The US Federal Aviation Administration wants operators of 86 US-registered ATR 42 and ATR 72 regional turboprops perform an inspection of the aircraft's elevator control to prevent possible pitch control problems.

The proposed airworthiness directive (AD), to be issued on 5 August, comes more than a year after the original mandate was issued by the European Aviation Safety Agency in July 2010. ATR released a service bulletin on the problem in May 2010.

Behind the AD was an incident in which an ATR operator, not identified by the FAA, who "experienced in-flight elevator travel limitations with unusual effort being necessary on pitch axis to control the aeroplane, while the 'pitch mistrim' message appeared on the ADU [advisory display unit] display", the proposed AD reads. "The elevators seemed to be jammed."

Inspectors after the flight found that the left-hand elevator's lower stop assembly was broken "at the level of the angles, which may have prevented the elevator to respond normally to the flight control input", according to the proposed AD.

According to US National Transportation Safety Board records, the incident appears to be the Christmas Day 2009 pitch control problem experienced by the pilots of an American Eagle ATR 72-500 enroute from Midland, Texas to Dallas. The pilots reported having approximately "1 inch" (2.54cm) of control wheel fore/aft movement during cruise, and jammed elevator procedures, which attempt to split the left and right elevators, did not solve the problem during two tries.

While the NTSB has not yet issued a final report on the incident, the preliminary report notes that airline personnel, during the post-flight inspection, found that the separated down limit stop had restricted movement to the left elevator.

If the AD, if finalised as proposed, it would require operators to perform a visual inspection of various hinges and fittings on both the left and right elevators, and fixing any damage uncovered while complying with the May 2010 ATR service bulletin.

Source: Air Transport Intelligence news