Piper Arrow IV Turbo Maintenance Manual page 359

GENERAL.
This chapter consists of instructions for the overhaul, inspection and adjustment of the various components
of the landing gear and brake system. Also are adjustments for the electrical limit, safety and warning
switches. This chapter does not cover the hydraulic function of the landing gear. (Refer to Chapter 29.)
DESCRIPTION AND OPERATION.
The airplanes are equipped with retractable tricycle air-oil strut type landing gear which are hydraulically
operated by an electrically powered reversible pump. A selector handle on the instrument panel to the left of
the control quadrant is used to select gear UP or DOWN positions.
Gear positions are indicated by three green lights located below the selector lever for gear down and
locked, and a red light located at the top of the instrument panel for gear unsafe positions. There is no light to
indicate the gear has fully retracted other than all lights are out. As the landing gear swings to the down
position and each downlock hook moves into its locked position, a switch at each hook actuates to the switch
normally closed (NC) circuit to indicate by a green light that the individual gear is safely down and locked.
The activation of all three downlock switches will also shut the hydraulic pump off. As the instrument lights
are turned on, the green light will dim. When the gear begins to retract and the downlock hook disengages, the
down limit switch actuates to the NC circuit and in series with the NC circuit of the up limit switch allows the
gear unsafe light to come on. The gear unsafe light will remain on until the gear is up and all up limit switches
are actuated to their normally open (NO) circuit.
The red gear unsafe light also operates simultaneously with the warning horn, and in conjunction their
purpose is to give warning when power is reduced below approximately 14 inches of manifold pressure and
the landing gear has not reached the down and locked position. This circuit is controlled by the three
paralleling down limit switches connected in series with a throttle switch (see Figure 32-23) located in the
control quadrant. When the airplane is setting on the ground, the warning circuit is controlled through the NO
side of the safety switch (squat switch) located on the left gear and the up position of the selector lever. Should
the airplane be raised from the ground, such as in flight, far enough to move the safety switch to its NC
position, then current is directed in series through the hydraulic pressure switch, the pump switch (providing
airspeed has actuated the switch to its NO position). The up limit, safety, throttle, pressure and selector switch,
and pump solenoids are all protected by the landing gear control and warning circuit protector. (Refer to
Chapter 91 for electrical schematic.)
Each landing gear is retracted and extended by a single hydraulic cylinder attached to the drag link
assembly of the nose gear and the side brace link assembly of the main gears. As the gears retract, doors
partially enclose each gear through mechanical linkage. The gears are held in their up position by hydraulic
pressure alone on the cylinder. There are no uplocks and loss of hydraulic pressure will allow the gears to drop.
It is preferred that the gears be extended and retracted with the use of the gear selector handle; however, in the
event of hydraulic loss or electrical failure, they can be lowered by pushing down on the emergency extension
lever between the pilot seats or they will drop themselves should airspeed drop below approximately 103
KIAS, engine power off. In either instant the hydraulic valve of the back-up extender unit opens to allow
hydraulic pressure to neutralize between each side of the cylinder pistons. The emergency extension lever can
also be used to manually overcome system malfunctions or to meet special pilot needs such as, a deliberate
wheels up landing needed for emergency landings on water, or during various flight maneuvers where airspeed
and power settings would normally allow the gear to extend. It also permits gear retraction after takeoff at
speeds lower than those normally permitted by the automatic system. When using the manual extension lever,
the gear position is controlled by the selector switch, regardless of airspeed/power combinations. An override
latch mechanism is installed which allows the pilot to latch the extension lever in the up override position, thus
bypassing the automatic portion of the system. A flashing warning light is mounted below the gear selector
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL
2D8
32-00-01
Page 32-01
December 1, 1978