landing gear of Air Berlin flight AB6777 – Boeing – B737-800 (D-ABKA)

Air Berlin flight AB6777 was a Boeing 737-800 (B738) scheduled for a flight from Nürnberg (EDDN) to Düsseldorf (EDDL); departure time 2030 hrs.

On board were six crew members and 125 passengers. Take-off run occurred with one hour delay at which the airplane veered to the right off the runway after about 150 m.

From 2107 hrs to 2118 hrs Air Berlin flight AB6777 was de-iced with 100% de-icing fluid type II (undiluted). While rolling to the runway the crew reported “… ready for departure“. The controller answered “braking action on runway medium, contact tower …“.

After the initial contact with the tower the controller instructed “… hold short, I call you”, which the crew acknowledged. When the controller asked “… ready for rolling” the answer was “affirm …”. Which was followed by the instruction “… line up one zero”.

At around 2128 hrs, about 13 seconds later, take-off clearance was given “… cleared take-off, company traffic is 6 miles“.

Rolling to and onto the runway occurred without stopping and with a ground speed of about 21 kt. The airplane lined-up on runway 10 (runway direction 099°) with a right-hand turn.

While lining-up on the runway the two main landing gears reached a position left of the runway centre line.

The crew of Air Berlin flight AB6777 steered the airplane to the right and stated that afterwards it was no longer possible to steer it to the left.

According to the Flight Data Recorder (FDR) both thrust levers were moved from about 36° to about 46° while passing a heading (HDG) of about 20° with a ground speed of about 12 kt. Thrust of both engines increased from about 21% N1 to about 43% N1. The recordings of the left and right N1 show that the engines accelerated with a difference of initially about 2% and later about 4%; the left engine showed the higher thrust values throughout. After that, N1 of the left engine remained at about 43.2% and of the right at about 42.5%; for the next 9 seconds both values remained constant. About 43% N1 of the left engine was reached at HDG 73°; at that time ground speed was about 12 kt.

The airplane accelerated in 12 seconds from about 12 kt to 19 kt ground speed. The heading of about 112° was passed with a ground speed of about 19 kt. During the acceleration phase the airplane passed a heading of about 120° with a ground speed of about 17 kt. Once these values were reached the thrust levers were pulled back to about 5° and within 9 seconds engine thrust decreased to about 21% N1. Within 6 seconds ground speed decreased from 19 kt to 0 kt.

Air Berlin flight AB6777 veered off the right runway edge with about 17 kt ground speed.

The nose wheel and the right main landing gear came to a stop after about 15 m (about 150 m after the threshold) and about 5 m alongside the runway in unpaved terrain; the left main landing gear remained on the runway. The fuselage was pointing into the direction of 107°.

The cause for the serious incident was :

• the increased ground speed during line-up on a snow-covered runway.

The investigation identified the following contributory factors:

• The rolling take-off was not conducted according to OM/B requirements.
• The procedure “static run-up” was not conducted even though, given the weather conditions, it would have been necessary.
• The continuously falling snow resulted in snow-covered operating areas in spite of continued snow clearing services.
• The published procedures for “adverse weather” and “initiating take-off roll” according to OM/B and FCOM were not conducted.