79-20-08 GREAT LAKES: Amendment 39-3580. Applies to Models 2T-1A-1 and 2T- 1A-2 airplanes having a Lycoming IO-360-B1F6 or AIO-360-B1G6 engine installed. \n\n\tCOMPLIANCE: Required as indicated unless already accomplished. \n\n\tTo preclude engine induction system blockage by pieces of failed alternate air doors and resulting power loss, accomplish the following: \n\n\tA)\tWithin the next 25 hours time-in-service after the effective date of this AD: \n\n\t\t1.\tVisually inspect the aircraft induction system drain fitting located in the induction elbow below the fuel injector for blockage or restriction. If the hole is restricted in the weld area or not drilled through the elbow, before further flight open up the restricted hole or drill a hole in the elbow at the fitting location using a No. 10 (.193) drill. \n\n\tB)\tWithin 25 hours time-in-service after the effective date of this AD and each 100 hours time-in-service thereafter: \n\n\t\t1.\tVisually inspect the alternate air door for distortion, heat damage and cracks. If any of these conditions are noted, before further flight repair the existing door or fabricate and install a new door in accordance with Figure I of this AD. \n\n\t\t2.\tVisually inspect the induction system including the filter for cleanliness, security and damage from backfire or induction system fires. Before further flight, repair or replace any damaged components necessary to restore the system to an airworthy condition. \n\n\tC)\tAny equivalent method of compliance with this AD must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region. \n\n\tThis amendment becomes effective on October 8, 1979. \n\n\nFIGURE 1