn=8&name=*P%3A%5CDOT%5Cairplane%20accidents%5Cwebsearch%5C080455.pdf [Broken link when checked 4-10-2023.]
Accessed 4-10-2023 at: https://rosap.ntl.bts.gov/view/dot/33532

Eckert, William G. “Fatal commercial air transport crashes, 1924-1981.” American Journal of Forensic Medicine and Pathology, Vol. 3, No. 1, March 1982, Table 1.

National Fire Protection Association. “Summary of Large Loss Aircraft Fires.” Quarterly of the National Fire Protection Association, Vol. 49, No. 3, April 1956, pp. 393-295.