Archer N6004H S-TEC System Twenty Autopilot
System Overview
The S-TEC autopilot is a more
functional and modern replacement
than the original Piper Autocontrol IIIb
autopilot installed in our aircraft.
While the old autopilot was “state-
based” in that it sensed the angle of the
aircraft’s orientation in relation to vertical,
the S-TEC is “rate-based” and senses
the rate of roll and turn. This results in
much smoother and more accurate
corrections to the ailerons while the
autopilot is in control, and also means
that when a turn needs to be made
under autopilot control, it happens at
standard rate rather than at unpredictable
bank angles. To sense roll and turn rate
requires a turn coordinator (TC) gyro, and in
fact a turn coordinator instrument is built into
the autopilot and the entire assembly replaces
the TC on the instrument panel.
The TC component of the autopilot operates exactly as the
instrument it replaces, complete with a red flag indicating that electrical power to the
instrument has been lost. The TC powers up along with the battery master as usual.
The autopilot component is powered separately and has its own power switch, so both the
battery master
and
the AP MASTER switch need to be on for the autopilot to power up. It
takes many seconds for the autopilot to become ready after power-on, because it has to wait
for the TC to become stable and align its own platform in addition to performing its own
computer self-checks. The expected sequence of indications at power-up is given in the
Power-Up Test below.
Our autopilot does not have pitch axis control, but since it was an option, pitch control lights
appear on the face of the instrument. Do not be confused by their presence; there is no
altitude or pitch control capability and the ALT and TRIM UP/DN lights will remain off at all
times.
The ability of the autopilot to provide optimum assistance and performance is
directly proportional to the pilot's knowledge of its operating procedures.
Therefore, pilots should develop a thorough understanding of the autopilot and its
operating procedures in practice flight under Visual Meteorological Conditions
(VMC) prior to using it IFR or in busy airspace with heavy pilot workloads.
N6004H S-TEC Autopilot Reference
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cvk
1/29/13
