CEN21LA035

The flight instructor and his student were departing on an instructional flight from a private grass airstrip. The pilots completed a before-takeoff engine runup with no anomalies or malfunctions reported. The flight instructor reported that his student performed the soft-field takeoff. After the airplane became airborne, the student reduced airplane pitch to remain within ground effect, and allowed the airspeed to increase to 80 knots. The flight instructor reported that during the initial climb there was a drop in engine speed (rpm). The flight instructor confirmed the throttle control was full forward, but there was “no significant engine performance.” The flight instructor took control of the airplane from his student, reduced pitch, and banked to avoid the highway and powerlines located at the end of the airstrip. The flight instructor stated that a lack of engine performance resulted in a forced landing before the airplane completed 90° of turn from the takeoff heading. The airplane landed on the northside of the highway, collided with a power pole, and came to a stop. The airplane’s left wing and engine mount were substantially damaged during the accident. According to the flight instructor, the airplane’s flaps were extended 10° for the soft-field takeoff based on a laminated checklist in the cockpit. The airplane’s owner’s handbook requires the flaps to be extended 25° for a soft-field takeoff. However, according to the flight instructor, the airplane became airborne and accelerated to a safe airspeed before it climbed out of ground effect. As such, the incorrect flap extension likely did not contribute to the accident. Postaccident engine examination revealed low cylinder compression and an oil-fouled lower spark plug for the No. 1 cylinder. Otherwise, the examination did not reveal any anomalies. The engine was subsequently started and run several times without any issues; however, the engine was not accelerated to maximum static rpm during the examination due to a damaged engine mount and the airplane being supported on jack-stands. The flight instructor reported a decrease in engine rpm during initial climb out of ground effect. Although engine performance would be diminished by a low cylinder compression and an oil-fouled lower spark plug for the No. 1 cylinder, those discrepancies would not result in a sudden loss of engine rpm during flight. As such, the low cylinder compression and/or oil-fouled spark plug likely did not result in the reported decrease in engine rpm as described by the flight instructor. The temperature and dewpoint at the time of the accident were in the range of susceptibility for the formation of serious carburetor icing at glide power. Although a formation of carburetor ice before takeoff could have resulted in a sudden decrease in engine rpm, the pilots completed a before-takeoff engine runup with no anomalies or malfunctions reported. The reason for the partial loss of engine power could not be determined.

On October 26, 2020, about 1410 central daylight time, a Piper PA-28-140 airplane, N32458, was substantially damaged when it was involved in an accident near Crystal Beach, Texas. The flight instructor and his student were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor reported that the accident occurred during a takeoff from a private airstrip. He estimated that the grass airstrip was about 2,500 ft long by 35 ft wide, and the grass runway condition was dry and had been recently used by other airplanes. The takeoff was made to the south-southeast. The airplane had about 26 gallons of fuel onboard before the flight, and the weight-and-balance and takeoff performance were verified and determined to be “suitable for the flight.” The flight instructor and his student taxied the airplane to the north end of the airstrip where they completed a before-takeoff engine runup. The pilots completed a before-takeoff engine runup with no anomalies or malfunctions reported. The flight instructor noted that the airplane was configured with 10° of flaps before a soft-field takeoff was initiated with about 12 knots of headwind. The flight instructor reported that his student performed the soft-field takeoff. After the airplane became airborne, the student reduced airplane pitch to remain in ground effect and allowed the airspeed to increase to 80 knots. The flight instructor reported that during initial climb there was a drop in engine speed (rpm). He confirmed the throttle control was full forward, but there was “no significant engine performance.” The flight instructor took control of the airplane from his student, reduced pitch, and banked to avoid the highway and powerlines located at the end of the airstrip. The flight instructor stated that a lack of engine performance resulted in a forced landing before the airplane completed 90° of turn from the takeoff heading. The airplane landed on the northside of the highway, collided with a power pole, and came to a stop. The flight instructor stated that following the accident the fuel selector, ignition switch, and electrical switches were turned off before he and his student exited the airplane uninjured. The student reported that after liftoff the airplane remained in ground effect until the airspeed increased to 75 knots, at which time his flight instructor took control of the airplane when it did not “react” after he increased airplane pitch to climb out of ground effect. The student reported that his flight instructor reduced airplane pitch and flew the airplane to the ground. A postaccident wreckage examination was completed by Federal Aviation Administration (FAA) inspectors and two aviation mechanics. The left wing and engine mount were substantially damaged during the accident. Flight control cable continuity was confirmed for the ailerons, stabilator, and rudder. The flaps were extended 10° and the flap handle was inthe first notch. Engine control continuity was confirmed for the throttle, mixture, and carburetor heat controls. The gascolator contained a fluid similar to the color and odor of uncontaminated 100 low-lead aviation fuel. Examination of the engine revealed low cylinder compression and an oil-fouled lower spark plug for the No. 1 cylinder. Otherwise, the examination revealed no anomalies. The engine was subsequently started and run several times without any issues; however, the engine was not accelerated to maximum static rpm during the examination due to a damaged engine mount and the airplane being supported on jack-stands. According to a carburetor icing probability chart contained in FAA Special Airworthiness Information Bulletin CE-09-35, Carburetor Icing Prevention, the recorded temperature and dew point at the time of the accident were in the range of susceptibility for the formation of serious carburetor icing at glide power. According to the bulletin, a pilot should use carburetor heat when operating the engine at low power settings or while in weather conditions in which carburetor icing is probable. The Piper PA-28-140 Owner’s Handbook required the flaps to be extended 25° for soft-field and short-field takeoffs. The flight instructor reported that there was a laminated checklist in the cockpit that indicated the flaps be extended 10° for a soft-field takeoff.