CHI94LA025

During the initial climb after takeoff, the instructor retarded the throttle to simulate an engine failure without applying carburetor heat. After a descent, the instructor advanced the throttle to regain power and the engine coughed. Shortly after this, the propeller stopped rotating. During an emergency landing roll in a grain field, the nose gear collapsed. No anomalies were found during a full power static runup. The temperature/dewpoint at an airport seven miles from the accident site was 52 and 41 degrees, which was conducive to carburetor icing.

On October 26, 1993, at 1800 central daylight time (CDT), a Cessna 150, N9259U, registered to the Rainbow Airport, Incorporated, of Franklin, Wisconsin, with a certificated flight instructor acting as pilot-in-command of a student training flight, was substantially damaged during an off airport forced landing. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 instructional flight was not operating under a flight plan. The instructor and student pilot reported no injuries. The flight originated from Franklin, Wisconsin, at 1715 CDT.

During an interview with the instructor it was revealed he had been training the student pilot on how to deal with emergencies while in the traffic pattern. He said he retarded N9259U's throttle during the departure leg after takeoff as the airplane passed over a tree line and was approximately 275 feet above the ground. The instructor stated the student began a turn toward a landing field while performing a checklist associated with a power loss. As the airplane was descending, the instructor said, he pushed the throttle in and the engine coughed. The instructor stated that shortly after the propeller stopped rotating he told the student to start the engine. He said the engine would not start and that he made the decision to perform a forced landing.

The airplane touched down on the main landing gear at 75 MPH according to the instructor. He said the airplane rolled approximately eight to ten feet before the nose gear contacted the ground and collapsed. The instructor was asked if he had applied carburetor heat prior to retarding the throttle. He stated he did not.

The owner of the company operating N9259U stated the airplane touched down in a field of cut grain that had a three to four inch high stubble. He stated the student pilot said the airplane stalled about 30 feet in the air.

During postaccident testing, the engine was statically run to maximum RPM. No anomalies were observed during the runup.

The company owner stated the damage to N9259U consisted of: Both wings were "...stretched..." downward, both wing struts were bent at the fuselage junction, the forward 1/3 of the fuselage skin was wrinkled, firewall and lower fuselage skin was bent, the nose gear was broken away from its mount, the rear spar of the wing was bent near the wing root, the vertical stabilizer was wrinkled, and the rotating beacon glass cover was missing.

Approximately ten minutes before the accident, the recorded temperature/dewpoint at an airport seven miles from the accident site was reported to be 52 and 41 degrees Fahrenheit respectively. According to carburetor icing probability chart found in the FAA's "Tips on Winter Flying" publication, the serious probability for carburetor icing existed with a glide power engine setting. The chart and associated information is appended to this report. The FAA Flight Training Manual states: "Rough or abrupt throttle usage may result in a delayed engine response or a complete loss of power...". An excerpt from the training manual is appended to this report.