A chartered business jet crashed at a South Carolina airport 18 months ago because of the operator's inadequate maintenance of the airplane's tires and the decision by the captain to attempt a high-speed rejected takeoff, which went against standard operating procedures and training, the NTSB determined today.
On September 19, 2008, at 11:53 p.m. EDT, a Bombardier Learjet Model 60 (N999LJ) operated by Global Exec Aviation and destined for Van Nuys, California, overran runway 11 during a rejected takeoff at Columbia Metropolitan Airport. After the airplane left the departure end of runway 11, it struck airport lights, crashed through a perimeter fence, crossed a roadway and came to rest on a berm. The captain, the first officer, and two passengers were killed; two other passengers were seriously injured.
The investigation revealed that prior to the accident the aircraft was operated while the main landing gear tires were severely underinflated because of Global Exec Aviation's inadequate maintenance. The underinflation compromised the integrity of the tires, which led to the failure of all four of the airplane's main landing gear tires during the takeoff roll.
Shortly after the first tire failed, which occurred about 1.5 seconds after the airplane passed the maximum speed at which the takeoff attempt could be safely aborted, the first officer indicated that the takeoff should be continued but the captain decided to reject the takeoff and deployed the airplane's thrust reversers. Pilots are trained to avoid attempting to reject a takeoff at high-speed unless the pilot concludes that the airplane is unable to fly; the investigation found no evidence that the accident airplane was uncontrollable or unable to become airborne.
The tire failure during the takeoff roll damaged a sensor, which caused the airplane's thrust reversers to return to the stowed position. While the captain was trying to stop the airplane by commanding reverse thrust, forward thrust was being provided at near-takeoff power because the thrust reversers were stowed. The Safety Board determined that the inadvertent forward thrust contributed to the severity of the accident.
The Safety Board also found that neither the Federal Aviation Administration nor Learjet adequately reviewed the Airplane's design after a similar uncommanded forward thrust accident that occurred during landing in Alabama in 2001. While the modifications put into place after the Alabama accident provided additional protection against uncommanded forward thrust upon landing, no such protection was provided for a rejected takeoff.
"This accident chain started with something as basic as inadequate tire inflation and ended in tragedy," said NTSB Chairman Deborah A.P. Hersman. "This entirely avoidable crash should reinforce to everyone in the aviation community that there are no small maintenance items because every time a plane takes off, lives are on the line."
The safety recommendations that the NTSB made to the Federal Aviation Administration as a result of this investigation are: provide pilots and maintenance personnel with information on the hazards associated with tire underinflation, including the required intervals for tire pressure checks, and allow pilots to perform pressure checks in air taxi operations to ensure that tires remain safely inflated at all times; require tire pressure monitoring systems for all transport category airplanes; identify and correct deficiencies in both Learjet's thrust reverser system safety analysis and the FAA's design certification process to ensure that hazards encountered in all phases of flight are mitigated; require that simulator training for pilots who conduct turbojet operations include opportunities to practice responding to events other than engine failures near takeoff speeds; require that pilots who fly air taxi turbojet operations have a minimum level of pilot operating experience in an airplane type before acting as pilot-in- command in that type; and require that airplane tire testing criteria reflect the loads that may be imposed on tires both during normal operating conditions and after the loss of one tire.
A synopsis of the Board's report, including the probable cause, conclusions, and recommendations, is available on the NTSB's website. The Board's full report will be available on the website in several weeks.