PAXSON, AK, USA
N4520C
Cessna 170B
The airplane was departing from the 3,500 feet msl airstrip in what the pilot described as 'optimum carb ice conditions' of 40 degrees F with 'lots of moisture.' The carburetor heat control was 'off' for takeoff. At 50 feet above ground level on climb out, the pilot applied carburetor heat and 'the engine died.' She deselected carburetor heat, the engine began to run rough, and the airplane began to lose altitude. When the pilot began a left turn to avoid trees, the left wing and nose dropped, and the airplane impacted terrain. The electric stall warning had been disconnected.
On September 1, 1997, about 1445 Alaska daylight time, a Cessna 170B airplane, N4520C, sustained substantial damage when it impacted terrain 24 miles to the northeast of Paxson, Alaska. The airplane came to rest 400 feet south of the departure end of a graded, unnamed, airstrip on the middle fork of the Chistochina River, at position 63-07.6 north latitude, 144-38.8 west longitude. The private certificated pilot and single passenger both sustained serious spinal injuries. The airplane was owned and operated by the two occupants. The flight was conducted under 14 CFR Part 91 as a personal flight, returning to Girdwood, Alaska. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. An FAA inspector's examination of the wreckage revealed that the carburetor heat control was in the cold position, and there was fuel in the wing tanks. NTSB interviews with the pilot and passenger revealed that there was a "torrential downpour" of rain the night before the accident, and "lots of dew and moisture" before the takeoff. The pilot also stated that it was "optimum carb icing conditions, and 40 degrees F." The pilot said she did a "longer warmup than normal," and used carburetor heat during back taxi. She said she placed carburetor heat off for the takeoff. She indicated that during the initial climb, passing 50 feet above ground level, she applied carburetor heat and the engine "completely died." She removed the carburetor heat, and the engine came back but, "ran rough, as if it was flooded," and the airplane began to lose altitude. Both occupants described tall trees in the flight path. The pilot described turning left toward lower terrain, the nose and left wing dropping, and impacting in a flat attitude. The pilot said in an interview with the NTSB that the stall warning had been disabled prior to her purchase of the airplane. She stated it was not needed because there is a noticeable buffet prior to the airplane stalling. Type Certificate Data Sheet A-799 states in part, "...the following items of equipment must be installed: ...stall warning kit... ." The Joint Rescue Coordination Center in Anchorage, Alaska, initiated a search after receiving a beacon from the airplane's emergency locator transmitter. The airplane was located about 1700, and the occupants transported to a hospital in Fairbanks, Alaska, at 2000. No NTSB Pilot/Operator Report was received from the pilot.
The pilot's improper use of carburetor heat during a takeoff in carburetor icing conditions. Factors associated with the accident were the pilot's decision to operate the airplane with known deficiencies (a disabled stall warning horn), an inadvertent stall, and the presence of carburetor icing conditions.
Source: NTSB Aviation Accident Database
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