NTSB Identification: CHI01IA124.
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Scheduled 14 CFR operation of TRANS WORLD AIRLINES INC
Incident occurred Monday, February 19, 2001 in Milwaukee, WI
Probable Cause Approval Date: 03/30/2004
Aircraft: Boeing 717-231, registration: N2410W
Injuries: 67 Uninjured.
NTSB investigators used data provided by various sources and may have traveled in support of this investigation to prepare this aircraft incident report.
A Boeing 717 sustained an in-flight thrust reverser deployment following a takeoff. The flight returned without further incident. After the prior flight the reverser was unlocked but not deployed. The flightcrew found the reverser unlock light during preflight. The crew could not clear the indication and contract maintenance was contacted to lock out the reverser. The contractor was not familiar and asked for the procedure to be faxed to him. The contractor used an incomplete set of procedures to lock out the reverser. Post incident inspection revealed the thrust reverser doors had over deployed. Four locking pins and their fork shaped locking triggers showed nicks and gouges on their mating surfaces. Subsequently Boeing revised their dispatch guide to include that maintenance would have to verify that "no more than one Thrust Reverser Proximity Sensor indicates Open" and that operators verify that the thrust reverser unlock indication is not present and red lockout pins are present on the inoperative reverser. Subsequent to the incident the overcenter links were redesigned. Boeing and the thrust reverser manufacturer issued service bulletins (SB) to retrofit the existing engines with the new link's design change, the link's associated hardware, and rub plates. Airplanes in production will incorporate the SB items as a production change. Boeing's SB 717-78-004 stated, "Operators have reported five instances of thrust reversers failing to deploy and ten instances of side beam gouging. Inspections revealed that gouging had occurred between the over center link bolts and side beam assembly. One recent event resulted in a relatively new thrust reverser having side beam gouging so deep, it required a doubler to restore airworthiness. Rohr Incorporated Service Bulletin R715.78-008 provides instructions to modify the thrust reverser actuation system. The purpose of modifying the thrust reverser actuation system is to minimize the possibility of gouging and inadvertent in-flight thrust reverser deployment procedures given in this service bulletin."
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The failure of the operator to provide complete and comprehensive thrust reverser lock-out maintenance procedures and guidance to the contract maintenance personnel resulting in a partial and inadequate securing of the faulty thrust reverser and a subsequent inadvertent deployment following takeoff. Contributing to the incident is the failure of the contract maintenance personnel to verify that the maintenance instructions received where complete, accurate, and up to date.
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