78-26-10 R1: Cockpit Heater System

78-26-10 R1 GREAT LAKES: Amendment 39-3384 as amended by Amendment 39-5460. Applies to Models 2T-1A-1 and 2T-1A-2 airplanes. COMPLIANCE: Required as indicated unless already accomplished. To preclude contamination of cockpit heater air with carbon monoxide, accomplish the following: A) Within the next 25 hours time-in-service after the effective date of this AD: 1. Determine if the airplane is equipped with a P/N 50146 cockpit heater system and, if not, make an entry in the airplane's maintenance record that the airplane complies with Paragraph A)1 and that further compliance with this AD is not required. This determination and maintenance record entry may be made by the owner or holder of a valid pilot certificate. 2. If the airplane is equipped with a P/N 50146 cockpit heater system, prior to further flight, install a revision in the walk around inspection (Section II C. 2) of the Flight Manual adding an inspection of the exhaust system hanger (Figure1 of this AD). 3. If the airplane is equipped with a P/N 50146 cockpit heater system, prior to further flight, and within each 25 hours time-in-service thereafter: a) Remove the cowl to gain access to the engine installation. b) Disconnect the two cockpit air heater ducts from the heater shroud and remove the shroud. c) Visually inspect the support plates of the heat exchanger at both ends for cracks between the five tube cluster. d) If no cracks are found, return the heat exchanger to service. e) If cracks are found, either replace the heat exchanger system with an airworthy part or, in the alternative, comply with Paragraph B) of this AD. B) Remove the optional heat exchanger system and: 1) Install P/N 50126-1 stack assembly on all aircraft and P/N 50172-1 shield on aircraft equipped with IO-360-BIF6 and AEIO-360-BIG6 engines using QS100-M32W or equivalent clamps. 2) Block existing cockpit heat control valve in closed position by safety wiring control arm to adjacent aircraft structure. 3) Block the cockpit air supply opening in the left vertical engine cooling baffle per AC 43.13 1 and 2. 4) Remove Aircraft Flight Manual Revision specified in Paragraph A)2 of this AD (if installed). C) The actions and inspections specified in paragraphs A)2. and A)3. of this AD may be discontinued upon either removal of the P/N 50146 cockpit heater system per paragraph B) of this AD, or replacement of the P/N 50146 cockpit heater system with a different FAA approved cockpit heater system. D) Any equivalent method of compliance with this AD must be approved by the Manager, Boston Aircraft Certification Office, Federal Aviation Administration, New England Region, 12 New England Executive Park, Burlington, Massachusetts 01803. Great Lakes Aircraft Company (GLAC) Service Bulletin No. 9, dated November 17, 1978, or later revisions, pertain to portions of this subject. This amendment revises AD 78-26-10, Amendment 39-3384, which became effective January 4, 1979. This amendment, 39-5460, becomes effective on December 17, 1986. FIGURE 1 AIRPLANE FLIGHT MANUAL REVISION (AD 78-26-10 requires this revision to remain in the below designated airplane flight manual when the airplane is equipped with the optional P/N 50146 cockpit heater system. MODEL N S/N In addition to the presently specified preflight procedures, prior to each flight: 1. Inspect the left engine exhaust tail pipe hanger for deformation or failure. 2. If found failed, the hanger must be repaired prior to further flight.