Hiller FH-1100 N598F

Summary

On 28 June 1996 at about 17:10 local time, a Hiller FH-1100 registered N598F, operated by Clearwater Helicopters, Inc., was involved in an accident near Webster, Florida, United States. 2 people were on board and 2 died. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

28 June 1996 at 17:10

Classification

Accident

Location

Webster, Florida, United States

Coordinates

28.6108, -82.0491

Aircraft

Hiller FH-1100

Registration

N598F

Category

Helicopter

Engines

1

Operator

Clearwater Helicopters, Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Odessa → Sanford

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

MIA96FA168

2 people died.

inadequate compliance with AD 77-07-08 (and SB FH1100-55-2A) by other maintenance personnel, and subsequent fatigue failure of plates in the tail rotor torsion tension bar. Factors related to the accident were: manufacturing discontinuities (scoring/indentations) in holes of plates of the tail rotor torsion tension bars, and failure of the pilot to follow emergency procedures (reduce power to attempt an autorotative landing, following loss of the tail rotor assembly).

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

Read the full NTSB narrative

The helicopter (N598F) was flying at about 750 to 1,000 ft, when witnesses heard a loud noise, then saw N598F descending & spinning to the right. N598F impacted the ground upright at the edge of a pond. Postcrash exam showed that a tail rotor blade had separated in flight, followed by the other tail rotor blade, hub, & gearbox. Metallurgical exam showed the tail rotor blade had separated due to fatigue fractures in 9 of 11 plates in the tail rotor blade torsion tension (TT) bar. Fatigue originated at machining discontinuities on the inner surfaces of eye holes at the bushing ends, which had been punched in the plates during the manufacturing process. In 1977, Airworthiness Directive (AD) 77-07-08 & Fairchild Hiller Service Bulletin (SB) FH1100-55-2A were issued to inspect for this problem. Records of N598F showed the AD & SB had been complied with on 3/9/77, but the tail rotor assembly had been removed & replaced with another assembly on 3/17/83. Records did not show if the AD & SB had been complied with on the replacement tail rotor assembly. Overhaul procedures did not allow disassembly of the TT bar to examine the holes. Weight & balance calculations showed that after tail rotor separated, the center of gravity moved about 2.1 inches forward of the forward limit. FH-1100 emergency procedure for tail rotor failure required that the pilot immediately reduce engine power to zero torque & perform an autorotative landing. Throttle was found in full power range. Helicopter was not equipped with shoulder harnesses.

Quoted verbatim from the NTSB record.