Arrow PA-28R-201 Pilot's Operating Handbook And Faa Approved Airplane Flight Manual page 222

SECTION 9
SUPPLEMENT 3
SECTION S - PERFORMANCE
No change.
PIPER AIRCRAFT CORPORATION
Pi\-28R.201, ARROW
SECTION 6 - WEIGHT & BALANCE
Factory installed optional equipment is included in the licensed weight
and balance data in Section 6 of the Basic Pilot's Operating Handbook.
SECTION 7 - DESCRIPTION AND OPERATION
The auxiliary dry air pump system provides an independent back-up
source of pneumatic power to operate the gyro flight instruments in the event
the engine driven air pump fails.
The auxiliary pump is mounted on the forward side of the firewall and
connects to the primary system at a manifold downstream of the vacuum
(
regulator. Isolation of the primary and auxiliary systems from each other is (
accomplished by check valves on each side of the manifold. The primary
system vacuum switch is located in the center of the manifold and senses
vacuum supplied to the gyros.
The control switch (labeled AUX VAC) for the auxiliary pump system is
located on the main electrical switch panel in the center of the instrument
panel above the throttle quadrant. The control switch operating modes are
push-for-on and push-for-off.
The switch button incorporates two annunciator light sections labeled
VAC OFF and AUX ON. The VAC OFF section is controlled by a vacuum
switch in the primary pneumatic system and illuminates an amber light when
the engine driven pump is inoperative or when the system vacuum falls below
the switch activation level. The AUX ON section is controlled by a vacuum
switch in the auxiliary pneumatic system and illuminates a blue light when
the auxiliary pump is operating and creating a vacuum in the system. When
the auxiliary pump is activated at high altitude, or if the system has
developed air leaks, the AUX ON light may fail to illuminate. This indicates
that the system vacuum is still below the AUX ON switch activation level
even though the auxiliary pump is operating and can be verified by observing
the vacuum system indicator.
REPORT: VB-136S ISSUED: SEPTEMBER IS, 1988
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