Accident Sequence
Witnesses observed the aircraft lift off from Lake Hood Seaplane Base with five occupants aboard. After takeoff, the flaps were retracted and the aircraft pitched into a climb attitude. However, it ceased climbing and began to settle, subsequently striking a utility pole at the airport boundary. The aircraft then impacted a road, and a fire erupted.
Aircraft Examination
Post-accident calculations indicated the aircraft was within allowable weight and balance parameters. Engine examination revealed a worn throttle arm, part number 632555-23, which had disconnected from the throttle linkage. The disconnection occurred where a hard steel bushing with splines had been pressed into a mounting hole in the relatively soft throttle arm. The mounting hole had become 'U' shaped with one side open. The opening was large enough to permit passage of the throttle linkage connecting bolt and bushing. Deposits of material from the throttle arm were found on the bushing splines. These deposits were consistent with rotational motion of the bushing within the mounting hole, as if rotation occurred during tightening of the bolt.
Maintenance History
Teledyne Continental Service Bulletin SB95-2, dated April 21, 1995, provided inspection and lubrication procedures for throttle linkages at each 100-hour, progressive, and/or annual inspection. The aircraft had accumulated 80 hours of flight time since its previous annual inspection on August 11, 1996.