GAA15LA265

The private pilot was conducting a personal flight and was on final approach to land at a remote backcountry airstrip. The pilot reported that he applied carburetor heat for the approach and that he observed 60 mph (52.1 knots) on the airspeed indicator. He subsequently "pushed the throttle forward, but the engine sound remained constant." According to the pilot-rated passenger, as the pilot began to level the wings to align with the runway, the right wing "instantly…dropped to a 45 degree angle." He then observed the pilot immediately reach for the throttle but saw him inadvertently grab the carburetor heat lever instead. 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 landing area. The airplane sustained substantial damage to both wings and the fuselage. The pilot reported no mechanical malfunctions or failures with the airplane that would have precluded normal operation. It is likely that, during the final approach, the pilot did not maintain adequate airspeed and exceeded the airplane's critical angle-of-attack, which resulted in an aerodynamic stall. Although the pilot attempted to add power to recover from the stall, he inadvertently grabbed the carburetor heat lever instead of the throttle.

On September 20, 2015, about 1210 Alaska daylight time, a Stinson 108-3 airplane, N6066M, impacted terrain during the final approach to land at a remote airstrip in the Knik Glacier area, about 19 miles south east of Palmer, Alaska. The pilot and pilot-rated passenger both sustained serious injuries. The airplane was registered to a private owner and was operated by the pilot as a 14 Code of Federal Regulations Part 91 personal flight. Day visual meteorological conditions prevailed for the flight, with no flight plan filed. The flight departed from Birchwood Airport (BCV), Birchwood, Alaska about 1140, and flew for 30 minutes prior to the accident. According to the pilot, he reported that the carburetor heat was applied for the landing. On final approach, the pilot remembered that the pilot-rated passenger stated, "Airspeed!" and he observed 60 MPH (52.1 knots) on his airspeed indicator. Subsequently, the pilot stated that he "pushed the throttle forward, but the engine sound remained constant." The pilot reported there were no mechanical malfunctions or failures with the airplane that would have precluded normal operation. According to the pilot-rated passenger who was sitting in the front right seat of the airplane, the pilot entered a 30 degree banked left turn to final, applied one notch of flaps, and stated his touchdown speed would be "55" Miles Per Hour (MPH) (47.8 knots). As the pilot began to level the wings for the final approach, "instantly the right wing dropped to a 45 degree angle." The passenger then observed the pilot immediately reach for the throttle, but saw him grab the carburetor heat lever. The airplane impacted terrain in a nose low, right wing down attitude, and came to rest on a hill side about 100 yards short of the landing area. The airplane sustained substantial damage to both wings and the fuselage. A witness on the ground, who was also a commercial pilot, observed the accident airplane's traffic pattern. The witness stated that the accident airplane was lined up with the runway and then "suddenly the right wing dropped, and the left wing came up" and added, "the airplane fell out of the sky, he just stalled." He also stated that he could hear a "steady low power setting, and never heard the engine get louder" during the approach. The witness was the first person to reach the airplane and observed the throttle quadrant; he stated that "the throttle lever was all the way out and was bent" and he could smell and see fuel leaking from both wings. ADDITIONAL INFORMATION According to 14 Code of Federal Regulations Part 61.56, "no person may act as pilot in command of an aircraft unless, since the beginning of the 24th calendar month before the month in which that pilot acts as pilot in command, that person has accomplished a flight review." The pilot reported that his last flight review was on May 1, 2012. According to the Stinson 108-3 Airplane Flying Manual, Performance Information Section, the stalling speed with flapsfull down is listed as 61.4 MPH (53.4 knots) and with flaps up is 64.5 MPH (56 knots). With a 10 degree angle of bank, the stalling speed listed with flaps full down is 62.0 MPH (53.9 knots) and with flaps up is 65 MPH (56.5 Knots). The Stinson 108-3 manual does not list stalling speeds for partial flap extensions.