Cyclic - can't maintain attitude?

I've tried with and without the AP but it seems impossible to hold your attitude in the Gazelle.

For example, if you bank, even slightly, then it just keeps rolling until you recenter the cyclic. It feels like flying with an ancient digital joystick. Is this correct behaviour?

I've tried with and without the AP but it seems impossible to hold your attitude in the Gazelle.

 

For example, if you bank, even slightly, then it just keeps rolling until you recenter the cyclic. It feels like flying with an ancient digital joystick. Is this correct behaviour?

Yes, that normal, on all helos.

If you move the stick for example to the right it will continue to roll untill the stick is recentered.

Moving the stick right causes the blades angles to induce a rolling moment to the helicopter. This doesnt dissapear until the stick is centered.

Depending on the main rotor direction you will have the stick slightly to the left or right during level flight, and about the same position in a steady turn.

OK, thanks. It feels very different to the other helos so it's probably just lack of seat time on my part. I've just put very generous axis curves on the cyclic and rudder and it's much more manageable.

I've tried with and without the AP but it seems impossible to hold your attitude in the Gazelle.

 

For example, if you bank, even slightly, then it just keeps rolling until you recenter the cyclic. It feels like flying with an ancient digital joystick. Is this correct behaviour?

I would think it's not normal, and it's only the Gazelle that behaves like this in DCS. Also see the following comment by Damcopter, which has IRL experience of the Gazelle.

https://forums.eagle.ru/showthread.php?p=3773687#post3773687

Also setting the position of the cyclic with the trim vs positioning it using joystick deflection behaves totally different. If you trim the cyclic to a certain position and do not apply any joystick deflection you do not get the rolling behaviour.

I would think it's not normal, and it's only the Gazelle that behaves like this in DCS. Also see the following comment by Damcopter, which has IRL experience of the Gazelle.

https://forums.eagle.ru/showthread.php?p=3773687#post3773687

 

Also setting the position of the cyclic with the trim vs positioning it using joystick deflection behaves totally different. If you trim the cyclic to a certain position and do not apply any joystick deflection you do not get the rolling behaviour.

And once again, PolyChop is working in an update for this year.

I've applied some drastic curves (and reduced the saturation) which does help but the default sensitivity seems extreme. Presumably the ratio is correct, or more realistic, for a full-length cyclic controller.

But I still cannot maintain a steady turn. The only way is to give the Gazelle a constant feed of short cyclic 'pulses' in order to remain at your desired bank angle. Very strange.

no problem here with a hog setup, but I never use curves, personally I would say try and go back to default settings and see if it will help you, she is sensitive but I find her easy to fly, I think adding too many curves deadens the flight characteristics, you don't need rudder to turn her softly in the air

I would think it's not normal, and it's only the Gazelle that behaves like this in DCS. Also see the following comment by Damcopter, which has IRL experience of the Gazelle.

First problem: the DCS Gazelle is never stopping rolling when you move your cyclic and maintain a steady position, for example 3cm left from neutral position). In the real Gazelle (and in most part of French helicopters) a displacement of the cyclic of x cm is corresponding to a steady x degrees roll angle of the helicopter.

You mean this part of his post ?

A helicopter in forward flight is statically stable but dynamically unstable. This means it will not continue in the same attitude if controls are leaved hands of even if trimmed out. There will be a small deviation causing for example nose drop, as speed increases this will raise the nose making the helo climb again and overshoot the original altitude until speed drops and nose drops. This will keep happening with increased amplitude for each time.

For a cordinated constand bank turn the stick will be at around the same position as straight and level flight. The helicopter doesnt really ”know” it is banked in a turn. As soon as the stick is moved from centre position( trimmed out for constant attitude) the rotor disc produces a torque on the helicopter causing it to continously roll or pitch up/down untill the stick is recentered again.

The idea that a 3cm displacement causes some kind of steady state where the helo stops rolling and continue in a constant bank is wrong.

The poster refers to for example the UH-1 in the post. First, the main function is the same as I did described above. But, the rotor system is a teetering rotor system which gives very different caracteristics compared to a fully articulated rotor system like the Gazelle. Besides this the huey has a stabilizer bar ( Bell Hiller) that act as a mechanical gyro and helps stabilising the helo. These two facts makes the UH-1 handle way different than the Gazelle.

