A late transition from autopilot to manual flying caused a Jet Airways Boeing 737-800 to over-pitch and lose airspeed as it came in to land at Kolkata airport, resulting in a tailstrike.
The aircraft, bearing registration VT-JGE was operating a Mumbai-Kolkata service with eight crew and 144 passengers on board when the incident happened at 09:10 local time on 14 January 2015.
In its final investigation report, India's Aircraft Accident Investigation Bureau found that visibility at the time of landing was 800 metres and that the pilot flying decided to carry out a dual autopilot approach with the intention of carrying out a manual landing.
Flight data shows that the pilot flying disengaged the autopilot at 161ft - well below the flight crew training manual's recommendation to disengage betweeen 300-600ft if a manual landing is planned.
"This allows the pilot to establish airplane control before beginning the flare. During dual mode autopilot approach, stabilizer trim automatically added nose up and this needs to be compensated for if the crew takes over manually," says the AAIB.The landing procedure took about 14 seconds to complete, during which time its pitch reached 9.14 degrees, while its airspeed at touchdown was 10kts below the reference speed. That caused the lower fuselage to come into contact with the runway, resulting in minor damage to the tail skid and scraping to the its aft lower fuselage. There were no injuries, however.
"Due to the late autopilot disengagement [the pilot flying] did not have adequate time to apply sufficient nose down trim to counter the bias added by the autopilot," says the AAIB.
The Bureau recommended that the Directorate General of Civil Aviation review the awareness among pilots of tailstrikes, and to emphasise that they should adhere to the procedures set down in operations manuals.