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Heading Hold or not

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Old 03-24-2019, 09:54 AM
  #1  
Agrav8ed
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Default Heading Hold/ Attitude assist or not

I heard once at a local field that heading hold/ attitude assist was bad for use in RC jets. However no one there could tell me why. Can anyone here educate me on this subject please. I have an Igyro3 with this feature and I would like to learn more about it before use.
Thanks,
Tone
P.S. I clarified the title as heading hold in planes is not quite the same as in helicopters. My question concerns attitude assist in gyros like the Igyro3e

Last edited by Agrav8ed; 03-25-2019 at 07:06 AM. Reason: Title clarification
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Old 03-24-2019, 10:09 AM
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Len Todd
 
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I have the Igyro3 built in my Mercury powerbox. The powerbox info warns against using HH for planes cause you are fighting the gyro to make a turn. I suspect it depends on the gain setting. But, …

Generally, speaking, Heading Hold was initially just used for helicopters to keep the tail from rotating. That is where you normally saw it applied. Then some 3D folks started using HH to help stabilize during high alpha maneuvers, etc. . Also, some of the new Landing Gear Controllers use HH on the nose wheel. Additionally, some LGCs use HH to adjust electric brakes to keep the jet straight when on the runway when it starts moving off previously the set course, etc.

I do not use heading hold on my control surfaces. I do have it set in the LGCs on the nose wheel and E brakes. I also have it in all my helis.
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Old 03-24-2019, 11:07 AM
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Something needs to be clarified here.
1. IGyro is not true heading hold its a hybrid of rate mode and heading hold. When a stick is centered, lets use elevator for example, heading hold is engaged, but move the elevator off the center and heading hold is released and the gyro switches to rate mode until its centered.

That is NOT how most gyros implement heading hold, its either on or in rate mode and most commonly used to torque roll and then then turned off to fly. The feeling of flying in heading hold is very un-natural and you can get yourself in trouble. It's hard to put in to words the way it affects a plane in the air but think of taking off a prop plane, you're in the habit of holding some rudder, well do that with a heading hold gyro and it will keep turning harder and harder till you spin out and hit something.
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Old 03-24-2019, 11:40 AM
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Originally Posted by BarracudaHockey View Post
Something needs to be clarified here.
1. IGyro is not true heading hold its a hybrid of rate mode and heading hold. When a stick is centered, lets use elevator for example, heading hold is engaged, but move the elevator off the center and heading hold is released and the gyro switches to rate mode until its centered.

That is NOT how most gyros implement heading hold, its either on or in rate mode and most commonly used to torque roll and then then turned off to fly. The feeling of flying in heading hold is very un-natural and you can get yourself in trouble. It's hard to put in to words the way it affects a plane in the air but think of taking off a prop plane, you're in the habit of holding some rudder, well do that with a heading hold gyro and it will keep turning harder and harder till you spin out and hit something.
That seems to make a little more sense. I was more curious about using the heading hold feature to hold a knife edge without the coupling that sometimes occurs. Thank you guys for the input
Tone
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Old 03-24-2019, 12:08 PM
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Len Todd
 
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Not sure if the independent IGyro works the same as the PBox Mercury SRS but here is what the PBox Gyro Instructions define the IGyro modes as:

- OFF: The iGyro is disabled.

- RATE MODE: The iGyro operates in Normal mode on all control surfaces. The gyro simply compensates for gusts of wind.

- ATT ASSIST STD: Since the English terms “Heading mode” and “Hold mode” are not quite applicable to the way the iGyro works, we have decided to adopt the name “Attitude Assist Mode” for its unique control characteristics. If the Attitude Assist Standard option is selected, the iGyro maintains the model’s attitude, as last commanded by the pilot, around the roll and pitch axes (aileron and elevator). At the same time the rudder operates in Normal mode, so that turns can be flown in the usual manner. The Attitude Assist Mode only operates at the neutral position of the sticks. As soon as the pilot gives a command, the iGyro switches to Normal mode. The result is 100% natural handling in the air. This function is recommended for all models, and can be left active for take-off, flying and landing. The control characteristics of the iGyro eliminate the need to worry about stalling, which can occur with conventional gyro systems.

- ATT ASSIST ALL: This setting is identical to the above option, except that attitude maintenance is also active on rudder. This makes it easy to fly slow rolls, as the rudder automatically maintains the correct attitude. However, this flight mode option must not be used for normal flying, as the rudder would then try to maintain heading through aileron turns, making the model reluctant to turn.

- TORQUE ROLL: In this mode the iGyro is capable of maintaining a model’s attitude once it is brought into the vertical position. When this option is selected, all three gyro axes are turned up to 100%, and Heading mode is active. This flight mode must not be selected unless the model’s forward speed is already close to zero. The torque roll is initiated as follows: you approach the maneuver by slowing the model down. The model is then rotated to the vertical position, and you activate the TORQUE ROLL option using the flight mode switch (usually FM3); you then adjust the throttle to maintain the model’s height. The other control functions should be left untouched. If you now wish to rotate the model around the roll axis, you can do that by giving an aileron command, taking care not to touch rudder and elevator at the same time. When you wish to terminate the maneuver, remember to disable the TORQUE ROLL option using the flight mode switch before opening the throttle.

