Friday, December 07, 2018

Thrust imbalance preceded Jet 737's excursion at Goa

Indian investigators have determined that a Boeing 737-800 crew did not allow the aircraft’s engines to stabilise their thrust before the twinjet suffered a runway excursion during take-off from Goa.

The aircraft, operated by Jet Airways and bound for Mumbai, had lined up on runway 26 after backtracking and performing a 180° turn.

India’s accident inquiry committee states that the crew advanced the thrust levers to the 40% setting.
But while the left-hand engine was running at 40% of N1, the right-hand one had only reached 28% when the captain commanded full take-off thrust.

This failure to allow the CFM International CFM56 engines to stabilise led to a thrust imbalance as the aircraft accelerated.

“As soon as [full thrust was commanded] the aircraft started drifting towards [the] right,” says the inquiry into the 27 December 2016 event.

Within 10-12s the aircraft departed the paved surface and the crew attempted to brake and use rudder and nose-wheel steering to correct its course.

The jet left the runway and turned in a wide right-hand arc, eventually coming to rest facing the opposite direction and 219m from the edge of the runway.

It collided with a path-indicator lamp as well as a 2.3m pillar during the excursion, and the aircraft suffered substantial engine, undercarriage and fuselage damage.

Sixteen of the 145 occupants, all passengers, suffered minor injuries, notably during the evacuation.
07/12/18 David Kaminski-Morrow/FlightGlobal