NTSB Identification: ENG10IA026
Scheduled 14 CFR Part 121: Air Carrier operation of JetBlue Airways, Inc. (D.B.A. JetBlue)
Incident occurred Monday, April 05, 2010 in Newark, NJ
Probable Cause Approval Date: 03/28/2011
Aircraft: AIRBUS A320, registration: N535JB
Injuries: 140 Uninjured.
NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft incident report.
An Airbus A320 airplane experienced a left engine fan cowl separation during takeoff. The flight crew was unaware of the fan cowl separation until passengers pointed out the loss of both halves of the left engine fan cowl assembly. The flight crew returned for an uneventful landing. After parking and deplaning the passengers, the flight crew noted additional damage to the left engine pylon, leading edge flaps, left main landing gear, and horizontal stabilator. Examination of the engine fan cowls revealed that the cowl latch assembly and keeper housing assembly were intact, showed no evidence of malfunction, and exhibited no distortion or damage and that the cowling structure revealed no evidence of failure. Some delamination was found, but determined to not be contributory to the separation. Maintenance records revealed that a scheduled maintenance inspection of the left engine had been performed prior to the flight which required the opening and closing of the engine fan cowls. According to the operator’s maintenance records, the left engine maintenance sign-off sheet revealed that a mechanic had latched and locked the fan cowls and this task had been verify by another mechanic. Both the ‘action’ and ‘inspection’ signature blocks on the left engine maintenance sign-off sheet for the fan cowl latch procedure had been signed off as part of the Required Inspection Item (RII) procedure.
The latch assembly is normally weighted and the inside and the sides of the latch handle are painted a different color (typically red or orange) than the cowling skin to visually highlight whether the latch is fully locked or not. If the latch is properly locked, the latch handle is flush with the cowling skin and painted portion of the latch handle is not visible. Examination of an exemplar Airbus A320 engine fan cowl revealed the possibility of a false latch condition that would mask an otherwise unlatched position. It was reported that mechanics working on the engine routinely push the latch assembly up against the latch keeper housing assembly in order to stow the latch to avoid inadvertent head injuries while working underneath engine. In this position, the latch is neither latched nor locked but the latch assembly may be flush with the cowling so that the paint on the latch handle is not visible, giving a false indication that the latch is properly locked
Examination of the latch hardware revealed no mechanical damage such as would be expected if the latches were secured and locked at the time of the cowling separation.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The separation of both halves of the left engine fan cowl assembly due to improper latching and locking of the all the fan cowl latches. The cause of the improper latching and locking of the fan cowls was due to the failure of the mechanic to unstow and properly latch and lock the fan cowl latches after the engine maintenance had been completed, and the failure of the maintenance inspector to detect and identify the unlatched condition. Contributing the incident is the design of the fan cowl latch assembly that can provide a false latch condition when the latch is neither latched or locked. Also contributing incident is the lack of adequate Airbus and Jet Blue fan cowl latch inspection guidance to detect and identify an unlatched condition. Full narrative available
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