December 19, 2019

Respect Aircraft Limitations: TSB


The Transportation Safety Board investigation into the crash in Whitehorse (CYXY) of a Cessna 170B on May 27 of this year has ended and the report was issued earlier this week. In it, the TSB highlights the use of flaps contrary to the manufacturer’s recommendation as outlined in the pilots operating handbook (POH) as a factor that may have led to the crash of the U.S.-registered Cessna, which killed the two pilots on board.

A post-crash fire consumed the aircraft, but the TSB was able to retrieve a video camera that had recorded the takeoff and the short flight. After examining it at the TSB’s laboratory in Ottawa, investigators were able to reconstruct the flight.

The aircraft had taken off from Runway 14R with the wind coming from 210° at 15 knots, gusting to 20. A windsock at the other end of the runway indicated calm winds.

Once airborne the aircraft entered the area of calm air. The pilot, who was a certified flight instructor and had accumulated over 9500 hours, deployed 40° flaps before later reducing them to 20° or 30°. This all took place with runway remaining. The aircraft never rose more than 50 feet above ground level. It then stalled, bounced and crashed outside the perimeter fence.

The density altitude at the time of the flight was 4069 feet. According to the Cessna’s POH, the use of flaps at higher density altitudes is not recommended; they would be producing significant drag while providing minimal lift.

Although TSB investigators were unable to determine the 170’s takeoff weight, they were able to determine it was at least at the gross takeoff weight of 2200 pounds.

Given the long operational days of 12 to 14 hours preceding the day of the flight, and the 11-hour-long operational day preceding the flight itself, fatigue may also have played a role in pilot decision-making.

The full report is appended below.

Photo credit: Henry Richard