With only the pilots on board, a Learjet LJ-60 was operating a flight from Dallas Love Field (Texas, USA) to Troy Municipal Airport (Alaska, USA on this day in aviation history, the 14th of January 2001. 23 years ago, to date.
The wreckage of the aircraft (Source & © NTSB)
After take-off, at 10:30 lt (local time), the ~1020 kilometre (~550 nautical miles) flight was uneventful and the aircraft was cleared to land at runway 7 of Troy Municipal Airport just before 13:45 lt (local time). The aircraft touched down on runway 7 with a speed of 123 knots, 1500 feet into the landing roll, two deer ran onto the runway in front of the aircraft. There was no avoiding the animals and the Learjet collided with both deer. Initially, the crew could keep the aircraft on the runway as it continued down the runway with the tires smoking, hardly decelerating. Toward the end of the runway, the aircraft veered off the right-hand side of the runway, crossed a taxiway and ran into a ditch bursting in flames. Airport staff were able to free the flight crew from the wreck before it was fully engulfed in flames.
Both of them sustained serious injuries.
The wreckage of the aircraft (Source & © NTSB)
The accident was investigated by the National Transportation Safety Board. As part of the investigation, the crew was interviewed and, with one exception, no abnormalities were reported. The one abnormality was the observation by both pilots that both the thrust reversers failed to operate when deployed. The weather was analysed and determined not to be a factor in the accident, An inspection of the runway revealed two deer carcasses on the runway and heavy black skid marks starting approximately 1500 feet from the beginning of the 5100-foot runway. The skid marks continued for approximately 2500 feet up to the point where the aircraft left the runway. From that point, the aircraft continued over soft ground for approximately 500 before coming to a stop on its left side. All three landing gears had collapsed with the main landing gear tires completely worn through. The flaps were found fully extended and both thrust reversers were found stowed, with the throttles in idle and the reverser levers in the stowed position.
The wreckage of the aircraft (Source & © NTSB)
Upon a detailed investigation of the landing gear, deer fur was found logged in the squat switch of the main landing gear. With the loss of the squat switch on the left main landing gear, the thrust reverser relay box would de-energize the deploy solenoid, and the thrust reverser would move to the stowed position. As the thrust reversers complete the stow cycle, the EEC's switch to the forward thrust schedule, and if the piggybacks remain at the max reverse position, the engine's rpm begins to increase to near takeoff power.
The NTSB determined that the probable cause of this accident was;
On-ground collision with deer during landing roll, and the inadvertent thrust reverser stowage caused by the damage to the landing gear squat switch by the collision, and subsequent application of forward thrust during rollout.
The NTSB report can be accessed by clicking on the .pdf file below;