What happened
On a flight from Edmonton to Winnipeg, a privately operated Piper PA-46-350P Jetprop DLX, registration C-FKKH, encountered severe flight difficulties while cruising at flight level 270. The pilot initially reported autopilot and altitude maintenance issues, followed by a report that the aircraft's gyro/horizon had toppled and was no longer reliable.
Following these reports, radar tracked the aircraft performing several erratic heading and altitude changes before entering a steep right turn and a rapid descent. During this descent, the aircraft's ground speed dropped significantly, indicating a near-vertical flight path. The aircraft eventually broke up in mid-air due to extreme aerodynamic loads, with the wreckage discovered near Wainwright, Alberta. All five people on board were killed.
The investigation
The TSB examined the wreckage, the aircraft's maintenance history, and the pilot's training records. Investigators found that the aircraft's primary attitude indicator, a King KI256 gyro/horizon, suffered from significant internal wear and damage to its bearings and shaft. This degradation, likely exacerbated by a vacuum system that was not providing sufficient pressure, caused the instrument to become unstable and eventually topple.
Furthermore, the investigation revealed that the aircraft was operating significantly overweight and with a center of gravity that was beyond the aft limit. This loading configuration increased the aircraft's pitch sensitivity and reduced its longitudinal stability. The TSB also noted that the pilot had not practiced partial panel instrument flying for several years, making it difficult to manage the loss of primary instrumentation in instrument meteorological conditions.
Findings
- The primary cause of the accident was the structural failure of the aircraft due to exceeding its aerodynamic limits during an uncontrolled descent.
- The gyro/horizon failure was caused by excessive internal wear and a lack of timely maintenance.
- The aircraft was operating in an unsafe configuration, exceeding its maximum gross weight and possessing an aft center of gravity that made the aircraft unstable and difficult to control.
- The pilot's inability to transition to partial panel flight following the instrument failure contributed to the loss of control.
- Deficiencies in the operator's safety management system and inadequate oversight by the CBAA prevented the identification of these operational risks.