Amateur-built ZODIAC 601XL N253DG accident near Seagoville, Texas

Probable cause

The engine overheating, which resulted in a partial loss of engine power, due to the pilot's operation of the engine with a higher-than-specified oil quantity level.

NTSB analysis

The sport pilot was conducting a personal cross-country flight in the experimental, amateur-built airplane. The pilot reported that, as the flight approached the destination airport, the high oil temperature warning light illuminated. The pilot's attempts to remedy the situation were successful but only for a few minutes, after which, the high oil temperature warning again illuminated, and the engine subsequently began running roughly. Smooth engine operation could only be obtained by reducing the engine speed. However, at that power setting, the airplane would not maintain altitude. The pilot subsequently executed a forced landing to a field, and during the landing roll, the nose landing gear collapsed, and the airplane then nosed over.

A postaccident examination of the engine did not reveal any mechanical failures. The pilot reported that he intentionally ran the engine with more oil than specified in an attempt to reduce the operating temperatures. When checked at the accident site, the engine oil quantity was higher than the upper limit on the oil dipstick. The engine manufacturer had previously issued a service bulletin, which noted that operating the engine with the oil quantity above the upper limit can result in oil temperatures significantly higher than when operating the engine at the lower limit. It is likely that the operation of the engine with a higher-than-specified oil quantity level resulted in the engine overheating and subsequently losing partial power.

Text from the NTSB. Open the NTSB docket for CEN15LA286 for the full record.