AD/Bell 412/44 Amdt 2 Tail Rotor Blade Fwd Tip Weight Retention Block and Aft Tip Closure (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/BELL 412/44 Amdt 1 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.

Bell Helicopter Textron 412 Series Helicopters

AD/BELL 412/44 Amdt 2 Tail Rotor Blade Fwd Tip Weight
Retention Block and Aft Tip Closure 13/2007

Applicability:

Model 412, 412CF, and 412EP helicopters with a tail rotor blade part number
212-010-750-009 through -129, all serial numbers, except serial numbers with a prefix of “A” or “AFS” and the number 11926, 13351, 13367, 13393, 13400, 13402, 13515, 13540, 13568, 13595 through 13602, 13619, and subsequent assigned numbers, installed.

Requirement:

1.    Inspect the tail rotor blade forward tip weight retention block and aft tip closure for adhesive bond voids.  Remove any tail rotor blade with a void in excess of that allowed by the Component Repair and Overhaul Manual limitations.

2.    Inspect the forward tip weight retention block attachment countersink screws in four locations to determine if the head of each countersink screw is flush with the surface of the abrasion strip.  The locations of these four screws are depicted on Figure 1 of Bell Helicopter Textron Inc. Alert Service Bulletin (ASB)
412-00-106 Revision D or 412CF-00-13 Revision D, or later FAA approved revisions, as applicable.  If any of these screws are set below the surface of the abrasion strip or are covered with filler material, install shear pins in accordance with the Accomplishment Instructions, Part A, Shear Pin Installation paragraphs, of ASB  412-00-106 Revision D or 412CF-00-13 Revision D, or later FAA approved revisions, as applicable.

3.    Install the aft tip closure rivets, re-identify the modified blade by adding an “FM”, and dynamically balance the tail rotor hub assembly in accordance with the Accomplishment Instructions, Part B, Aft Tip Closure Rivet Installation paragraphs, of ASB 412-00-106 Revision D or 412CF-00-13 Revision D, or later FAA approved revisions, as applicable.

Note:  FAA AD 2007-22-02 Amdt 39-15238 refers.

Compliance:

Within 100 hours time in service after 20 December 2007, unless already accomplished.

This Amendment becomes effective on 20 December 2007.

Background:

The FAA received reports of five occurrences of missing tail rotor blade forward tip weight retention blocks or aft tip closures that resulted in minor to substantial damage.  Such damage could result in loss of a tail rotor blade, and subsequent loss of control of the helicopter.

Amendment 1 included the Agusta Model AB412 helicopter in applicability, and update Applicability and Requirement information to the latest manufacturer’s documentation.

Amendment 2 is issued in response to a new FAA AD, which expands the applicability to include other part and serial-numbered blades.  Additionally, the AD clarifies the requirement to re-identify the modified blade by adding “FM” after the part number, and requires dynamically balancing the tail rotor.  The previously included requirements for Agusta Model AB412 helicopters have been relocated to a new Bell 412 Series Helicopter AD in Issue 13/2007.

David Villiers
Delegate of the Civil Aviation Safety Authority

7 November 2007