Page:CAB Aircaft Accident Report, Trans-Canada Air Lines Flight 304.pdf/4

 The path of one propeller blade passed completely through the oil cooler of No. 3 engine and the forward portion of the passenger cabin. Major cabin damage occurred in the area of the two most forward rows of seats. A small piece of propeller blade that matched with the No. 2 blade was recovered from the cabin. The remaining propeller blades were found to be intact.

The No. 4 engine r. p. m. indicating system and propeller feathering system up to the point of separation of the nose case were checked and both functioned satisfactorily. Subsequent checks at Winnipeg of the individual components which make up these systems showed them to be satisfactory.

The No. 4 engine revealed evidence of oil starvation throughout. Investigation disclosed that the driven bevel gear of the bevel box drive had suffered a fatigue failure and rotation of the drive was completely disrupted. Laboratory study revealed the fatigue failure started on the load side of one tooth. Other than the fatigue fracture, this tooth was relatively undamaged, whereas the teeth that remained in place on the gear exhibited gross damage.

There is no known history of failure of driven bevel gears and a laboratory study showed no manufacturing or metallurgical defects in this one. The bushing within which this gear rotates had turned and worn panel material away until its thrust face was .030" below the machined surface or the panel