IAD01LA031 · Enstrom F28A
Enstrom F28A · Accident: airframe, component or system failure on approach
From Henry County Airport (7W5) to an unrecorded destination
Event
- NTSB case
- IAD01LA031
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Enstrom F28A
- Aircraft type
- Enstrom F28
- Category
- Helicopter
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N98PM
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Henry County Airport (7W5), Napolean, OHTo not recorded
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Approach · VFR pattern final
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Airframe, component or system failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Rotor system, main rotor › Fatigue
- Rotor system, main rotor › Separation
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
The helicopter developed a vibration, and the pilot elected to return to the departure airport. On final approach to landing, approximately 10 feet above the ground, the main rotor mast fractured, and the main rotor system departed the helicopter. The pilot and two passengers were not injured. Examination of the fracture surfaces by a Safety Board metallurgist revealed the mast failed in fatigue in the area of the fillet radius. Microscopic examination revealed that a portion of the fatigue region had been painted over with paint that matched the exterior of the mast. The mast installed in the accident helicopter had a narrower fillet radius than masts subsequently produced by the manufacturer. An FAA Airworthiness Directive (AD) that required inspecting and strengthening of the fillet radius affected the narrower masts. As a result of this investigation, the FAA amended the AD to immediately retire some transmission/mast combinations, and to ultimately remove all of the narrower masts from service.
Probable cause
The fatigue failure in the fillet radius of the mast, which resulted in the separation of the main rotor system.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record IAD01LA031
- Event ID
- 20010212X00436
- Case number
- IAD01LA031
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, coordinates. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: f919a7432d73ebf22144e2fdfff76c76849d801dd7b8c22f84c61555249858b6; retrieved 2026-09-22T12:11:31.394Z.