- VECTOR THRUST: This option is specially tailored to suit model jets with thrust vector control. This flight mode option has several aspects: • All gyro outputs including vector control are set to 100% gain. • Attitude Assist is disabled. This is important with a jet, because there is no propwash over the control surfaces. • The control functions for the assigned vector outputs (these are established later as part of the Assistant procedure) are activated. This means that rudder and elevator mixers must not be set up at the transmitter, as the Mercury SRS carries out these functions. When the flight mode option is disabled again, thrust vector control is restored to the neutral position which was detected when the PowerBox was first switched on. • The Airspeed factor is set to a value of 5; this provides more time to switch flight modes as the model approaches and leaves the hover, without a tendency for the model to oscillate due to the high gain setting.
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Old 03-24-2019, 12:22 PM
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That's exactly what I said Len
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Old 03-24-2019, 01:20 PM
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Originally Posted by BarracudaHockey View Post
That's exactly what I said Len
I understand that. Initially, I was not sure just how to approach the topic as the term "Heading Hold" was used. So, I added "Generally, speaking" to the first time I addressed the topic. I was thinkin' the OP was shopping around to make comparisons and just not sure of the terms, etc..

This darned Gyro subject gets complicated when the manufacturers start swapping around terms and doing things a bit differently, etc.. Especially the first time you program one. I am still not sure I got my Mercury set right. But I know it works the way I want to. I suspect that I just need to do a bit more fine tuning this year. The plane flies great even w/o it.
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Old 03-25-2019, 02:58 AM
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The warning is about rudder, where it should never be used. Some airframes benefit from attitude assit (HH), if there is a big balance shift with fuel, or a flying fuselage like the F-35.
I have a small amount set on the ailerons of my Mephisto too.

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Old 03-25-2019, 04:23 AM
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Originally Posted by Dave Wilshere View Post
The warning is about rudder, where it should never be used.


I almost lost a model to this overlook on it's maiden flight. Took off and try to fly the circuit. The model went invert because of HH on the rudder. Quickly switch off the igyro and land safely.
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Old 03-25-2019, 04:38 AM
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I cant stand heading hold. In my cortex gyros I hook it up to the software and disable it before I even attempt to install it in the plane. I have had 2 maidens on customers planes that where in heading hold and while I was able to fly them it was not a good time. I have also had the powerbox guys doing the setup on a power box system in a friends plane while I was flying. They switched it to heading hold without telling me it was heading hold in a turn and the plane started to fly away and scared the **** out of me. I had to yell turn it off turn it off.

It would be a better option to learn how to do the knife edges and get the coupling dialed out in your transmitter so you always have a good flying aircraft whether the gyro is on or off. Most planes don't need a lot anyway but some need quite a bit and it can take around 10 to 20 flights to get it just right. I would never use heading hold on a fixed wing aircraft even if its the PB heading hold.
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Old 03-25-2019, 04:59 AM
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I started flying jets last year after flying Scale Aerobatics for a couple of decades. It was a truly eye opening experience in learning all the "ins & outs" of all the available technology. I do have a Powerbox Mercury installed and learning exactly what the gyro does and how it affects the flight of the aircraft was very apparent even with the first flight (second flight of the aircraft) with the technology.

After getting comfortable with the "Rate Mode," I decided to experiment with the "Attitude Assist Mode" so that I could verify the difference and whether or not to use it for aerobatic practice with the Leonardo. I did find in only ONE maneuver that the "Attitude Assist" made the Leo easier to fly. This was a Knife Edge pass. And since there is no sustained horizon to horizon Knife Edge pass in any of the F3S maneuvers, I realized that it (Attitude Assist) would be of no help to me whatsoever. There were instances during testing that the aircraft had unnatural tendencies, hence my reluctance to use the "AA" any further in practice. The "Rate Mode" has been working effectively during all of my practice until the demise of the Leo, which is being replaced with another one.

I also tried it on the front steering channel for take-off & landing and did not feel much of a difference between both modes....so I decided to stick with "Rate Mode" on steering also.
Wayne
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Old 03-25-2019, 05:21 AM
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Good dialogue here. I have been using iGyro in "HH" in jets for a few years. I'm not a great acrobatic pilot, so maybe I don't realize that the gyro may be "fighting" me, but I can tell you that my experience with it has been excellent. Note that you can't get the rudder into "HH" mode by accident. It needs to be setup using a computer. i think those of us who are not excellent acrobatics pilots will enjoy it.
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Old 03-25-2019, 05:39 AM
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The T-One with the PBox Mercury flies just fine with attitude assist on all surfaces, including the rudder. The only peculiarity I noticed during set up was one time I got a little oscillation on the rudder. I set the gain back a couple % and the oscillations are gone. The T-One flies like a dream with or with out the gyro anyway. Point being I do have some hold on the rudder, with Att.Assist and it works just fine for me.

As far as HH on the nose gear, I am trying the LGC 15 in HH mode. Still have to get the plane out on the runway to set the gains and see if it all works. But on the bench, you move the nose of the fuse over to a side and the nose wheel compensates. Also, the brakes, when on, are compensated too. In theory it should work to keep the plane on track when on the ground. Time will tell. I am sure there will be a lot of testing to get the LGC adjusted correctly. Can't just switch that one off either. But at the very least, I finally got the brakes to drag evenly, have great resolution and work proportionally.
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Old 03-25-2019, 06:40 PM
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Great discussion.... on the Mercury's are you guys using the GPS units to adjust gain or the regular non-GPS units??
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Old 03-25-2019, 07:32 PM
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non-GPS for me.
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