Safety

An in-flight collision with at least one Canada Goose damaged the stabilator on a University of North Dakota twin-engined Piper PA-44-180 Seminole at 4,500ft (1,370m) on a cross-country flight over Minnesota on the night of 17 October 2007, making the aircraft uncontrollable, says a recently released probable cause finding by the US National Transportation Safety Board.

A university flight instructor and a commercial/instrument student at the college were killed after the aircraft crashed in a bog less than 30s after the collision. Twenty-four seconds of recovered data from the Avidyne pilot flight display indicated that the piston-powered twin "abruptly departed controlled flight", rolling about 20° left wing down, yawing 30° left and pitching nose down 40°. The aircraft then began a descending right turn for the duration of the flight.

Investigators found the left half of the aircraft's horizontal stabilator bent upward roughly 90°, inconsistent with the damage to the aircraft, but "consistent with the initial left yaw and nose-down pitch recorded during the upset". DNA material removed from below a depression and tear on the upper wing skin near the left wing tip was found to be from a Canada Goose, a species whose "natural history" is consistent with "the location, time and date of this accident", the NTSB found.

In addition, the NTSB says analysis of bird strike data between 1990 and 2004 by the US Department of Agriculture shows that 7% of bird strikes occurred above 3,500ft, and that bird strikes in general (above 500ft) were seven times more likely to occur at night. Strikes also increase in September and November, and April and May. Canada Geese were attributed to 668 civil collisions between 1990 and 2002, 112 of which resulted in "substantial" damage to the aircraft.