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Reissued: August 1, 1986
2D16
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
CHART 3403. TROUBLESHOOTING (AIRSPEED TUBES AND INDICATOR) (cont)
Instrument reads low. Internal fault. Replace instrument.
Leaking static system. Find leak and correct.
Pitot head not aligncd Realign pitot head.
correctly.
Airspeed changes as aircraft Watcr in pitot line. Remove lines from static in
is banked. struments and blow out lines
from cockpit to pitot head.
—NOTE—
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.
—CAUTION—
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.
Trouble Cause Remedy
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