What happened
On March 27, 2008, a Boeing 737-524, registration N23661, was operating a scheduled domestic passenger flight from Will Rogers International Airport (KOKC) to George Bush Intercontinental Airport (KIAH) under instrument flight rules. The aircraft arrived in Houston under visual meteorological conditions with a wind of 170 degrees at 16 knots and 10 miles of visibility.
The flight crew operated the aircraft knowing the anti-skid system was inoperative, a condition permitted under the airline's minimum equipment list. Prior to landing, the crew had briefed procedures to use minimal braking to prevent tire damage. Per the required checklist for this condition, the crew ensured the auto brake system was off and adjusted landing speed for the wind.
Upon touchdown on runway 26R, the captain felt an immediate shudder and suspected a flat tire. While the captain reported not applying brakes as the aircraft slowed rapidly, the aircraft eventually came to a stop approximately 2,000 feet from the end of the runway. A small fire was observed on the right main gear, which was extinguished by Houston Aircraft Rescue Fire Fighting (ARFF) personnel. There were no injuries among the 113 passengers and six crew members.
The investigation
An FAA inspector noted the aircraft touched down in the touchdown zone of runway 26R. Subsequent examination of the aircraft revealed that all four main landing gear tires had blown.
On April 3, 2008, the wheels, tires, and brakes were examined at a facility in Houston. The investigation found:
- Wheel assemblies three and four had damage from extended contact with the runway.
- Tires one and two were severely blown out across their entire circumference.
- Tires three and four exhibited flat spots from initial runway contact.
- The four brake assemblies showed no anomalies other than runway contact damage.
Data extracted from the flight data recorder (FDR) covered 1 minute and 40 seconds of the landing. The data showed an increase in left and right brake pressure to 3,000 pounds per square inch at the same time the nose gear weight-on-wheels sensor activated. This pressure later decreased to zero. The FDR also revealed that the speed brakes were not extended and the thrust reversers were not used during the landing.