The United States Federal Aviation Administration (FAA) is adopting a new airworthiness directive (AD) for MD Helicopters, Inc. model 500N, 600N and MD900 helicopters.
The MD requires determining the cure date for each NOTAR fan blade tension-torsion strap (T-T strap), establishing a calendar-time retirement life for certain T-T straps, reducing the retirement life of certain T-T straps, marking each T-T strap with the expiration date, creating a component record card for each T-T strap, and revising the airworthiness limitations section of the maintenance manual to reflect the changes to the retirement life.
This AD was prompted by a report from the T-T strap manufacturer that, over a period of time, moisture may reduce the strength of a T-T strap. The actions are intended to prevent failure of a T-T strap, loss of directional control and subsequent loss of control of the helicopter.
The AD is effective March 15, 2013. The complete text can be found on the FAA website.
