Approved Replacement Part Number:
Cessna 172R with STC SA4428SW
The engine air induction system receives ram air through an intake on the lower front portion of the engine cowling. The intake is covered by an airfilter which removes dust and other foreign matter from the induction air. Airflow passing through the air control unit which is under the engine, and then is ducted to the engine cylinders through intake manifold tubes.
In the event induction ice is encountered, or the intake air filter becomes blocked, an alternate heated air can be obtained from a shroud around an exhaust riser through a duct to a valve, in the air box, operated by the alternator air control located on the instrument panel. Unfiltered heated air is drawn from the lower cowl area around an exhaust riser through the shroud into a duct on the air box. Use of full alternate air will result in a loss of approximately 75 to 150 RPM