On March 27, 2008, a BOEING 737-524 (registration N23661) operated by Continental Airlines was involved in an aviation accident near Houston, TX. No fatalities were reported. Investigators recorded the probable cause as: The flight crew's improper landing technique for an inoperative anti-skid system resulting in locked brakes and four blown main landing gear tires. This summary draws on records from NTSB; 12 related events involving the same aircraft type or operator are linked below.
On March 27, 2008, Continental Airlines flight N23661 sustained minor damage during landing at KIAH, Houston, Texas. All four main tires blew out, and a small fire occurred on the right main gear. No injuries were reported.
Incident Overview and Flight Details On March 27, 2008, at 1808 central daylight time, N23661, a Boeing 737-524 operated by Continental Airlines, sustained minor damage during landing at George Bush Intercontinental Airport (KIAH) in Houston, Texas. The scheduled domestic passenger flight departed Will Rogers International Airport (KOKC) in Oklahoma City, Oklahoma, at 1656. Visual meteorological conditions prevailed, and the flight was conducted under Title 14 Code of Federal Regulations Part 121 on an instrument flight rules flight plan. The aircraft carried a captain, first officer, three cabin crew members, and 113 passengers, none of whom were injured. ## Operational Context and Crew Actions Continental Airlines reported that the flight departed KOKC with knowledge that the anti-skid system was inoperative. The system had been placarded inoperative and was included on the minimum equipment list (MEL) for flight permissions. Before the flight and several times during the flight, the captain and first officer discussed procedures for operating with the anti-skid system inoperative, including using minimal braking to avoid tire damage. Before landing, the flight crew compensated their landing speed based on reported wind information and ensured the auto brake system was off, as required by the checklist for an inoperative anti-skid system. Upon touchdown, the captain reported feeling an almost immediate shudder and suspected a flat tire. He took control of the aircraft and stated that he did not apply brakes because the airplane was slowing rapidly. He maintained runway centerline using the tiller. The aircraft stopped toward the end of the runway, and the flight crew and passengers disembarked using air stairs. ## Scene Investigation and Initial Findings An FAA inspector who responded to the scene reported that the aircraft touched down in the touchdown zone of runway 26R and came to rest on the runway approximately 2,000 feet from the departure end. A small fire was observed on the right main gear, and Houston Aircraft Rescue Fire Fighting (ARFF) responded and extinguished it. An examination of the aircraft revealed that all four main landing gear tires had blown out. The landing gear wheels, brakes, and tires were secured for further examination. ## Component Examination On April 3, 2008, the wheels, tires, and brakes were examined at Honeywell’s facility in Houston, Texas. Each wheel and tire assembly was disassembled and examined. Wheel assemblies three and four showed damage from extended contact with the runway. Tires one and two were severely blown out throughout the entire circumference, with little tread area remaining. Tires three and four exhibited a flat spot where initial contact was made with the runway surface. Examination of the four brake assemblies revealed no anomalies aside from damage created by contact with the runway. ## Applicable Procedures and Flight Data According to the 737 Flight Crew Operations Manual, when operating with the anti-skid inoperative, locked wheel protection is not available during landing. The checklist directs the crew to turn the auto brake select switch off, not to arm the speed brakes, and not to apply brakes until the nose wheels are on the ground and the speed brakes are extended. The quick reference handbook (QRH) further specifies that speed brakes are to be deployed manually immediately upon landing and that braking should be applied with caution. The aircraft was equipped with an L-3 Communications Fairchild Model FA2100 Flight Data Recorder (FDR). The FDR unit was removed and sent to the National Transportation Safety Board Vehicle Recorders Laboratory in Washington, DC, for data extraction. Data from the accident flight was extracted, and one minute and 40 seconds of data from the landing event was plotted. Parameters included left and right brake pressure and the nose gear weight on wheels sensor. The extracted data showed an increase in left and right brake pressure to 3,000 pounds per square inch, the upper limit of the pressure range, at the same time the nose gear weight on wheels sensor was activated. The pressure then decreased to 1,200 pounds per square inch and to zero pounds per square inch several seconds later. This pressure increase and decrease is consistent with the application of brakes upon landing. Additional study of the FDR data revealed that the speed brakes were not extended and the thrust reversers were not used for this landing.
