FUTABA GY502 User manual

AVCS GYRO
GY502
INSTRUCTION MANUAL
YAW-AXIS STABILIZER FOR MODEL HELICOPTER
(RATE GYRO)

2
Thank you for buying a GY502 AVCS gyro.
Before using your new gyro, please read this manual thoroughly and use the
gyro properly and safely. After reading this manual, store it in a safe place.
FOREWORD
The GY502 is an AVCS (Angular Vector Control System) rate gyro
developed for use with .60 type and other model helicopters.
[Features]
•High-speed arithmetic processing by microcomputer allows high-speed
pulse drive of servos. (Compatible with high-speed digital servos)
•Sensor vibration resistance and neutral characteristics have been improved
by the use of a low back aerofoam case.
•Amplifier mounts an LCD for accurate data setting.
[Applicable servos]
Gyro performance largely depends on the servo used. The higher the speed
and response of the servo, the higher the gyro gain and the better the gyro
performance. From this standpoint, a digital servo is perfectly suited for use
with a gyro. We recommend the use of a high-speed digital servo especially
developed for gyro use.
•No part of this manual may be reproduced in any form without prior permission.
•The contents of this manual are subject to change without prior notice.
•This manual has been carefully written. Please write to Futaba if you feel that any
corrections or clarifications should be made.

3
FOR SAFETY
•Meaning of Special Markings ---------------------------- 4
•Mounting/Operating Precautions ------------------------ 5
•Fuselage Maintenance Precautions ---------------------- 7
TABLE OF CONTENTS
BEFORE USE
•Set Contents------------------------------------------------- 8
•AVCS Gyro ------------------------------------------------- 9
•Digital Servo Compatibility -----------------------------11
INSTALLATION AND ADJUSTMENT
•Installing to Fuselage -------------------------------------32
•Flight Adjustments ----------------------------------------37
DATA SETTING
•Name and Function of Each Part------------------------12
•LCD Display and Edit Keys -----------------------------13
•Function Map ----------------------------------------------14
•GY502 Functions Setting --------------------------------15
•Remote Gain Function------------------------------------21
•Initialization------------------------------------------------30
REFERENCE
•Specifications ----------------------------------------------40
•Definition of Abbreviations------------------------------41
•GY502 Parameters Sheet---------------------------------42

4FOR SAFETY
FOR SAFETY
To ensure safe use, observe the following precautions.
Meaning of Special Markings
Pay special attention to the safety at the parts of this manual that are
indicated by the following marks.
Mark Meaning
Procedures which may lead to a dangerous
condition and cause death or serious injury to
the user if not carried out properly.
Procedures which may lead to a dangerous
condition or cause death or serious injury to
the user if not carried out properly, or proce-
dures where the probability of superficial
injury or physical damage is high.
Procedures where the possibility of serious
injury to the user is small, but there is a
danger of injury, or physical damage, if not
carried out properly.
Symbol:
; Prohibited ; Mandatory

5
FOR SAFETY
Insert the connectors fully and firmly.
If a connector works loose due to vibration during flight, control may
be lost and result in a dangerous situation.
Mounting/Operating Precautions
Always use the accessory sensor tape to install the sensor to the
fuselage.
This is necessary to securely fasten the sensor to the fuselage so that
operation of the gyro does not transmit unwanted fuselage vibrations
directly to the sensor.
When mounting the sensor, provide a little surplus so that the
sensor connection cables are not too taut.
If the sensor cables are too taut, the gyro will not display its full
performance. If the sensor peels, control will be lost and result in a
dangerous situation.
Mount the sensor and control amp so that metals or other
conductive objects do not touch these cases.
The GY502 uses a conductive resin case to reduce electromagnetic
interference. Because the surface of the case is conductive, metal
objects may cause a short circuit.
Mount the sensor and servo at least 2cm apart.
When using a GV-1 governor, mount the sensor and GV-1 amp
at least 5cm apart.
When using the GY502 with a motor-driven helicopter, mount
the sensor and drive motor at least 10cm apart.
Noise from the servo motor, GV-1 amp and drive motor may cause
the performance of an erroneously operated gyro to drop.

