The National Transportation Safety Board today determined that the probable causes of the crash of an American Airlines MD-82 during landing at Little Rock airport in 1999 were "the flight crew's failure to discontinue the approach when severe thunderstorms and their associated hazards to flight operations had moved into the airport area, and the flight crew's failure to ensure that the spoilers had extended after touchdown."
Contributing to the accident were "the flight crew's (1) impaired performance resulting from fatigue and the situational stress associated with the intent to land under the circumstances, (2) continuation of the approach to a landing when the airline company's maximum crosswind component was exceeded, and (3) use of reverse thrust greater than 1.3 engine pressure ratio after landing."
The accident occurred on June 1, 1999, as AA flight 1420 was arriving from Dallas/Fort Worth with 139 passengers and six crewmembers on board. The aircraft overran the runway, passed through a chain link fence, went down an embankment and collided with a structure supporting the runway lighting system. The captain and 10 passengers were killed; over 100 others were injured. The aircraft was destroyed by impact forces and post-crash fire.
In its final report on the investigation, the five-member Safety Board concluded that the local air traffic controller provided appropriate and timely weather information to the flight crew and that, given the rapidly deteriorating conditions in the airport area and crosswinds that exceeded the airline's guidelines for landing, the crew should have abandoned the approach.
Noting that, industry-wide, the penetration of thunderstorms by airliners occurs on a regular basis, the Board recommended that the FAA establish a Government-industry working group to develop strategies for reducing the frequency of such potentially hazardous actions.
The Board also determined that the lack of spoiler deployment was the "single most important factor" in the flight crew's inability to stop the accident aircraft within the available runway length. Consequently, the Board made recommendations to the FAA aimed at changing airline procedures to ensure the effective use of spoilers to facilitate safe landings.
Noting that the flight crew had been on duty for about 13 hours and that the crew's degraded performance was consistent with the known effects of fatigue, the Board reiterated a previous recommendation that the FAA establish scientifically-based regulations that limit hours of service and provide for predictable work and rest schedules.
The Board also found that the crew's use of reverse thrust at levels greater than 1.3 engine pressure ratio on a wet and slippery runway significantly reduced the effectiveness of the airplane's rudder and vertical stabilizer, thereby contributing to directional control problems. The Board made two recommendations in this area regarding measures to inform flight crews of the negative effects of utilizing excess reverse thrust power with such runway conditions.
As a result of the investigation, the Board made 22 new recommendations to the FAA and two to the National Weather Service. An abstract containing the Board's findings and recommendations can found on the NTSB web site. The complete final report will be available on the web site at a later date.