SCOTTSDALE, AZ, USA
N999FA
Mitsubishi MU-2B
The right engine lost power after an uncontained engine failure during the initial takeoff climb. The airplane would not climb and the pilot was forced to land. The pilot selected a street for a forced landing area. The pilot landed gear up while maneuvering to avoid hitting street light poles and automobiles. After touchdown, the airplane slid into a block wall. A fire erupted as a result of a postimpact fuel leak in the left wing. The airplane's engines were examined at the manufacturer's facilities. The right engine exhibited evidence of an uncontained separation of the second stage turbine rotor disk. Examination of the disk fragments revealed a low cycle fatigue fracture mode. The fatigue initiated from multiple areas at and adjacent to the inside diameter bore surface near the aft side of the disk. According to the engine manufacturer, the multiple indication areas were associated with uninspectable size porosity and the primary carbides in the cast material. There were no material or casting defects detected on any of the fractures through the wheel.
On July 20, 1996, at 0857 hours mountain standard time, a Mitsubishi MU-2B, N999FA, landed off the airport after a loss of power during the initial takeoff climb from the Scottsdale Municipal Airport, Scottsdale, Arizona. The airplane was subsequently destroyed by fire and the airline transport pilot was not injured. The airplane was being operated as a business flight under 14 CFR Part 91 when the accident occurred. The airplane was destined for the Phoenix Sky Harbor International Airport, Phoenix, Arizona. Visual meteorological conditions prevailed at the time. The pilot told the Safety Board that the right engine sustained an uncontained engine failure after lift-off while the landing gear was being retracted. After the loss of power, the airplane would not climb. The pilot selected a street about 2 miles northwest of the airport for a forced landing area. The pilot elected to land gear up, while maneuvering to avoid hitting street light poles and automobiles. After touchdown, the airplane slid into a block wall. A fire erupted as a result of a postimpact fuel leak in the left wing destroying the airplane. The airplane's engines were examined by the Federal Aviation Administration at manufacturer's facilities in Phoenix, Arizona. According to the manufacturer, the left engine damage was indicative of engine rotation and operation at the time of impact. The right engine exhibited evidence of an uncontained separation of the second stage turbine rotor disk. Three fragments of the disk remained inside the engine and numerous other fragments exited. Not all of the fragments were recovered. Examination of the three disk fragments revealed a low cycle fatigue fracture mode. The fatigue initiated from multiple areas at and adjacent to the inside diameter bore surface near the aft side of the disk. According to the engine manufacturer, the multiple indication areas were associated with uninspectable size porosity and the primary carbides in the cast material. During the examination, there were no material or casting defects detected on any of the fractures through the wheel. According to the manufacturer, the rest of the damage to the right engine was secondary resulting from the fatigue separation of the second stage turbine wheel.
an uncontained failure of the second stage turbine wheel due to fatigue. Factors were: obstructions in the forced landing area and the inability of the airplane to climb after the turbine wheel failure.
Source: NTSB Aviation Accident Database
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