AD 67-03-01    Exhaust Gas Heat Exchanger

January 14, 1967

This AD applied to early 150s from #1 thru the ’65 “E.”

This AD required an inspection of the right-hand muffler for cracks that could pass exhaust gas into the cockpit through the heater. This is something we all do on every annual, but this went a little further by comparing carbon monoxide readings in the cabin and in the free air in front of the airplane.

67-03-01 CESSNA: Amdt. 39-338 Part 39 Federal Register January 14, 1967. Applies to Model 150 Series Airplanes, Serial Numbers 17001 through 15061328, Equipped With Right-Hand Exhaust Gas Cabin Heat Exchanger (Muffler).

Compliance required within the next 50 hours’ time in service after the effective date of this AD, unless already accomplished within the last 50 hours’ time in service, and thereafter at intervals not to exceed 100 hours’ time in service from the last inspection, until the exhaust system is modified in accordance with Cessna Service Letter No. 65-72 dated July 27, 1965, or later FAA-approved revision, or an equivalent approved by the Chief, Engineering and Manufacturing Branch, FAA Central Region.

Several cases of exhaust gas cabin heat exchanger cracking have occurred, allowing carbon monoxide to enter the cabin with cabin heat “ON.” To minimize the possibility of carbon monoxide contamination of cabin air, accomplish either of the following or an FAA approved equivalent:

(a) Inspect right-hand exhaust gas cabin heat exchanger (muffler) for cracks by conducting a pressure test of 1 1/2 p.s.i. in accordance with paragraph 12-93 of Cessna 100 Series Service Manual dated November 1962. Replace cracked exhaust gas cabin heat exchanger before further flight with an exchanger inspected in accordance with this AD and found free of cracks.

(b) Conduct a ground test with a carbon monoxide indicator by heading the airplane into the wind, warming the engine on the ground, advancing throttle to full static r.p.m. with cabin heater “ON”, and taking carbon monoxide readings of the heated air stream at the cabin heater deflector, P/N 0411824, on the firewall inside the cabin and another reading immediately thereafter in free air 15 feet in front of the propeller, with engine shut down. If carbon monoxide indication in the cabin is greater than in free air, comply with (a) before further flight.

This supersedes AD 64-17-03.

This directive effective January 14, 1967