62-24-03: Cabin Heat System

62-24-03 CESSNA and SILVAIRE: Amdt. 505 Part 507 Federal Register November 10, 1962. Applies to All Cessna 120, 140, or 140A Aircraft and All Silvaire (Luscombe) 8E, 8F, or T8F Aircraft Modified to Incorporate McKenzie Aircraft Repair, Inc. Installations of Various Lycoming Engines in Accordance With Supplemental Type Certificates Nos. SA4-95, SA4-173, SA4-376, SA4-581, SA4-629, SA4-639, SA4-640, SA4-641, SA4-642, SA4-1159, SA4-1201, and SA4-1286 and With FAA Engineering Approved Repair and Alteration Forms ACA-337 Dated March 30, 1955, and June 21, 1955. Compliance required as indicated. Failures of the exhaust stacks have occurred in the area of the cabin heat muffs. Such failures can cause hazardous carbon monoxide contamination of the cabin when cabin heat is used. To preclude additional failures and cabin CO contamination, accomplish the following: (a) If continued use of the cabin heat system is desired: (1) Within the next 10 hours' time in service after the effective date of this AD: (i) Render the cabin heat system inoperative by positively securing the heat control in the "OFF" position; or (ii) Install, adjacent to the cabin heat control, a placard with the following wording, "DO NOT USE CABIN HEAT-CONTROL MUST REMAIN IN 'OFF' POSITION."; or (iii) Accomplish the inspection and rework required by (2). (2) Unless already accomplished in accordance with (a)(1)(iii), not later than 50 hours' time in service after the effective date of this AD: (i) Remove the cabin heat muff and perform a visual inspection of the exhaust stack for cracks. Pay particular attention to the area where the muff attaching straps are welded to the stack. Reinspect at intervals not to exceed 50 hours' time in service. Replace or repair by welding all cracked stacks; (ii) Cut off the cabin heat muff attaching straps adjacent to the welds. Discard the straps and reattach the heat muff to the stack in accordance with McKenzie Aircraft Repair, Inc. Service Bulletin No. 1 dated September 6, 1962, or an FAA approved equivalent; (iii) Unsecure the heat control required by (a)(1)(i), if secured; and (iv) Remove the placard required by (a)(1)(ii), if installed. (b) If use of the cabin heat system is not desired: (1) Within the next 10 hours' time in service after the effective date of this AD: (i) Remove the cabin heat muff and associated ducting and controls; and (ii) Close any openings in the firewall that result from the removal of the ducting and controls in accordance with Civil Air Regulations 3.624. (2) The cabin heat system may be reinstalled upon compliance with (a)(2)(i) and (ii). This directive effective November 21, 1962.