Fatal mid-air breakup of Lancair IV-P near Sundre, Alberta

Casualties unknown • CA

A Lancair IV-P crashed near Sundre, Alberta, after encountering severe weather, resulting in two fatalities and the mid-air disintegration of the aircraft.

What happened

On 09 August 2005, a Lancair IV-P, registration N750F, departed Calgary, Alberta, on an instrument flight rules (IFR) flight plan bound for Grande Prairie, Alberta. The flight had originally begun at Vance Brand Airport in Colorado with a final destination in Alaska. After leveling off at flight level 200, radar data showed the aircraft began a descent at 1918 MDT. The radar signal was lost at approximately 14,500 feet, with the final returns recorded at 1920 MDT.

The wreckage was distributed over a 1.3 nm debris field southwest of the main impact site. The fuselage and left wing spar were located roughly eight nautical miles southeast of Sundre, Alberta. The crash resulted in two fatalities, involving the pilot and the passenger.

Prior to the flight, the pilot had received a weather briefing from the Edmonton Flight Information Centre. While no significant weather was forecast for the flight path, there were reports of developing towering cumulus clouds northwest of Calgary, with some cumulonimbus clouds expected to have tops reaching 32,000 feet. The pilot had expressed concern during the briefing regarding the limitations of his onboard weather information system, which lacked Canadian radar imagery.

The investigation

Investigators examined the aircraft's performance and the environmental conditions at the time of the accident. The investigation focused on the aircraft's interaction with the cloud formations and the physical state of the airframe. The probe also looked into the aircraft's weight and balance, noting that the aircraft was operating 250 to 350 pounds above its recommended gross take-off weight.

Findings

  • The aircraft entered the tops of towering cumulus clouds, where it likely accumulated significant airframe ice.
  • This ice accumulation prevented the aircraft from maintaining acceleration during cruise flight, leading to an aerodynamic stall.
  • The pilot was unable to recover from the resulting stall and subsequent dive.
  • The aircraft underwent structural failure and broke up due to the extreme speeds reached during the dive.
  • The aircraft's weight, being over the recommended limit, had increased the stall speed by approximately 17 knots.

Probable cause

The aircraft entered towering cumulus clouds and accumulated enough ice to cause an aerodynamic stall, which the pilot could not recover from, leading to a high-speed dive and mid-air breakup. This was further complicated by the aircraft being operated above its recommended gross weight.

Frequently asked questions

What happened in the 2005-08-09 Sundre, Alberta, 8 nm SE accident near CA?

A Lancair IV-P crashed near Sundre, Alberta, after encountering severe weather, resulting in two fatalities and the mid-air disintegration of the aircraft.

What aircraft was involved and where did it happen?

The accident on 2005-08-09 involved a Sundre, Alberta, 8 nm SE, operated by Lancair IV-P N750F, at CA.

What was the probable cause of the accident?

The aircraft entered towering cumulus clouds and accumulated enough ice to cause an aerodynamic stall, which the pilot could not recover from, leading to a high-speed dive and mid-air breakup. This was further complicated by the aircraft being operated above its recommended gross weight.

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