COBHAM S-TEC Twenty Owner's manual

3rd Ed. Feb 15, 07 i
S–TEC
List of Effective Pages * Asterisk indicates pages changed, added, or deleted by
currentrevision.
Record of Revisions Retain this record in front of handbook. Upon receipt of a
revision, insert changes and complete table below.
Revision Number Revision Date Insertion Date/Initials
1
st Ed. Feb 01, 00
2
nd Ed. Jun 24, 02
3
rd Ed. Feb 15, 07

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3rd Ed. Feb 15, 07 iii
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Table of Contents
Sec. Pg.
1Overview...........................................................................................................1–1
1.1 Document Organization....................................................................1–3
1.2 Purpose..............................................................................................1–3
1.3 General Control Theory....................................................................1–3
1.4 Modes of Operation...........................................................................1–4
1.4.1 Roll Axis Control.................................................................1–4
1.4.2 Pitch Axis Control...............................................................1–4
1.5 Block Diagrams..................................................................................1–4
2Pre-FlightProcedures...................................................................................2–1
2.1 Power-Up Test....................................................................................2–3
2.1.1 System Twenty.....................................................................2–3
2.1.2 System Thirty.......................................................................2–7
2.1.3 System Thirty ALT...............................................................2–13
2.2 Pre-Flight Test....................................................................................2–17
2.2.1 System Twenty.....................................................................2–17
2.2.2 System Thirty.......................................................................2–25
2.2.3 System Thirty ALT...............................................................2–35
3In-FlightProcedures......................................................................................3–1
3.1 Normal Operating Procedures........................................................3–3
3.1.1 Stabilizer (ST) Mode, System Twenty / Thirty...................3–3
3.1.2 Heading (HD) Mode, System Twenty / Thirty...................3–4
3.1.3 Low Track (LO TRK) Mode, System Twenty / Thirty........3–5

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3.1.4 High Track (HI TRK) Mode, System Twenty / Thirty........3–6
3.1.4.1 LOC Course Tracking........................................3–6
3.1.4.2 GPS Course Tracking........................................3–6
3.1.4.3 VOR Course Tracking........................................3–6
3.1.5 Altitude Hold (ALT HOLD) Mode, System Thirty / ThirtyALT.....3–7
3.1.5.1 System Thirty........................................................3–7
3.1.5.2 System Thirty ALT................................................3–8
3.1.6 Manual Elevator Trim Prompts, System Thirty / ThirtyALT.....3–8
3.1.6.1 System Thirty........................................................3–8
3.1.6.2 System Thirty ALT................................................3–8
3.2 Approach Procedures.......................................................................3–11
3.2.1 Straight-In LOC Approach.................................................3–11
3.2.1.1 Heading System DG..........................................3–11
3.2.1.2 Heading System HSI.........................................3–11
3.2.2 Straight-In VOR Approach.................................................3–11
3.2.2.1 Heading System DG..........................................3–11
3.2.2.2 Heading System HSI.........................................3–11
3.2.3 LOC Approach with Procedure Turn..............................3–16
3.2.3.1 Heading System DG..........................................3–16
3.2.3.2 Heading System HSI.........................................3–16
3.2.4 VOR Approach with Procedure Turn..............................3–19
3.2.4.1 Heading System DG..........................................3–19
3.2.4.2 Heading System HSI.........................................3–19

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3.3 Yaw Damper Operation....................................................................3–22
3.3.1 AUTO Mode..........................................................................3–22
3.3.2 ON Mode..............................................................................3–22
3.3.3 Yaw Damper Trim..............................................................3–22
3.4 Autopilot Disconnect ........................................................................3–23
3.4.1 System Twenty / Thirty.......................................................3–23
3.4.2 System Thirty ALT...............................................................3–23
4OperatingParameters..................................................................................4–1
4.1 Roll Axis Limits..................................................................................4–3
4.2 Pitch Axis Limits.................................................................................4–3
5Glossary...........................................................................................................5–1

