Unresolved Engine Power Loss Near San Antonio International Airport (N21590)

Incident Overview and Location Details An aircraft experienced a loss of engine power while descending approximately 4 miles north of San Antonio International Airport (SAT). Following the power loss, the pilot-rated passenger manipulated the flight controls while the pilot attempted an unsuccessful engine restart. The airplane eventually came to rest in a grassy field adjacent to power lines and trees, located about 1.5 miles northwest of Runway 12L. ## Post-Accident Examination and Findings A thorough examination of the airplane and engine did not reveal any structural or mechanical defects. Testing of the engine-driven fuel pump accessory showed that it was flowing fuel from the overboard drain at a rate of 1/2 gallon per minute. Despite this, the pump was still delivering fuel to the engine at 25 PSI and 275 lbs/hr. On-site examination of the aircraft confirmed that usable fuel remained in both wing tanks. ## Fuel System Anomalies and Investigation Conclusion A teardown of the fuel pump revealed worn 'O' rings that displayed square cross sections. Additionally, the inlet screen to the fuel servo contained non-metallic debris in the fitting, and the screen was observed to be partially clogged. The investigation determined that the anomalies found with the fuel system accessories were inconclusive. Consequently, the reason for the loss of engine power could not be determined.