I havent flown the Gazelle, but I have enough experience of both teetering rotors, fully articulated and rigid rotors to be sure abut this.

I havent bought the DCS Gazelle(yet), but are looking into this meanwhile I wait for the Bo105 module, thats why Im following the threads.

[Edit]I googled to find info from R.Prouty(I got all his books, supplied by my work).

He is a very well seen expert in helicopter aerodynamics. Very few people, if any, question hes knowledge.

https://books.google.se/books?id=rxryAgAAQBAJ&pg=PA100&lpg=PA100&dq=uh-1+bell+hiller+stabilisation+bar&source=bl&ots=p-CenpwkZg&sig=ACfU3U22zSvuyjeTfjb6L_k44vXBU8gizw&hl=sv&sa=X&ved=2ahUKEwjs5-DGnqjgAhVFDiwKHReCAOgQ6AEwEnoECAQQAQ#v=onepage&q=uh-1%20bell%20hiller%20stabilisation%20bar&f=false

Ouch, long link. If interrested, read s.77.

The net result is that cyclic pitch is rate control. That is, a steady cyclic pitch change from trim produces a steady rate of pitch or roll

Just to add from my experience a joystick may not be the best for helicopter cyclic doubly so for the Gazelle.

I have made a cyclic using a gimbal from a 3D pro which has no springs and no centering but has dampers to provide some resistance to movement with effectively a 25cm extension. The cyclic of the Gazelle seems rather sensitive but it also seems about as sensitive as that of an R44 with this setup. (no I am not a pilot)

The reason I mention this is until I built the cyclic I found the Gazelle twitchy and just for context that was in the original FM comparatively it is tame compared to previous FM.

Saturation/curves may help initially until you get accustomed to it, but a mechanical center detent and springs and a short throw joystick mask a lot of the fine control input which saturation/curves may kinda help with.

As I understand there are some "issues" that have been taken on board by PC and will be addressed.

Depending on the main rotor direction you will have the stick slightly to the left or right during level flight, and about the same position in a steady turn.

The Gazelle is a french helo, main totor is rotating clockwise.

This means the stick will be needed to displace a bit to the right during forward flight to keep it from rolling left( different displacement in different speeds).

This flight test report show this clearly on page 47 ( Lateral control position):

https://apps.dtic.mil/dtic/tr/fulltext/u2/a016921.pdf

There’s a lot of info about how the sa342 handle, and good data for making a fine flight model or checking the validity of the actual one in this report.

Thank you for the document very interesting read. :thumbup:

The Gazelle is a french helo, main totor is rotating clockwise.

This means the stick will be needed to displace a bit to the right during forward flight to keep it from rolling left( different displacement in different speeds).

 

This flight test report show this clearly on page 47 ( Lateral control position):

https://apps.dtic.mil/dtic/tr/fulltext/u2/a016921.pdf

There’s a lot of info about how the sa342 handle, and good data for making a fine flight model or checking the validity of the actual one in this report.

Here is a good video of a SA341C. The camera is static so you an stick a post-it on the screen to see how the position of the cyclic varies slightly during different parts of the flight.

I havent bought the DCS Gazelle(yet), but are looking into this meanwhile I wait for the Bo105 module, thats why Im following the threads.

Did you try the module at least? I have no problem with the Gazelle being sensitive on the controls, twitchy, etc. with minimum cyclic input. What I am talking about is that any input from the joystick (your computer joystick, no matter the position of the cyclic) causes an accelerating rolling behaviour.

A small experiment to show the problem: while hovering, use either magnetic brake or trim hat to trim the position of the cyclic forward. The helicopter will start to accelerate forward as expected. The helicopter will not keep rolling forward, no corrections are necessary with the joystick.

Instead of allowing the helicopter to accelerate, recenter the cyclic to the starting center position through joystick deflection. You will then get the accelerating rolling backwards as long as you apply a joystick deflection. The behaviour is the same wether SAS is enabled or not.

That being said, this is nitpicking and I still think the Gazelle is a blast to fly. And as some people say it seems that Polychop are working on improvements so hopefully this will be resolved at some point.

