Commonwealth legislation

AD/S-76/67 - Attitude and Heading Reference Warning

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Commonwealth

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legislative instrument

Plain English Summary

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What it does: This Airworthiness Directive requires owners/operators of specified Sikorsky S‑76B and S‑76C helicopters to modify the No.1 and No.2 AHRS WARN electrical circuits so the 28‑volt supply is changed, following Sikorsky Alert Service Bulletin 76‑34‑7A Rev A. Who it affects and why it matters: CASA issued the directive to prevent simultaneous AHRS fail warnings that could disable both autopilots after an essential-bus failure; compliance was required by 21 April 2002.

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AIRWORTHINESS DIRECTIVE

View image in the official source

View image in the official source
For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Sikorsky S-76 Series Helicopters

AD/S-76/67 Attitude and Heading Referenc

AD/S-76/67 Attitude and Heading Reference Warning 3/2002

Applicability: Model S-76B helicopters, serial numbers (S/N) 760430, 760441 through 760445, 760448 through 760452, 760454, 760455, 760458, 760462, and 760465.

Model S-76C helicopters, S/N 760420, 760436, 760438, 760440, 760453, 760456,

760457, 760459, 760460, 760461 760463, 760464, 760466 through 760487.

Requirement: Modify the number 1 and 2 AHRS WARN circuits in accordance with the Accomplishment Instructions, paragraphs 3.A. through 3.D, of Sikorsky Aircraft Corporation Alert Service Bulletin 76-34-7A (320A), Revision A, dated 17 September 2001.

Note: FAA AD 2001-25-06 refers.

Compliance: No later than 21 April 2002.

This Airworthiness Directive becomes effective on 21 March 2002.

Background: The United States Federal Aviation Administration has advised that during a ground test simulating loss of the essential bus, both autopilots went off-line.

This Directive requires modification of the electrical power distribution system to change the source of the 28 volts supplied to Nos. 1 and 2 attitude and heading reference system (AHRS) WARN circuits. These actions are intended to prevent an AHRS fail signal to both autopilots due to a failure of the essential bus, loss of autopilot functions, and subsequent loss of control of the helicopter.

Signature of Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority

Eugene Paul Holzapfel

Delegate of the Civil Aviation Safety Authority 7 February 2002

View image in the official source

The above AD is notified in the Commonwealth of Australia Gazette on 27 February 2002.

Source text

Sourced from the Federal Register of Legislation (legislation.gov.au), CC BY 4.0.

AIRWORTHINESS DIRECTIVE AIRWORTHINESS DIRECTIVE

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Sikorsky S-76 Series Helicopters

AD/S-76/67 Attitude and Heading Referenc AD/S-76/67 Attitude and Heading Reference Warning 3/2002

AD/S-76/67 Attitude and Heading Reference Warning 3/2002

Applicability: Model S-76B helicopters, serial numbers (S/N) 760430, 760441 through 760445, 760448 through 760452, 760454, 760455, 760458, 760462, and 760465.

Model S-76C helicopters, S/N 760420, 760436, 760438, 760440, 760453, 760456,

760457, 760459, 760460, 760461 760463, 760464, 760466 through 760487.

Note: FAA AD 2001-25-06 refers.

Compliance: No later than 21 April 2002.

This Airworthiness Directive becomes effective on 21 March 2002.

Background: The United States Federal Aviation Administration has advised that during a ground test simulating loss of the essential bus, both autopilots went off-line.

Eugene Paul Holzapfel

Delegate of the Civil Aviation Safety Authority 7 February 2002

The above AD is notified in the Commonwealth of Australia Gazette on 27 February 2002.