Section
VII
Systems
Description
BEECHCRAFT
Duchess
76
STATIC SYSTEM
Static air
is
taken from a flush static port located on each side
of the aft fuselage. The static airis routed
to
the rate-of-c1imb
indicator, altimeter, and airspeed indicator.
The alternate static air source is designed to provide a
source of static pressure
to
the instruments from inside the
fuselage should
the
outside static air ports become blocked.
An abnormal reading
of
the instruments supplied with static
air could indicate a restriction in
the
outside static air ports. A
lever
on
the lower sidewall adjacent to the pilot, is placarded
OFF NORMAL - ON ALTERNATE. When it is desired or
required to use this alternate source of static air, select the
ON
ALTERNATE position.
To
recognize the need and proce-
dures for the use
of
alternate static air, refer
to
the EMER-
GENCY PROCEDURES section. Airspeed Calibration and
Altimeter Correction graphs are in the PERFORMANCE
section.
I
The static air plumbing is drained
by
placing the lever in the
ON ALTERNATE position momentarily and then returning it
to the OFF NORMAL position.
PRESSURE SYSTEM
Pressure for the flight instruments and autopilot (if installed)
is supplied by two, engine-driven, dry, pressure pumps inter-
connected to form a single system. Ifeither pump fails, check
valves automatically close and
the
remaining pump contin-
ues to operate all gyro instruments. A pressure gage on the
pilot's subpanel indicates pressure in inches ofmercury. Two
red buttons on
the
pressure gage serve
as
source failure
indicators, each
for
its respective side of the system. The
pressure system incorporates a central filter which protects
the instruments. This disposable filter
is
installed in the nose
compartment and must be replaced
in
accordance with the
recommendations in
the
SERVICING section.
7-40
April
1979
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