Description And Principles Of Operation - Piper PA-31-350 Maintenance Manual

PIPER AIRCRAFT
T-1020
MAINTENANCE MANUAL
GENERAL.
This chapter provides instructions for remedying difficulties which may arise in the operation of the land-
ing gear and brake systems. The instructions are organized so that the mechanic can refer to Descriptions and
Principles of Operation for a basic understanding of the systems; Troubleshooting for a methodical approach
in locating the difficulty; Corrective Maintenance for the removal, repair and installation of components; and
Adjustment and Test for the operation of the repaired systems.
DESCRIPTION AND PRINCIPLES OF OPERATION.
The tricycle landing gear system incorporates air-oil oleo type struts that are hydraulically operated and
fully retractable with the nose gear retracting aft into the nose section and the main gear retracting inboard
into the wing. Doors completely cover the gear when retracted. The nose and outboard main gear doors
operate by mechanical linkage and remain open when the gear is extended. The main gear inboard doors
operate hydraulically and are controlled by the limit switches opening during gear extension and closing again
when the gear has fully extended. To prevent the gear from retracting while the airplane is on the ground, an
anti-retraction safety switch is located on the left gear upper torque link, which will not allow the gear actuator
lever to move to the gear up position until weight is off the landing gear allowing the strut to extend to within
one-quarter of an inch of full extension.
The nose gear is steerable through a 40 degree arc by the use of the rudder pedals. As the gear retracts,
the steering linkage becomes separated from the gear and is centered, so that the rudder pedal action with the
gear retracted is not impeded by the nose gear operation.
Located on the instrument panel, to the right of the gear selector control, are one red and three green
indicator lights. The red light will show an indication when the gear is not locked in either the up or down posi-
tion and the green lights will show when each individual gear is down and locked. There is no indication light,
when the gear is up and locked. The red light will also show an indication whenever the inboard gear doors are
not completely closed. A warning horn in the cockpit will sound whenever power from one or both engines
is reduced below 10 to 12 inches of manifold pressure when the gear is not in the down locked position. This
horn will also sound whenever the landing gear selector handle is in the gear up position while the airplane
is on the ground and the master switch is on. If the gear selector handle can be moved to the up position with
the airplane on the ground, it is an indication of an improperly adjusted selector mechanism or the anti-
retraction system is inoperative.
Two means of emergency extension are available. The emergency blowdown system and the hand pump
located in the cockpit between the pilot seats, under the floor access panel. The emergency blowdown system
employs a logic circuit which senses the gear(s) not extended such that when the system is activated by pulling
the control ring located between the pilot's and copilot's seats the remaining gear(s) is (are) extended and
locked in place. Besides the emergency blowdown system the gear can also be pumped down. A hand pump
under a floor access panel between the pilot's and copilot's seat can be used to extend the gear should the
hydraulic pump system fail. If a problem does develop however, and time permits, it is suggested that the hand
pump be tried first, because once the emergency blowdown system is activated, the affected mechanism and
hydraulic system must be purged and serviced.
The brakes are hydraulically actuated by individual master cylinders mounted on the left (optional on
right) set of rudder pedals. A reservoir, accessible through the access door on the upper right portion of the
nose section, supplies fluid to each master cylinder. From these cylinders, hydraulic fluid is routed through
lines and hoses to a parking brake valve located on the left aft side of the forward cabin bulkhead, through
the cabin and wings, to the brake assemblies on each main landing gear. To operate the brakes, apply toe
pressure against the top of the rudder pedal. The parking brake may be actuated by applying toe pressure and
at the same time pulling out on the brake handle. To relieve parking brake pressure, apply toe pressure on the
pedals and at the same time push in on the parking brake handle.
Servicing of the hydraulic and brake system is found in Chapter 12.
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Page 32-01
Revised: February 23, 1982
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