On April 28, 2006, an Air Tractor Inc. AT-502 (registration N1014D) was involved in an aviation accident near Monroeville, AL. Investigators recorded the probable cause as: Partial loss of engine power for undetermined reasons, which resulted in a forced landing and subsequent nose over. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During climb, the pilot noticed rising internal turbine temperature and loss of engine power, executed a forced landing into a soft field, resulting in a nose-over and post-impact fire. Examination revealed fractured power turbine and compressor turbine blades.
Incident Summary
According to the pilot, the airplane was climbing to 500 feet above ground level en route to a field located 10 miles northeast of the private airstrip when the internal turbine temperature began to rise and engine power diminished. The pilot performed a forced landing into a soft field, during which the airplane nosed over. A post-impact fire ensued, localized to the engine compartment.
Examination Findings
Following the incident, an examination of the engine was conducted. The power turbine blades were found fractured with some axial movement noted. Circumferential rub marks were present on the aft side of the blade roots and disk fir tree slots. The compressor screen was removed and showed no dents; all first stage blades were observed intact and rotated freely. No foreign object damage was detected. The engine was split at the "C" flange, revealing several compressor turbine blades fractured at mid-span with trailing edge deformation. No discrepancies were observed in the P3 system. The fuel control unit sustained impact damage. The teardown inspection indicated that the engine was operating at the time of impact. Examination did not reveal evidence of uncontainment, case rupture, pre-impact malfunction, or in-flight fire.