Technical data

13773-001
78-20
Page 1
NOISE SUPPRESSOR
1. DESCRIPTION
Noise suppression is accomplished through use of an exhaust muffler connected to the exhaust header
assembly. The muffler incorporates a heat exchanger to supply warm air to the cabin. Heat sinks are
welded to the exterior of the muffler to improve efficiency. A shroud with accommodations for ducts sur-
rounds the muffler. Positive ventilation of the heat exchanger is provided at all times by air passing through
the outer compartment and entering the cabin, or by venting overboard depending on the cabin heat valve
position. The forward end of the muffler/heat exchanger is held in place by a support extending from the
engine mount. Ball joints support this portion of the exhaust system, allowing for relative motion between
the engine and airframe. A second ball joint connects the muffler to the exhaust tail pipe. The tail pipe pro-
vides a path for the exhaust gas from the muffler/heat exchanger though a hole in the bottom aft end of the
cowl and clear of the aircraft. The tail pipe is supported by a flexible hanger mounted to the firewall.
2. MAINTENANCE PRACTICES
A. Exhaust Muffler/Heat Exchanger (See Figure 78-201)
(1) Removal - Exhaust Muffler/Heat Exchanger
(a) Remove engine cowling. (Refer to 71-10)
(b) Remove tail pipe. (Refer to 78-10)
(c) Loosen hose clamps of the air intake and cabin heat hose, remove both hoses from muf-
fler/heat exchanger.
(d) Remove cotter pins, bolts, washers, springs, and nuts securing muffler/heat exchanger to
engine mount bracket.
(e) Remove cotter pins, bolts, washers, springs, and nuts from forward ball joint securing muf-
fler/heat exchanger to mid-pipe/exhaust header assembly.
(f) Remove muffler from airplane.
(2) Disassembly - Exhaust Muffler/Heat Exchanger
(a) Remove clamping screws on exhaust muffler/heat exchanger and remove heat exchanger
shroud.
(3) Assembly - Exhaust Muffler/Heat Exchanger
CAUTION: Failure to properly align heat exchanger shroud to exhaust muffler/heat
exchanger will result in poor cabin heating.
(a) Position heat exchanger shroud on exhaust muffler/heat exchanger so that shroud baffle
is located between duct flanges and install clamping screws.
(4) Installation - Exhaust Muffler/Heat Exchanger
(a) Position exhaust muffler/heat exchanger on mid-pipe/exhaust header assembly and install
bolts, springs, washers, nuts, and cotter pins. Tighten nuts to snug, then turn three com-
plete revolutions to compress springs. Slight adjustment of nuts for cotter pin installation is
allowable.
(b) Install tail pipe. (Refer to 78-10)
(c) Install bolts, springs, washers, nuts, and cotter pins securing muffler/heat exchanger to
engine mount bracket. Slight adjustment of nuts for cotter pin installation is allowable.
(d) Adjust aft ball joint nuts as required to ensure the overall length of each compression
spring is 0.50 inch (1.27 cm).
(e) Install hose clamps for air intake and cabin heat hose, and connect both hoses to muffler/
heat exchanger.
(f) Install engine cowling. (Refer to 71-10)
30 Nov 2000