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elevator gyro question

Old 04-11-2013, 05:59 AM
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HarryC
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Default elevator gyro question

I have a couple of questions for those who have flown with a gyro or perhaps iGyro, on the elevator of their jet. I am considering elevator gyro for a jet that has pronounced pitch trim changes caused by three different controls - retracts, flaps and throttle. I could mix them out but an active device such as a gyro that does it precisely would be nicer.

Q1 – I presume that you are using the gyro in heading hold rather than rate mode? The reason I think this is because the iGyro advertising says it gets rid of any pitch change when changing the flaps etc. A rate gyro requires some rotation to be happening in order to work so it can’t stop a long term change in trim because if it stopped the trim change then there is no rotation and it will remove the trim. So it seems that the only way for the gyro to alter the elevator trim is to be in heading hold mode.

Q2 - Heading hold mode can have some unexpected effects. Is it safe to use on elevator for all stages of normal flight? For example it would try to stop the nose going down as airspeed reduces or the stall approaches.

Thanks for any advice or hints.

H.
Old 04-11-2013, 06:31 AM
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BarracudaHockey
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Default RE: elevator gyro question

I don't fly jets but I fly a lot of fixed wing, and helicopters and I'm pretty familiar with gyros.

That said, i would never fly headling hold in fixed wing unless I was trying to do something specific like hover (I played with this while reviewing the Eagle Tree).

You want pitch dampening, which rate mode will provide. I can see your thinking with heading hold but I think the results in flight aren't going to be what you want.

What you're trying to accomplish should ideally be done with flight modes and mixing.
Old 04-11-2013, 06:49 AM
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HarryC
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Default RE: elevator gyro question


ORIGINAL: BarracudaHockey

I don't fly jets but I fly a lot of fixed wing, and helicopters and I'm pretty familiar with gyros.

That said, i would never fly headling hold in fixed wing unless I was trying to do something specific like hover (I played with this while reviewing the Eagle Tree).
That's why I am asking for people who have flown it in their jets, for example the iGyro does use heading lock on elevator and aileron
Old 04-11-2013, 07:40 AM
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tp777fo
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Default RE: elevator gyro question

Look at the gizmo Duke (aero65) has been using in Hawaii...seems to work well.
Old 04-11-2013, 11:41 AM
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stevekott
 
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Default RE: elevator gyro question

Never use heading hold mode on a jet. It will crash you.

The gyro will do more to stabilize you, fight gusts of wind. But it is not good at correcting trim. You are best off using flight conditions with seperate trim or mix it in. I have seen guys crash due to improper gyro set-up.
Old 04-11-2013, 12:38 PM
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Default RE: elevator gyro question

FWIW, whats the difference between flying fixed wing and a fixed wing that happens to be powerd by a turbine?

To qualify, I do fly EDF
Old 04-11-2013, 05:26 PM
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Terry Holston
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Default RE: elevator gyro question

For what it is worth, The I-Gyro would do what you want. The instructions for it say to NOT use any mixes OR Trim changes for flap deployment as the I Gyro will compensate for you. Works like a charm.
Old 04-11-2013, 06:02 PM
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felker14
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Default RE: elevator gyro question

See page 3 of instructions ( http://www.powerbox-systems.com/shar...yro_en_v02.pdf ). It explains use of heading mode with iGyro being used. I do think it (heading mode) is used for certain maneuvers then switched off.
Old 04-12-2013, 12:17 AM
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HarryC
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Default RE: elevator gyro question

Some of the replies above such as stevekott and barracudahockey demonstrate why I asked for people who had done it, not speculators or people whose knowledge is behind the times. Plenty of models now use heading hold on elevator. I have been using the Eagle Tree Guardian on fixed wing prop models in heading hold mode for entire flights and it works very well, and the Powerbox iGyro uses heading hold mode on elevator and the instructions say not to use mixes or trim modes/conditions to adjust for things like flap because the iGyro will re-trim the model.

Can I ask again for people who do have up to date experience to give their thoughts or experiences on using a heading hold gyro on elevator. I can’t use an iGyro on this particular model as it is not compatible with the radio.
Old 04-12-2013, 01:09 AM
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Alex48
 
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Default RE: elevator gyro question

Hi Harry

Ive flown my A4 with the i-gyro and helped set up a few other models with them.

The i-gyro will give you HH in all three axis, personally I don't like the feel of the model with HH on so I've switched the HH function off on my A4. FM1 is off FM2 can be normal gyro on all three axis + HH on elevator & aileron with FM3 HH rudder.

When the sticks are neutral HH is on as you move away from neutral the normal gain effectively reduces and HH turns off. I found even with HH on with my A4 the HH function would not work when deploying flaps, this is explained in the instructions.

