Landing and Rollout
The airplane touched down approximately 1,900 feet from the approach end of a 6,000-foot runway. During the rollout, the pilot reduced power by pulling the power levers aft to the flight idle stop. He then depressed the latch levers and pulled the power levers further aft, through the beta range and into the reverse range.
Beta Light Indication
During the power reduction, the pilot noticed a red beta light indication and responded to it. Guidance from the manufacturer and operator prohibited the use of reverse thrust on the ground when the red beta light was illuminated. The pilot subsequently pushed the power levers forward out of the reverse range, inadvertently continuing through the beta range—where aerodynamic braking was optimal—and beyond the flight idle gate into flight idle, a positive thrust setting.
Runway Excursion
The airplane continued to the departure end of the runway in a skid. It departed the runway and taxiway in a skidding turn, dropped over a 60-foot embankment, and came to rest at the bottom.
Performance and Testing
The computed landing distance over a 50-foot obstacle, using braking and ground idle (beta) only with no reverse thrust applied, was 3,900 feet. Ground-taxi testing after the accident revealed that the airplane could reach groundspeeds upwards of 85 knots with the power levers at idle and the condition levers in the flight position. Simulator testing based on flight data recorder (FDR) information consistently resulted in runway overruns.
Mechanical and System Examination
Examination of the airplane and component testing revealed no mechanical anomalies. Review of the beta light indicating system showed that illumination of the red beta light on the ground was not an emergency situation but only indicated a switch malfunction. Additionally, a loss of reverse capability would have had little effect on computed stopping distance, and none at all in the United States, where performance credit for reverse thrust was not permitted.