In September 2008 Bell Helicopter began an investigation into the cause of a fatal accident involving a Bell 206L1. Findings from this investigation prompted the issuance of Alert Service Bulletin 206L-09-159.
The investigation revealed that fatigue caused one of the main rotor blades to fracture. A fatigue crack may occur with the combination of residual stress in the spar and a large void in the adhesive between the spar and the internal lead inertia weight. This area is located between station 100 and 145. Centrifugal force that occurs during the start/stop cycle may induce the fatigue crack.
In order for a blade to be at risk both conditions must be present. Bell Helicopters composed a list of blades that may have residual stress in the spar. The presence of a void between the Inertia weigh and spar is unknown. The only method of determining the existence of an unacceptable void is by performing radiography. Part III of the alert service bulletin provides procedures to perform a one-time x-ray inspection of the blade.
After the radiography has been reviewed by a Bell Engineer a letter will be issued. The letter will contain one of the following statements:
1) The Blade can remain in service with no further action required or
2) The blade can remain in service however Part II of this Bulletin requires accomplishment until retirement from service or
3) The blade must be removed form service before further flight.
Radiography can only be performed by an NDT facility approved by the Governing Aviation Authority. Rotorcraft Support, Inc. is FAA authorized to conduct these services. In addition to the FAA credential RSI offers you the professionalism, knowledge and experience only found in Bell Helicopters Platinum Customers Service Facility.
RSI radiography equipment is portable therefore we can send a technician to your facility to perform the inspection with the blade installed on the aircraft. This will drastically reduce your down time. All Technicians performing radiographic inspection are qualified and certified to level II or Level III requirements established in NAS 410 and/or SNT-TC-1A and/or EN 4179.
Please give us a call to discuss your inspection options. Our Highly experienced NDT staff is waiting to assist you. Call Lewis Santos in the NDT Department at (818) 997-7667 ex. 247