NTSB Identification: MIA07IA088
Nonscheduled 14 CFR Part 121: Air Carrier operation of OMNI AIR INTERNATIONAL INC
Incident occurred Wednesday, May 02, 2007 in Atlanta, GA
Probable Cause Approval Date: 01/29/2009
Aircraft: MCDONNELL DOUGLAS DC-10-30, registration: N270AX
Injuries: 306 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
While flying at 13,000 feet mean sea level (msl), and decelerating to 250 knots in a DC-10-30 airplane, the horizontal stabilizer could not be moved by either commands from the autopilot or using the primary and alternate control switches from the cockpit. The horizontal stabilizer remained at approximately 1 degree airplane nose-up which resulted in excessive cockpit control forces. An emergency was declared with air traffic control and the flight landed uneventfully on runway 27R at ATL. The inoperative horizontal stabilizer trim system was caused by improper overhaul of the horizontal stabilizer chain drive unit drive assembly (horizontal stabilizer drive assembly) P/N AJH 7337-507, S/N DCA-418 by omission of one pin (P/N 3D0009-5-4), one nut (P/N MS21043-08), and one washer (P/N NAS 1252-BL) which secure the drive gear of the horizontal stabilizer drive assembly. The omission of the parts resulted in fatigue failure of another pin (P/N AJH7378-1) and shear failure of the single installed pin (P/N 3D0009-5-4). This prevented output of the horizontal stabilizer drive assembly being transmitted to acme screws of the horizontal stabilizer. There was no flight crew write-ups for the previous 93 days related to pitch trim. The horizontal stabilizer drive assembly was overhauled on April 30, 1999, and installed in the incident airplane on April 23, 2006. The airplane had accumulated 2,421 hours and 473 cycles since the overhauled assembly was installed.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The improper overhaul of the horizontal stabilizer chain drive unit drive assembly. Full narrative available
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