Trio Avionics EZ Series Specification sheet

EZ Series
Altitude Control Systems
Operation and Installation Manual
Trio Avionics Corporation
Rev 1.8

2
Notice and Warnings
Warning: Any failure to comply with the following warnings can
lead to property damage, and serious injury including death.
Although Trio Avionics has taken reasonable steps to test its product, the final determination of safe
operation lies with you, the installer and pilot. Your workmanship in installing, cabling, and testing the
Altitude Hold system in your airplane is critical to safety. If you are not the original builder of your aircraft,
and do not hold a valid “Repairman’s Certificate” for your aircraft, you must have the installation done by a
qualified A&P aircraft mechanic or the original builder. You must comply with all current FAA regulations
regarding installation of this device in your airplane.
This product is to be used on homebuilt, experimental aircraft only. It is not approved for, nor is it legal to
install it in, certified aircraft. It is not approved by any governmental or non-governmental agency.
Prior to installing or flying this altitude hold system, read the manual completely. If you have any questions
about the installation or operation of the system, STOP and then call or email Trio Avionics for clarification.
The servo that is a part of this altitude hold system is attached directly to your elevator control system. It is
possible to install or adjust it in a manner that may result in improper or unexpected elevator movement that
could result in dangerous aircraft maneuvers. Install it only after you have read and understand the
installation instructions. You must thoroughly inspect and test your installation prior to flight. Mistakes in
any modification to your aircraft can be life threatening!
Each homebuilt aircraft is individual in its construction, maintenance and flying characteristics. Therefore,
while Trio Avionics has tested the product in a variety of aircraft, we do not represent or warrant that it is
appropriate or suitable for use in your particular aircraft. Only you can make that determination and
ultimately only you are responsible for its safe installation and use.
This product is designed for use as an en route navigation aid only, and only at safe altitudes in
unobstructed airspace. It must not be relied upon for any other purpose. It is not to be used for flight in
instrument meteorological conditions (IFR), or approaches into airports in either IFR or visual (VFR)
conditions. Power to the servo must be turned “off” for takeoffs and landings.
In operation, this product relies upon data provided by solid state sensors, gyros and electronic
components. Always keep in mind that such systems should never be thought of as totally reliable. They
may be disrupted by electromagnetic interference, close proximity of transmitting antennas and cables, and
other problems.
When flying an aircraft with this, or any, altitude hold system enabled, you must be constantly vigilant for
any sign of improper operation of the system. When there is even a suspicion that the altitude hold system
is not operating properly, you must immediately disable the altitude hold system by any of the various
methods detailed in this manual. Do not fly the altitude hold system without incorporating the remote servo
disconnect switch that is described in this manual.
There may be a tendency to concentrate on the instrument display when test flying this or any other new
system in your aircraft. Do not allow it to distract you from the need to “see and avoid” other aircraft.
The safe practice of aviation demands the consistent exercise of pilot skill, knowledge of
airmanship and weather, judgment and focused attention at a level which is appropriate to the
demands of each individual situation. Pilots who do not possess or exercise the required
knowledge, skills and judgment are frequently injured or killed. Therefore, although an altitude
hold system can serve as a useful navigation aid, no altitude hold system can be relied upon and
you must be at full attention at all times while flying any aircraft.
If you do not agree to comply with any of the warnings or notices above, do not
install or fly this altitude hold system in your aircraft. Call Trio Avionics for a
Return Material Authorization (RMA) and return the unused system for a full
refund.

