AD/Bell 407/33 Tailboom Assembly (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.

Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters

AD/BELL 407/33 Tailboom Assembly 5/2009 DM

Applicability:

Bell Helicopter Textron Canada (BHTC) Model 407 helicopters with tailboom part number 407-030-801-201, -203 or -205 installed.

Requirement:

1.    Verify whether tailboom part number 407-030-801-201, -203 or -205 is installed on the helicopter; and,

Enter the appropriate part number as indentified into the helicopter technical records and also the accumulated flight hours of the tailboom.  If the accumulated flight hours of the tailboom is unknown, for the purpose of this Directive, it shall be considered to have more than 8,600 flight hours.

Using the following, establish the inspection schedule applicable to the tailboom affected.

2.    Inspection schedule:

-      Less than 6,900 tailboom flight hours:

Accomplish Part II of BHTC ASB 407-08-84 original issue, or later Transport Canada approved revision.

-      Less than 8,600 but more than 6,900 tailboom flight hours:

Accomplish Part II and Part III of BHTC ASB 407-08-84 original issue, or later Transport Canada approved revision.

-      With 8,600 or more tailboom flight hours:

Accomplish Part II, Part III and Part IV of BHTC ASB 407-08-84 original issue, or later Transport Canada approved revision.

Note:  Transport Canada AD CF-2009-07 refers.

Compliance:

1.    Within 25 flight hours after 6 April 2009.

2.    Inspection schedule compliance for Part II, Part III and Part IV of ASB
407-08-84:

Part II. At intervals not to exceed 300 flight hours inspect with a 10x magnifying glass.

Part III. At intervals not to exceed 150 flight hours inspect with a 10x magnifying glass; or,

At intervals not to exceed 500 flight hours inspect by Eddy Current Method.

Part IV. At intervals not to exceed 50 flight hours inspect with a 10x magnifying glass; or,

Daily Visual Check during the pre-flight check followed by a 10x magnifying glass inspection at the next scheduled inspection.

This Airworthiness Directive becomes effective on 6 April 2009.

Background:

A recent stress analysis of the chemically milled tailboom skin has revealed a possibility of skin cracking due to high stress concentration areas.  This condition, if not detected, could result in serious damage to the tailboom.

David Villiers
Delegate of the Civil Aviation Safety Authority

20 March 2009