# Accident 19960703020029A: Hiller OH23G, Marathon, FL, July 3, 1996

- Type: FAA accident report (Accident/Incident Data System), as reported
- Date: July 3, 1996, 20:15 local time
- Place: Marathon, FL
- Airport: Marathon Airport
- Damage: Substantial damage
- Phase of flight: Pwr Off Vert Land/Autorotate
- Operating rules: General operating rules (Part 91)
- Location: 24.7101° N, 81.0800° W: From the FAA, an estimate near the named town, within about 3 miles
- Nearby events: https://openairdocs.org/map.md?lat=24.7101&lon=-81.0800&mi=10
- Aircraft: N301CH (not matched to a registry record)
- Reported make and model: HILLER OH23G
- Reported engine: FRNKLN 6V335B
- Fatal injuries: 0
- Pilot flight hours: 5,961 total, 30 in this make and model
- NTSB investigation: [NTSB MIA96LA176](https://openairdocs.org/ntsb/MIA96LA176) (OpenAirDocs)
- FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/)
- Page: https://openairdocs.org/incident/19960703020029A

## Narrative

As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^.

(.4)DURING A PREVIOUS FLIGHT, THE HELICOPTER WAS REPORTED TO HAVE EXCESSIVE VERTICAL VIBRATION AND TO REQUIRE EXCESSIVE COLLECTIVE FORCES DURING FLIGHT. MECHANICS WORKED ON THE MAIN ROTOR BLADES TO CORRECT THE PROBLEM, THEN THE HELICOPTER WAS FLOWN ON A MAINTENANCE TEST FLIGHT. DURING THE TEST FLIGHT, THE PILOT NOTED THAT THE VERTICAL VIBRATION HAD 'GONE AWAY,' BUT BEFORE LANDING, THE VERTICAL VIBRATION RETURNED. SHORTLY THEREAFTER, THE PILOT HEARD A LOUD 'POP'. AS HE FLARED FOR LANDING, THE BLUE MAIN ROTOR BLADE SEPARATED AND THE HELICOPTER CRASHED. EXAMINATION OF THE SEPARATED BLADE SHOWED THE WOOD IN THE AREA OF THE BLADE GRIP HAD FAILED, ALLOWING THE BLADE TO SEPARATE. EVIDENCE OF A PREVIOUS REPAIR WAS PRESENT IN THIS AREA, WHICH LACKED ADEQUATE ADHESIVE BETWEEN SOME OF THE MATING SURFACES. ALSO, AN UNAPPROVED SEALANT HAD BEEN USED OVER THE REPAIRED AREA, AND OIL HAD CONTAMINATED THE WOOD IN THIS AREA. THERE WAS NO EVIDENCE OF DRY ROT IN THE FAILED AREA. THE LOGBOOK RECORDS DID NOT SHOW THE PREVIOUS BLADE REPAIR.

## The NTSB's investigation of this event (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB MIA96LA176](https://openairdocs.org/ntsb/MIA96LA176), Jul 4, 1996: Hiller OH-23C (N301CH), Marathon, FL, substantial damage. Probable cause: Improper repair of a previous crack in the blue main rotor blade by unknown persons; improper inspection of the main rotor blades by maintenance personnel, following a reported vibration problem; and…

From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record.

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