Amateur-built Dragonfly N24TL accident near Freeport, Illinois

Probable cause

The airplane’s degraded climb performance due to its being over its maximum gross weight and a hole in the engine exhaust.

NTSB analysis

The private pilot was conducting a personal flight in the experimental airplane. The pilot reported that, during the takeoff roll, he observed a "puff" of smoke emanate from the engine's left side and noted that the airplane did not accelerate as quickly as it normally did. The pilot leaned the mixture control, which was at 3/4 rich, and the engine subsequently started to develop normal power. The airplane lifted off about midfield and 80 mph. When the airplane reached about 150 to 200 ft above the ground, the pilot noticed that it was not climbing as he would have expected. The manifold pressure was 47 inches, and he was concerned about "overboosting" the engine, so he reduced the manifold pressure to 40 inches, and the airplane then started to descend. The pilot increased the manifold pressure to 45 inches, but the airplane continued to descend. The pilot chose to perform a forced landing to a field, during which the airplane struck a wire fence and then the ground.

During postaccident examination, the engine started without hesitation and ran up to 40 inches of manifold pressure for several minutes. Examination of the engine revealed a 1/2-inch square crack in the exhaust pipe. No other anomalies were noted with the engine or its systems. An examination of the airframe, flight controls, and remaining systems revealed no anomalies.

The takeoff weight of the airplane at the time of the accident was estimated to be 1,310 lbs, which was 110 lbs over the airplane's maximum gross weight. It is likely that the combined effects of the hole in the exhaust pipe and the airplane being over its maximum gross weight negatively affected the airplane's climb performance during takeoff.

Text from the NTSB. Open the NTSB docket for CEN15LA402 for the full record.