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Gyros FAQ

I did not find the answer to my question here. How do I get further assistance?

I have my gyro mounted onto a graphite plate in my chopper and am seeing some slight drifting. Is there anything I can do about this?

Yes. We believe the graphite is slightly affecting the sensor's readings. The later shipments of GY240, 401, 502, and 601 gyros all include a small steel plate to resolve this mild drift. You mount the steel plate between 2 pieces of double-sided tape and mount the sensor onto the top side tape.

Please note that MOST helis have no need for this added plate, nor the space it takes up and added complexity of mounting as well as extra mobility of their sensor, so use it only if needed in your heli. If your GY501 did not come with a plate, please fax or mail us a copy of this FAQ with a copy of your proof of purchase for the gyro and we will send you a plate for your gyro.

Can I use a gyro in an airplane? When is it a good idea?

Aircraft gyros are fairly new, and some people consider them a bad idea while other people consider gyros to be the perfect tool for just about everything. Let's take a look at some of the common uses along with the pluses and minuses associated.

Will they help me learn to torque roll?

The most common request is how to set up gyros for learning to torque roll. (Don't know what a torque roll is? Please consider purchasing GPMZ0220, A Look at Aerobatics.)

One modeler describes torque rolling as the equivalent of balancing two plates on top of broom sticks, with your eyes closed, while bouncing a top a large rubber ball. So, if it doesn't come quickly and easily, don't fret! It takes a lot of time and practice. And don't be upset if a gyro doesn't suddenly make your model torque roll alone—it won't. But it will help a little to a lot, if everything is set up properly.

Using gyros in an aircraft to aid in torque rolling has its advantages and its drawbacks. Gyros can assist a modeler in learning to torque roll because it will correct SOME to ALL (depending on the type, quality and settings of the gyro) of the yaw and pitch movements caused by the torque and instability of the aircraft in this precarious position; however, it will also be countering corrections made by the modeler so the modeler has to think and move even faster and give even more input to make corrections against the gyro and the aircraft.

Basically, a torque roll is an extremely unnatural action for an aircraft which requires incredible pilot skill to maintain and complete. The model is being suspended solely by the power of the engine/thrust from the prop, with just the right amount of throttle being given to keep the model from climbing or tail sliding. The torque of the engine will pull the model around to the left, with no amount of aileron input in the world being able to stop the rotation UNLESS the model has ailerons extending all the way in against the fuselage or has ailevators functioning as ailerons. This torque, and gravity, are also twisting the model on both the yaw and pitch axes, which requires extreme skill by the modeler to correct.

If you wish to use gyros to help ease the difficulty of this complex maneuver, you will want to install one gyro each for the elevator and rudder surfaces. Note that if your model uses twin elevator servos which are plugged into separate ports you will need a product like the Hobbico Aircraft Gyro (HCAM4010) or the Futaba GYA351 (FUTM0817) which supports 2-channel input and output for a single axis.

We used to recommend AGAINST heading hold gyro settings for torque rolling, as the gyros sometimes seemed to lag behind, and improperly correct as the model got farther and farther into the torque roll. However, the new Futaba GYA350 and 351 gyros have changed our minds! These specialty gyros specifically for aircraft use perform superbly in AVCS (heading hold) mode in torque rolls and similar circumstances. (Always remember to switch out of AVCS mode for 'normal' flying.)

It is important to remember that, while heading holds are the only gyros which will truly return the model to its initial orientation (other gyros just correct for movement, but not necessarily back to the starting point), there are MANY situations in which you and your model can be unintentionally in danger when the heading hold returns the model to a position you did not intend.

Please remember that normal gyros will not 'do it for you'. They are not a 'missile lock' or 'heading lock' and do not fixate on a position in the sky and maintain it. They simply dampen unwanted (and wanted!) motion, so they will not make torque rolling suddenly easy. But depending on your skill, your model, and your understanding of the dynamics, they can be a good training aid for torque rolling.

How about other maneuvers?

Gyros ARE a great aid in many other aerobatic maneuvers. They are amazingly beneficial, for example, when used during maneuvers such as snaps, tumbles, and stall turns. In some cases the heading hold or AVCS option will be beneficial, and in others not. Always remember....if you try to change your yaw line without moving the rudder servo and have a heading hold gyro on the rudder (for example, doing a banked turn with just aileron and elevator), the heading lock gyro will immediately return the model to the initial direction of travel! Therefore, it is best to leave the gyro in standard mode, not heading lock mode, except in specific circumstances where you want the 'dead on tracking' of heading lock mode.

  • A gyro on the rudder will minimize the yawing caused by torque on a slow up line such as entry to a stall turn, and minimize the tail wag on the exit.
  • A gyro on elevator and rudder will cause snaps, spins, rolls and tumbles to stop essentially instantaneously when a modeler releases the inputs with no over rotation.
  • A gyro on elevator and rudder can dramatically decrease the pilot inputs required to slow roll, and other precision rolling maneuvers such as ratchet rolls, rolling circles, 4-point rolls, etc.
  • Straight lines of all types—whether horizontal, vertical, or anything in between, can benefit from the aid of a gyro.

