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replaced with temporary bolts and the aircraft proceeded to Santa Maria. On landing, inspection showed that the temporary bolts had sheared. At this time the snubber was removed and the aircraft was flown to Idlewild where the same snubber was reinstalled. Testimony of Pan American representatives at the public hearing indicated that no damage occurred to the antirotation bolt on either the Boston takeoff or the Santa Maria takeoff. They also stated that the damage inflicted on the bolt in this accident was the result of the contact between the truck beam and the bolt after the beam failed. One additional round trip between New York and London was made, without incident, before trip 102.
Analysis
The Board believes that the landing gear truck beam on N 707PA was damaged on a previous flight by contact with the lower torsion link assembly antirotation bolt.
The design of the landing gear is such that this damage can occur only if the snubber is removed or is broken from one of its end fittings. The beam could have been peened during the flight from Boston, July 7, after the snubber failed, or on its flight from Santa Maria, July 9, when the snubber had been removed. Also, since the examination of the fracture indicates multiple loading, the damage may have been done during both of the flights.
Because the beam and the end of the antirotation bolt are angled 15 degrees from each other at the point of their contact, the end of the bolt must be deformed to that angle to leave a flat mark on the beam surface. If, as PAA claimed, the bolt installed at the time of the accident was damaged during the accident, another bolt would have had to have been installed previously. This bolt would have had to have been flattened as mentioned before in order to peen the truck beam in the manner it did. This previously damaged bolt, if there was one, was either replaced without appropriate notation in the records or was the bolt in place at the time of this accident. Either action indicates improper maintenance practice.
The longitudinal fatigue-like crack originated at this flat peen mark. As the snubber was properly installed at takeoff, no contact between the beam and the bolt was possible until the forward truck beam had separated from the aircraft as a result of forces to which the weakened beam was subjected on takeoff.
Although a considerable number of unauthorized persons were on the landing area during the emergency, none was closer to the runway than taxiway Q, which is 850 feet north, during the actual landing. The Board takes cognizance of the fact that the normal Saturday night visitor population of Idlewild is upwards of 10,000 people. In addition, there are over 200 doors by which these persons could gain entrance to the aircraft operating areas.
It is to be noted here that there was no interference by spectators during the actual landing of the aircraft. The runway was cleared of all personnel during this time and it was not until the aircraft had come to rest that the numerous persons crowding around became a serious problem. Ground preparations were adequate and well executed.
