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 CASR 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-76/73 Dual Inverter Wiring 6/2004 DM

Applicability: Model S-76 A, B and C helicopters with dual channel autopilot and dual inverters installed.

Note 1: Helicopters with the following serial numbers were manufactured with the dual channel autopilot and dual inverters installed:

S-76 A

Requirement: 1. Determine if the No. 1 inverter is wired to the DC essential bus by carrying out the operational test specified in the Accomplishment Instructions, paragraph 3.B. of Sikorsky Aircraft Corporation Alert Service Bulletin (ASB) No. 76-24-14A, Revision A, dated 9 October 2003.

2.         If, following the Requirement 1 operational test, the No. 1 inverter is determined to be wired to the DC essential bus, accomplish the following:

1. Install a placard near the airspeed indicator that contains the limitation “Maximum IMC Airspeed 120 KIAS” and annotate this airspeed limitation in the Operating Limitation section of the Aircraft Flight Manual (AFM).

Annotating the airspeed limitation in the AFM may be accomplished by inserting a copy of this Directive in the applicable section of the AFM.

b.        Modify the electrical wiring so that the No.1 inverter, which powers the co- pilot's Automatic Flight Control System (AFCS) computer, is wired to the No. 2 DC primary bus and the No. 2 inverter, which powers the pilot's AFCS computer, is wired to the DC essential bus by following the Accomplishment Instructions, paragraph 3.C. of the ASB.

3.         Remove the “Maximum IMC Airspeed 120 KIAS” placard and AFM annotation.

Note 2: FAA AD 2004-06-04 Amdt 39-13530 refers.

Compliance: For Requirement 1 - Before further flight after the effective date of this Directive.

For Requirement 2.a. - Before further flight after the Requirement 1 operational test is completed.

For Requirement 2.b. - Within 30 days after the effective date of this Directive.

For Requirement 3 - After modifying the electrical wiring in accordance with Requirement 2.b.

This Airworthiness Directive becomes effective on 28 April 2004.

Background: This directive requires a test to determine if the No. 1 inverter is wired to the DC essential bus, and if so, it requires modifying the wiring so that the No. 1 inverter is wired to the No. 2 DC primary bus and the No. 2 inverter is wired to the DC essential bus. If the wiring modification is required and is not performed before further flight, then the revision of the AFM together with the installation of a placard near the airspeed indicator is also required before further flight to limit the maximum airspeed in instrument meteorological conditions (IMC).

These actions are intended to prevent both autopilots from disengaging following a No. 2 DC generator failure, and subsequent loss of control of the helicopter during IMC operations.

James Coyne

Delegate of the Civil Aviation Safety Authority 21 April 2004

The above AD is notified in the Commonwealth of Australia Gazette on 28 April 2004.