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 42/18 Pitot Probe Current Sensors 10/2007 Applicability: All ATR 42 series aircraft models, all serial numbers, except aircraft modified per ATR modification 05469 (Installation of new current sensors for pitot probes) during production (ie MSN 631 and subsequent) or per ATR Service Bulletin (SB) ATR42-30-0072 at any approved revision whilst in service. Requirement: 1. Verify the three pitot probes' heating resistance in accordance with the instructions of SB ATR42-30-0074 dated 14 May 2007 or later revision approved by the European Aviation Safety Agency (EASA). 2. If, during the Requirement 1 verification, any resistance exceeding 50 Ohms is found, replace the pitot probe in accordance with the instructions of SB ATR42-30-0074 or later revision approved by the EASA. 3. Replace the three pitot probe current sensors in accordance with the instructions of SB ATR42-30-0072 Revision 1 dated 1 June 2005 or later revision approved by the EASA. Replacement of the pitot probe current sensors is terminating action for the Requirement 1 repetitive verification tests. Note: EASA AD 2007-0179 refers. Compliance: For Requirement 1 - Within the next 550 hours time in service (TIS) after the effective date of this Directive and thereafter at intervals not to exceed 550 hours TIS until the pitot probe current sensors are replaced in accordance with Requirement 3. For Requirement 2 - Before next flight after the Requirement 1 verification test. For Requirement 3 - Within the next 5 000 hours TIS after the effective date of this Directive. This Airworthiness Directive becomes effective on 27 September 2007. Background: The EASA has received a report that a recent incident indicated that some failures of the pitot probe heating resistance may not be detected by the low current detection system on aircraft not equipped with modification 05469 (SB ATR42-30-0072). This Directive requires repetitive verification of the pitot probes' resistance and replacement of any defective probes, together with ultimate replacement of the three low current sensors for Captain, First Officer and Standby pitot probes. Charles Lenarcic Delegate of the Civil Aviation Safety Authority 3 August 2007