AD/ATR 42/21 - Thermal Acoustic Insulation Blankets on Frame 24 (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 42/21 Thermal Acoustic Insulation Blankets 12/2007 DM on Frame 24

Applicability: ATR 42-400 and 42-500 models, all serial numbers, except aircraft modified with ATR modification No. 05117 or 05322 or 05791 or Service Bulletin (SB) ATR 42-25-0134. Requirement: Unless previously accomplished, remove the metallised PET insulation blankets installed on the left and the right sides of the aircraft over frame 24 between stringers 5 and 14, as detailed in the accomplishment instructions of SB ATR 42-25-0155.

Note: EASA AD 2007-0106-E, effective 20 April 2007 refers. Compliance: Accomplish within 25 flight hours after the effective date. This Airworthiness Directive becomes effective on 25 October 2007. Background: On two ATR 42-500 aircraft, some burnt spots were found on insulation blankets installed over frame 24. Investigations concluded that due to the proximity of the hot bleed air duct, installation of thermal-acoustical insulation blankets having a metallised PolyEthylene Terephtalate (PET) covering (Mylar), may represent a fire risk. This AD requires the removal of metallised PET blankets covering frame 24.