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List of Figures
Fig. Pg.
1–1 SystemTwenty Block Diagram....................................................................1–5
1–2 System Thirty Block Diagram......................................................................1–6
1–3 System Thirty ALT Block Diagram...............................................................1–7
1–4 Yaw Damper Block Diagram.......................................................................1–8
2–1 AP Display, Lamps Illuminated at Power-Up (System Twenty)...............2–4
2–2 AP Display, All Lamps Extinguished (System Twenty).............................2–4
2–3 AP Display, RDY for Operation....................................................................2–5
2–4 AP Display, Turn Coordinator Failure (System Twenty)...........................2–5
2–5 AP Display, Low Voltage Flag (System Twenty).........................................2–6
2–6 AP Display, Lamps Illuminated at Power-Up (System Thirty).................2–8
2–7 AP Display, TRIM UP Lamp Extinguished (System Thirty).......................2–8
2–8 AP Display, ALT Lamp Only Illuminated (System Thirty)...........................2–9
2–9 AP Display, All Lamps Extinguished (System Thirty)................................2–9
2–10 AP Display, RDY for Operation (System Thirty).......................................2–10
2–11 AP Display, Turn Coordinator Failure (System Thirty)............................2–10
2–12 AP Display, Low Voltage Flag (System Thirty).........................................2–11
2–13 ALT HOLD ON/OFF Switch Display, Lamps Illuminated at Power-Up (System Thirty ALT)....2–14
2–14 ALT HOLD ON/OFF Switch Display, UP Lamp Extinguished (System Thirty ALT)...............2–14
2–15 ALT HOLD ON/OFF Switch Display, DN Lamp Extinguished (System Thirty ALT)..............2–15
2–16 ALT HOLD ON/OFF Switch Display, ALT ON Lamp Extinguished (System Thirty ALT).........2–15
2–17 AP Display, ST Mode Engaged (System Twenty)....................................2–19
2–18 AP Display, HD Mode Engaged (System Twenty)...................................2–19
2–19 AP Display, LO TRK Mode Engaged (System Twenty)...........................2–21

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2–20 AP Display, HI TRK Mode Engaged (System Twenty)...........................2–21
2–21 AP Display, ST Mode Engaged (System Thirty).......................................2–27
2–22 AP Display, HD Mode Engaged (System Thirty)......................................2–27
2–23 AP Display, LO TRK Mode Engaged (System Thirty)..............................2–29
2–24 AP Display, LO TRK Mode Engaged (System Thirty)..............................2–29
2–25 AP Display, HI TRK and ALT HOLD Modes Engaged (System Thirty)........2–31
2–26 AP Display, HI TRK and ALT HOLD ModeS Engaged, TRIM UP Required (System Thirty).....2–32
2–27 AP Display, HI TRK and ALT HOLD ModeS Engaged, TRIM DN Required (System Thirty).....2–32
2–28 ALT HOLD ON/OFF Switch Display, ALT HOLD Mode Engaged (System Thirty ALT).......2–36
2–29 ALT HOLD ON/OFF Switch Display, ALT HOLD Mode Engaged, TRIM UP Required (System Thirty ALT).....2–36
2–30 ALT HOLD ON/OFF Switch Display, ALT HOLD Mode Engaged, TRIM DN Required (System Thirty ALT).....2–36
3–1 AP Display, ST Mode Engaged....................................................................3–3
3–2 AP Display, HD Mode Engaged...................................................................3–4
3–3 AP Display, LO TRK Mode Engaged...........................................................3–5
3–4 AP Display, HITRK Mode Engaged............................................................3–6
3–5 AP Display, ST and ALT HOLD Modes Engaged (System Thirty)............3–7
3–6 ALT HOLD ON/OFF Switch Display, ALT HOLD Mode Engaged (System Thirty ALT)............3–8
3–7 AP Display, Manual Trim Prompts (System Thirty)...................................3–9
3–8 AP Display, Manual Trim Prompts (System Thirty ALT)..........................3–10
3–9 Straight-In LOCApproach (DG)..................................................................3–12
3–10 Straight-In LOC Approach (HSI)..................................................................3–13
3–11 Straight-In VOR Approach (DG)..................................................................3–14
3–12 Straight-In VOR Approach (HSI)..................................................................3–15
3–13 LOC Approach with Procedure Turn (DG)................................................3–17

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3–14 LOC Approach with Procedure Turn (HSI)...............................................3–18
3–15 VOR Approach with Procedure Turn (DG)................................................3–20
3–16 VOR Approach with Procedure Turn (HSI)...............................................3–21
3–17 Yaw Damper Master Switch........................................................................3–22
3–18 Yaw Damper Trim Knob..............................................................................3–22
List of Tables
Table Pg.
2–1 Power-Up Test, System Twenty...................................................................2–3
2–2 Power-Up Test, System Thirty.....................................................................2–7
2–3 Power-Up Test, System Thirty ALT.............................................................2–13
2–4 Pre-Flight Test, System Twenty...................................................................2–17
2–5 Pre-Flight Test, System Thirty.....................................................................2–25
2–6 Pre-Flight Test, System Thirty ALT.............................................................2–35

