Accident Sequence
According to a report from the certified flight instructor (CFI) involved, the flight was conducting practice of agricultural turns at an altitude of a few hundred feet over fields. The CFI and a rear seat occupant were alternating control of the aircraft. After the CFI had completed several turns, the rear seat occupant took control and performed a few turns. During one of the turns, the CFI applied power abruptly, causing the engine to hesitate or cough. The CFI then applied full aft elevator control input and reached the limit of elevator control travel. Shortly thereafter, the airplane impacted the ground.
The CFI noted that the carburetor lacked an accelerator pump and stated he did not perceive any preimpact flight control malfunction. He also indicated that he did not believe the engine hesitation caused the accident. A passenger, who spoke with the aircraft owner after the accident, reported that during the flight at approximately 150 feet above ground level and an airspeed of 60-70 mph, the left wing dropped. The passenger further stated that the CFI said "my aircraft" just before the ground impact. No witnesses to the accident were identified.
Postaccident Examination
An examination by a Federal Aviation Administration (FAA) inspector found evidence that the airplane first contacted the ground with the left main landing gear, with a piece of landing gear tubing remaining in the initial ground scar. The airplane slid approximately 20 feet before coming to rest upright. The fuselage was broken aft of the aft seat, and the empennage was displaced to the left. The engine and engine cowling were displaced to the right. Fuel was observed in the fuselage tank and in the carburetor bowl; the carburetor was fractured near the flange but remained secured by the throttle control cable.
Following recovery, a National Transportation Safety Board (NTSB) examination found no evidence of preimpact failure or malfunction of the flight controls for roll, pitch, or yaw. Impact damage was noted to the left wingtip. The ignition switch operated satisfactorily. The engine exhibited crankshaft, camshaft, and valve train continuity, with suction and compression in all cylinders. The magnetos produced spark at all spark plugs through the ignition leads during hand rotation of the engine.
Bench testing of the carburetor revealed fuel leakage from the main metering nozzle when 6 psi was applied to the inlet. Disassembly showed the float was properly installed and a plastic needle valve was present, with a slight amount of dirt in the throttle bowl area. The carburetor was not equipped with a mixture control or an accelerator pump.