BOEING 737SOUTHWEST AIRLINES CO
Houston, TX, USA · 2009-05-13·N371SW
What happened
NTSB summary, verbatimPrior to the flight, the flight crew and dispatcher were aware that the anti-skid system was inoperative. They had requested and were granted use of the longest runway for landing. The captain made a normal landing in the target area. After touchdown, he reduced the thrust levers to idle, rapidly brought the speed brake to the full-up detent, employed reverse thrust, and applied manual wheel braking. Marks on the runway showed that about 550 feet after initial touchdown, the right main landing gear tires blew. The tower controller and other aircraft advised the flight crew that there was a fire in the area of the right main landing gear. After the airplane came to a stop, the captain initiated an emergency evacuation on the runway. All 54 persons on-board exited the airplane in 57 seconds, and the fire was extinguished soon after. Two passengers reported minor injuries. The airplane sustained minor damage to the right main landing gear and a portion of the right flap. Examination of data retrieved from the flight data recorder showed that during the touchdown and landing roll, at 19:45:31, the recorded left brake pressure was 770 pounds per square inch (psi). The maximum recorded right brake pressure was 1430 psi at 19:45:32. The maximum recorded left brake pressure was 990 psi. With the anti-skid system disabled, the pilot applying excessive braking during touchdown would cause the wheels to lock and the associated tires to blow. The airplane's quick reference handbook states "Use minimum braking consistent with runway conditions to reduce the possibility of a tire blowout."
Photographs
18the aircraft, and what the investigators foundPhotographs are NTSB docket attachments — works of the US government, in the public domain. Captions are the Board’s own.
Probable cause
the Board's determinationThe pilot's inadvertent application of excessive braking after touchdown, which caused the right wheels to lock and several tires to blow and resulted in a subsequent brake fire.
Occurrence sequence
4 stepsNTSB coding · CICTT taxonomy- 1 · Prior to flightMiscellaneous/other
- 2 · Landing-landing rollFire/smoke (non-impact)defining event
- 3 · Post-impactFire/smoke (post-impact)
- 4 · Post-impactEvacuation
Findings
2 causal · 2 contributing- CAUSEAircraft › Aircraft oper/perf/capability › Performance/control parameters — Incorrect use/operation
- CAUSEPersonnel issues › Action/decision › Action › Incorrect action performance — Pilot
- FACTORAircraft › Aircraft systems › Landing gear system › Brake — Not specified
- FACTORAircraft › Aircraft systems › Landing gear system › Tire casing — Not specified
Sequence of events
3 timed eventsfrom the FDR factual report · claude-fable-5-1 (in-session)- approach into KHOU (plots 1-2)approachp.3Basic, landing gear and brake parameters plotted from just before gear extension to about two minutes after engine shutdown
- about 19:45:31-19:45:32 CDTtouchdownp.4Touchdown and landing roll: recorded left brake pressure 770 psi at 19:45:31 while the right brake pressure peaked at 1,430 psi at about 19:45:32 (tires blew at touchdown)
- 19:45:57 and 19:46:03 CDTlanding rollp.4Maximum left brake pressure 990 psi recorded twice during the landing roll; plot 3 ends when ground speed reaches zero
NTSB analysis
from the final reportPrior to the flight, the flight crew and dispatcher were aware that the anti-skid system was inoperative. They had requested and were granted use of the longest runway for landing. The captain made a normal landing in the target area. After touchdown, he reduced the thrust levers to idle, rapidly brought the speed brake to the full-up detent, employed reverse thrust, and applied manual wheel braking. Marks on the runway showed that about 550 feet after initial touchdown, the right main landing gear tires blew. The tower controller and other aircraft advised the flight crew that there was a fire in the area of the right main landing gear. After the airplane came to a stop, the captain initiated an emergency evacuation on the runway. All 54 persons on-board exited the airplane in 57 seconds, and the fire was extinguished soon after. Two passengers reported minor injuries. The airplane sustained minor damage to the right main landing gear and a portion of the right flap. Examination of data retrieved from the flight data recorder showed that during the touchdown and landing roll, at 19:45:31, the recorded left brake pressure was 770 pounds per square inch (psi). The maximum recorded right brake pressure was 1430 psi at 19:45:32. The maximum recorded left brake pressure was 990 psi. With the anti-skid system disabled, the pilot applying excessive braking during touchdown would cause the wheels to lock and the associated tires to blow. The airplane's quick reference handbook states "Use minimum braking consistent with runway conditions to reduce the possibility of a tire blowout."