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SECTION 1
OVERVIEW

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1.1 Document Organization
Section 1 Overview
Section 2 Pre-Flight Procedures
Section 3 In-Flight Procedures
Section 4 Operating Parameters
Section 5 Glossary
1.2 Purpose
This Pilot's Operating Handbook (POH) provides Pre-Flight and In-Flight
operating procedures for the S-TEC System Twenty / Thirty / Thirty ALT Autopilot
(AP).
Note:
This POH must be carried in the aircraft and made available to the pilot at all
times. It can only be used in conjunction with the Federal Aviation
Administration (FAA) approved Aircraft Flight Manual (AFM) or Aircraft Flight
Manual Supplement (AFMS). Refer to the applicable AFM or AFMS for
aircraft specific information, such as unique ground tests, limitations, and
emergency procedures.
Note:
The System Twenty / Thirty / Thirty ALT autopilot is a tool provided to aircraft
owners, that serves to assist them with cockpit workload management. The
ability of the autopilot to provide optimum assistance and performance is
directly proportional to the pilot's knowledge of its operating procedures.
Therefore, it is highly recommended that the pilot develop a thorough
understanding of the autopilot, its modes, and operating procedures in
Visual Meteorological Conditions (VMC), prior to using it under Instrument
Flight Rules (IFR).
1.3 General Control Theory
The System Twenty / Thirty / Thirty ALT is a rate based autopilot. When in control
of the roll axis, the autopilot senses turn rate, along with the non-rate quantities
of heading error and course deviation indication. When in control of the pitch
axis, the autopilot senses acceleration, along with the non-rate quantity of
altitude. These sensed data provide feedback to the autopilot, which processes
them in order to control the aircraft through the use of mechanisms coupled
to the control system. The roll servo is typically coupled to the ailerons, and
the pitch servo is coupled to the elevator.
The System Twenty controls only the roll axis.
The System Thirty controls both the roll axis and pitch axis. Activation of roll axis
control must always precede activation of pitch axis control.
The System Thirty ALT controls only the pitch axis.

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The optional Yaw Damper senses excessive adverse yaw about the yaw axis,
and responds by driving the yaw servo in the proper direction to provide
damping. The yaw servo is coupled to the rudder.
1.4 Modes of Operation
1.4.1 Roll Axis Control
Each press/release of the optional MODE SEL Switch typically located on the
Control Wheel, or PUSH MODE Switch located on the bezel, successively
engages the roll modes below.
Stabilizer (ST) Mode
Used to Hold Wings Level
Heading (HD) Mode
Used to Turn onto a Selected Heading and Hold it
Low Track (LO TRK) Mode
Used to Track a VOR Course
High Track (HI TRK) Mode
Used to Track a LOC Course
Note:
A heading system (HSI or DG) is optional. If the aircraft is equipped with a
heading system, then the heading mode can be engaged. Otherwise, the
heading mode cannot be engaged (i.e., it will be skipped over).
1.4.2 Pitch Axis Control
Each press of the ALT ENG/DSNG Switch typically located on the Control
Wheel (optional for System Thirty ALT only), or ALT HOLD ON/OFF Switch
located on the instrument panel (System Thirty ALT only), successively engages
and disengages the single pitch mode below.
Altitude Hold (ALTHOLD) Mode
Used to Hold Altitude
1.5 Block Diagrams
The System Twenty Block Diagram is shown in Fig. 1-1.
The System Thirty Block Diagram is shown in Fig. 1-2.
The System Thirty ALT Block Diagram is shown in Fig. 1-3.
The Yaw Damper Block Diagram is shown in Fig. 1-4.

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Fig. 1-1. System Twenty Block Diagram

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Fig. 1-2. System Thirty Block Diagram

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Fig. 1-3. System Thirty ALT Block Diagram

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Fig. 1-4. Yaw Damper Block Diagram

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SECTION 2
PRE-FLIGHT PROCEDURES

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2.1 Power-Up Test
2.1.1 System Twenty
Perform the actions shown in Table 2-1. For each action, verify the corresponding
response where applicable.
Table 2-1. Power-Up Test, System Twenty
ACTION RESPONSE
1. Set Yaw Damper Master Switch to
OFF position (if installed).
------
2. Set Battery Master Switch to ON
position.
------
3. Set Avionics Master Switch to ON
position.
------
4. Set Autopilot Master Switch to ON
position.
RDY, ST, HD, LO TRK, and HI TRK
lamps illuminate on AP display as
shown in Fig. 2-1 for 7 seconds, and
then extinguish as shown in Fig. 2-2.
RDYlampalonere-illuminatesonAP
display within 3 minutes, as shown in
Fig. 2-3 (Note 1).
Notes:
1. Should a Turn Coordinator failure be detected, the RDY lamp on the AP
display will not re-illuminate as shown in Fig. 2-4, and the autopilot will not
operate.
2. Should T&B A+ be 30% below its rated value, the Low Voltage Flag will be in
view on the AP display as shown in Fig. 2-5.