FAA AD Warns Of 757 Stabilizer Control Failure
FAA AD Warns Of 757 Stabilizer Control Failure More than 700 Boeing 757s operated by U.S. airlines will need to be inspected for potential problems that "could lead to loss of control of the horizontal stabilizer," according to a proposed Airworthiness Directive from the FAA. The FAA says that it is responding to a report of extensive corrosion of a mechanism essential to the aircraft's horizontal stabilizer trim. Failure of the mechanism (a ballscrew) could lead to loss of control of the airplane like that experienced by Alaska Airlines Flight 261 on Jan. 31, 2000. In that case, a McDonnell Douglas MD-83 suffered failure of the jackscrew that controlled stabilizer trim by moving the stabilizer itself. The aircraft crashed into the Pacific after flipping inverted, killing all 88 aboard.
The proposed AD would require repetitive detailed inspections to check the 757 ballscrew assembly for measurement discrepancies and freeplay, and requires repetitive lubrication of the part. It is intended to "prevent undetected failure of the primary and secondary load paths for the ballscrew in the horizontal stabilizer." The FAA is estimating cost of compliance of this AD, which would affect 730 aircraft, at $1,105 per aircraft for inspection and about $2,210 for replacement work (excluding the cost of parts). The FAA is seeking comments by Dec. 9. The full document is available online, here.