Autopilot Mystery (At least to me)

[Pogo]

Hi,

 

I've had Black Shark for a couple of weeks and I just want to start off by giving props to ED on the wonderful simulation they've built. I'd all but given up on ever seeing a simulation of this quality being released into a market where games are routinely dumbed down to the lowest common denominator. But, that is a whole other discussion.

 

I've been slowly advancing through the training missions and I am pretty happy with how I am progressing and coming to grips with the different systems in the aircraft. There is one thing however, that I just can't get my head around, and that is how the Autopilot handles the aircraft's heading.

 

I understand how trimming works, and how you can set the autopilot's heading with the trim switch when you are not in Route Mode, and I understand the differences between Desired Heading and Desired Track.

 

What I don't get is how constantly fighting the helicopter while changing heading is considered normal.

 

I've read through the various threads where some people recommend turning off the heading switch on the Autopilot, but the problem I see with that is that you also turn off the dampening effect which that function provides.

 

Others say to hold the trimmer switch and release it only when you are at the desired attitude and heading, but again, I find that the aircraft loses some of its more desirable flight characteristics as you do this. In other words, these options just don't feel right.

 

The last option is to use Flight Director Mode, and this does work and is a viable option except for two things that I have noted.

 

The first is that according to what I have read, using Flight Director Mode for this purpose, as well as turning off the Heading function of the Autopilot, or holding the Trim Switch, go against flight doctrine and training on the KA-50.

 

The second thing that I have noted is that if you fly the training mission for learning the Landing Pattern, the Black Shark handles like a dream in that lesson. You can go into Route Mode and the Autopilot will fly the desired heading or track to the waypoint, but outside of Route Mode the helicopter goes where you point it without having to use any of the somewhat clumsy techniques I've described. Even when you trim the aircraft you are not locking the current heading into the Autopilot and you can continue to painlessly fly to whatever heading you'd like.

 

Now, I've looked and I've searched, and I've searched and I've looked, but the only difference that I can find in the aircraft configuration for that lesson, is that the ADI is set to manual and the NDB switch is set to the inner NDB. I can't for the life of me figure out why the aircraft behaves so differently in that lesson as opposed to any other lesson or mission that I've flown.

 

I'm really hoping that someone here or from ED can enlighten me.

 

Again, this is a great sim with a great community and I'm very glad that I've found it.

 

Cheers,

Pogo

(Witty signature to follow.....)

[sinelnic]

With the new trim implemented in 1.0.1, there´s a slight difference that you probably haven´t noticed. Try this with FD off, and see if it helps at all:

 

- Fly level

- Press and hold trim, initiate a turn (set to i.e. 15 deg, 30 deg and apply rudder appropriately)

- release trim

- See the world rotate below you. There is no spoon.

- Press and hold trim, level up the helicopter

- Release trim

 

Did that help?

[JG14_Smil]

I think training missions are the easy gamer flight model.

 

You've covered the points about the AP, so you already know how things work. You need to practice, just like others have done.

[Pogo]

With the new trim implemented in 1.0.1, there´s a slight difference that you probably haven´t noticed. Try this with FD off, and see if it helps at all:

 

- Fly level

- Press and hold trim, initiate a turn (set to i.e. 15 deg, 30 deg and apply rudder appropriately)

- release trim

- See the world rotate below you. There is no spoon.

- Press and hold trim, level up the helicopter

- Release trim

 

Did that help?

 

Thanks sinelnic, that will certainly help in flying precision patterns, but that still doesn't reconcile the difference between the Landing Pattern lesson and other lessons/missions.

 

I think training missions are the easy gamer flight model.

 

You've covered the points about the AP, so you already know how things work. You need to practice, just like others have done.

 

I don't believe that the lessons use a different or easier flight model than the missions. Aside from not having to fight the AP on heading, the helicopter pretty much feels the same. If I fly the Control Hover lesson, for example, the heading issues are present in that lesson.

 

I would encourage you to try the Landing Pattern Lesson to see what I mean.

 

Cheers,

Pogo

(Witty signature to follow.....)