3
Table of Contents Page
Notice and Warnings ....................................................................................................................2
1.0 Introduction...................................................................................................................................4
2.0 General Information......................................................................................................................4
3.0 Operation.......................................................................................................................................4
3.1 Startup....................................................................................................................................5
3.2 “Alt Hold” Mode.......................................................................................................................5
3.2.1 Fine Adjustments to Altitude .............................................................................6
3.2.2 ADJUST TRIM Annunciator ..............................................................................6
3.3 Pilot Command Steering (PCS) Mode....................................................................................7
3.4 System Gain, Brightness, Contrast, Servo Deadband & Trim settings...................................7
3.5 Safety Warning Features........................................................................................................8
3.5.1 Audible Warning................................................................................................8
3.5.2 G Force Limit.....................................................................................................8
3.5.3 Servo Clutch Slip...............................................................................................9
3.5.4 Servo CW (or CCW) Limit.................................................................................9
3.5.5 Servo Fault......................................................................................................10
4.0 System Safety Features .............................................................................................................10
4.1 Aircraft G-Load Sensing .......................................................................................................10
4.2 Servo Electronics Monitoring................................................................................................10
4.3 Clutch Slip Detection ............................................................................................................10
4.4 Rotation Limit Detection .......................................................................................................10
4.5 Supervisory Processor Monitoring........................................................................................10
4.6 Servo / Trim Driver Chip Fault Detection..............................................................................11
4.7 Disconnect Solenoid.............................................................................................................11
4.8 SMP and Supervisory Processor Watchdog Interrupts.........................................................11
5.0 Installing the Altitude Hold Control Module…… ………………...............……………………….11
5.1 Installing the LCD Switch......................................................................................................12
5.2 Installing the Encoder Switch................................................................................................12
5.3 Installing the Wiring Harness................................................................................................12
6.0 Servo Installation Setup...............................................................................................................13
6.1 Installing the Servo...............................................................................................................13
6.2 Servo Mounting Hardware....................................................................................................14
6.3 Selecting a Site for the Servo ...............................................................................................15
6.4 Install the Servo Pushrod......................................................................................................16
6.5 Setting Servo Override Force (Slip Clutch)...........................................................................16
6.6 Adjustment of Servo Rotation Direction and Servo Neutral..................................................17
6.6.1 Servo Direction Setting.....................................................................................17
6.6.2 Setting Trim Motor Direction.............................................................................18
6.6.3 Restore Factory Defaults..................................................................................18
7.0 SYSTEM GAIN and SERVO DEADBAND.....................................................................................18
7.1 System Gain ...........................................................................................................................18
7.2 Servo Deadband…..................................................................................................................19
8.0 The EZ-2 Altitude Hold System with Climb and Descent capability........................................19
8.1 EZ-2, EZ-3 Operation..............................................................................................................20
8.1.1 VS Mode...........................................................................................................20
8.1.2 Minimum and Maximum Airspeed Control........................................................21
8.1.3 Setting Minimum and Maximum Airspeed ........................................................22
8.1.4 Vertical Rate and Airspeed Track Pilot Command Steering (PCS) ..................23
9.0 The EZ-3 Altitude Control System with Altitude Pre-select......................................................24
9.1 EZ-3 Operation.....................................................................................................................25
9.1.1 Elevation (Baro) Set .........................................................................................25
9.1.2 EZ-3 Menu System...........................................................................................26
9.1.3 Enter Vertical Speed (VS) ................................................................................28
9.1.4 Enter a Destination Altitude..............................................................................28
10.0 Altitude Hold Wiring Diagram .....................................................................................................29
11.0 Automatic Trim.............................................................................................................................30
12.0 Glossary of Terms................................................................................. ……………………….…..32
13.0 Contact Information.....................................................................................................................32

4
SYSTEM
TEST
EZ Altitude Control System
1.0 Introduction
Congratulations on choosing the EZ Altitude Control System. The EZ-1 System is designed to
hold a precise altitude of the aircraft. The EZ-2 system has all the features of the EZ-1 system
and adds additional safety features, vertical rate selection and vertical speed or airspeed capture
capabilities. The EZ-3 system builds on the capabilities of the EZ-1 and EZ-2 systems adding
airspeed management modes and altitude preselect and capture features. The following
paragraphs describe the EZ altitude control systems in detail. The EZ-2 system description
begins in paragraph 8 of this manual. The EZ-3 system is described in section 9.
The EZ-1 will precisely maintain a desired pressure altitude for your experimental aircraft up to an
altitude of 20,000 feet. In smooth air it will hold the aircraft altitude to within +/- 20 feet (generally
less). In turbulent air or turns of 15 to 20 degrees bank angle it will hold to within +/- 50 feet.
While the EZ-1 is simple to use, this manual is a guide to understanding its basic functions and
employing its many features. Operation is as simple as pressing the “ALT HOLD” button.
