Procedure for replacement of acoustic liner in integrated exhaust duct muffler for use with airborne auxiliary power units

The present invention provides a method for replacing an acoustic liner through the forward end or aft end of an integrated exhaust duct muffler ("IEDM"). The IEDM includes a bellmouth coupled to a forward end of the IEDM and an exhaust pipe coupled to an aft end of the IEDM. A muffler section, including the acoustic liner, is positioned between the bellmouth and exhaust pipe. In one embodiment, the method of replacing the acoustic liner from the forward end of the IEDM includes decoupling the bellmouth and forward end cap of the muffler section from the forward end of the IEDM and withdrawing the acoustic liner from the muffler section. A new acoustic liner is then inserted into the muffler section and the bellmouth and forward end cap are recoupled to the forward end of the IEDM. In another embodiment, a method of replacing an acoustic liner of an IEDM from an aft end is disclosed. The method includes removing the exhaust pipe from the aft end of the IEDM and withdrawing the acoustic liner from the muffler section. A new acoustic liner is then inserted into the muffler section and the exhaust pipe is attached to the aft end of the IEDM. In another embodiment, a method of replacing an acoustic liner of an IEDM from a forward end is disclosed. The method includes removing the bellmouth from the IEDM and withdrawing the acoustic liner from the muffler section. A new acoustic liner is inserted into the muffler section and the bellmouth is reattached to the IEDM.