Primary finding
Probable cause
The inadvertent raising of the flaps.
Investigator assessment
Analysis narrative
The pilot-in-command selected the 40 degree flap position for his approach and landing. The airplane 'fell out of the sky' on short final. After exiting the airplane he noticed the flap handle was in the 30 degree position. Examination of the airplane and flap system showed that the handle would not stay in the 40 degree selected position if bumped. The flap handle was very stiff when positioned from the 30 degree to the 40 degree position and would not completely latch on the 40 degree position.
Source record
Factual narrative
On August 7, 1993, at 2215 Alaska daylight time, a wheel equipped Cessna 180 airplane, N3654C, registered to Tony Turinsky of Anchorage, Alaska, and operated by the Pilot-in-Command, landed short of the Lake Hood Airstrip, Anchorage, Alaska. The personal flight, operating under 14 CFR Part 91, departed Lake Hood for a local flight. No flight plan was filed and visual meteorological conditions prevailed. The Commercial Certificated Pilot-in- Command and the two passengers were not injured and the airplane was substantially damaged. According to the Pilot-in-Command, he was on short final, landing to the south, when the airplane suddenly fell out of the sky. It landed short of the runway. After exiting the airplane, he noticed the flap handle set at the 30 degree flap position. He stated he had selected the 40 degree position during the approach. Examination of the airplane and flap handle by a NTSB Investigator showed that when the 40 degree flap position was selected initially, the handle would stay in position. However, when the handle was lightly bumped it immediately jumped back to the 30 degree flap position. The test was performed a number of times with the same results. Occasionally, the handle would remain in the flaps 40 degree position but only after pulling up against the stop a number of times. The flap handle travel from the 30 degree to 40 degree position was stiff and as the handle neared the 40 degree position it became harder to pull and required effort to ensure that it would latch in the flaps 40 degree position. -