Lastly, gyros are extremely popular on the rudder of scale aircraft, especially complex nostalgic aircraft which are notorious for difficult ground handling. In this case many modelers DO use a heading lock gyro or AVCS (heading hold) mode in a switchable gyro, but then turn off the heading lock feature the moment the model breaks ground. This way the model will literally track perfectly straight with no rudder input from the pilot whatsoever.

On the 351 gyro, can I use flaperons while in heading hold mode?

No. Flaperons may be activated and will operate normally in normal mode. This is the reason for the twin servo output capability. However, in heading hold mode the gyro will attempt to obey the input to the aileron channel and will go hard roll to the aileron channel on flaperon input. Please be aware though that you CAN use flaperons in "Normal" mode with no problems.

My model shows no wag in a hover, but after a pirouhette the tail wags briefly.

Turn the delay up gradually until this wag just terminates. Then you may be able to readjust your gain setting as well.

What is the proper way to turn on my heli/aircraft, and then carry it out to the flight line?

ALWAYS turn on your receiver AFTER your transmitter is on and in AVCS (heading hold) mode.

Then, either:

a) set gyro to normal mode, carry to take off point, return to HH mode; or
b) leave in HH mode, carry to take off point, wagging rudder stick left then right occasionally and last immediately before setting down the chopper.

If you do not do A or B and you change the direction the model is facing while carrying it, when you go to lift off the AVCS gyro will return the model to the orientation when it was turned on. It has no idea that your hands rotated the heli and not the wind!

What is proper setup for my non-heading hold gyro? What should I expect from my new non-heading hold gyro or heading hold gyro in NORM mode?
  1. First, we need to be sure your gain is set going the proper direction.
    If it is set up correctly, the gyro will dampen any input, whether the wind, rudder stick, or you moving the plane by hand. So left rudder stick will move the rudder left but as the aircraft rotates left the gyro will dampen this movement by lessening the left rudder given.

    With the plane sitting still the rudder works normal. When the plane moves the gyro moves the rudder to counteract the movement. Does not matter what made the plane yaw wind or rudder input the gyro will dampen the movement.

    If the gyro is backwards the yaw created by the rudder input will increase as the plane rotates; so, if the gain is reversed, when you pick up and move the tail to the right, the gyro moves rudder further right. Use rudder stick to move rudder right, gyro pushes further right.

  2. Next, we need to set the maximum gain. To do so, take off with the gain turned off, and the gain setup to be adjustable in flight. Fly the model wide open at your absolute maximum intended airspeed (IE full throttle partial dive, or whatever is your max flying speed). Gradually turn the gain up until the tail starts to "wag" uncontrollably. Turn the gain down until the wag is completely gone. This is your maximum operational gain.

  3. What exactly will the gyro do? Normal gyros simply dampen movement. If something pushes the model off track for .1 seconds, the gyro corrects for .1 seconds. These are NOT heading lock gyros, and they do not continue to "push" until the model is back on course. They simply correct for seen movement with a reasonable counter movement. As such, the counter movement may be insufficient to completely correct for the issue.

For these reasons, non-heading hold gyros are NOT good choices if your desired end result is keeping a model straight during the torque of take off, holding a model's orientation in complex maneuvers such as harriers and hangars, etc. They ARE good choices for fixed wing airplanes for keeping reasonably straight lines, being able to do no-rudder reverses of direction and not fighting a gyro, etc.
How can I adjust the pirouette rate?

Adjustments to the rudder servo's ATV will result in changes to the pirouette rate, without having any effect on the actual total travel commanded/allowed by the gyro.

The reason this works in this manner is that the gyro will accelerate the servo to its maximum speed if you are trying to make what it perceives as a large change in position, vs making a small change. When making small changes, it does so more slowly to avoid overshooting. Therefore, the larger the ATV to get to maximum travel, the more travel the gyro will command to the servo to try to get close to your desired stopping point as quickly as possible.

Back to main FAQ/Contact Info page

Basics of AVCS/heading hold gyros

AVCS is an advanced version of heading hold which doesn't have the temp related drift problems of most of the older HH gyros.

Heading hold and AVCS mean that the gyro is acting almost like it has GPS to hold it onto its direction. If something other than a rudder input moves the heli off hte desired positioning, the gyro reads how many degrees it has been moved and will continue to give input until it gets back to that heading or until you move the rudder stick to tell it to do something else.

Compare that to normal mode, or a non-HH gyro....in those cases, if something moves the heli, lets say 2 seconds to the left, then the gyro will give input for 2 seconds back to the right. It has no idea if the heli actually mvoed back in place or not, it just tries to soften the undesired movement and goes on with its day.

