Southwest Airlines Main Landing Gear Fire (Houston, 2009)

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Update: A variety of accident investigation records are available at http://tiny.cc/southwestfire.

On May 12, 2009, at 1945 central daylight time, a Boeing 737-3H4 (tail number N371SW) operated by Southwest Airlines as Flight 519, experienced a fire in the area of its right main landing gear when three of its four main landing gear tires blew-out during landing on Runway 22 at William P. Hobby Airport in Houston, Texas. The airplane sustained minor damage. The 2 flight crew, 3 flight attendants, and 48 passengers evacuated the airplane and 2 passengers suffered minor injuries during the evacuation.

The airplane had been dispatched from New Orleans with several inoperative items as permitted on the minimum equipment list (MEL), including an inoperative automatic brake system. A landing on Runway 22 was required because of MEL operational requirements. The captain provided a statement to NTSB investigators that he had made a stabilized flaps 40 final approach with a normal landing in the target area. After touchdown, he took the thrust levers to idle, rapidly brought the speed brake to the full-up detent, employed reverse thrust, and applied manual wheel braking. Both flight crew members reported they thought the tires blew soon after touchdown.

After the airplane came to a stop, the crew received confirmation of fire and smoke from the control tower and, were told that aircraft rescue fire fighting (ARFF) units were en route. Other aircraft also confirmed the presence of fire and smoke. The captain conferred with the first officer and the flight attendants, and ordered an emergency evacuation from the left side doors.

The flight attendants opened only the forward entry door and the aft entry door on the left side of the airplane. The associated emergency slides inflated. The ARFF units arrived and began to extinguish the fire as passengers were evacuating down the slides.

After all 48 passengers, including one lap child, had exited from the airplane, two flight attendants evacuated down the slides and began to gather the passengers, direct them away from the airplane, and screen for injuries. The remaining crewmembers made a sweep through the cabin to confirm no one was left on-board and then also evacuated down the slides. All passengers and all crewmembers successfully exited the airplane 57 seconds after the evacuation began.

ARFF units were able to knock down the fire approximately 32 seconds after the emergency evacuation began. The ARFF commander declared that the fire was out four minutes later. After an initial on-scene triage by emergency medical services, the passengers and crew were bused to the airport terminal.

All four main landing gear tires, wheels and brake assemblies were examined at the Honeywell facility in South Bend, Indiana. No pre-event anomalies in the tires, wheels, or brakes were discovered that would have prevented normal operations.

The anti-skid system is designed to provide touchdown protection during the air-to-ground transition. Touchdown protection prevents brake application prior to touchdown and wheel spin-up. With the touchdown protection feature operative, brake pressure can reach the brakes only 3 seconds after the air-ground switch logic indicates ground, or once each wheel has spun up to a velocity of 60 knots. The touchdown protection is not available when the anti-skid system is in the off position or is not operative, as was the case for this flight.

If you are surprised by the existence of a minimum equipment list (a list of things which can be broken on a plane without grounding it) and you are in the mood for more surprises, I recommend Googling “speed tape.” (Then look carefully at the skin of the next commercial aircraft you travel on.)




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