Description

On 26 May 2010, a Boeing 737-800 being operated by Air India Express on a passenger flight from Dubai UAE to Pune, India was in the cruise at night at FL370 near PARAR when a sudden high speed descent occurred without ATC clearance during which nearly 7000 feet of altitude was lost in a little over 30 seconds before recovery was made. The remainder of the flight was uneventful. Despite the abnormal pitch, pitch change and ‘g’ variation, none of the 113 occupants had been injured.

Investigation

An Investigation was carried out by the Indian DGCA. Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) data were available. The cabin crew reported that during the excursion, there had initially been “commotion in the cabin for a couple of minutes (with) the (senior Cabin Crew) asking the passengers to fasten (their) seat (belts) and making an attempt to secure the cabin”.

It was established that when the aircraft commander had left the flight deck with the intention of using the toilet, he had discovered that it was occupied and had immediately attempted to return. However, his door entry signal had not been answered and he had then activated the emergency flight deck entry system. By the time it was possible to get back into the flight deck as a result of this action, the overspeed warning was sounding and the aircraft was in a steep descent with thrust levers fully retarded. A recovery was then commenced.