# AD 87-12-06: Generator Control Unit

- Type: Airworthiness directive
- Status: Current
- Products: Sikorsky S-76A and S-76B
- Effective: June 10, 1987
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-5602
- Registered aircraft: 53 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/010677A5AB0E795386256A4D00743CB1.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/87-12-06

## The airworthiness directive

87-12-06 SIKORSKY AIRCRAFT: Amendment 39-5602. Applies to all Model S-76A/B series helicopters, certified in all categories.

Compliance is required within the next 25 hours' time in service unless already accomplished.

To prevent possible loss of electrical power due to DC generator ground failure, accomplish the following:

  (a) Perform inspection to determine the wiring configuration and connections of the GCU. Inspect the ground and power path connections of both generators for corrosion and proper torque, and inspect the ground connections of the GCU to determine their configuration. Modify and repair, as necessary. Accomplish these inspections and modifications in accordance with the Sikorsky Alert Service Bulletin, ASB-76-24-8, dated January 30, 1987.

  (b) Upon request, with substantiating data, an alternate means of compliance which provides an equivalent level of safety or adjustment in the compliance time may be used when approved by the Manager, Boston Aircraft Certification Office, Aircraft Certification Division, Federal Aviation Administration, New England Region, 12 New England Executive Park, Burlington, MA 01803.

These procedures shall be accomplished in accordance with Sikorsky ASB-76-24-8, dated January 30, 1987. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a)(1). Copies may be obtained from Sikorsky Aircraft, 6900 North Main Street, Stratford, Connecticut 06601-1381. Copies may be inspected at the Office of the Regional Counsel, FAA, Southwest Region, 4400 Blue Mound Road, Fort Worth, Texas, or at the Office of the Federal Register, 1100 L Street, NW., Room 8401, Washington, D.C.

This amendment becomes effective June 10, 1987.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H1NE](https://openairdocs.org/tcds/H1NE): Sikorsky Aircraft Corporation; names 2 of 4 models: S-76B, S-76A

## 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: 53 (53 by airframe model, 0 by engine model)
- Makers: Sikorsky 53

Models with the most aircraft:

- [Sikorsky S-76B](https://openairdocs.org/model/sikorsky-s-76b): 34 aircraft (airframe model)
- [Sikorsky S-76A](https://openairdocs.org/model/sikorsky-s-76a): 19 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/87-12-06/models.md
Every aircraft: https://openairdocs.org/ad/87-12-06/aircraft.md

Its text cites no advisory circulars or STCs.

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