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. Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes AD/CESSNA 170/77 Main Electrical Power Junction Box 9/2005 Applicability: Cessna Model 172R and 172S aeroplanes as follows: Model Serial Numbers 172R 17281186 through 17281232 172S 172S9476 through 172S9689 and 172S9691 through 172S9770 inclusive Requirement: 1. Unless already accomplished, inspect any MC01-3A I.C. 9 (part number (P/N) S3100-297) or MC01-3A I.C. 10 (P/N S3100-344) main electrical power junction box for any incorrect amperage (amp) circuit beaker installed in place of the required 40-amp circuit breakers in accordance with Cessna Service Bulletin (SB) SB05-24-01 dated 31 January 2005. 2. Replace any incorrect amp circuit breaker found during the Requirement 1 inspection with the required 40-amp circuit breaker in accordance with SB05-24-01. 3. Only 40-amp circuit breakers may be installed as spares in any MC01-3A I.C. 9 or MC01-3A I.C. 10 main electrical power junction box. Later revisions of the above SB, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2005-13-10, are considered acceptable for compliance with the equivalent Requirements of this Directive. Note: FAA AD 2005-13-10 Amdt 39-14147 refers. Compliance: For Requirement 1 - Within the next 30 days after the effective date of this Directive. For Requirement 2 - Before further flight after the Requirement 1 inspection. For Requirement 3 - As of the effective date of this Directive. This Airworthiness Directive becomes effective on 1 September 2005. Background: The FAA has received several reports of circuit breakers that are not the correct 40-amp circuit breaker installed in the MC01-3A main electrical power junction box. Incorrectly rated circuit breakers could result in premature tripping of the power junction box main feeder circuit breakers and could lead to partial or complete loss of all electrical power on the airplane. This Directive requires the inspection of the main electrical power junction box and, if necessary, the replacement of any incorrect circuit breaker David Villiers Delegate of the Civil Aviation Safety Authority 22 July 2005