This causes the aircraft to maintain the current pressure altitude. The following sections illustrate
the built in safety measures, messages and the many features available in your new system.
2.0 General Information
The EZ altitude control system is comprised of 4 major hardware elements:
1Elevator Servo
2Electronics Module
3LCD push button switch
4Rotary encoder control
In addition, an external Sonalert or other warning device may be connected to provide an audible
warning prior to system disconnect. An audio tone is also available as an input to the aircraft
intercom system. An auxiliary small remote push button (momentary – normally open) switch
mounted to the stick or yoke will allow access to the many additional features of this system.
3.0 Operation
When power is applied, the amber SYSTEM TEST message will be
displayed for approximately 8 seconds. After this stabilization period
the unit will become fully functional. The LCD switch will display a
green READY message. The altitude hold function is activated by
pressing the LCD switch which will then annunciate the hold condition
1 2
3
4

5
READY
ALT
HOLD
with a green ALT HOLD message on the LCD display. (At this time servo activation should be
detected by resistance to manual yoke or stick movement forward or backward)
To disconnect the EZ altitude control system servo activation either the REMOTE AUTOPILOT
DISCONNECT switch or the LCD SWITCH may be momentarily pressed.
During normal operation in the altitude hold mode the ENCODER knob may be used to dial in
very fine corrections to the engaged altitude. Rotating the knob clockwise will cause an altitude
increase, rotating the knob counterclockwise will result in an altitude decrease.
In addition to the servo disconnect function the REMOTE AUTOPILOT DISCONNECT switch can
be used to “fly to” another altitude. This is accomplished by pressing and holding the REMOTE
AUTOPILOT DISCONNECT switch for a period of more than three seconds. When pressed, the
servo will immediately disengage so the airplane can be flown to a different altitude and will rearm
after the three second delay period. While in the armed mode the LCD switch will flash the
amber backlight and will display ALT HOLD. On the EZ-1 system, releasing the remote
disconnect switch (after the 3 second interval) will engage the servo, show a green LCD ALT
HOLD message and hold the aircraft at the proper altitude. The EZ-2 and EZ-3 systems add a
VS rate capture or an airspeed capture as additional options to this sequence (section 8.1.4)
3.1 Startup
It is strongly recommended that a 3 to 5 amp switch or circuit breaker be used to power
the EZ altitude control system. This switch or circuit breaker will provide absolute
emergency disconnect of the altitude hold servo should all other disconnect measures
fail. Once the aircraft engine is started, part of the pre-taxi checklist should be to apply
power to the system by engaging the switch or circuit breaker. Power should be applied
as soon as possible after engine start to ensure the inertial components within the
system are stabilized prior to takeoff.
After power is applied, the system will undergo a brief startup
sequence which will last approximately 8 seconds. During this
time the amber SYSTEM TEST message will be displayed.
After this short period the unit will become fully functional and
the LCD switch will display a green READY message.
3.2 “ALT HOLD” Mode
The altitude hold function is activated by momentarily pressing
the LCD switch which will then annunciate a green ALT HOLD
message on the LCD display. (During pre-taxi checks, servo
activation can be detected by resistance to manual yoke or
stick movement forward or backward).
IMPORTANT: Prior to taxi, momentarily press the remote
disconnect switch to disengage the servo. The LCD switch will
then display the READY message. A pre-flight checklist item
should be created to ensure the altitude hold system is disengaged (in the READY
mode). An additional safety feature available on the EZ-2 and EZ-3 systems is an
automatic servo disconnect on takeoff.
Once the aircraft is in flight, and the desired altitude has been reached, the aircraft should
be trimmed for stable, level flight. The pilot may then simply press the LCD switch and
the EZ altitude control system will enter the altitude hold mode and the LCD switch will
display ALT HOLD while it is employed. The servo will engage the elevator system and
control the elevators to maintain the desired altitude.
To disconnect the EZ altitude control system, the pilot may momentarily press either the
LCD switch or the REMOTE AUTOPILOT DISCONNECT switch on the stick or yoke.