6FOR SAFETY
When the rudder neutral position was changed by the linkage,
the rudder neutral position in the AVCS mode must always be
re-read before use.
Re-reading method:
Turn on the transmitter in the AVCS mode, then turn on the
gyro . Or quickly switch (interval of within 1 second) the
remote gain channel switch between the AVCS mode and
Normal mode at least three times and switch the AVCS side
with the transmitter in the ON state. This memorizes the new
rudder position inside the GY502.
During initialization, the message “-Hello-” appears on the GY502
LCD screen.
Do not move the helicopter until this message disappears (in
about 3 seconds).
Also, do not move the transmitter rudder stick from the neutral
position during this period.
Precautions When Turning on the Power Switch
Always check the direction of operation of the servos.
If you attempt to fly the model when a servo operates in the wrong
direction, the fuselage will spin in a fixed direction and enter an
extremely dangerous state.
Avoid sudden temperature changes.
Sudden temperature changes will cause the neutral position to
change. For example, in the winter, do not fly immediately after
removing the model from inside a heated car and in the summer, do
not fly immediately after removing the model from inside an air
conditioned car. Allow the model to stand for about 10 minutes and
turn on the power after the temperature inside the gyro has stabilized.
Also, if the gyro is exposed to direct sunlight or is mounted near the
engine, the temperature may change suddenly. Take suitable mea-
sures so that the gyro is not exposed to direct sunlight, etc.

7
FOR SAFETY
Check the remaining receiver/gyro/servo nicd battery operating
time during the adjustment stage and decide how many flights
are remaining.
Never use the transmitter rudder trim in the AVCS mode.
When the rudder is trimmed during flight, the neutral position will
change.
When using the GY502 in the AVCS mode, set revolution mixing
to OFF.
Fuselage Maintenance Precautions
Use a tale rotor drive tube or other part with a high torsion
performance for the tail drive.
Take the strength of the tail into account during inspection and
adjustment.
The amount of improvement of gyro performance has a considerable
effect on the fuselage vibration level or the size, type, linkage
method, looseness, etc. of the tail rotor.
Since a higher gain than usual can be used then the tail rotor is more
effective, the load on the tail is also greater.
Always perform proper maintenance for ultimate performance.
The rigidity of the fuselage tail has a large effect on gyro perfor-
mance.
Make the fuselage vibration as small as possible.
Fuselage vibration has an adverse affect on gyro operation.

8BEFORE USE
Set Contents
After unpacking the GY502 set, first check if the following parts are
provided:
BEFORE USE
Sensor tape (x3)
Mini screwdriver (x1)
GY502 sensor (x1)
GY502 control amp
(x1)

9
BEFORE USE
Differences Between AVCS Gyro and Conventional Gyro
Compared to a convention gyro, the AVCS gyro has a substantially im-
proved tail control capacity. Gyro operation also differs from that of
conventional systems in a number of ways.
The following sequentially describes the conventional gyro and the AVCS
gyro.
Conventional gyro
The conventional gyro detects movement of the helicopter's tail and controls
the rudder servo so that movement of the tail stops.
Now, consider hovering when the helicopter is exposed to a side wind, the
tail drifts. When the tail drifts, the gyro detects the tail rotation angular
velocity and operates the servo in the direction that stops the tail from
moving. Drifting of the tail is stopped by control from the gyro. When the
tail stops drifting, the control amount from the gyro becomes zero. Since the
helicopter is always exposed to side wind, even in this state, the tail starts to
drift again. When the tail drifts, the gyro tries to stop it again. The "drifting
stop" operation is repeated and the tail continues to drift in the wind
direction in this manner. The higher the gyro sensitivity, the smaller the
amount of this drift. However, if the sensitivity is high, hunting will occur
and, therefore, the sensitivity amp has a limit.
• Drifting stop
Forward
Side wind
AVCS Gyro
AVCS gyro
This following describes how the AVCS system works when the helicopter
is exposed to a side wind while hovering, the same as the preceding item.
When the helicopter is exposed to a side wind, the tail begins to drift. The

