PIPER COMANCHE SERVICE MANl:AL FIGURE 3·1. TYPICAL MUFFLER FATIGUE AREAS Removal of the tail pipe and stacks is required for inspection of the muffler baffle. Remove or loosen all exhaust shields. carburetor and cabin heat muffs. shrouds. etc.. as required to permit inspection of the complete system. Perform the necessary cleaning operations and inspect all external surfaces for dents. cracks and missing parts. Pay particular attention to welds. clamps. supports and support attachment lugs. slip joints. stack flanges and gaskets. Inspect internal baffle or diffusers. Any cracks. warpage or severe oxidation are causes for replacement of the muffler.
If any component is inaccessible for a thorough visual inspection. accomplish one of the following: a. Accomplish a submerged pressure check of muffler and exhaust stack at 10 psi air pressure. b. Conduct a ground test using a carbon monoxide indicator by heading the airplane into the wind. warming the engine on the ground. advancing the throttle to full static RPM with cabin heat valves open. and taking readings of the heated airstream inside the cabin at each outlet (including rear seat heat outlet. if installed). Appropriate sampling procedures applicable to the particular indicator must be followed.
If carbon monoxide concentration exceeds 0.005 percent or if a dangerous reading is obtained on an indicator not calibrated in percentages. the muffler must be replaced. Check cabin heat outlets for cabin monoxide after installation of new muffler. ISS LED: 8/18/72 tDt7 INSPECTION INSPECT fOIl CRACKS IN THESE AREAS ONE CRACK IS C.AUSE FOR REJECTION .SPEel Fill CUCKS II TItS AIU,-"",- _