History of the Flight
The crew conducted an ILS approach for a Flaps 30 landing on Runway 04 at Stansted Airport. At 500 ft above aerodrome level, with the aircraft stabilised, the co-pilot (pilot flying) disconnected the autopilot and autothrottle and continued manually. The wind in the final 200 ft varied slightly from the reported 330° at 7 kt, and the co-pilot applied left aileron into wind, resulting in touchdown on the left main landing gear first. The commander reported the aircraft then bounced "a few feet" back into the air. Three or four seconds later, a second much firmer touchdown occurred with a high nose attitude. The landing rollout was normal. After shutdown, cabin crew commented that the second landing was hard, prompting the commander to conduct a visual inspection, which revealed damage to the lower rear fuselage.
Recorded Data
Initial touchdown occurred at 144.5 KCAS with 5.1° nose-up pitch and a peak normal acceleration of 1.3g. Recorded engine N1 values after touchdown were 59% (left) and 56% (right). The speed brake was armed before touchdown but switched to not armed during the initial touch. The air/ground parameter then returned to air. Approximately 2 seconds after initial touchdown, the thrust levers were retarded to idle. The speed brake then became armed, the handle moved to deployed, and the flight spoilers deployed. The highest radio altimeter height during this period was 5 ft. The pitch attitude initially remained just over 5°, reduced to 4° just before spoiler deployment, then increased. 4.4 seconds after the initial touchdown, normal acceleration rapidly increased to a peak of 2.07g. Pitch reached a peak of 8.9° nose-up and remained constant for 1 second before reducing. During the hard landing, engine N1 values reduced to 31%, the auto brake became active, and ground spoilers deployed. Eight seconds after the second touchdown, the nose gear registered on the ground.
Damage
The visible damage consisted of a large scrape along the skin of the tail section. Numerous stringers and frames beneath the surface were also damaged, requiring a substantial repair before the aircraft returned to service.
Comment
The commander considered that the aircraft bounced because the first touchdown occurred with higher than idle thrust. When the thrust lever was selected to idle during the bounce, the speed brakes deployed automatically; this caused a loss of lift, the nose to pitch up, and the subsequent tailstrike on touchdown. The Boeing 737 Flight Crew Training Manual includes advice that bounced landings can occur if higher than idle power is maintained through initial touchdown, disabling automatic speed brake deployment. Retarding the thrust levers to idle during a bounce can cause automatic speed brake deployment, resulting in loss of lift and a nose-up pitching moment that may lead to a tail strike or hard landing.