AD/ATR 42/22 Vertical Stabilizer Fin Tip Upper Closure Rib (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.

Avions de Transport Regional ATR 42 Series Aeroplanes

AD/ATR 42/22 Vertical Stabilizer - Fin Tip Upper Closure Rib 12/2007

Applicability:

ATR 42-500 aircraft, fitted with modification No 4440 (composite vertical fin) and on which modification No. 5426 (Service Bulletin ATR 42-55-0012) has not been accomplished, except serial numbers 618 to 623 inclusive.

Aircraft modified in accordance with SB ATR 42-55-0012, original issue, are not affected by this Airworthiness Directive.

Requirement:

Unless already accomplished, modify the vertical stabiliser leading edge fairing at the fin tip in accordance with SB ATR 42-55-0012, Revision 1 or later revision.

Note:  DGAC AD F-2005-059, issued 13 April 2005, refers.

Compliance:

Within the next 4,000 flight hours from the effective date of this AD or
30 April 2008, whichever is earlier.

This Airworthiness Directive becomes effective on 22 November 2007.

Background:

Following rudder operation difficulties experienced on an ATR 42-500, DGAC AD 2002-506R1 was issued to mandate the repetitive inspection of the vertical fin tip upper closure rib, in order to identify possible fatigue cracks induced by installation stress.  These cracks could lead to interference between the vertical fin tip upper closure rib and the rudder horn, causing the rudder to jam with consequent reduced controllability of the aircraft.

This AD provides a terminating action to correct the interference condition and to eliminate the potential for further cracking that could interfere with rudder movement.

David Villiers
Delegate of the Civil Aviation Safety Authority

9 October 2007