VACUUM
SYSTEM
The vacuu111 requirel-r~ents of the Mark
21
are supplied by an
er~gine driven vacuuln pump. The output of the pulrlp
is
controlled
by a regularor which
~i~ainrains vacuum between
4.50
and
5.00
inches of EvIercury. The red indicator lights on the artificial
horizon will indicate if the
vacuum is below
4.05
inches of
Mercury or above
5.20
inches of Mercury. These lights may be
tested by pressing the test switch located to the left of the arri-
ficial horizon.
To
dill? these lights during night flight, turn the lens housings
clockwise. The
vacunnl systetn powers the artificial horizon,
the directional gyro, the Mooney Positive Control
systern, and
the auto~natic retractable step.
A
vacuuln servo will raise the
step when the engine is
started and sufficient vacuu111 is pi-o-
duced.
A
spring will pull the step down when the engine is stop-
ped arid
vacuui~l is relieved.
BRAKES
The Mark
21.
is equipped with hydraulic disc brakes on the main
gear which are operated ind&pendently by toe pressure on the
rudder pedals. The brakes
may be
set
for parking by dep1:press-
ing the toe pedals and pulling out the lock valve control which
is located on the panel to the right of the pilot's
control colurnn.
Hydraulic fluid for the brake and flap systelns is stored in a
reservoir on the top aft side of the firewall. Copilots brakes
are
available as optional equipment.
HEATING AND VENTILATION SYSTEMS
The Lower Heat and Vent System
Cabin heat is obtained fro111 a rrtuff which surrounds the engine
exhaust manifold.
From this muff, a flexible duct transiits
heated air to a junction box on the aft side of the firewall on the
copilot's side. Cool air is also ducted to this junction box
fro1-n
the flush air scoop on the right side of the airplane. The warm
and cool air entering the junction box can be individually con-
trolled to provide the combination required for the desired
tem-
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