6
ALT
UP
A
DJUST
ALT
DOWN
A
DJUST
The system will then immediately release the elevators from servo control and enter the
READY mode. Turning off power to the unit will also release the servo.
3.2.1 Fine Adjustments to Altitude - While flying with the ALT HOLD engaged,
the ENCODER knob may be used to dial in very fine corrections to the engaged
altitude. Rotating the knob clockwise will cause an altitude increase (and cause
the LCD to indicate “ALT UP ADJUST”), while rotating the knob
counterclockwise will result in an altitude decrease and corresponding display.
Each “click” of the rotating knob will change the altitude by approximately 5 feet,
up or down, depending on the direction of rotation. When the altitude change is
completed, the green ALT HOLD display will appear. Alternatively, the encoder
knob may be pressed at any time to stop the adjust feature.
3.2.2 ADJUST TRIM Annunciator – As the flight progresses the aircraft may
require occasional trim changes as the fuel burn lightens the aircraft, or if the
throttle setting is changed. The servo will hold the proper altitude in all but
extreme out-of-trim conditions, but it is prudent to keep the aircraft properly
trimmed to avoid sudden excursions when the servo is disengaged.
The EZ-1 will sense when the aircraft is out of trim. If
the out-of-trim condition is minor it will not alert the
pilot. However, when the out-of-trim forces on the
servo exceed a predetermined amount, it will present a
message (flashing up or down arrows) to the pilot
advising that the aircraft trim should be adjusted. The
arrows on the display indicate the required direction of
trim adjustment. The altitude will be maintained even
though this alert is present.
When a trim adjustment is sensed by the computer the
“Trim” message will be removed, and the normal ALT
HOLD message will return. Pressing the ENCODER
switch while the “Trim” message is present will erase
the message, remove the trim correction provided by
the system and replace it with the ALT HOLD
message. If the out of trim condition remains after a
correction has been made, or the message has been
cleared the message will return in a short period of time.
Probably the quickest way to eliminate the out-of-trim condition is to momentarily
disconnect the ALT HOLD function by pressing the LCD switch, re-trim the
aircraft for level flight, and then reengage the ALT HOLD.
The EZ altitude control system is available with an automatic trim option which
will automatically trim the aircraft to remove any trim errors. This feature will
control a separate trim motor (customer provided) such as the Ray Allen
Corporation model T3-12A or similar motor.
NOTE – If the ADJ TRIM arrows appear on the LCD, but when the ALT HOLD is released there is
very little trim correction required to the aircraft, the SYSTEM GAIN setting is probably too low, not
allowing the system to properly control the aircraft. See section 6.0 for proper adjustment of the
SYSTEM GAIN setting,
TRM
DWN
TRM
UP

7
BRITE
SET
GAIN
SET
45
SERVO
DBAND
6
CONTR
SET
If the pilot wishes to re-trim the aircraft without disconnecting the ALT HOLD,
trim adjustments should be made in small increments. When each adjustment is
made, the pilot should wait for approximately 30 seconds to allow the system to
sense the change. If the “Trim” message remains, continue further adjustments
until the ALT HOLD message returns.
3.3 Pilot Command Steering (PCS) Mode
In addition to the servo disconnect function, the REMOTE DISCONNECT switch can be
used to “fly to” another altitude. This is accomplished by pressing and holding the
REMOTE DISCONNECT switch for a period of more than three seconds. The servo will
immediately disengage so the airplane can be flown to a different altitude manually and
will “re-arm” after the three second interval. While in the “armed” mode the LCD switch
will flash an amber backlight and will display ALT HOLD. Releasing the remote
disconnect switch will engage the servo and cause the LCD switch to present a solid
green color while displaying the ALT HOLD message. The aircraft will then hold the
selected altitude.
3.4 System Gain, Brightness, Contrast, Servo Deadband and (optional)
Trim Speed settings
The SYSTEM GAIN, BRIGHTNESS, CONTRAST, SERVO DEADBAND and
(optionally) the TRIM SPEED settings are adjustable with the system in the ALT HOLD
mode. The same settings are available in the READY mode with the exception of the
SYSTEM GAIN setting. This menu mode is entered from either the READY mode or the
ALT HOLD mode by pressing in and holding the encoder switch knob for at least 3
seconds.
