AD/Dauphin/4 Amdt 5 Fin to Tailboom Attachments (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/DAUPHIN/4 Amdt 4 and issues the following 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.

Eurocopter SA 360 and SA 365 (Dauphin) Series Helicopters

AD/DAUPHIN/4 Amdt 5 Fin to Tailboom Attachments 6/2005

Applicability:

Models SA 360C, 361, 365C, C1, and C2 helicopters; pre. Mod. 07-2457 or SB 53.09 installation.

Requirement:

1.    Unless coated with a clear lacquer, strip the paint from the external surface of the ‘fairing’ plate joining the upper tailboom to the lower fin leading edge; and perform a detailed visual inspection of the ‘fairing’ plate for cracks at the rivet lines and bend radius.

Note:  DGAC AD 80-238-9(B) and Aerospatiale Dauphin Service Bulletin No. 05.04 refer.

2.    Perform a detailed external and internal visual inspection for cracks in the fin to tailboom attachment structure.  Pay particular attention to the crown attachment finger doubler, the tailboom end rib, the ends of the tailboom stringers and the inclined fenestron rib P/N 360A23.1061.01.

3.    Perform an X-ray inspection of the fin to tailboom attachment structure in accordance with NDT Procedure RAD/DAUPHIN/4 or other scheme approved by the Authority, to check for cracks in the crown attachment finger doubler.

Compliance:

1.    Inspect in accordance with Requirement 1:

a.     for models modified to AMS 365A.07.2457 with a 1.6mm chemically milled fairing’  -  at intervals not to exceed 100 hours time in service; or,

b.    for models not modified to AMS 365A.07.2457  -  at intervals not to exceed 25 hours time in service.

2.    Inspect in accordance with Requirement 2 at each 100 hourly `S’ inspection.

3.    Inspect in accordance with Requirement 3 at whichever 3.a. or 3.b. time occurs later; and at the 3.c. time:

a.     before the tailboom to fin attachment finger doubler exceeds 500 hours total time in service; or,

b.    before exceeding 500 hours time in service after the installation of a CAR 35 designed and approved repair to the subject crown tailboom to fin attachment finger doubler.

c.     thereafter at each 100 hourly `S’ inspection.

Note:  Any CAR 35 repair scheme must include a re-verification of the effectiveness of each of the above inspections in the presence of the repair.

This Amendment becomes effective on 9 June 2005.

Background:

There has been a history of fatigue cracking at the tailboom to fin attachment area in the reinforcement fairing plate, the crown attachment finger doubler, the tailboom end flange, the tailboom stringers and the inclined fenestron rib P/N/ 360A23.1061.01.  Reports of multiple site cracking in the crown attachment finger doubler of two Australian SA 365C-1’s extending, in one case, over a total length of 395mm, indicate that aircraft modified to AMS 365A.07.2457 are still subject to fatigue.  Post modification aircraft are cracking underneath the 1.6mm chemically milled reinforcement fairing plate and are not amenable to visual inspection, due to the location of the internal frame.

Amendment 1 introduced an X-ray inspection for modified aircraft with the inspection interval aligned to the 25 hour visual inspection interval for unmodified aircraft. 

Amendment 2 extended the X-ray inspection interval to 100 hours and introduced an inspection threshold of 500 hours for repaired aircraft, as a result of laboratory investigation.  There is now also a detailed visual inspection.  Further variations to the threshold and interval will be considered if a fracture mechanics based analysis is received.

Amendment 3 introduced some operational flexibility by aligning the X-ray and visual inspections with the 100 hour `S’ inspection.  The visual inspection is now a separate requirement and applies to all models.

Amendment 4 enhanced the visual inspection of Service Bulletin No. 05.04 by requiring the external paint to be removed.  This followed the discovery of a 45mm crack in a ‘fairing’ plate - inspection of this part was hindered by a thick flexible paint coating.  To alleviate the burden of repetitive paint stripping, an option of coating with a suitable clear lacquer was introduced.

Amendment 5 is issued to clarify applicability by specifying affected helicopters; with no change to technical content.

The original issue of this Airworthiness Directive became effective on 28 February 1981.

David Villiers
Delegate of the Civil Aviation Safety Authority

19 April 2005