Gyro Horizon; Air Driven Attitude Horizon - Piper Dakota Maintenance Manual

CHART 3403. TROUBLESHOOTING (AIRSPEED TUBES AND INDICATOR) (cont)
Trouble
Instrument reads low.
Airspeed changes as aircraft
is banked.
When any connections in static system arc opened for checking,
system must be checked per F.A.R. 23.1325.

GYRO HORIZON

GENERAL
Both air and electric attitude horizons are used, depending on the option package installed. Both types are
displacement type gyros with free rotors mounted in gimbal assemblies. It is important to consult the A F C S
manufacturer's service manual if a flight director or autopilot is coupled to the attitude horizon.

AIR DRIVEN ATTITUDE HORIZON

The air driven attitude horizon is driven by either air pressure or vacuum, by engine driven dry pneumatic
pumps. Air volume, not air pressure, spins the gyro motor. The air filter can become contaminated and restrict
air flow, reducing gyro rotor speed, while the pressure regulator will automatically adjust air pressure within
proper limits.
The gyro air filter must be clean or replaced before adjusting
gyro air pressure
The instrument case moves freely about the spinning gyro rotor in three dimensions by the use of a gimbal
assembly. The display is stable and can show minute attitude changes of only 1° . Unlike the directional gyro,
the erection mechanism activity can be seen by a rapidly wobbling and leveling horizon bar when power is
first applied. The instrument can be adjusted for parallax by turning a knob on the instrument face. This knob
when held in, engages forks which cage the gyro rotor.
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
Cause
Internal fault.
Leaking static system.
Pitot head not aligncd
correctly.
Watcr in pitot line.
—NOTE—
—CAUTION—
2D16
Remedy
Replace instrument.
Find leak and correct.
Realign pitot head.
Remove lines from static in
struments and blow out lines
from cockpit to pitot head.
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Page 34 - 08
Reissued: August 1, 1986