Amateur-built RV7 N849GS accident near Ocean City, Maryland

Probable cause

The disconnection of the propeller governor control arm from the propeller governor due to a missing attachment bolt, which resulted in a partial loss of engine power during takeoff when the governor control vibrated to a high pitch, low rpm setting.

NTSB analysis

The pilot reported that, during takeoff, the airplane was about 500 ft above ground level when the engine lost partial power. The pilot verified that the throttle, mixture, and propeller were in the full forward position and chose to stay in the airport traffic pattern and land on the runway. The pilot noted that, during short final on approach, the airplane was "high and fast," but he still wanted to land on the runway to avoid landing in the water beyond the runway. The airplane landed hard, continued into the grass, and then nosed over and came to rest inverted, which resulted in substantial damage to the rudder.

A postaccident engine examination was conducted. The propeller governor control arm was found disconnected from the propeller governor, and the control arm locking bolt was missing. In addition, the secondary control arm/spacer and spring were not located. No other anomalies were noted with the engine.

The propeller governor control arm was reattached (without the missing parts), and fuel was plumbed into the engine; the engine started and ran smoothly. The propeller lever was operated with no anomalies noted. Then, the governor control arm was positioned in the low pitch, high rpm position to simulate takeoff conditions, and the governor control arm was disconnected. The engine was restarted and the throttle was advanced, but the engine rpm would not rise above 1,400 at maximum power, which was similar to the accident flight data downloaded from the engine information system on board the airplane. After the engine was shut down, examination of the governor control revealed that it had vibrated/turned to a high pitch, low rpm setting. It is likely that the absence of the control arm locking bolt that secured the propeller governor control arm to the propeller governor resulted in the control arm separating from the governor and then the governor control vibrating/rotating into a high pitch, low rpm setting, which resulted in a partial loss of engine power. The investigation could not determine if the bolt was not installed during the engine overhaul 28.5 flight hours before the accident or if the bolt backed out of the propeller control arm.

Text from the NTSB. Open the NTSB docket for ERA19LA232 for the full record.