10 BEFORE USE
Differences in rudder control method
The following describes the differences between conventional gyro and
AVCS gyro rudder control.
The conventional gyro sends the rudder control signals from the transmitter
to the rudder servo and starts to move the tail. When the tail moves, the gyro
detects this movement and generates a signal to stop it. If the tail continues
to move even in this state, a rudder control signal larger than the signal from
the gyro must be applied from the transmitter. That is, the difference
between the rudder control signal from the transmitter and the control signal
that attempts to stop this from the gyro becomes the actual amount of
movement of the tail. Ordinarily, the rudder control signal is amplified
• The tail remains extremely stable.
Forward
Side wind
gyro controls the servo so that the movement of the tail stops, the same as a
conventional gyro. At the same time, a sensor is controlled so that the tail is
rotated in the opposite direction (returns to the original position). In short,
the conventional gyro performs an operation known as "drifting stop", but
the AVCS system performs an operation that "stops drifting and returns to
original position". The "return to original position" operation added to the
AVCS system improves rudder trim operation. In other words, the gyro can
automatically trim the rudder against side winds. This also applies to reverse
flight. When a helicopter is flying in the forward and reverse directions, the
rudder trim is changed to advance, but with the AVCS system, this trim
change is performed automatically and instantaneously so that the tail
remains extremely stable even during high-speed reverse flight.
The AVCS system requires a high-precision angular velocity sensor. The
GY501 realizes a high-precision angular velocity detection function and
extremely small output drift by using a new type of gyro sensor. This
minimizes rudder neutral position drift during flight and eliminates the need
to trim the rudder during flight.

11
BEFORE USE
several times over by the gyro amp and is balanced with the gyro control
signal so that the transmitter can be used at the normal steering angle.
The AVCS system uses a different rudder control method. As described in
the preceding section, it has additional functions that "attempt to return
movement by external force to the original position" and that generate an
angular velocity proportional to the rudder control signal. That is, it func-
tionally controls the speed of rotation of the tail. The original AVCS
(Angular Vector Control System) came from this.
•In the AVCS mode, when the transmitter rudder stick is moved when
the helicopter was stopped, the rudder servo controls operation until
the tail reaches the specified rotational speed.
•Trim deviation of the rudder control signal also becomes a signal that
causes the tail to turn so that even a little trim deviation causes the
tail to move. Therefore, the rudder trim is made the same in all flight
states and must match the neutral reference signal at the gyro. The
method of reading the rudder neutral signal at the gyro will be
described separately.
•Since the rudder mixing signals from the transmitter also become a
tail rotation signal, all the rudder mixing functions must be disabled.
•In the AVCS mode, the gyro automatically trims the rudder so that
linkage changes cannot be verified. Initially, the GY502 trims the
rudder by flying in the Normal mode to take the rudder linkage neutral
position. This centers the linkage. At this time, this rudder neutral
reference point is read to the GY502.
Giving the gyro the rudder neutral reference signal and performing
tail operation by referring to this signal in the AVCS mode in this
way is how the AVCS system differs from the conventional system.
Digital Servo Compatibility
Gyro performance largely depends on the servo used. The GY502 displays
top performance when used with a digital servo.
When using a digital servo, set the servo frame rate (Frm) function to High.
(For a description of the setting method, see page 19.)

12 DATA SETTING
DATA SETTING
GY502 control amp
Name and Function of Each Part
LCDcontrasttrimmer
Allows adjustment of the contrast so that the LCD display is easiest to see.
It is adjusted with the accessory mini screwdriver.
(Receiverconnectors)
Remotegaininput
Rudderinput
Editkeys
Used when setting data.
Operated by pushing with the
accessory mini screwdriver.
(Input/outputterminals)
Gyrosensorinput
Rudderservooutput
GY502 gyro sensor
LCDdisplay
Displays the set data. (8 characters X 1 line)
Stick to the body using the accessory
sensor tape.
To control amp

13
DATA SETTING
LCD display
Set data display and operation
status monitoring are possible.
LCD Display and Edit Keys
Edit keys
Setup screen call
The setup screens can be sequen-
tially called with the FUNC+ or
FUNC- key. For the order in which
the setup screens are called, see the
function map.
Data setting
Perform data setting with the DATA+
or DATA- key. When setting a value,
the data is increased when the
DATA+ key is pressed and is
decreased when the DATA- key is
pressed. The mode can also be
selected using either the DATA+ or
the DATA- key.

14 DATA SETTING
Function Map
Normal screen display
(P15)
Gyro Gain Adjustment
(P16)
Gyro Reverse
(P16)
Rudder Control Gain
(P17)
Control Delay I
(P17)
Gain Tracking
(P18)
Servo Frame Rate
(P19)
Operation Mode Setting
(P18)
Linkage Limit Setting
(P20)
FUNC ”-” key
FUNC ”+” key
Power ON
Power on screen display
(P15)
Control Delay D
(P17)
AVCS sense
(P20)

