NTSB: Northwest mechanics at fault in cowl incident

Washington DC
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US NTSB investigators say Northwest Airlines mechanics diverted their attention from engine maintenance on an Airbus A319 on 9 January, resulting in the in-flight departure of an engine cowling.

Flight attendants on Northwest Flight 853, carrying 68 passengers and five crew from LaGuardia to Detroit, alerted the pilots on climbout that a passenger had reported that “the number two engine (right side) cowling was flapping after takeoff”, according to the NTSB final accident report, issued Monday.

Pilots continued the flight, while monitoring the engine for vibration, according to the report. Vibration levels for the suspect engine were twice the levels of the normal engine during climbout, the crew stated, but did not trip the aircraft’s alerting system.

NTSB reports that the flight was then otherwise normal except for an event 20 minutes into cruise, when the aircraft “shuddered”, pilots stated.

After an uneventful landing, flight attendants informed the pilots that “part of the right engine had come off”, according to the report.

NTSB determined that half of the engine cowl had departed the aircraft when it was on a one-mile final for landing, substantially damaging the right horizontal stabilizer. The other half fell off when the aircraft touched down.

Also damaged were the fan cowl doors, right side engine pylon, thrust reverser and right wing “number one” slat.

In addition, the aircraft that landed behind Northwest 853 hit the cowling on the runway, though the NTSB does not state whether that aircraft was damaged.

Investigators found that Northwest “contract maintenance personnel” had changed an N1 engine sensor in the incident engine the previous evening and failed to latch the cowl when finished, as required by the maintenance manual.

Mechanics stated that they were called upon for help from another mechanic on a different aircraft during the final portions of the work diverting their attention. Each had thought the other had latched the cowl, according to the NTSB.

Responding to the report, Northwest in a statement says: “Northwest has a sterling safety record. Safety is our top priority and while this incident was unfortunate, at no time was the safety of our passengers compromised.”

Source: Air Transport Intelligence news