COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes AD/CESSNA 170/56 Instrument Panel Light Dimming Rheostat 3/94 Applicability: Cessna aircraft as follows; Model Serial Numbers 172E, 172F, 172G, 172H, 172I and 172K (T-41A) 17250573 through 17259223 F172E, F172F, F172G and F172H F172-0019 through F17200754 FR172E, FR172F and FR172G FR17200001 through FR17200225 R172E, R172G and R172H (T-41B, T-41C and T-41D) R172-0001 through R172-0452 Requirement: Unless previously accomplished, replace the existing instrument panel light dimming rheostat (some installations will also require the fitting of a doubler) in accordance with the Accomplishment Instructions of Cessna Single Engine Service Bulletin SEB92-33 Revision 2 dated 10 September 1993. Note: FAA AD 93-24-15 Amdt 39-8764 refers. Compliance: Prior to 3 October 1994. Background: The FAA has advised of a report of an inflight fire in a Cessna Model 172. The fire was caused by a short in the electrical wiring controlled by the instrument panel light dimming rheostat. This Directive requires the rheostat to be replaced with an improved version, which is both current-limiting and heat-protected, thus decreasing the probability of an inflight fire being caused by a defective rheostat. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES