Piper Navajo PA-31 Service Manual page 191

PIPER NAVAJO SERVICE MANUAL
SECTION V
SURFACE CONTROLS
5-1. INTRODUCTION. This section explains the removal, installation and rigging and adjustment
procedures for the various control surfaces of the airplane. The different control surfaces do not have to be
removed in order of Paragraphs in this section, since individual paragraphs describe the removal, installation
and rigging of each control surface or system. A troubleshooting chart is located at the end of this section.
5-2. DESCRIPTION. The primary flight controls are of the conventional type, operated by dual control
wheels and rudder pedals. On the forward end of each control column is a tube and sprocket assembly. A
chain is wrapped around the sprockets to connect the right and left controls. Over an additional sprocket
on the left assembly is a chain that connects to cables that operate the aileron bellcranks and push-pull
rods. Also on each control column is a roller assembly that connects through links to control arms, a torque
tube and a sector assembly. Attached to the sector are control cables that operate the elevator bellcrank
and push-pull rod. Attached to the left set of rudder pedal arms are control cables that lead to the rudder
horn. The rudder pedals also control the action of the brakes and nose wheel steering. For coordinated
action of the rudder and ailerons, their control cables are interconnected through a cable-spring system.
Aileron, elevator and rudder trim is operated by knobs or wheels and controlled by cable wrapped drums
located in the control pedestal. As the cable and drum in the pedestal rotates, it in turn is connected to and
rotates a drum in the right wing, right horizontal stabilizer or vertical fin. With the rotation of the drum. a
screw is moved fore or aft to allow for the positioning of the trim tab. To indicate the position of the trim tab. a
sender unit attached to each screw assembly in the various surfaces will transmit a signal to an indicator in the
central pedestal indicating the position of the tab. An electric pitch trim servo motor drum is wound in the
pitch trim control cable. This servo is controlled manually by a switch on the pilot's control yoke or
automatically by the autopilot computer amplifier when the pitch axis of the autopilot is engaged. Refer to the
appropriate autopilot service manual when servicing the electric pitch trim motor.
The wing flap system consits of a flap selector switch located on the instrument panel to the left of
the right control column, a reversible permanent magnet motor mounted under the center floor panel of
the cabin with braking provided through an external relay, a flap transmission in the trailing edge of each
wing and interconnecting flexible shafts. As the flap is extended or retracted by the rotation of the
transmission screw, sender units located in the wings and attached to the flaps will transmit a signal to an indi-
cator located on the instrument panel above the flap selector switch indicating the position of the flap. On
serial numbered aircraft 31-855 and up. the gear warning horn will also sound when the flap selector switch is
in the down position and the gear is not in the down and locked position regardless of the actual flap or throttle
position. When the switch is in the "OFF" or "UP" position and the gear is not down and locked, the warning
horn will only sound when the throttles are retarded.
For a visual description of the various control systems, refer to the illustrated figures throughout this
section.
Revised: 1/29/82
SURFACE CONTROLS
1H23