Accident Overview
A certified flight instructor (CFI) was providing dual flight instruction to a commercial pilot working toward a flight instructor certificate. The flight had included practice of a simulated engine failure. While in cruise flight at an altitude of 2,200 feet mean sea level, the engine rpm suddenly dropped to 800. The CFI was unable to restore engine power and executed a forced landing to a field. During the landing, the airplane's left wing struck a tree stump, resulting in substantial damage to the aircraft.
Post-Accident Findings
After the accident, a test run of the engine revealed rough operation with intermittent surges. The fuel injector servo was removed and replaced with a serviceable unit. Following replacement, the engine ran smoothly through 2,500 rpm. Examination of the removed fuel injector servo showed that the fuel inlet screen had more than 50 percent of its exterior surface covered in light brown corrosion/contamination. Additionally, two-thirds of the inlet fitting was blocked by debris, and contamination was noted throughout the fuel servo.
Inspection History
The airplane had been operated for about 5 hours since its most recent annual inspection, which was performed approximately 3 months prior to the accident. The airplane manufacturer's annual inspection guidelines included inspecting the fuel injection system and cleaning the screens in accordance with the engine manufacturer's recommendations.