To activate this feature, perform the following steps when either READY or ALT HOLD
message is displayed on the LCD switch:
1. Press and hold the encoder switch knob until the GAIN SET message
appears on the LCD switch
2. Press (click) the encoder switch knob repeatedly
until the desired selection is displayed.
3. Rotate the encoder switch knob to change the
setting.
The GAIN setting (ALT HOLD only) controls
the response characteristics of the system.
The proper adjustment of the GAIN setting is
fully discussed in paragraph 6.0.
The BRIGHTNESS setting controls the
illumination level of the LCD background. This
setting is best done in subdued light.
The CONTRAST adjustment will allow
setting the optimum contrast for the pilots
viewing angle.
The SERVO DEADBAND setting controls
the “deadband” width of the servo. The
proper adjustment of this parameter is fully
discussed in paragraph 6.0.

8
G
FORCE
L
IMIT
TRIM
SPEED
10
The TRIM SPEED setting is only available if
the AUTO TRIM option is installed. The TRIM
SPEED setting allows the pilot to tailor the
speed of the trim correction for the particular
airplane and trim drive motor.
4. Press and hold the encoder switch knob for 3
seconds to exit back to READY or ALT HOLD display
mode
3.5 Safety Warning Features
3.5.1 Audible Warning
Whenever the servo disconnects from the elevator control system, an audio tone
is generated, consisting of 3 beeps. This tone may be routed into the aircraft
audio system, as shown on the wiring diagram on page 19. Alternatively, an
sequential DC voltage is also provided on the connector to allow use of an
external warning device, such as a Sonalerttm or other warning instrument.
3.5.2 G Force Limit
When giving elevator control over to a servo, the pilot
must be constantly vigilant to assure that any
unexpected system activity such as that caused by
extreme turbulence or meteorological wave activity
cannot impose excessive acceleration forces on the
aircraft. To assist in this endeavor, the EZ altitude
control system incorporates an accelerometer system
that continually monitors the G forces being experienced by the aircraft.
In the event the aircraft experiences abnormal G forces, the EZ altitude control
system is designed to automatically disconnect from the control system before
structural damage can occur. The software is designed to detect acceleration
(G) forces that can cause structural damage due to system activity (or pilot
override action). The system will monitor, but not react to, accelerations due to
moderate turbulence. However, the system may automatically disconnect in
high end moderate or severe turbulence. The pilot is always cautioned to use
proper judgment as to whether to engage the EZ altitude control system in these
types of conditions. The pilot should always follow the aircraft designer’s
recommendations with regard to autopilot engagement, maneuvering speed
limitations, etc.
System Response – When the EZ altitude control system detects an
excessive G force condition it will immediately issue a servo disconnect
tone and disconnect the servo from the control system. The LCD switch
will illuminate red while displaying “G FORCE LIMIT”.
Pilot Action – Determine the cause of the excessive G force problem.
If the disconnect was due to turbulence or pilot action, the alarm may be
cleared by pressing the LCD switch, which will put the system back in the
READY condition. Altitude hold may then be re-engaged by pressing the
LCD switch. Pilot judgment should be exercised in accordance with the
NOTE: Even when the Contrast / Brightness / Gain / or Servo Deadband is selected, the LCD switch or the
REMOTE DISCONNECT switch can be pressed to disengage the servo and return to the
READY mode. Likewise, if the selection was entered from the READY mode, pressing the LCD
switch will terminate the SETUP mode and activate the ALT HOLD mode

9
SERVO
CLTCH
SLIP
S
ERVO
CW
L
IMIT
SERVO
CCW
L
IMIT
airframe designer’s limitation regarding use of an autopilot system in
turbulent conditions. If an EZ altitude control system control problem is
suspected, turn off power to the system and contact Trio Avionics for
direction before further use.
3.5.5 Servo Clutch Slip
The EZ altitude control system incorporates an
important special safety feature: a clutch within the
servo that can be overridden when actived by moderate
manual stick or yoke pressure. Sensors are provided
in the servo to detect slippage of the mechanical clutch
assembly. The message “SERVO CLTCH SLIP” will
appear as a flashing amber message if the condition is
sensed.
