Piper AZTEC D PA-23-250 Owner's Handbook Manual page 82

SECTION V
THE PIPER AZTEC "D"
The operation of the landing gear oleos is standard for the
air-oil type; hydraulic fluid passing through an orifice serves as
the major shock absorber while air compressed statically acts as
a taxiing spring. The piston tube has a total travel of 8", and
about 3" of, tube should be exposed under normal static loads.
All of the oleos are inflated through readily accessible
valves on the top of the unit, at the front. The nose wheel unit
is steerable through the rudder pedals, and incorporates a shimmy
dampening device at the bottom of the outer housing. All major
attachments and actuating bearings are equipped with grease
fittings for lubrication of the bearing surfaces, and shwld be
lubricated periodically. (See Lubrication Chart.)
To add air to the oleo struts, a strut pump is attached at the
air valve and the oleo pumped up until 3" of piston tube is ex-
posed with normal static weight on the gears. To add oil, first
release all the air thrwgh the valves, allowing the oleo to extend
fully. Next remove the air valve and fill the unit through this
opening. Compress the oleo again to within 1/4 inch of full com-
pressim, allowing excess oil to overflow and working out trapped
air. Then reinsert the valve core and pump up the strut.
If a landing gear oleo has been completely emptied of oil
during servicing, the following procedure should be used to refill
it, to make sure that no air remains trapped in the unit. First, a
clear plastic tube should be attached to the valve stem, from
which the core has been removed. The other end of the tube
should be placed in a container of hydraulic fluid. When the oleo
is extended, fluid wiH be sucked into the oleo cylinder. The
oleo should be compressed and extended until it is full of fluid
and no more air bubbles appear in the plastic tube. About one
pint of fluid is required to fill the oleo.
To check shimmy of the nose wheel, if it should develop,
tighten the bolt on the dampening device at the base of the nose
wheel forging. The bolt should be tightened just enough to keep
the nose wheel from moving freely, but not enough to require
excessive pressure to move the wheel by hand.
It
may be neces-
sary to remove shims from the shimmy dampening collar to permit
tightening
of
the device.
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