The function of the exhaust system is to move the hot combustion gases away from the APU and overboard. This occurs with the minimum exhaust noise that is possible.

The exhaust system uses the exhaust tailpipe duct, a large diameter duct, to move the hot combustion gases overboard. The rear end of the exhaust tailpipe duct attaches to the aft exhaust support. The aft exhaust support attaches to the tail cone skin with rivets.

The forward end of the exhaust tailpipe duct attaches to the APU exhaust diffuser. Because of the exhaust diffuser shape, there are air chambers. This shape supplies the clearance necessary for the operation of the eductor system. It also helps to decrease the exhaust noise. There are also internal components in the exhaust duct which help decrease the exhaust noise.

The exhaust tailpipe duct is made from sheet metal. There is an exhaust muffler in the middle of the exhaust tailpipe duct. This muffler has an acoustic liner. The acoustic liner and the chamber decreases the exhaust noise.

The rear end of the exhaust tailpipe duct has a seal which engages to the aft exhaust support. The forward end of the exhaust tailpipe duct has the bell mouth. The bell mouth is on the external part of the APU exhaust diffuser. The shape of the exhaust diffuser and the location of the bell mouth supplies the necessary openings for the eductor.

You can remove the bottom half of the bell mouth which is necessary to install and remove the APU. The exhaust tailpipe duct has two brackets that have serrations. These let you adjust the position of the bell mouth.

The exhaust tailpipe duct seal is a component of the exhaust tailpipe duct. It is installed on the rear end of the exhaust tailpipe duct, and seals against the aft exhaust support. A strap holds the exhaust tailpipe duct seal tightly in position.