Plain English Meaning

A metal jacket built around the exhaust muffler. Outside air flows through the gap between the muffler and the jacket, picks up heat from the hot muffler, and is then piped into the cabin to warm the pilot or into the carburetor to prevent ice.

Full Definition

A metal casing that wraps around the exhaust muffler on a piston aircraft engine, creating an enclosed space where outside air is heated by contact with the hot muffler before being routed to the cabin heater and the carburetor heat system.

Context Anchor

Seen in discussions of aircraft exhaust systems, cabin heat, and of heating parts near the engine.