 

Here is a good video of a SA341C. The camera is static so you an stick a post-it on the screen to see how the position of the cyclic varies slightly during different parts of the flight.

That is amazingly how it feels in the sim interesting video, question 4 mins in transitioning forward the amount of forward deflection in cyclic is small almost like you have to let the nose come up (as in the sim) rather than push the cyclic more forward as in an R44, is that a correct observation?

Did you try the module at least?

 

A small experiment to show the problem: while hovering, use either magnetic brake or trim hat to trim the position of the cyclic forward. The helicopter will start to accelerate forward as expected. The helicopter will not keep rolling forward, no corrections are necessary with the joystick.

No, didnt try it(yet). Som gaming friends try to talk me to get it.

What I comment is the statements that really cant be true.

For the stick forward ”by a clic on the trim” or mag brake for the same amount, there will be a difference from lateral inputs during forward flight. When accelerating past translational(might be spelled wrong?) lift the rotor will be met by relative wind that increases the lift of the (left) forward moving blade and reduces the lift on the (right) retreating blade.

The gyroscopic pressession makes lift come 90 degrees later, making left/forward blade giving more lift straight ahead an retreating blade less lift over tail. This will raise the nose and counter the normal [stick input = rate]. This is the reason why the cyclic will be more forward the faster you fly.

In the real helo without stab system you also need to correct for ’statically stable but dynamically unstable” with cyclic to be able to see this( otherwise itll be all over the place).

[YOUTUBE]

 

Here is a good video of a SA341C. The camera is static so you an stick a post-it on the screen to see how the position of the cyclic varies slightly during different parts of the flight.

The cyclic is hidden sometimes, so not a 100% view.

Not a SA342 but a clear view of cyclic.

Note the stick position during right turn from around 7:50: constant right turn but stick well left of centre, touching left knee( very common in the Bo105).

The Main rotor turns anti clockwise so stick to the left instead right of centre when not rolling the helo.

Here is my observation.

I think that FM is excellent. What is not excellent is control deflection on cyclic. It is way too tight, and it has precession delay, that IMHO, is a bit long. Basically you have to think 1/2-3/4 of second ahead of the helicopter. Any cyclic deflection registers slightly later. That leads to over-control, and under-control at times. I am practicing. Collective has slightly longer delay that IMHO, is due to simulation of engine power. The commanded power comes after slight delay of 1/2 to 3/4 of a second, which appear somewhat longer in flight.

With both cyclic and collective , you have think in terms of applied pressure, rather actual deflection. It is that tight on cyclic, and it may not even register on control diagram by pitch/roll diamond.

Anti-torque, on other hand has very precise and very sharp response. Which can get confusing, as changing collective and/or cyclic requires simultaneous change in anti-torque rotor pedal deflection. Becouse anti-torque is much more sensitive and responsive, its effect becomes pronounced before cyclic and collective (power) response takes effect. So it is difficult to coordinate everything.

Unless you are taking off into strong wind, cyclic should be neutral or near neutral (pressure not deflection) and collective rise should be slow and smooth. The helicopter will almost always takeoff on a slight forward flight. Cyclic trim is dangerous in this module. For now I a staying away from using magnet brake trim.

Sideslip indicator. Seriously ! String tied to a small antenna-like appendage ! A critical instrument for judging relative wind and it is a silly string on a stick! Issue with that is that it is not simulated at same FPS as rest of the helicopter. It looks like it is a non-realtime cloth simulation preview from Maya nCloth, or Houdini ClothDOP, or whatever cloth sim engine that 3DS MAX uses. It appears slow and has delay on it. My rig runs 72-96 FPS with Gzl. Silly string needs to be simmed at at least 48FPS.

Here is my observation.

 

I think that FM is excellent. What is not excellent is control deflection on cyclic. It is way too tight, and it has precession delay, that IMHO, is a bit long. Basically you have to think 1/2-3/4 of second ahead of the helicopter. Any cyclic deflection registers slightly later. That leads to over-control, and under-control at times. I am practicing. Collective has slightly longer delay that IMHO, is due to simulation of engine power. The commanded power comes after slight delay of 1/2 to 3/4 of a second, which appear somewhat longer in flight.

