AD/S-92/6 Main Gearbox Filter Bowl Assembly Mounting Studs (Cth)

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 39.001(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-92 Series Helicopters

AD/S-92/6 Main Gearbox Filter Bowl
Assembly Mounting Studs 5/2009 TX

Applicability:

Sikorsky Aircraft Corporation S-92A helicopters with a main gearbox assembly, part number (P/N) 92351-15110-042, -043, or -044, that is not marked with “TS-062-01” near the P/N.

Requirement:

1.    Remove the titanium studs by following the accomplishment instructions in Sikorsky Alert Service Bulletin (ASB) No. 92-63-014, Rev A dated
20 March 2009 paragraph 3.A.

2.    Visually inspect the tapped holes and the main gearbox housing lockring counterbore for damage.

Note 1:  Figure 1 of the ASB contains guidance for removal and installation of the studs.

3.    Install steel studs and mark the main gearbox housing as “TS-062-01” near the P/N by following the accomplishment instructions of Sikorsky ASB No.
92-63-014 Rev A paragraph 3.C.

Note 2:  FAA Emergency AD 2009-07-053 dated 23 March 2009 refers.

Compliance:

Before further flight after the effective date of this AD unless previously accomplished.

This Airworthiness Directive becomes effective on 27 March 2009.

Background:

This AD is in response to the failure of 2 main gearbox filter bowl studs that were found broken during a fatal accident investigation in Canada.  Prior to this accident the manufacture was investigation a July 2008 incident in Australia that also involved broken studs.  In both cases the broken studs resulted in rapid loss of oil.

This AD requires the replacement of titanium studs with steel studs.

James Coyne
Delegate of the Civil Aviation Safety Authority

25 March 2009