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.

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.

RE: elevator gyro question
 

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

RE: elevator gyro question
 

Look at the gizmo Duke (aero65) has been using in Hawaii...seems to work well.

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.<br type="_moz" />

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

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.

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.

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.

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.

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.

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.

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

RE: elevator gyro question
 

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.

RE: elevator gyro question
 

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

RE: elevator gyro question
 

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

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
<br type="_moz" />

RE: elevator gyro question
 

Jack,

That is my understanding as well.

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

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

RE: elevator gyro question
 

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.

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

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.

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!

RE: elevator gyro question
 

I'll have a look...anyway, I've just started using a DX18 as I needed the extra channels for all the functions on the A4 so its going to be set up from scratch so I'll know there are no unknown transmitter mixes/rates present. In your experience using the i-gyro with these jets do you find HH worked when adding flap/slat? Al's large T33 was the same when we set the i-gyro up but he hated HH anyway so it all got turned off rather quickly.

RE: elevator gyro question
 

When using Heading Hold for elevator, what is the gyro trying to 'hold'? Does it hold flight path or pitch angle? If the former then I'd be very interested to know how it does it.

If it holds pitch angle then I'm not sure how good it would be during flap deployment? Dropping flap changes the camber of the wing and increases lift and if the gyro holds pitch angle constant then the model will balloon. Conversely, if pitch angle is held constant when the flaps are retracted, then the model will descend. The pitch attitude needs to be adjusted when flaps are moved for the aircraft to stay level and I'm wondering if the gyro would have all the information to be able to put in the required correction.

RE: elevator gyro question
 

It will keep the pitch angle (or heading) constant until it runs out of throw or airspeed.

RE: elevator gyro question
 

IGyro maintained Heading mode for me when I had it in my Classic Flash. I did not like the Heading hold thing either and ended up taking the iGyro out as I realised that I was not enjoying flying Flash as much as I did without it. No question, in a gusty wind you would notice the extra stability, but I did not like the rather artificial feel that it gave to the handling. Something like the Flash just does not need it. I do think that anything large and/or scale would benefit greatly from the iGyro. It's a seriously well thought out system.

Harry, I would certainly consider this as an excellent option for your Lightning.<br type="_moz" />

RE: elevator gyro question
 

You and some others are not saying why though. You need to explain why, and in the light of products like the i-Gyro and Eagle tree Guardian using heading hold you need to explain why you are still fundamentally against it.

Alex, would be very interested to hear from you or Ali about why HH was not liked.

Andrew B, would also like to hear what it was that you didn't like about the feel of HH on elevator.

I have been using the Eagle Tree Guardian in prop models, in HH and rate modes. HH mode works well except that whatever you apply on the Guardian works to all 3 axes, and HH on rudder is bad as it makes the model sideslip in every turn. It isn't a fault, it's just that the control logic is optimised for 3D aeros rather than normal flight and HH on rudder would be good for things like Harrier rolls. However HH on the aileron and elevator works very well. Initially I feared that HH on the elevator would lead to unexpected stalls but it doesn’t. The thing is that you need a certain amount of back stick, usually a lot, to provoke a stall. The gain you set is in effect a max travel that the gyro can cause and if that is less than the elevator required to stall, the gyro in HH can’t stall the model because it simply can’t pull the stick back far enough. You only need a little gain to maintain attitude in normal flight speeds, any more and it starts hunting, and that low level of gain just won’t cause a stall.

I tried flight testing a trainer model in HH with a good amount of gain. What happens when you slow down? I put the model into a climb about 30 degrees and throttled to idle. Instead of immediately lowering the nose and maintaining speed, it stayed in that attitude as the gyro applied more and more elevator. Then still with some speed left the gyro reached its max gain/travel and the nose started to come down, until the model was descending still with the up elevator applied by the gyro. So the nose drops before the stall is reached as long as the gyro gain is less than required for the stall. I added power gently and the model just lifted its nose a bit, I added more power and so on and it just kept lifting the nose until it got back to the 30 degree nose up where it started.

I tried the same thing in level flight, throttle to idle, the gyro kept the fuselage level as the model slowed and started losing height, it ended in a level attitude descent at low speed but safely above the stall.

I then flew the model in level flight right to the point of the stall and released the stick. Since the gyro gain could not pull the elevator as much as I could, it promptly reduced elevator! The model nosed down a bit and descended but now well clear of the stall. I slowly applied power and it lifted the nose as I kept slowly applying more power, until it got the model into the same nose high attitude where I had let go of the stick but of course it now had more power and speed and was climbing. As I applied more power it just kept that same nose up attitude but accelerated up the climb.

You can get some unexpected effects when pulling higher angles of attack. For example if the gain means the gyro can pull about ¼ up elevator and you have it in slowish flight where the gyro is applying all of that, you start to pull back on the stick yourself which immediately cancels HH mode but you may have pulled back 1/8 stick, the gyro was applying ¼ stick so though you have pulled back the elevator has reduced not increased and the nose goes down in response to you pulling back a little. I also found that I lost some of the feedback about angles and speeds that pulling back on the stick gives me in slow flight.

For normal flying around I found that HH on elevator worked very well, but that at higher angles of attack/slower speeds it can give some odd effects and remove some of the information the pilot gets from the stick position about how the model is performing.

RE: elevator gyro question
 

What I think might get you in trouble is in those critical flight phases where the gyro may be holding the nose up. Normally we set the CG of our planes slightly nose heavy so in situations where there is less airspeed (approaching stall) the nose wil drop increasing airspeed. If the CG is too far aft the tail will drop instead of the nose increasing the likelihood of a stall.

The gyro can't sense airspeed, just attitude. So if the airspeed gets low there will be no tendency for the nose to drop so you will need to be much more keen to it. That's one place I've seen guys pancake it in with a gyro.

