What happened
On February 8, 2001, at approximately 15:45 local time, a Learjet LR35A crashed into a forest approximately 300 meters north of the threshold of Runway 10 at Nuremberg Airport. The flight, which was a return trip to Rome, had departed from Nuremberg only minutes earlier.
Shortly after takeoff, approximately three minutes into the flight, the left engine failed without warning. The crew declared an emergency and requested an immediate return to the airport. While the approach initially appeared stable, witnesses on the ground observed the aircraft performing unusual maneuvers and wobbling at a low altitude. During the short final approach, the aircraft drifted north of the centerline and suddenly pitched left, entering an inverted flight attitude before impacting the ground in a near-upside-down position. The impact and subsequent post-crash fire destroyed the aircraft and killed all 3 occupants, including the two pilots and a technician.
The investigation
The BFU investigation focused on the mechanical failure of the left engine and the flight dynamics during the emergency landing. Investigators examined the wreckage, analyzed flight data recorders and cockpit voice recorders, and reviewed maintenance logs. The investigation also involved international representatives from the NTSB (USA), ANSV (Italy), and the FAA (USA), as well as specialists from Honeywell and Bombardier.
Technical analysis of the left engine revealed that several turbine blades and attachment lugs from the high-pressure turbine disc had broken away. Metallurgical testing identified intercrystalline cracking within the turbine wheel, which led to the structural failure of the disc components.
Findings
- The primary cause of the engine failure was intercrystalline fractures on the high-pressure turbine disc.
- Inaccurate maintenance records resulted in the turbine disc being operated far beyond its certified life limit.
- The disc had accumulated 9,313 cycles, exceeding the maximum allowable limit of 5,200 cycles by 4,113 cycles.
- This discrepancy occurred because 3,956 cycles were not recorded when the disc was transferred from a previous engine (SN 89508) to the engine involved in the accident (SN 89224).
- The flight crew's execution of the single-engine landing procedure was insufficient, leading to an excessive pitch attitude and a loss of control at low altitude during the final approach.