With both cyclic and collective , you have think in terms of applied pressure, rather actual deflection. It is that tight on cyclic, and it may not even register on control diagram by pitch/roll diamond.

Anti-torque, on other hand has very precise and very sharp response. Which can get confusing, as changing collective and/or cyclic requires simultaneous change in anti-torque rotor pedal deflection. Becouse anti-torque is much more sensitive and responsive, its effect becomes pronounced before cyclic and collective (power) response takes effect. So it is difficult to coordinate everything.

 

Unless you are taking off into strong wind, cyclic should be neutral or near neutral (pressure not deflection) and collective rise should be slow and smooth. The helicopter will almost always takeoff on a slight forward flight. Cyclic trim is dangerous in this module. For now I a staying away from using magnet brake trim.

 

Sideslip indicator. Seriously ! String tied to a small antenna-like appendage ! A critical instrument for judging relative wind and it is a silly string on a stick! Issue with that is that it is not simulated at same FPS as rest of the helicopter. It looks like it is a non-realtime cloth simulation preview from Maya nCloth, or Houdini ClothDOP, or whatever cloth sim engine that 3DS MAX uses. It appears slow and has delay on it. My rig runs 72-96 FPS with Gzl. Silly string needs to be simmed at at least 48FPS.

Okay Have a look here.

This is something that I thought I had sorted until I did a fresh OS and DCS install and it might be worth checking.

As for the slip string yeah it's okay and works fine albeit at maybe 20FPS but that's enough for me.

 

I think that FM is excellent. What is not excellent is control deflection on cyclic. It is way too tight, and it has precession delay, that IMHO, is a bit long. Basically you have to think 1/2-3/4 of second ahead of the helicopter. Any cyclic deflection registers slightly later. That leads to over-control, and under-control at times.

The SA-342 has a fully articulated rotor. The flapping hinge can be seen quite close to the rotor mast, making the rolling moment of the rotorblade less and demanding more deflection before giving a quick roll to this helo compared to ones with the flapping hinge longer away from the rotor mast.

This means that there will be a higher time lag between stick input and rolling power. The amount of lag, I really cant tell but it should be less than teetering rotors like UH-1 and B206 and R22/44 and more than helos where the flapping hinge is positioned longer out. The fact that you have found a time lag is good. The rest is solely a tuning of the lag, if needed.

Collective has slightly longer delay that IMHO, is due to simulation of engine power. The commanded power comes after slight delay of 1/2 to 3/4 of a second, which appear somewhat longer in flight.

This is not right, if you have analyzed it correctly. I dont have the SA-342 DCS so I cant help with that analyze.

The collective response should come a.s.a.p, but the weight of the helo will cause a acceleration making it take some time from applied power to full climb. This is not the same as engine slow command. If the problem was engine slow command the initial climb would still come a.s.a.p but the rotor speed would decay until the engine has responded and regained the rpm.

=The response from collective comes from rotor speed only, not from engine response.

That is not right. Even in DCS. Deflection of cyclic places certain attitude of helicopter. If cyclic is re-centered, so would attitude. Its just that in DCS: Gazelle, the deflection is very small, and most overreact, requiring counter cyclic motion.

UH-1H and KA-50 modules have correct cyclic behavior.

Deflection of cyclic places certain attitude of helicopter. If cyclic is re-centered, so would attitude.

The description above is not how cyclic works on real helicopters. Period.

I sincerely hope that the guys making these modules don't listen to stuff like this.

You clearly don't fly real helicopters or aircrafts.

Collective increases AOA of blades, thus blades also pick up drag. That drag, given same power, would decreases rotor RPM, and percentage of lift would be lost. Governor regulates fuel flow to increase engine RPM, to maintain required rotor RPM. Thus when pilot commands collective up, he is asking for more power. Governor is there so that rotor RPM is maintained. Now , in my short experience with DCS: Gazelle. There is a short delay between collective increase, and for helicopter to start rising, assuming cyclic is held constant. I adjudge that delay at between 1/2 to 3/4 of a second, but it may be shorter.

