Piper ARCHER III Pilot Operating Handbook page 416

SECTION 9
SUPPLEMENT 27
SECTION 4 - NORMAL PROCEDURES (continued)
Autopilot Operation
The Garmin GNS430W may be coupled to the STEC 55X Autopilot when
operating as prescribed in the LIMITATIONS section of this supplement. For
lateral guidance, the STEC 55X Autopilot may utilize GPSS or GPS Roll
Steering in lieu of the analog deviation information. For autopilot operational
instructions, refer to the FAA approved Flight Manual or Flight Manual
Supplement for the autopilot.
Coupling the Autopilot during Approaches
The Garmin GNS430W supports analog and digital (GPSS) control interfaces
to the STEC 55X Autopilot. The STEC 55X may use digital GPS roll
steering commands (GPSS) during GPS enroute, terminal, and LNAV
approach operations only. When switching between GPS and VLOC, the
pilot should be aware that the autopilot will need to be re-engaged in GPSS or
NAV/APR, depending on the CDI nav source last selected or the type of
approach desired.
Autopilot coupling to GPS vertical guidance requires that the autopilot be
engaged in an analog APR mode identical to coupling to an ILS. To capture
the vertical guidance, the pilot may engage the autopilot in APR mode at
any time when the GPS Glide Slope (VDI) becomes valid (displayed
without a FLAG).
Should a missed approach be required per the published missed approach
procedure, the autopilot must be engaged in GPSS mode for proper
guidance.
Do not operate the autopilot in the approach
(APR) mode when conducting the published
missed approach procedure.
REPORT: VB-1611
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CAUTION
PA-28-181, ARCHER III
ISSUED: JULY 12, 1995
REVISED: JULY 29, 2010