Probable cause
The in-flight separation of the main rotor mast following a mast bumping event. The reason for the mast bumping event could not be determined due to postaccident damage.
NTSB analysis
The helicopter was on a cross-country flight when it experienced a separation of the main rotor mast 8 inches below the teeter bolt, and the main rotor blade assembly separated from the flying helicopter. Subsequently, the helicopter impacted terrain and a postimpact fire ensued. Examination of the mast revealed fracture features consistent with overload failure and mechanical damage indicative of mast bumping. An examination of the airframe, engine, and remaining systems revealed no preimpact anomalies. The reason for the mast bumping event could not be determined due to the amount of thermal damage to the wreckage.
Text from the NTSB. Open the NTSB docket for CEN12FA001 for the full record.
Event
- Date
- Oct 1, 2011
- Type
- Accident
- Place
- Philip, South Dakota
- Highest injury
- Fatal
- Fatal injuries
- 1
- Weather
- Visual (VMC)
- Light
- Day
Robinson Helicopter Co R66
- N-number
- N266CY
- Category
- Helicopter
- Year built
- 2011
- Damage
- Destroyed
- 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.