So to clarify HH will only work when the sticks are around neutral as you move away from neutral HH will turn off and Normal rate will take effect, as you increase deflection this normal rate gyro will reduce gain automatically. So yes it is safe to have HH function on all the time (flying the aircraft sensibly within its normal envelop) with the igyro because the igyro turns it off automatically as soon as you move from neutral. The rudder HH facility clearly isn't safe to have on all the time but can be activated it with FM3. Having said that I haven't closed the throttle and left the sticks neutral but I should imagine it would end in tears. I wont even experiment with it as the risk is too great with a large highly loaded model like the A4. Perhaps put the igyro into a club model and see but I'm sure your hypothesis would be correct. As for the approach when I experimented with the A4 the HH function would not activate with flaps deployed so there was no risk when landing.

I just didn't like the way the model felt with HH but the elevator normal rate gyro did help control the balloon effect the A4 seems to do on landing. It certainly helps me consistently land the model nicely.

If you have any further questions your welcome to ring me.
Old 04-12-2013, 01:43 AM
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HarryC
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Default RE: elevator gyro question

Thanks Alex that's very helpful. Like you I really didn't like HH on rudder, that's one flaw with the Eagle Tree Guardian that if you want HH it is on all 3 axes, you can't separate the rudder to rate mode. HH on rudder makes the model drag the tail in turns.
Curious that you found HH elevator didn't work when deploying flaps.

I have experimented with prop models using HH on elevator, going into a gentle climb and closing the throttle. HH does try to keep the nose up as the speed bleeds off but the amount of elevator travel the gyro can use is limited by the gain. Low gains means the gyro can only use a small amount of up elevator, it is not able to apply full back stick. At modest gain the gyro can't apply enough up to stop the nose from dropping before the stall and the model ends up in a stable position slightly nose down.

However I don't want to do that sort of experimenting with a heavy, highly swept jet so I will take your experience and try it using rate mode plus some mixing.

H.
Old 04-12-2013, 01:49 AM
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Alex48
 
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Default RE: elevator gyro question

ahhh that makes sense re the elevator gain with HH.

Its worth noting if you want to only use rate gyro don't use the new 'fly in assistant' on the V16 i-gyro. This sets up both normal an HH at the same time. Go through the settings and assign a channel to one of the axis for normal rate gain only, if you have three spare channels you can put the gains on three separate levers/knobs and do it all at once or land between each axis set up.

edit.

If you have large flaps or large camber changing devices LE slats for example the HH function wont work presumably because the trim change is too great and there isn't enough gain to maintain level. Maybe with a small first stage of flap/slat it would still work.
Old 04-12-2013, 08:44 AM
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Jack Diaz
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Default RE: elevator gyro question

Hi Harry, another things to consider:
I am not familiar with the iGyro, but on the Eagle Tree the 3D mode has 3 sub modes:
-rate mode (regular gyro)
-direct rate (inputs are interpreted as desired angular rate of rotation; plus rate gyro is active)
-heading hold

If you trim each of your flight modes for level flight without using gyros, the "direct rate" will interpret the trim changes as commanded angular rotation when the gyro is active. This is not desirable.

We experimented with 3 axis heading hold on a large Hawk. It was not pleasant to fly at all.


My advise would be:
-Perfectly trim your airplane for the different flight configurations (modes) without a gyro.
-Set the gyro on rate mode. This is all the help you will need while maintaining the desired control.


Just for experimenting, I just installed a Guardian on my Rafale canards only. I will try the behaviour with the 3 sub modes. Being on the canards only, the results may be interesting. Will post the results.

Again, I am not familiar with the iGyro, but basic concepts should apply though.

Jack
Old 04-12-2013, 08:52 AM
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Henke Torphammar
 
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Default RE: elevator gyro question


ORIGINAL: HarryC

That's why I am asking for people who have flown it in their jets, for example the iGyro does use heading lock on elevator and aileron
I have tried it and it does work. It keeps the jet in the same state as you left it. ie rolling to knifedge and letting go it will stay, well almost any way.(depending on gain settings) However this is probably not what most want from the gyro. In non lock mode the gyro lets your plane fly like there was no gyro AND no wind. You don't notice the gyro and it eliminates the bumpiness from the wind, thats what I'm after. The heading lock makes it feel artificial like an old flight sim but do work.

Old 04-12-2013, 09:10 AM
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Jack Diaz
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Default RE: elevator gyro question


ORIGINAL: Henke Torphammar


ORIGINAL: HarryC

That's why I am asking for people who have flown it in their jets, for example the iGyro does use heading lock on elevator and aileron
I have tried it and it does work. It keeps the jet in the same state as you left it. ie rolling to knifedge and letting go it will stay, well almost any way.(depending on gain settings) However this is probably not what most want from the gyro. In non lock mode the gyro lets your plane fly like there was no gyro AND no wind. You don't notice the gyro and it eliminates the bumpiness from the wind, thats what I'm after. The heading lock makes it feel artificial like an old flight sim but do work.

Hi Henke, I agree with you.
The problem with the knife edge in HH mode is that the gyro will maintain the rudder (yaw) heading, that is true. But the gyro doesn't know that the airplane is loosing altitude (it doesn't have a radio altimeter LOL). So, you will always have to act the rudder to increase the fuselage angle of attack to allow it to hold altitude, regardless of the gain.