The clutch adjustment should be set during installation so that the system can
drive the elevator control system under normal conditions but be easily
overridden by a manual pilot input. Pilot override will force the clutch to slip,
allowing the pilot to take positive control away from the EZ-1 system in
emergency situations such as unexpected traffic. On the other hand, a clutch
slip message that appears for no apparent reason is probably due to the clutch
not being adjusted properly or by extreme out-of-trim conditions, thereby not
allowing the control system to be driven correctly.
System Response – the message “CLUTCH SLIP” will flash with amber
illumination. The message is advisory in nature and will not cause a
servo disconnect.
Pilot Action – If this message occurs under conditions other than a
manual servo override, the clutch adjustment should be checked to
ensure it is tight enough to drive the control system under normal
conditions including light to moderate turbulence and normal out of trim
conditions. However, you must assure that it is set loose enough that
the pilot can easily overcome it in an emergency.
3.5.4 Servo CW (or CCW) Limit
This red message indicates the servo crank arm has been
moved to a clockwise or counterclockwise position outside of
its normal range of operation. This error will result in an
immediate servo disconnect. The cause of this error is most
likely a manual system override by the pilot.
System response – immediate servo disconnect
and servo power down. Red SERVO CW (or CCW)
LIMIT message displayed.
Pilot Action – Determine the cause of the SERVO
CW (or CCW) LIMIT message. If not due to pilot
manual override, tighten the servo slip clutch to allow
greater servo control of the elevator system.

10
SERVO
FAULT
3.5.5 Servo Fault
This red message can be due to several factors
based on sensors within the servo and will always
cause an immediate disconnect and power down of
the servo.
System Response - In all cases the servo will be
immediately disconnected from the system, servo
power will be automatically removed and a red error message will be
displayed
Pilot Action - If the SERVO FAULT closely followed an extreme out of
trim condition, CLUTCH SLIP or G FORCE LIMIT alarm , press LCD
switch and continue normal operation. If the cause is unknown, or
occurs in conditions other than described above, perform ground tests of
the system paying particular attention to the wiring from the servo to the
electronics module and the mechanical linkage. If the problem persists,
contact Trio Avionics for assistance.
4.0 System Safety Features
The EZ altitude control system incorporates many safety features to ensure the system
cannot force the airplane into an un-commanded, unsafe flight regime. The following items
are implemented to ensure flight safety.
4.1 Aircraft G-load sensing.The AH module contains an accelerometer interfaced to
the main processor that is used to detect unusual positive or negative flight loads.
Software algorithms prevent unnecessary detection due to turbulence, but allow
shutdown of the servo if the flight loads exceed preset g-force limits. The intent of this
implementation is to prevent aircraft structural failure caused by an un-commanded
excursion of the servo or trim actuators. The fault condition is annunciated on the LCD
switch with the G FORCE LIMIT message
4.2 Servo Electronics monitoring. The servo and trim motor drive circuits are
instrumented and monitored by the servo main processor (SMP). The SMP commands
the magnitude and direction of the servo motor drive output. Any error in the
commanded state of these signals is reported back to the AH module via a digital data
link and results in a SERVO FAULT message on the LCD.
4.3 Clutch Slip Detection.Circuitry and software is provided that detects any slipping of
the safety clutch in the servo. Normally, this condition would only exist in the event the
pilot manually forced the control system into a position that exceeded the commanded
drive position of the servo. This event is reported to the AH module for resolution. The
amber CLUTCH SLIP message is displayed for a momentary slip condition.
4.4 Rotation Limit Detection. Under normal conditions the servo arm moves less than
20 degrees in either direction from the neutral (servo zero) position. If, for any reason
(commanded, un-commanded or pilot manual override), the crank arm transitions
approximately + / - 10 degrees outside of this range servo power is disconnected and a
red error message (CW or CCW LIMIT) is displayed.
4.5 Supervisory processor monitoring. The Servo Main Processor (SMP) is
continuously monitored by an independent supervisory processor to ensure it is
executing its program as designed. This is implemented via a “heartbeat” signal from
the SMP each 10 milliseconds. If for any reason the processor does not provide a