AD/B737/225 - Proximity Switch Electronics Unit (Cth)

COMMONWEALTH OF AUSTRALIA (Civil Aviation Safety Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES

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 39.1 (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.

Boeing 737 Series Aeroplanes

AD/B737/225 Proximity Switch Electronics Unit 6/2004

Applicability: Model 737-600, -700, -700C, -800, and -900 series aeroplanes, as listed in Boeing Alert Service Bulletin (ASB) 737-32A1343 dated 26 July 2001.

Requirement: 1. Remove Proximity Switch Electronics Unit (PSEU) part number (P/N) 285A1600-2 or 285A1600-3 and replace it with a PSEU P/N 285A1600-4, in accordance with the Accomplishment Instructions of ASB 737-32A1343.

2. PSEU P/N 285A1600-2 or 285A1600-3 may not be installed on any aeroplane as a replacement part.

Note: FAA AD 2004-07-10 Amdt 39-13554 refers.

Compliance: For Requirement 1 - Within 18 months after the effective date of this Directive.

For Requirement 2 - As of the effective date of this Directive. This Airworthiness Directive becomes effective on 10 June 2004. Background: This Directive requires replacement of the PSEU with a new, improved unit. This action is necessary to prevent a malfunction of the aural warning for the landing gear, leading the crew to open the circuit breaker for the aural warning horn which stops the operation of other aural warnings of malfunctions in other systems and, thus, could jeopardize a safe flight and landing.