I put an FY-30 stabilization system on my Skymaster F-18. It showed some promise but occasionally it hit some random vibration (it was very welll insulated) and made the jet react violently. I took it out. I still use a simple rate gyro on the nose-wheel. The thing with jets is everything happens so fast.

It's always fun to play with new stuff just make sure you have a good "OFF SWITCH" option and you know exactly how to hit in a split second.


<br type="_moz" />

RE: elevator gyro question
 

Questions for Jack D. and others on this thread. At the recent Toledo R/C Expo, I purchased an Eagletree Guardian for application in my SMGripen jet. As you may know this jet is a high workload on landings with PIO from the canard. I have tamed this somewhat by reduced throws and CG adjustments but would like to try the Guardian stabilizer also. To Jack with the Rafale; I presume you used the "2nd Elevon Reversed" function to control the canard, true? Also, have you tried the "Derivative Gain" option on the unit for your Rafale? I feel that it would work well especially on the wing elevons for roll stability. Any other recommendations would be most appreciated. Note that I plan to install the Guardian in several sport models before the Gripn to gain familiarity with the unit. Thanks in advance.

Art ARRO

RE: elevator gyro question
 

I had my first experience with the IGyro this month helping Joe Castelao setup his Cougar. It worked pretty much as advertised, but HH on the elevator did not work to keep the aircraft level with flaps deployed. We originally had arrived at 15% up elevator mixed in with flaps to keep the airplane level. Before setting the HH gain, we disabled this additional trim and when flaps were deployed the nose did not hold attitude and dropped. We ended up disabling the HH on elevator and restoring the elevator up trim in the flap system. That was my experience with it.

Now my opinion... I agree that different airplanes are going to need different angles of attack to maintain altitude in different configurations of flap, gear, and airbrake deployment. The HH on elevator can't compensate for all of this unless it also factors in rate of climb/descent as well as airspeed. I don't believe the Igyro does this. On top of that, as soon as you move the stick anywhere off of center, the HH disables and now you are on your own to keep the AoA correct.... well who is disciplined enough to not even breathe on the elevator in order to keep HH active? How do you turn the airplane without adding additional elevator and deactivating HH? Theoretically, the HH would hold the nose up in a turn for you, but in practice it does not. It's possible for certain aircraft types that don't require large trim adjustments with flap deployment to probably get away with using the HH to maintain a rough trim, but it seems to me that it won't be able to compensate for large trim changes that some models require, especially at slow speeds when elevator effectiveness begins to diminish.

Nice piece of gear, but I would stick to using it in rate mode for elevator.

KennyMac

RE: elevator gyro question
 

Hi Harry

I have flown the Guardian in HH on my MB339 for testing. I had it in low rate mostly a non event, at high speed it just kind went where you pointed it if the plane could hold it aerodynamically.
I have a Gen 1 Skymaster MB339 that is pretty heavy 43 lbs Dry approximately so with the PST 1300R it doesn't hold much for long lol.
Our field also has a very tight pattern so its hard to do long legs to see how some of the HH worked.

It made 4 points easy, I was also able to land it in HH mode without issue, as you have seen as long as the gain Is low enough it won't drive the plane to stall.

I don't think that It will be super successful in killing small trim changes, I believe that over time the plane will still drift a bit especially as you may not be generating much acceleration, or angular acceleration in that situation.
it should dampen big changes like putting flaps down at high speed ok, but after things settle down I still think and out of trim bird will feel that way.
(HH really reduced the amount of elevator I had to hold during the 4 point so for that trim change it did work well)

During normal high-speed flight I felt the plane felt notchy in pitch, It was hard to put the plane in a level flight attitude that I was satisfied with. It was always climbing or diving slightly

Here is my Mig-21 from global 6 oz tail heavy during its maiden Guaridan in normal mode. https://www.youtube.com/watch?v=6FLoY3bz5i8
Would have been real fun without the Gyro lol.

I liked HH in some situations it would be nice if we could turn it on and off like the IGyro.

With the same plane I also tried HH with a Futaba Gyro on pitch only to try and get the MB339 to hold a commanded Angle of Atttack, didn't work too well the plane kept wanting to pitch more and more up it did not hold an attitude as I had hoped. It was to
scary to continue with that line of testing so I stopped that experiment.

Been playing with this unit pretty neat so far, have not put it a jet yet.
http://www.bluelight-tech.com/

RE: elevator gyro question
 

Art, I don't have elevons on my Rafale.
I have separate elevators and ailerons.
Canards is an aux channel mixed to elevator. Both canards are connected to a Matchbox for reversing and travel.
Guardian is connected to the canards matchbox.
I have a regular gyro on the Rudder only. For some reason, Rudder gyro corrects any aileron wing rocking on the Rafale. I don't feel any need for an aileron gyro.

Unfortunately, I have not been able to test anything, since we are going thru a very tense and dangerous political situation after the recent elections.
When safe to get to the field I will test and post.

If you plan to use the Guardian, I recommend to program it with your PC.

Jack

RE: elevator gyro question
 

Harry, it is quite hard to explain "feeling" with words (at least for me).

You have to try it and see if you like and if it really helps. Start with low gain.

Jack

RE: elevator gyro question
 

Jack D., thanks for your timely response to my earlier questions regarding the use of the Guardian for my SMGripen. Currently the canards are mixed in the transmitter to the elevator function and I have a JR rate gyro for nose gear steering. Will try to adapt the Guardian on rudder, and elevons initially, and then try to mix in the canards. I'll use a PC for programming the unit.
Keep your head down and stay safe. I've had my years of living dangerouslyduring similar "disturbances" in Argentina, India, Thailand and Viet Nam. Take care andI appreciate your response in these tense times.

Art ARRO</p>