Collective increases AOA of blades, thus blades also pick up drag. That drag, given same power, would decreases rotor RPM, and percentage of lift would be lost. Governor regulates fuel flow to increase engine RPM, to maintain required rotor RPM. Thus when pilot commands collective up, he is asking for more power. Governor is there so that rotor RPM is maintained. Now , in my short experience with DCS: Gazelle. There is a short delay between collective increase, and for helicopter to start rising, assuming cyclic is held constant. I adjudge that delay at between 1/2 to 3/4 of a second, but it may be shorter.

I don't find that at all, set power as required adjust attitude with cyclic fine tune settings, I do find the Gazelle more finicky with cyclic here small "adjustments" and wait and kinda average it out over a few seconds tends to reduce PIO.

I think you'll find the smaller helicopters are more susceptible to conditions and need more attention to controls, you should also avoid pumping the collective, occasional adjustment as necessary.

Collective increases AOA of blades, thus blades also pick up drag. That drag, given same power, would decreases rotor RPM,

The inertia in the rotorsystem makes the initial increase in pitch give immediate response. There is no delay IRL, but the mass of the helo makes the response to seem slow in the beginning, specially small changes in collective.

The engine governor is helped by a ”droop compensator” or anticipator. Wiring from the collective is connected to the fuel control/GOV to help knowing that the collective is raised and a demand of increased torque will come. There was a few helos that didnt have the droop compensator (or by other reasons had slow engine response) SA330 was one of them( at least the UK Armed forces), and there was some crashes because of the slow response of the engines. Still, att hover, the first response from increased pitch was good, cause of inertia.

I am not certain. Something aint right with this thread. Its like I have fallen into alternate universe.

Granted I don't fly helicopters in real life. However in DCS I am fairly allright with UH-1H and KA-50. Getting Gazelle under control.

In DCS UH-1H. Lets say I want to test hover or hover taxi. To do that with properly loaded and started helicopter. Pedals deflection to the left, cyclic deflection back and to the left, as that is where UH-1H (2 blade) rotor disk center of lift. Add collective smoothly helicopter rises about 3 meters off deck, and I hover with minor corrections. Cyclic cannot be brought to center. If it is UH-1H will fly forward as expected. Cyclic has to be held at that sweetspot, adjusted for headwind, it is not centered. I can activate cyclic trim, in which case the current held cyclic deflection becomes a center, and allows me to re-center cyclic. This is for pilot releif, and is not required for safe flight or safe hover.

To fly fwd, from hover, in UH-1H,allow cyclic fwd, and maintain height with collective and maintain heading with pedals as helicopter transitions into forward flight. Translational lift begins to take effect at above 20 knots, with slight shaking of the rotor disk. To achieve maximum fwd speed, cyclic forward of center as needed, reducing collective as speed increases. As speed increases torque pedals deflection is reduced until not needed at all. To maintain fwd speed, cyclic has to be held at the deflection forward of center. This is how H-1H is flown.

KA-50 is flown similarly, except that deflection amounts are different, and there is less pedal work, but is still required.

In both, in stable forward flight, without use of cyclic trim, if cyclic is centered the aicraft will pitch up.

This, I believe is how DCS and real world helicopters are flown. Many YT videos of vertical instructors (real world) show that. So when I am being told that to achieve and maintain fwd flight in Gazelle, a pilot has to cyclic fwd and then once fwd flight is achieved, re-center the cyclic, and gazelle will continue fwd flight with same attitude. This is counter to every lesson of helicopter flight I have watched, and read, and practiced, and counter to UH-1H and KA-50 control in DCS. Gazelle is small and light, but it is a bit underpowered for its weight, and it is still a helicopter. So yclic fwd then return to center for sustained forward flight is not what am not experiencing. But perhaps I am, because the cyclic deflection is so tiny, it is hard to tell.

In Gazelle, the deflections in cyclic are so tiny , I can only describe them as pressure on the cyclic and not really a deflection. On visible control indicator, from stable IGE hover to VNE forward flight, tight banked turns, any aircraft maneuver that uses cyclic, the usable cyclic deflection area is no more then the little diamond indicating control position of cyclic. If cyclic deflection is larger then area of diamond, it result is severe helicopter control. Great for snap turns, I suppose, but you can easily find yourself with out of control helicopter.

I tried the "Easier Control" option , but find no difference, and have it turned off. I am not certain what it does.