Rush City, MN, USA
N9646Q
Cessna 172
The student pilot and his flight instructor completed an uneventful 15- to 20-minute flight in the airport traffic pattern before the flight instructor deboarded so the student pilot could continue on his first solo flight. The engine was not shut down while the flight instructor deboarded the airplane. The student pilot then taxied to the hold-short line for the runway where he completed an abbreviated before takeoff check, which included verifying that elevator trim was positioned for takeoff, carburetor heat was turned off, flaps were fully retracted, and that the fuel mixture control was full rich. The student pilot did not complete an engine runup before takeoff. The student pilot stated that after takeoff, the airplane climbed to about 200 ft above the runway where the engine began to splutter briefly before a total loss of power. The airplane sustained substantial damage to the fuselage and both wings during a forced landing in a wooded area. The flight instructor stated that he taught his students to pull the mixture control knob aft about 1 1/2 inches during taxi to avoid fouling the sparkplugs. The flight instructor recalled that he told the student pilot to lean the fuel mixture while they taxied back to the ramp at the completion of their dual-instruction flight. The flight instructor stated that shortly after the accident, the student pilot told him that the mixture control was pulled aft about 1 1/2 inches and that the carburetor heat control was on. The student pilot subsequently reported that that he did not lean the fuel mixture during taxi and that leaning typically was only completed during cruise flight. Additionally, before he exited the airplane, the student pilot turned off the electrical master switch and both magnetos, repositioned the fuel selector from both to off, and pulled the mixture control knob full aft. Postaccident examination revealed uncontaminated 100 low-lead aviation fuel present in the fuel strainer and the carburetor bowl. There was no evidence of fouling or excessive carbon deposits on the sparkplugs that would have prevented normal engine operation. The lack of fouling or excessive carbon deposits on the sparkplugs was consistent with a proper air-fuel mixture and normal carburetor function during the flight. Additionally, a postaccident engine test run did not reveal any mechanical anomalies with the engine that would have prevented normal operation during the flight. Although the carburetor heat control system did not function properly during the test run, the sparkplugs did not exhibit features consistent with a carburetor icing situation that would have resulted in an excessively rich air-fuel mixture had the airflow through the carburetor venturi become restricted due to carburetor icing during the flight. Additionally, the engine test run confirmed that while at maximum static speed, the engine would stop running due to fuel starvation with the mixture control knob moved aft about 1 1/2 inches. It is likely that the student pilot did not reposition the mixture control to full rich before takeoff, which resulted in a total loss of engine power due to fuel starvation.
HISTORY OF FLIGHTOn December 21, 2019, about 1306 central standard time, a Cessna 172M airplane, N9646Q, was substantially damaged when it was involved in an accident near Rush City, Minnesota. The student pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The student pilot stated that he completed an uneventful 15- to 20-minute flight in the airport traffic pattern with his flight instructor immediately before the accident flight. After the dual-instruction flight, the student pilot did not shut down the engine while his flight instructor deboarded the airplane on the airport ramp. The student pilot then began his first solo flight by taxiing to the hold-short line for runway 16 where he completed an abbreviated before takeoff check, which included verifying that elevator trim was positioned for takeoff, carburetor heat was turned off, flaps were fully retracted, and that the fuel mixture control was full rich. The student pilot acknowledged that he did not complete an engine runup before takeoff. The student pilot taxied the airplane onto the runway 16 centerline where he briefly held the brakes as he advanced the throttle to takeoff power. He stated that the takeoff roll was uneventful, and that liftoff was achieved with about half of the runway remaining. The airplane climbed to about 200 ft above the runway at which time the engine began to splutter and then had a total power loss. The propeller continued to windmill after the loss of engine power. The student pilot stated that he momentarily "froze-up" before he reduced airplane pitch to establish best glide airspeed and avoid an aerodynamic stall. He initially thought the airplane could land in a field directly south of the runway, but he subsequently determined that the airplane would not clear a powerline preceding the field. The student pilot stated that the airplane collided with trees as he maneuvered to avoid the powerline. After the accident, fuel was "raining down" into the cabin from the damaged wings. Before he exited the airplane, the student pilot turned off the electrical master switch and both magnetos, repositioned the fuel selector from both to off, and pulled the mixture control knob full aft. PERSONNEL INFORMATIONThe accident occurred during the student pilot’s first solo takeoff. METEOROLOGICAL INFORMATIONAccording to a carburetor icing probability chart contained in Federal Aviation Administration (FAA) Special Airworthiness Information Bulletin CE-09-35 Carburetor Icing Prevention, the recorded temperature and dew point were in the range of susceptibility for the formation of carburetor icing at glide (descent) and cruise engine power. According to the bulletin, a pilot should use carburetor heat when operating the engine at low power settings, or while in weather conditions where carburetor icing is probable. WRECKAGE AND IMPACT INFORMATIONThe airplane wreckage was in a wooded area about 1,100 ft past the runway 16 departure threshold and about 360 ft right of the extended runway 16 centerline. The airplane came to rest in a nose-down attitude with substantial damage to both wings, aft fuselage, and the rudder. Both wing leading edges exhibited crushing damage consistent with tree impact. The propeller appeared undamaged. A FAA maintenance inspector examined the airplane after it was recovered from the accident site to a salvage facility. The FAA inspector stated that uncontaminated 100 low-lead aviation fuel was present in the fuel strainer and the carburetor bowl. The throttle and fuel mixture control cables were intact between the cockpit controls and the carburetor. The locking feature for the mixture control knob was found stuck in the fully depressed position, which prevented the mixture control from locking in any position. The intake airbox was clear of any obstruction. The carburetor heat valve was attached to the shaft with a hose clamp and the shaft bushings were significantly worn. The FAA inspector could rotate the carburetor heat valve on the shaft without the shaft rotating. Except for the lower sparkplugs for cylinder Nos. 1 and 3 that were oil soaked, the remaining sparkplugs did not exhibit any evidence of fouling or excessive carbon deposits. An engine test run was completed with the engine installed on the airframe using the existing engine controls. The engine started without hesitation and ran smoothly between idle and 2,500 rpm. A magneto check confirmed proper function of the ignition system. The engine speed did not change appreciably with the carburetor heat control engaged. With the engine at 1,800 rpm there was no change in operation until the mixture control was moved aft about 1 1/2 inches. With the engine at maximum static speed, about 2,500 rpm, there was no change in operation until the mixture control was moved aft about 1 inch, and the engine stopped running due to fuel starvation when the mixture control was moved aft about 1 1/2 inches. Except for the non-functioning carburetor heat, the engine test run did not reveal any mechanical anomalies that would have prevented normal operation during the flight. ADDITIONAL INFORMATIONThe flight instructor told a FAA inspector that he had received feedback from maintenance personnel that he should lean the fuel mixture during taxi to avoid fouling the sparkplugs. The flight instructor stated that he taught his students to pull the mixture control knob aft about 1 1/2-inches during taxi. The flight instructor recalled that he told the student pilot to lean the fuel mixture while they taxied back to the ramp at the completion of their dual-instruction flight. The flight instructor stated that he spoke with the student pilot shortly after the accident, and the student pilot told him that the mixture control was pulled aft about 1 1/2-inches and that the carburetor heat control was on. The student pilot subsequently told the FAA inspector and the National Transportation Safety Board investigator that that he did not lean the fuel mixture during taxi, and that leaning typically was only completed during cruise flight.
The total loss of engine power due to fuel starvation because the student pilot failed to reposition the fuel mixture control to full rich before takeoff.
Source: NTSB Aviation Accident Database
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