Amateur-built THORP T-18 N78DW accident near San Antonio, Texas

Probable cause

The loss of engine power after takeoff for undetermined reasons.

NTSB analysis

The pilot was planning a short cross-country flight with his passenger. Prior to takeoff, he fueled the airplane with 10-15 gallons of fuel and added one quart of oil to the engine. He performed an engine run-up that included checking the carburetor heat. The takeoff and initial climb were normal, but as he turned the airplane onto the downwind leg to depart the traffic pattern, the engine began running rough and lost total power. The pilot attempted to regain engine power by adjusting the engine mixture, but no change in engine performance was noted. Unable to maintain altitude, he performed a forced landing into trees. The airplane came to rest on its nose and sustained substantial damage.

Postaccident examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. Weather conditions reported at the time of the accident were conducive for serious carburetor icing at glide power. However, the pilot applied the carburetor heat during the engine run-up before takeoff, which should have either melted any ice that may have accumulated on the ground or resulted in a rough running engine, which the pilot did not report. The application of carburetor heat during the run-up combined with the high-power setting during takeoff and initial climb reduced the likelihood of carburetor ice.

Text from the NTSB. Open the NTSB docket for CEN21LA390 for the full record.