The Army announced today that its Apache helicopter fleet (AH 64 A & D) will undergo a one time inspection and possible replacement of a specific series (basic configuration) hanger bearing assembly. The assembly is part of the tail rotor system.
A recent failure of a basic configuration hanger bearing assembly resulting in the loss of an aircraft and minor injuries to the two-man crew was determined to have been caused by hydrogen assisted corrosion cracking. Preliminary indications are that hydrogen embrittlement, a hardness heat-treat process, may be the cause for the stress corrosion fractures.
The Army changed the manufacturing process in 1993 and hanger bearing assemblies produced after that change do not have the potential for stress corrosion fractures.
The inspection of all 743 AH-64 aircraft will determine if the specific series of hanger bearing assemblies are installed, and if they are, they will be replaced. Unaffected aircraft will be returned to flight status immediately.
This inspection, which takes about an hour, is to take place as soon as practical but prior to the aircraft's next flight and no later than one week from notification.
The Army stated it anticipates no problems with readiness because of the inspections. While some aircraft will be grounded for hanger bearing assembly replacement, other training and maintenance activities will continue and the Army will work to get its priority, first-to-fight units returned to flight.
The Army is working with the hanger bearing assembly contractor, Boeing, to ensure that adequate replacement assemblies are manufactured and supplied to the fleet. It is an Army-Industry team effort to return to flight operations as quickly as possible.
For further information, contact Army Public Affairs, (703) 697-7591.