Interesting thread

Jack








Old 04-12-2013, 11:34 AM
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Terry Holston
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Default RE: elevator gyro question


ORIGINAL: Jack Diaz



Hi Henke, I agree with you.
The problem with the knife edge in HH mode is that the gyro will maintain the rudder (yaw) heading, that is true. But the gyro doesn't know that the airplane is loosing altitude (it doesn't have a radio altimeter LOL). So, you will always have to act the rudder to increase the fuselage angle of attack to allow it to hold altitude, regardless of the gain.

Interesting thread

Jack

Ah, But isn't that part of what the GPS sensor is for? Altitude and speed?






Old 04-12-2013, 02:02 PM
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Jack Diaz
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Default RE: elevator gyro question

Hi Terry, as far as I know, the GPS only senses speed to reduce the overall gain accordingly to avoid overcorrections.
Am I right?

Jack

Old 04-12-2013, 02:13 PM
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Default RE: elevator gyro question


ORIGINAL: Alex48
When the sticks are neutral HH is on as you move away from neutral the normal gain effectively reduces and HH turns off. I found even with HH on with my A4 the HH function would not work when deploying flaps, this is explained in the instructions.
The HH on your iGyro probably stopped working on flap deployment because you still had some sort of flap/elevator mix set up. As soon as the signal moves away from centre stick the HH is disengaged.
Andrew

Old 04-12-2013, 02:55 PM
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Default RE: elevator gyro question


ORIGINAL: Jack Diaz

Hi Terry, as far as I know, the GPS only senses speed to reduce the overall gain accordingly to avoid overcorrections.
Am I right?

Jack

Jack,

That is my understanding as well.
Old 04-12-2013, 03:04 PM
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Default RE: elevator gyro question

I've been flying a few of the UMX models.... I have the beast and have tried a friends Mig
This as3x system is just awesome in these small models and makes it possiable to fly in much higher wind with such a small light model.
Everytime I fly it I keep think I would love to try this system in one of my larger models (jet or warbird)
It seems like it would do a great job! but I'm not sure how well it will work in a large model

[youtube]http://www.youtube.com/watch?feature=player_embedded&v=I2XgFgo86xg#![/youtube]


I see spektrum has a large 6 channel recevier.... would be fun to mess with

http://www.spektrumrc.com/Technology/AS3X.aspx

Eagle tree has the guardian system....seem like it may be along the same line. This could be great on a warbird that is tough to handle or a jet with narrow gear like an F-18

http://eagletreesystems.com/guardian/

I say use all the moderen help we can use to make the flights that much better
Old 04-12-2013, 04:37 PM
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Default RE: elevator gyro question

I have been flying jets for about 15 years and using gyros for about 5or 6 and I would never use head lock or anything similar. I use rate
Old 04-13-2013, 12:24 AM
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Alex48
 
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Default RE: elevator gyro question

The HH on your iGyro probably stopped working on flap deployment because you still had some sort of flap/elevator mix set up. As soon as the signal moves away from centre stick the HH is disengaged.
Andrew
Hi Andrew, I have no mix set up. The instructions do state that HH on will not work with certain types of flaps on page 20. This has been my experience with the models Ive set up using an igyro.
Old 04-13-2013, 12:41 AM
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Default RE: elevator gyro question

Hi Alex, mmm... The manual on page 20 says:-

"Note: if your model features other superimposed functions, such as camber changing flaps and ailerons, please note that the iGyro does not work in Heading mode when the flaps are deployed; in this case the gyro system only works in Normal mode, since the transmitter control is no longer at the centre point to which the gyro is calibrated when the system is initially switched on."

So, if the iGyro switches from Heading mode to Normal mode on flap deployment it must be because you have something going on in your radio setup which changes the output on elevator stick centre. Anyway, actually I think that this is an advantage because I preferred to have normal mode on elevator in landing configuration.

Cheers

Andrew

ORIGINAL: Alex48

The HH on your iGyro probably stopped working on flap deployment because you still had some sort of flap/elevator mix set up. As soon as the signal moves away from centre stick the HH is disengaged.
Andrew
Hi Andrew, I have no mix set up. The instructions do state that HH on will not work with certain types of flaps on page 20. This has been my experience with the models Ive set up using an igyro.
Old 04-13-2013, 12:54 AM
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Alex48
 
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Default RE: elevator gyro question

Yeah your right but I cant find a reason in my transmitter... When I deploy my flaps with the A4 in rate mode there is a huge trim change! I always assumed when I initially tried it in HH that the gyros just couldn't cope with such a huge change in attitude.
Old 04-13-2013, 01:03 AM
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Default RE: elevator gyro question

I guess you could be using Conditions (when you deploy flap or change your rates) in your setup with different trim/subtrim setups. There has to be something going on in there!

ORIGINAL: Alex48

Yeah your right but I cant find a reason in my transmitter... When I deploy my flaps with the A4 in rate mode there is a huge trim change! I always assumed when I initially tried it in HH that the gyros just couldn't cope with such a huge change in attitude.

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