Piper Cherokee LANCE Service Manual Download

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PIPER CHEROKEE SIX / LANCE SERVICE MANUAL

07/15/06

IX - INSTRUMENTS

2K13

CAUTION: DO NOT APPLY VISE PRESSURE TO THE OUTSIDE DIAMETER OR OVERALL

LENGTH OF THE PUMP.

When a vise is used to hold the pump while installing fittings, suitable caution must be exercised to
avoid pump damage. The square mounting flange must be held between soft wood blocks and only
at right angles to the vise jaws. Use only enough vise pressure to hold the pump firmly.

The ports of the AIRBORNE pump have been treated with a dry film lubricant and the AIRBORNE
fittings are cadmium plated thus eliminating any need for thread lubricants. If thread lubricant is
required, use a powdered moly-sulfide or graphite in dry form or in an evaporating vehicle; or
employ a silicone spray. Apply sparingly to external threads of fittings only.

With the pump properly secured in the vise, insert fittings in ports and hand tighten firmly.

Using a wrench, tighten each fitting one-half (1/2) to two (2) turns only. Do not overtighten.

9-17b. INSTRUMENT AIR SYSTEM. (Refer to Figure 9-5.)

The instrument air system consists of a pitot air system and a static air system. Refer to Figure 9-5 for
system layout.

Pitot air system consists of a pitot mast located on the bottom side of the left wing, with its’ related
plumbing. Impact air pressure entering the pitot is transmitted from the pitot inlet through hose and
tubing routed in through the wing to the airspeed indicator on the instrument panel.

Static air system consists of a static port located on the bottom of the pitot mast. The static port is
directly connected to the airspeed indicator, altimeter and rate of climb indicator, on the instrument
panel, by means of hose and tubing routed through the wing along with the pitot line. An alternate static
air source is located below the instrument panel in front of the pilot. The alternate static source is part of
the standard system and has a shutoff valve which closes the port when it is not needed. A placard giving
instructions for use is located on the instrument panel.

NOTE: If installed, the Piper Electric Trim system is integrated into the pitot-static system by a pressure

sensor assembly/switch (P/N’s 79657-003/486-416). See the Pitch Trim System Service
Manual, P/N 753-771 for adjustment/calibration.

9-18.

DIRECTIONAL GYRO.

9-19.

GENERAL. The directional gyro is a flight instrument incorporating an air driven gyro stabilized in

the vertical plane. The gyro is rotated at high speed by lowering the pressure in the air tight case and
simultaneously allowing atmospheric air pressure to enter the instrument against the gyro buckets. Due
to gyroscopic inertia, the spin axis continues to point in the same direction even though the aircraft yaws
to the right or left. This relative motion between the gyro and the instrument case is shown on the
instrument dial which is simular to a compass card. The dial, when set to agree with the airplane
magnetic compass provides a positive indication free from swing and turning error. However, the
directional gyro has no sense of direction and must be set to the magnetic compass, since the magnetic
compass is subject to errors due to magnetic fields, electric instruments etc., the directional gyro is only
accurate for the heading it has been set for. If the gyro is set on 270°, for instance, and the aircraft is
turned to some other heading, there can be a large error between the gyro and the magnetic compass due
to the error in compass compensation, this will appear as gyro precession. The gyro should only be
checked on the heading on which it was first set, also due to internal friction, spin axis error, air
turbulence and airflow, the gyro should be set at least every 15 minutes for accurate operation, whether it
has drifted or not.

Piper Cherokee LANCE, Service Manual

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