Now, to give you real world examples...

Your heli is sitting on the ground. You pick up the tail and rotate it 180 degrees. In normal mode, the gyro would give some rudder briefly, figure it did enough, and stops giving input, probably long before you go to take off. In heading hold mode, the gyro says "I am off course by 180 degrees!" and it will give full rudder input until that heli comes around those 180 degrees—thus doing half a pirouette the minute you break ground. This is why you need to be careful with a heading hold gyro on the ground.

PIRO RATE: the rate at which the heli pirouettes when using a gyro depends upon your ATV settings for your rudder servo. The higher the ATV the faster the heli will pirouette as the gyro is giving maximum command to try to get to that commanded position.

GYRO REVERSE: If the gyro is commanding the model in the wrong direction—ie you move tail right and it gives even more right—simply reverse the gyro direction on the unit in this screen.

GAIN at the GYRO? GAIN at the radio? If you leave the gain at the gyro set to 100%, then you can adjust the end points of the gyro sensitivity channel at the radio and they will be linear. That is to say, they will be the same size steps as if you changed the gain at the gyro itself. If yuou set the gyro gain on the gyro to 50%, then each 1% change at the radio would have twice the effect (since there is half as much room to adjust) as if 1% change was made at the gyro.

DELAY: affects how rapidly the gyro responds when input is given, and when the stick is returned to neutral. If hte delay is too low on return and you have a slow servo, it will think the servo should have been there already and give more input, then overshoot, then give more input to corret, and so on, causing a wag. Faster servos can handle smaller and smaller delays.

GAIN TRACKING: used when the gyro overshoots to one direction but not the other, creating a 'hunting' sensation only in one direction.

MODE - NOR, AVC, CMT. Decides if hte gyro can be switched in and out of normal and AVCS in flight or if it is set to only one or the other. CMT is combined and allows use of both.

FRAME RATE: HIGH or fast frame rate is in place just for digital servos and must not be used with standard servos as they can not handle the commands at that rate and it will burn out the servo.

LIMIT: This setting tells the gyro how far it can move the rudder servo. REMEMBER do NOT use rudder ATV to adjust the rudder servo total travel, use the LMT function on the gyro.

RUDDER CONTROL GAIN (NCGA): this adjustment affects how responsive the rudder feels in AVCS mode. Adjust this to match how your rudder feels in normal mode so you do not have an unexpected 'expo' response at the rudder from the AVCS mode.

Compare the 401 to the 502.

The 502 provides far more flexibility than the 401, including:

  • Easy to program servo endpoints and center position.
  • Low battery alarm.
  • ATV limiting on rudder control.
  • Gain tracking (adjustable).
  • Rudder gain control.
  • Servo frame rate.
  • Adjustable gain from your transmitter (two position gain).
  • (0-100% remote gain adjustment)
  • Rudder stick delay.
  • Gyro reverse.
  • Easy to read LCD aids in easy set-ups.
  • Support for transmitters without in-flight gain adjustment.
  • Patented, 100% solid state anti-vibration design, with built-in temperature and drift compensation.

Why does my rudder servo bind in AVCS (heading hold) mode?

The GY240 does not offer LIMIT adjustment capability, which is available on the higher end gyros. Therefore, you must mechanically setup your rudder travel so that the servo does not bind, you cannot use end point adjustment (EPA/ATV) to adjust the travel. End Point adjusts the pirouette rate.

I am setting up my GY401, and I am having problems getting symmetrical stick movement on my rudder stick, I cannot figure out how to get the same amount of rudder travel. Can you help me?

Unfortunately, you cannot get mechanically equal travel left and right of your hovering tail rotor pitch, as more than 95% of models do not have a mechanically equal tail rotor pitch change mechanism that has a center point based on hovering pitch.

Can I use a Heading Hold/AVCS for takeoff's on my airplane, but then turn it off in flight?

Yes, you will plug the gyro into the desired channel (6, 7, or 8), with your ATV set at around 50% on both the low and high sides. This will make the gyro setting as "Off" at center, all the way left will be 50% in the Heading Hold mode, and all the way right will be 50% in the Normal mode.

Over time I notice some slight drift in my gyro, its not a programming issue as everything is set up correctly. It's just that after quite a few flights, the tail drifts slightly to one side. Is this a defect in my Gyro? Should I send this in to be repaired?

Before sending this in to the service center, you may want to try one quick fix. Remount your sensor on a new piece of foam tape. Whether you remount it in the same place or not, just make sure that you use new foam tape. The sensor is so delicate that it can detect even the slight amount of wear in the foam tape itself. If you are using the GY401, and you have it mounted on just one piece of foam tape, try using a second piece of foam tape when you remount it, this should eliminate the drift that may occur. Just remember that you will not need to use as much gain if you use the second piece of tape.

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