Tragic Accident Killed CFI and Student

An investigation into the night-time training accident that killed two pilots in the fall of 2007 has revealed some troubling data... with strong evidence that a goose collision contributed to the outcome. Pilot Adam Ostapenko (20), of Duluth, Minn., and CFI Annette Klosterman (22), of Seattle, were lost in this tragedy.

The Probable Cause report states that, "The accident flight was the third of a three-leg dual instructional night cross-country flight. The airplane was established in normal cruise flight at 4,500 feet mean sea level (msl) when the airplane abruptly departed controlled flight and impacted a bog. The bog was about 15 to 20 feet deep, with a thin layer of vegetation floating on the surface. The airplane came to rest inverted, and damage to the airframe was consistent with an inverted impact to the surface of the bog. Data recovered from the airplane's flight display system indicated that the airplane was in stable flight on a 320-degree magnetic heading, at 4,500 feet msl, and approximately 160 knots true airspeed prior to the accident, when it abruptly departed from controlled flight. The airplane rolled approximately 20 degrees left wing down, yawed to the left about 30 degrees, and simultaneously pitched nose-down about 40 degrees. It then reversed and immediately entered a descending, right roll for the duration of the flight. The airplane impacted the bog within 30 seconds of the upset. The post accident examination noted that the left half of the horizontal stabilator was bent upward approximately 90 degrees, inconsistent with the damage to the remainder of the airframe. This damage was consistent with the initial left yaw and nose down pitch recorded during the upset. In addition, a depression and tear were observed on the upper wing skin near the left wing tip. Microscopic examination and DNA testing of material on the inside surface of the wing skin was identified as remains of a Canada goose. The natural history of this species was consistent with the location, time, and date of the accident."

The aircraft's problems seemed to have happened "abruptly." According to the investigating report, the Seminole's (file photo, below)  Avidyne avionics "normally retain flight parameters in non-volatile memory within the Primary Flight Display (PFD) and Multifunction Display (MFD) units. Download of the data associated with the MFD was not successful due to damage sustained in the accident. Download of the PFD data was successful, however."

The PFD data indicated that the airplane was in stable flight on a 320-degree magnetic heading, at 4,500 feet msl, and approximately 160 knots true airspeed prior to the accident. About 2211:46, the airplane abruptly departed from controlled flight. It rolled approximately 20 degrees left wing down, yawed to the left about 30 degrees, and simultaneously pitched nose down about 40 degrees. The airplane then reversed and immediately entered a descending, right roll for the duration of the flight. The recorded data ended about 2212:10.

A section of upper wing skin was taken from near the left wing tip, at a point about mid-chord. The post accident examination noted the presence of material on the inside surface of the wing skin inconsistent with those used in the construction of an aircraft. The wing skin section was along a tear in the skin, adjacent to the spar. This portion of the airplane was submerged in the bog after the accident until recovery of the airplane.

Microscopic examination and DNA testing by forensic ornithologists identified the material on the wing skin section as remains of a Canada goose. The ornithologists further noted that the natural history of this species was consistent with the location, time and date of the accident.

Of additional note, in the NTSB data, was an observation concerning a portion of the wreckage, "The left half of the stabilator was bent upward approximately 90 degrees at the tip, which was inconsistent with the damage to the remainder of the airframe. The inboard leading edge skin was torn from the spar. The spar was deformed but appeared otherwise intact. The stabilator section remained attached to the airframe by the spar, remaining stabilator skin aft of the spar, and the anti-servo trim tab."

The NTSB reports added some interesting info to this report: Analysis of bird strike data from 1990 through 2004 by the United States Department of Agriculture, Wildlife Services, determined that 74 percent of bird strikes occurred within 500 feet of the ground, 19 percent between 500 feet agl and 3,500 feet agl, and 7 percent above 3,500 feet. Of the 26 percent of bird strikes that occurred above 500 feet, about 7 times more strikes occurred at night than during daylight hours. This was due to the fact that about 61 percent of the reported strikes above 500 feet agl occurred at night while only 18 percent of aircraft movements occurred at night. In addition, a proportionally higher incidence of strikes occurred between September and November, and between April and May, as compared to the number of flight operations.

Further review of the data indicated that the probability of a bird strike decreased by 32 percent for every 1,000-foot increase in altitude. Outside of the airport environment, the altitude zone from 500 feet agl to 3,500 feet agl was the most hazardous, especially at night.

Canada geese were attributed to 668 strikes with civil aircraft between 1990 and 2002. Of those strikes, 112 resulted in substantial damage to the aircraft. The average mass of a Canada goose is 9.2 lbs for a male and 7.8 lbs for a female, with a maximum mass of 13.8 lbs. This species exhibits strong flocking behavior.

The University of North Dakota provided additional pilot training regarding bird strike hazards and mitigation. In addition, they recommended to all of their pilots and flight instructors that when possible higher cruise altitudes should be selected, especially on night cross-country flights, in order to minimize the probability of a bird strike.

The NTSB's Probable Cause determinations states that "An in-flight collision with at least one Canada goose, and the resulting damage to the left stabilator that caused the airplane to become uncontrollable. Contributing to the accident was the night lighting condition, which precluded any possibility of the flight crew seeing the bird(s) prior to impact."

FMI: www.ntsb.gov/ntsb/brief.asp?ev_id=20071102X01708&key=1, (ANN thanks Chuck Szmurlo for the use of the photo of the Canada Goose).