15
DATA SETTING
GY502 Functions Setting
Power on screen display
Whenthegyropoweristurnedonafterthetransmitterpowerwas
turnedon,-Hello-blinksforaboutthreesecondstoinitializethedata
insidethegyro.Duringthisperiod,donotmovethetransmitter
rudderstickorthehelicopter.Ifthetransmitterrudderstickorthe
helicopterismovedbymistake,therudderneutraldatawillnotbe
correctlyread.
Normal screen display
•Operation mode display
N : NOR mode
A : AVCS mode
: Neutral offset
•Actual gain (sensitivity)
display •Power supply voltage display
•During rudder neutral reset operation,
**** is displayed.
•During rudder servo reset operation by
rudder stick, ---- is displayed.
Low battery alarm
Whenthe powersupply voltagedrops to3.8V orless,
LOWBattisdisplayed.Whenthismessageisdisplayed,
immediatelystopuseandrechargetheNicdbattery.

16 DATA SETTING
Gyro Reverse Initial value: NOR
Setsthegyrooperationdirection.NORorREVcanbeselected.
Setsothatwhenthehelicopterisbankedright,leftcorrectionrudder
isappliedandwhenthehelicopterisbankedleft,rightcorrection
rudderisapplied.
Gyro Gain Adjustment Initial value: 100%
Adjuststhe gyrogain.Setting rangeis0to120%.
Two-point(G:1,G:2)gainadjustmentispossible.WhenAis
displayed, the gyro is in the AVC mode and when N is displayed, the
gyroisintheNORmodeinaccordancewiththeoperationmode
setting.

17
DATA SETTING
Rudder Control Gain Initial value : ACG: 100%, NCG: 120%
Adjuststherudderstickoperationgain.Settingrangeis10%to
250%.
AVCSandNORmodegaincanbesetindependently.IntheAVCS
mode,ACGisdisplayedandinthe NORmode, NCGis displayed.
ThedisplayautomaticallychangestoAorBaccordingtothe
directionoftherudderstickandthegainofeachdirectioncanbeset.
Thisfunctionisusedwhentrackingrudderoperationgainbetween
theAVCSandNORmodes.
Control Delay I Initial value : 0%
Setsthedelaywhentherudderstickwaspushedoperated.Setting
rangeis0to100%.Rudderstickleftandrightcanbesetseparately.
Control Delay D Initial value : 0%
Setsthedelaywhentherudderstickwasreturned.Settingrangeis0
to100%.Rudderstickleftandrightcanbesetseparately.

18 DATA SETTING
Gain Tracking Initial value : +0%
Adjustsleftandrighttailbrakingtracking.Settingrangeis-20%to
+20%.
Forexample, whenthereis asenseof huntingwhenstopping left
pirouetteorthehelicopterdriftswhenstoppingrightpirouette,shift
Trkin the+direction. Intheoppositecase,shift Trkinthe -direc-
tion.
Operation Mode Setting Initial : CMT
Setsthegyrooperationmode.SettingsareNOR,AVC,andCMT.In
theNOR mode,bothG1andG2 operatein theAVCSmode.Inthe
CMTmode,G1 operatesintheAVCSmodeand G2operatesinthe
NORmode. Inthe NORmode,theGY502operates thesameasan
ordinarygyro.IntheAVCmode,theGY502alwaysoperatesinthe
AVCS mode. In the CM mode, the GY502 can be used in both the
AVCSandNORmodes.

19
DATA SETTING
Servo Frame Rate Initial value : Low
Switchestheservooutputpulses.
TheLowmodeoutputspulsesforanordinaryservo.Switchtothe
Highmodeonly whenusing adigitalservo.
When using a servo that cannot be driven by high-speed pulses,
other than a digital servo, never set servo frame rate to the High
mode.
Theservomaybedestroyed.

20 DATA SETTING
AVCS Sense Initial value : 100%
AdjuststheruddercontrolcharacteristicintheAVCSmode.Setting
range is 50 to 150%.
Adjustbycheckingtherudderoperationfeelandstoppingcharacter-
istic.
Linkage Limit Setting Initial value : 100%
Setstherudderservotravellimit.
Operatetherudderstickandadjusttherudderservotravellimitby
pressingthe +/-key sothat theservomovestothemaximumlinkage
position.Usethesameproceduretoset boththeleft andrightlimits.
Whensetting,movetheservosubstantiallysothattherudderangle
automaticallybecomes200% andlimitsetting iseasy.A orBis
displayedfortherightandleftdirections.
Note:When thisscreenis displayed,theGY502 doesnotoperateas
agyro.Tocheckoperation,returntotheinitialscreen,etc.