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 170/47 Amdt 1 Crankcase Breather Tube and Oil Seal 4/86 Applicability: All models 170A, 170B, 172, 172A to 172P, 175, 175A, 175B, 175C, R172D and R172E fitted with Lycoming 0-320 series or 0-360 series engines. Requirement: To reduce the possibility of rapid loss of engine oil caused by ice obstruction of the engine crankcase breather, accomplish the following: 1. Visually examine the engine crankcase breather to determine if an alternate air outlet is drilled or cut in the tube as shown in Figure 1. If any of these provisions exist, make an appropriate entry in the aircraft maintenance records. No further action is necessary. 2. If the hole or cutout shown in Figure 1 is not in the engine crankcase breather tube: (a) Inspect the crankcase to crankshaft seal and ensure that the seal is secure. (This seal is located behind the starter ring gear in the forwardmost part of the crankcase). Reinstall or replace this seal if it is not flush with the forward face of the crankcase. (b) Drill the engine crankcase breather tube line to include an alternate air outlet as shown in Figure 1. Compliance: Unless already accomplished, within 100 hours time in service after 30 June 1982. Background: This AD has been amended to clarify the situation where the breather is still in close proximity to the exhaust outlet. Although this may currently prevent the breather from freezing, the exhaust system has been redesigned and the outlet moved to the opposite side. The original exhaust system is no longer available, and if a new exhaust is fitted the breather will then be unprotected. Therefore all breathers should be modified regardless of position. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES