Probable cause
A partial loss of engine power due to the No. 1 spark plug being liberated from the cylinder head due to the stripped threads in the cylinder head. Contributing to the accident was the pilot’s decision to attempt to return to the airport while at a low altitude.
NTSB analysis
The pilot reported that, after takeoff, the airplane's engine lost partial power about 100 ft above ground level and that he then attempted to return to the airport. The pilot further stated that "the engine would not keep me flying and the airplane just fell into the forest."
During the on-scene examination, the No. 1 spark plug was found missing from the cylinder head but still attached to the ignition lead. The threads were stripped out of the cylinder head. It is likely that the No. 1 spark plug was liberated from the cylinder head due to the stripped threads, which led to the partial loss of engine power.
Text from the NTSB. Open the NTSB docket for ERA15LA311 for the full record.
Event
- Date
- Aug 14, 2015
- Type
- Accident
- Place
- Allentown, Pennsylvania
- Nearest airport
- Allentown Queen City Muni (XLL)
- Highest injury
- Serious
- Serious injuries
- 1
- Weather
- Visual (VMC)
- Light
- Day
Amateur-built ZENITH CH 750
- N-number
- N1750Z
- Category
- Airplane
- Year built
- 2012
- 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.