AD 69-15-03

69-15-03 CESSNA: Amendment 39-798. Applies to all Cessna Model 170, 172, and 175 series airplanes modified in accordance with Supplemental Type Certificates SA3-13, SA3-126, SA3-571, SA3-672, SA3-674, SA135CE, SA420CE, SA421CE, or SA424CE, incorporating a Piper Muffler Assembly, P/N 10308-00, with the installation of a Lycoming engine.

Compliance required as indicated.

To detect cracks in the muffler assembly, accomplish the following:

(a) Inspect muffler assemblies with less than 950 hours' time in service on the effective date of this AD, in accordance with paragraph (c) below within the next 50 hours' time in service and thereafter at intervals not to exceed 100 hours' time in service from the last inspection until accumulating 950 hours' time in service, then comply with paragraph (b) below.

(b) Inspect muffler assemblies with more than 950 hours' time in service on the effective date of this AD, in accordance with paragraph (c) below within the next 50 hours' time in service and thereafter at intervals not to exceed 50 hours' time in service from the last inspection.

(c) Inspect the engine exhaust muffler and shroud assembly (including the internal baffle tube and tail pipe), carburetor heat shroud and air duct, support braces, clamps and brackets, exhaust stacks and manifolds. Remove muffler assembly, disconnect air ducts, stacks, and shrouds as necessary, and visually inspect exterior and interior surfaces with a probe light and mirror for signs of cracks, corrosion, burn-throughs, heat damage, collapsed stack, or weld separations. Special attention should be given to the exhaust stack under the carburetor heat shroud. Except for the initial inspection, the muffler assembly need not be removed from the airplane if the shroud is opened for inspection of external portions of the muffler and the internal portions are inspected through the muffler tail pipe outlet and one end of the muffler at the stack connection.

CAUTION:Do not alter these mufflers to remove the internal baffle tube without prior FAA approval.

(Piper Service Letter No. 324B describes the critical areas.)

(d) Replace or repair parts having any of the defects listed in paragraph (c) before further flight, and thereafter comply with the inspection requirements of paragraph (a) or (b), whichever is applicable. Make welding repairs and pressure test in accordance with Advisory Circular AC 43.13-1 or an FAA approved equivalent. Care should be exercised when reinstalling the exhaust system components to prevent distortion or preloading of parts.

This amendment becomes effective August 20, 1969.