Turbine Fatigue Cited in Fatal California Helo Crash
Yesterday the NTSB released the finding of the cause of the May 24, 2008, Island Express helicopter accident in Two Harbors, Avalon, on Catalina Island, in California. The Eurocopter AS350D collided with terrain while landing after a flight from the Queensway Bay Heliport, Long Beach, Calif. The commercial pilot, a company employee, and one passenger were killed and three passengers were seriously injured. The helicopter was destroyed by impact damage and fire.
Witnesses reported that the helicopter was approaching the island about 300 feet above the surface. Several witnesses heard a “pop” sound and then saw flames emitting from the back of the engine. The helicopter then entered a descent and hit the ground.
According to the report, the helicopter's Turbomeca Arriel 1B engine had been removed and a Honeywell LTS101-600-A3 engine installed in its place, and the FAA issued the helicopter a new airworthiness certificate as an AS350D.
According to the NTSB, an examination of the Honeywell engine indicated a power turbine blade had fractured due to fatigue, with two adjacent blades receiving secondary damage. The power turbine blades are a hollow-core design in which the core is created as part of the casting process for the blade. Platinum pins are positioned on both sides of the molds to hold the center core in place when the blade is cast. After casting, the center core is removed and the platinum pins remain in place on both sides of the finished blade.
“Metallurgical analysis showed that the fatigue emanated from the area of the pins. The blades are no longer being manufactured as the casting has been modified to reduce the number and placement of the platinum pins,” it stated.
A Honeywell spokesman told AIN the company does not completely agree with the finding and is evaluating its options.