Specifications

Information Manual 7-91
Cirrus Design Section 7
SR20 Airplane Description
The S-Tec System Twenty Autopilot features:
• Roll Stabilization.
• Turn Command.
• Heading Hold interfaced with DG coupled heading bug.
• NAV/LOC/GPS tracking, HI and LO sensitivity.
Avionics Configuration 2.1:
These airplanes are equipped with an S-TEC System Thirty Autopilot.
This two-axis autopilot system receives roll axis control inputs from an
integral electric turn coordinator and altitude information from an
altitude transducer plumbed into the Pitot-Static system. The
programmer, roll computer/amplifier, and annunciators are contained
entirely within the turn coordinator case. The Multi-function Control
Knob at the upper left of the turn coordinator provides mode selection,
disengage, and turn command functions. A button on each control
yoke handle may be used to disengage the autopilot. A separate pitch
computer provides the ALT hold function. Roll axis steering is
accomplished by autopilot steering commands to the aileron trim
motor and spring cartridge. Pitch axis command for altitude hold is
accomplished by pitch computer commands to the elevator servo. The
autopilot operates on 28 VDC supplied through the 5-amp
AUTOPILOT circuit breaker on the Essential Bus. The S-Tec System
Thirty Autopilot features:
• Roll Stabilization;
• Turn Command;
• NAV/LOC/GPS tracking; HI and LO sensitivity;
• Altitude Hold; and
• GPS Steering (GPSS) for smoother turns onto a course or
during course tracking.
A separate GPSS converter provides GPS roll steering to the
autopilot. A GPSS/HDG button allows the operator to switch between
HDG and Roll Steering modes. In the HDG mode the autopilot
responds to the HDG bug on the HSI. In the GPSS mode, the autopilot
responds to roll steering inputs from the GPS navigator.
Refer to S-TEC System Thirty Autopilot Pilot’s Operating Handbook
(P/N 8777) dated Feb 1999 or later and the applicable POH
March 2010