Probable cause
A loss of propeller thrust due to a failure of the reduction drive unit resulting from the improper installation of the unit. Contributing to the accident was a lack of documentation for the reduction drive unit installation.
NTSB analysis
While in the airport traffic pattern, the airplane sustained a complete loss of thrust and an increase in engine speed, which the pilot interpreted as a loss of engine power to the propeller. He subsequently executed a forced landing to an open field. A postaccident examination revealed that the propeller reduction drive pulley had moved downward within the mounting bracket slot, creating slack in the cog belts that resulted in a loss of input drive power to the propeller. The reduction drive manufacturer did not provide any formal documentation for the installation. As a result, the pilot/builder was not aware that a secondary fitting to secure the pulley within the bracket needed to be installed with the drive unit components.
Text from the NTSB. Open the NTSB docket for CEN14LA235 for the full record.
Event
- Date
- May 10, 2014
- Type
- Accident
- Place
- Yates City, Illinois
- Nearest airport
- Tri-County (2C6)
- Highest injury
- Minor
- Minor injuries
- 1
- Weather
- Visual (VMC)
- Light
- Day
Amateur-built PL 4
- N-number
- N44PL
- Category
- Airplane
- Year built
- 1972
- Damage
- Substantial
- Operating rule
- Part 91 (general aviation)
- Purpose of flight
- Personal
From the NTSB aviation accident database: N-registered aircraft, events since 2008, data through Oct 28, 2026. The file is published monthly, so the latest weeks are incomplete and recent records can change. The official source is the NTSB aviation investigation search. CheckAero is independent and not affiliated with the NTSB.