Hiller OH-23C N301CH

Summary

On 4 July 1996 at about 00:15 local time, a Hiller OH-23C registered N301CH was involved in an accident near Marathon, Florida, United States. 2 people were on board and 2 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

4 July 1996 at 00:15

Classification

Accident

Location

Marathon, Florida, United States

Nearest airport

Marathon (MTH)

Coordinates

24.7101, -81.0800

Aircraft

Hiller OH-23C

Registration

N301CH

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Unknown

Phase of flight

Not recorded

Aircraft damage

Substantial

Weather

VMC

Light

Dusk

NTSB number

MIA96LA176

2 people had minor injuries.

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 subsequent failure of the main rotor blade, which resulted in an uncontrolled collision with the terrain.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.