THE NEW PIPER AIRCRAFT, INC.
PA-32-301FT / 301XTC
MAINTENANCE MANUAL
PAGE 1
Feb 19/04
1K7
APPENDIX 1
S-TEC SYSTEM 55/55X
WARNING: FAILURE TO CONSULT APPLICABLE VENDOR PUBLICATION(S), WHEN SERVICING
OR INSPECTING VENDOR EQUIPMENT INSTALLED IN PIPER AIRCRAFT, MAY
RENDER THE AIRCRAFT UNAIRWORTHY. SEE INTRODUCTION - SUPPLEMENTARY
PUBLICATIONS.
1. S-TEC System 55X
The S-TEC System 55X may have been installed as an option in:
A. Piper 6X S/N’s 3232003 and up.
B. Piper 6XT S/N’s 3255001 and up.
2. Description (See Figure 1.)
The S-TEC System 55X is a rate based autopilot that controls the roll and pitch axis of the aircraft. The
autopilot's main function is to convert pilot commands to logic signals for the roll and pitch computers. As
the pilot enters the desired mode by pressing the appropriate mode selector switch, the computer
acknowledges the mode, causing the appropriate annunciator to illuminate.
The Roll Computer receives select input signals from the Directional Gyro (DG) or Horizontal Situation
Indicator (HSI), VHF Omnidirectional Radio (VOR), Localizer (LOC) or Global Positioning System (GPS),
Deviation Indicators, and the Turn Coordinator. It then computes roll servo commands for stabilization,
turns, navigation intercepts, and tracking.
The Pitch Computer receives select input signals from the Altitude Pressure Transducer, Accelerometer,
Glideslope Deviation Indicator and Altitude Selector/Alerter (if installed). It then computes pitch servo
commands for vertical speed, altitude hold and glideslope intercept and tracking. Sensing for trim
annunciation or automatic stabilator trim is provided by the pitch servo. Drive for the stabilator trim servo
is provided by the pitch computer.
A typical S-TEC System 55X Autopilot installation includes the following:
A. Panel Mounted:
Programmer/Computer, Turn Coordinator, Annunciator, and D.G. or HSI.
B. Remote Mounted:
Roll Servo, Pitch Servo, Trim Servo, Trim Monitor, A/P Disconnect switch, and Altitude (Pressure)
Transducer.
Servo installations use aluminum brackets to secure the servos to the airframe. Attachment to the
airplane’s primary flight control and trim systems is accomplished with bridle cables and extension
attachments.
3. Troubleshooting
System functionality can be determined using functional checks descibed in the AFM Supplement and
autopilot Pilot’s Operating Handbook. More detailed troubleshooting should be accomplished by
authorized S-TEC Dealers, holding the appropriate FAA certification, with required test equipment and
service data.
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