# AD 77-07-08: Tail Rotor Tension Torsion Bars

- Type: Airworthiness directive
- Status: Current
- Products: FH1100 Manufacturing 1100 and FH-1100
- Effective: August 5, 1977
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-2992
- Registered aircraft: 8 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/09009DE23564F47B86256E1200498472.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/77-07-08

## The airworthiness directive

77-07-08 FAIRCHILD (HILLER): Amendment 39-2866 as amended by Amendment 39-2992. Applies to Model 1100 and FH-1100 type helicopters certified in all categories.

Compliance required as follows:

To detect improper surface finish in the bolt holes at each end of the tail rotor tension torsion bars, P/N's 24-55106 which could lead to cracking of the bar plates, accomplish the following within the next 25 hours in service after the effective date of this AD unless already accomplished.

Inspect the two tail rotor tension torsion bars, P/N's 24-55106 which have serial numbers prior to 1922 or illegible serial numbers, in accordance with Fairchild FH-1100 Service Bulletin No. SBFH1100-55-2A dated 19 January 1977, Section 2 "Accomplishment Instructions" or equivalent procedure approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.

If tension torsion bars are found unacceptable in accordance with the service bulletin or those procedures approved bythe Chief, Engineering and Manufacturing Branch, replace the bar with one that has been inspected and found acceptable in accordance with the service bulletin or an equivalent procedure approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.

Upon submission of substantiating data by an owner or operator through an FAA Maintenance Inspector, the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region may adjust the inspection interval specified in this AD.

Amendment 39-2866 became effective April 11, 1977. This Amendment 39-2992 becomes effective August 5, 1977.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H2WE](https://openairdocs.org/tcds/H2WE): Air Space Design and Manufacturing LLC; names 2 of 2 models: 1100, FH-1100

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 8 (8 by airframe model, 0 by engine model)
- Makers: Fairchild Hiller 8

Models with the most aircraft:

- [Fairchild Hiller FH-1100](https://openairdocs.org/model/fairchild-hiller-fh-1100): 8 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/77-07-08/models.md
Every aircraft: https://openairdocs.org/ad/77-07-08/aircraft.md

Its text cites no advisory circulars or STCs.

## NTSB investigations that cite this AD (2)

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 MIA06LA126](https://openairdocs.org/ntsb/MIA06LA126), Jun 8, 2006: Fairchild Hiller FH-1100 (N4035G), Navarre, FL, substantial damage. Probable cause: The inadequate manufacturing of the plates of the tail rotor tension-torsion bar assembly resulting in fatigue failure.
- [NTSB MIA96FA168](https://openairdocs.org/ntsb/MIA96FA168), Jun 28, 1996: Hiller FH-1100 (N598F), Webster, FL, substantial damage, 2 fatal. Probable cause: 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…

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