Specifications

52 of 56 11934-S37
Section 9 Cirrus Design
Supplements SR20
Environmental System
Cabin heating and ventilation is accomplished by supplying
conditioned air for heating and windshield defrost and fresh air for
ventilation. The environmental system consists of a fresh air inlet in
the lower RH cowl, a heat exchanger around the RH engine exhaust
muffler, an air mixing chamber, air ducting for distribution, a distribution
manifold, a windshield diffuser, and crew and passenger air vents. An
optional 3-speed blower fan is available to supplement airflow when
ram air may be inadequate such as during ground operation.
Fresh air enters the cabin air distribution system through a NACA vent
on the RH lower cowl and is ducted to the air mixing chamber mounted
to the forward side of the firewall. Fresh air also enters the upper RH
cowl inlet, flows through the upper cowl, and is ducted to a heat
exchanger surrounding the RH engine exhaust muffler. The heated air
is then routed to the air mixing chamber to be mixed with the fresh air.
The mixed air is then distributed by either ram air or by optional blower
fan to the distribution manifold mounted to the center, aft side of the
firewall. The distribution manifold uses butterfly valves to control
airflow to the floor and defrost vents. Airflow is ducted directly to all
panel air vents.
The crew panel air vents are chest high outlets mounted in the RH and
LH bolster panels. The crew floor air vents are mounted to the bottom
of each kick plate. The passenger panel air vents are chest high
outlets mounted in the armrests integral to the LH and RH cabin wall
trim panels. The passenger floor air vents are mounted to the bottom
portion of the LH and RH cabin wall trim panels. The windshield
diffuser, located in the glareshield assembly, directs conditioned air to
the base of the windshield. Temperature, volume, and flow selection
are regulated by manipulation of the cabin airflow, cabin vents, and
cabin temperature selector knobs on the lower RH side of the
instrument panel. The optional blower fan is powered by 28 VDC
supplied through 15-amp Fan breaker on Main A/C Bus 2.
Revision 01: 08-26-09