Accident Details
On September 20, 2015, at about 1210 Alaska daylight time, a Stinson 108-3 airplane, registration N6066M, impacted terrain while on final approach to a remote airstrip in the Knik Glacier area, approximately 19 miles southeast of Palmer, Alaska. The airplane was operated by the pilot as a personal flight under 14 Code of Federal Regulations Part 91. Day visual meteorological conditions prevailed, and no flight plan was filed. The flight departed Birchwood Airport (BCV), Birchwood, Alaska, around 1140 and was airborne for about 30 minutes before the accident.
Pilot and Passenger Accounts
The pilot reported that carburetor heat was applied for landing. During the final approach, the pilot-rated passenger called out "Airspeed!" and the pilot observed 60 MPH (52.1 knots) on the airspeed indicator. The pilot then stated he pushed the throttle forward, but the engine sound remained constant. He noted no mechanical malfunctions or failures that would have precluded normal operation.
The pilot-rated passenger, seated in the front right seat, stated that the pilot entered a 30-degree banked left turn to final, applied one notch of flaps, and announced a touchdown speed of 55 MPH (47.8 knots). As the pilot began leveling the wings for final approach, "instantly the right wing dropped to a 45 degree angle." The passenger saw the pilot reach for the throttle but instead grab the carburetor heat lever. The airplane impacted terrain in a nose-low, right-wing-down attitude and came to rest on a hillside about 100 yards short of the intended landing area. Both wings and the fuselage sustained substantial damage.
Witness Account
A ground witness, also a commercial pilot, observed the accident airplane's traffic pattern. He stated the airplane was lined up with the runway when "suddenly the right wing dropped, and the left wing came up" and added, "the airplane fell out of the sky, he just stalled." The witness reported hearing a steady low power setting and never heard the engine increase in power during the approach. He was the first to reach the airplane and noted that the throttle lever was fully aft and bent, and he could smell and see fuel leaking from both wings.
Additional Information
The pilot's last flight review was on May 1, 2012, according to his report. 14 Code of Federal Regulations Part 61.56 requires a flight review every 24 calendar months. The Stinson 108-3 Airplane Flying Manual lists stalling speeds with full flaps down at 61.4 MPH (53.4 knots) and with flaps up at 64.5 MPH (56 knots). With a 10-degree angle of bank, the stalling speed with full flaps down is 62.0 MPH (53.9 knots) and with flaps up is 65 MPH (56.5 knots). The manual does not provide stalling speeds for partial flap extensions.