[26-J39]

Just on your heading question, i find it best to turn off your heading hold, turn to your chosen heading, then heading hold back on if you want... Heading hold does not turn off any dampeners it simply tries to correct your yaw rate. The pitch and bank auto buttons will turn off your dampeners. Practice, you will find what is most comfortable for you. :smilewink:

 

[Zembla]

Most of the times questions about the autopilot come from a misunderstanding of the avionics. I see that this is not the case with you.

 

I fly by holding down the trim button, and then releasing it when I've reached my required attitude. Indeed, it sometimes can be a bit cumbersome to overcome the autopilot heading hold channel, but there isn't much you can do about it.

 

The solutions you listed basically are valid options. When I am autohovering near the peak of a mountain and I want to yaw my helicopter, I need to retrim for the new direction I want my nose to be facing in. If I don't, the autopilot and all of its 20% authority will force me back.

 

So, a way to avoid having the autopilot force your nose in a direction other than the one you want to be in, when you release the stick, is to trim it in that position. Basically, whenever you want to keep the helicopter still, or want to "lock her up" so to speak, to keep her from moving without you touching the controls, or to have her in a controlled/locked attitude, a retrim is in order.

 

Whenever it comes to strafing, when you really do not want to be fighting the heading hold, I'll usually use flight director. Strafing with rockets that is, so not really strafing, though I do it for the gun in manual mode too.

 

About the Flight Director mode, or why the landing pattern mission doesn't lock your controls, but doesn't have you fighting the AP either, that's because the FD doesn't hold any heading. The FD mode basically only dampens your controls, but does not have any control authority. It does not hold your controls, i.e. it disables heading hold, and the rest, but it does keep their damping function.

 

Really, it's a feature of the helicopter you're going to have to get used to I'm afraid :)

 

-Z

[sinelnic]

No, it´s true, the pattern training mission has something slightly different.

 

I just flew it many times, and other missions as well, and I think somehow, the AP authority in heading hold in that mission is lower than in the normal flight.

 

It does not use FD, btw. Probably we´ll need Matt himself to corroborate.

 

Nice find! Sad thing is, there´s no way to replicate what happens in that training mission over to the rest of the game.

[Pogo]

On any other flight sim I would chalk it up as peculiarity, shrug and say "That's life!", and move on. But I have found that in Black Shark, the fidelity is such that everything happens for a reason. I'll give you an example.

 

As I was first learning how to fly, I was practicing transitioning from forward flight into a hover and then engaging Auto Hover. Every once in a while as soon as I engaged Auto Hover, the helicopter would turn into a bucking bronco that was, for the most part, uncontrollable.

 

I finally figured out that this happened when I tried to engage Auto Hover with the aircraft outside of the recommended parameters for speed, height, attitude or trim. The reason that it was happening is that the Hover Autopilot, in an effort to correct , was issuing extreme pitch commands to the cyclic controls and this was causing the rotor RPMs to drop, which would in turn cause an under-volt condition that would cause all of the Autopilot settings to recycle and the Autopilot would turn off. I'd look down and all of the Autopilot lights would be off. As soon as I re-engaged them the helicopter would become much easier to control again.

 

It is also on these boards that I read through a multi-page thread discussing why the pilot has to compensate for what seems to be torque on an aircraft with counter-rotating rotors and no tail rotor.

 

Perhaps ED did "dumb down" the Autopilot system for that training lesson, but that would go against everything I've experienced or read about this sim so far. Maybe it is a bug in that training lesson?

 

Sinelnic, I am glad you've been able to corroborate what happens in the Pattern Lesson. At least I know that it isn't just me.

 

I guess the mystery continues....

 

Cheers,

Pogo

(Witty signature to follow.....)

[Pogo]

Most of the times questions about the autopilot come from a misunderstanding of the avionics. I see that this is not the case with you.

 

I fly by holding down the trim button, and then releasing it when I've reached my required attitude. Indeed, it sometimes can be a bit cumbersome to overcome the autopilot heading hold channel, but there isn't much you can do about it.

 

The solutions you listed basically are valid options. When I am autohovering near the peak of a mountain and I want to yaw my helicopter, I need to retrim for the new direction I want my nose to be facing in. If I don't, the autopilot and all of its 20% authority will force me back.

 

So, a way to avoid having the autopilot force your nose in a direction other than the one you want to be in, when you release the stick, is to trim it in that position. Basically, whenever you want to keep the helicopter still, or want to "lock her up" so to speak, to keep her from moving without you touching the controls, or to have her in a controlled/locked attitude, a retrim is in order.

 

Whenever it comes to strafing, when you really do not want to be fighting the heading hold, I'll usually use flight director. Strafing with rockets that is, so not really strafing, though I do it for the gun in manual mode too.

 

About the Flight Director mode, or why the landing pattern mission doesn't lock your controls, but doesn't have you fighting the AP either, that's because the FD doesn't hold any heading. The FD mode basically only dampens your controls, but does not have any control authority. It does not hold your controls, i.e. it disables heading hold, and the rest, but it does keep their damping function.

 

Really, it's a feature of the helicopter you're going to have to get used to I'm afraid :)

 

-Z

 

In watching the Demo Tracks I've discovered that an alternative method of changing heading in combat is to engage the Turn to Target mode and slew the Shkval target gate to the desired heading and the helicopter will turn to follow the gate. I have yet to try this technique myself but I suspect that it would work quite well.

 

Cheers,

Pogo

(Witty signature to follow.....)

[sinelnic]

You mean this thread?

http://forums.eagle.ru/showthread.php?t=44306&highlight=yaw+high+speed&page=2

 

Also, the sim is made to an incredible degree of detail, but also by humans. Matt´s videos were made before the sim was finished, so it´s possible that he was using code that was still being tuned- AP authority is a parameter of the flight model. As an example, they spent a lot of time on things like manually "tightening" the individual rotor blades lateral dampers to avoid an effect called "resonance"... or fine tuning the simulated engine to ensure it operates at proper EGT thus releasing all its power when it´s needed...

 

Turn to Target works very well, specially when in auto hover mode, although it usually requires additional help from the rudder to center the shkval reticule.

[mjolner]

Holding a constant heading and smoothly changing heading are more difficult in any heli than in a fixed wing. It really takes practice, patience and a smoothe hand.

 

I myself never hold down the trimmer while completing maneuvers, I find that a quick tap is all that is needed with small delibrate corrections. I also find as in a fixed wing that smoothe and correct coordinated use of the rudder and cyclic is required for turns. Then once the turn is complete I ensure the rudder is neutral or at the proper position for torque correction.

 

In addition I always have all four channels engaged and I use the collective brake for small alltitude changes.

 

If you view Frazer's amazing demo tracks realize that he (Frazer ) has stated that during most of those maeuvers he trimmed very little if at all. I keep quoting him on this but I think its an important point.

Edited September 5, 2009 by mjolner

[ARM505]

When you're new, turn the Heading AP channel off. That will save a lot of hassles, IMHO, at least until it all makes some sense. There's no use trying to fight both the natural pedal requirement changes as you change speed, AND the heading AP channel trying to point your nose in the trimmed direction. Just turn it off, and fly naturally.

[Chonker]

As I was first learning how to fly, I was practicing transitioning from forward flight into a hover and then engaging Auto Hover. Every once in a while as soon as I engaged Auto Hover, the helicopter would turn into a bucking bronco that was, for the most part, uncontrollable.

 

I finally figured out that this happened when I tried to engage Auto Hover with the aircraft outside of the recommended parameters for speed, height, attitude or trim. The reason that it was happening is that the Hover Autopilot, in an effort to correct , was issuing extreme pitch commands to the cyclic controls and this was causing the rotor RPMs to drop, which would in turn cause an under-volt condition that would cause all of the Autopilot settings to recycle and the Autopilot would turn off. I'd look down and all of the Autopilot lights would be off. As soon as I re-engaged them the helicopter would become much easier to control again.

 

Ah so that's what that was, I though it was just me!!!

 

I tried to record this but could never seem to recreate the situation with fraps running. I thought it could't be a bug as the buttons would blink with some sort of significance. I'm still working my way through the flight manual so I guess that will be explained at some point!

[btaft]

In watching the Demo Tracks I've discovered that an alternative method of changing heading in combat is to engage the Turn to Target mode and slew the Shkval target gate to the desired heading and the helicopter will turn to follow the gate. I have yet to try this technique myself but I suspect that it would work quite well.

 

 

This works very well IMO, particularly if you have a Track IR and use the helmet mounted site. I have even used it for basic manuevering.....basically fly where you look

[isoul]

In trainning missions the flight model is set to EASY... its obvious to anyone who tried to fly in REALISTIC for more than 30 minutes. In training you ll notice how things are done smoothly and easily (for example the slideslip above the runway in basic flight lesson) and that includes the easy turning to whatever heading the trainer likes... this can't be done so easy in realistic flight model.

 

To the original question... in order to manouver (especially when i am above target area or being attacked) I switch on FD. This gives me the much wanted freedom to turn to any way I think important in order to evade/acquire a new target/etc. The same goes when i am flying inside a narrow canyon...

 

I think thats why the FD mode is there... it overrides AP augmentation for such reasons!

[159th_Viper]

In training missions the flight model is set to EASY... its obvious to anyone who tried to fly in REALISTIC for more than 30 minutes. In training you ll notice how things are done smoothly and easily (for example the slideslip above the runway in basic flight lesson) and that includes the easy turning to whatever heading the trainer likes... this can't be done so easy in realistic flight model......

 

 

Are you sure? For what it's worth, I would disagree with you there :)

 

And yeah - I have been flying in realistic mode for more than 30min..........

 

 

 

 

I think thats why the FD mode is there... it overrides AP augmentation for such reasons!

 

 

Wrong again........

 

 

All it takes is practice ;)

[Pogo]

You mean this thread?

http://forums.eagle.ru/showthread.php?t=44306&highlight=yaw+high+speed&page=2

 

Also, the sim is made to an incredible degree of detail, but also by humans. Matt´s videos were made before the sim was finished, so it´s possible that he was using code that was still being tuned- AP authority is a parameter of the flight model. As an example, they spent a lot of time on things like manually "tightening" the individual rotor blades lateral dampers to avoid an effect called "resonance"... or fine tuning the simulated engine to ensure it operates at proper EGT thus releasing all its power when it´s needed...

 

Turn to Target works very well, specially when in auto hover mode, although it usually requires additional help from the rudder to center the shkval reticule.

 

I agree that it is certainly possible that there could be differences between how things actually work in the different code versions. I seem to be seeing discrepancies between the manual and the current version of the code, but I need to do more testing.

 

If you view Frazer's amazing demo tracks realize that he (Frazer ) has stated that during most of those maeuvers he trimmed very little if at all. I keep quoting him on this but I think its an important point.

 

Now that is interesting. I've only seen the video, is the track available for download somewhere?

 

When you're new, turn the Heading AP channel off. That will save a lot of hassles, IMHO, at least until it all makes some sense. There's no use trying to fight both the natural pedal requirement changes as you change speed, AND the heading AP channel trying to point your nose in the trimmed direction. Just turn it off, and fly naturally.

 

Maybe it is just me, but I do find that there is a loss of yaw stability with the Heading AP

channel switched off.

 

Ah so that's what that was, I though it was just me!!!

 

I tried to record this but could never seem to recreate the situation with fraps running. I thought it could't be a bug as the buttons would blink with some sort of significance. I'm still working my way through the flight manual so I guess that will be explained at some point!

 

Well this was my working theory but now I am not so sure. I had the same thing happen again with no extreme cyclic excursions or rotor RPM drops. I now think that if Auto Hover can't properly compensate it just turns off the Autopilot.

 

This works very well IMO, particularly if you have a Track IR and use the helmet mounted site. I have even used it for basic manuevering.....basically fly where you look

 

That's good to know.

 

Are you sure? For what it's worth, I would disagree with you there :)

 

And yeah - I have been flying in realistic mode for more than 30min..........

 

I agree, the Training Missions do not use the Game Mode flight model.

 

I appreciate all of your answers and advice, I am sure it prove useful to me. The question still remains, why does the helicopter behave differently in the Landing Pattern Training Mission?

 

Cheers,

Pogo

(Witty signature to follow.....)

[Frazer]

Tracks can be found in the following threads:

- New Video: Frazer Demo

 

- Flying backward indications

 

During demonstrations I do not use any timmers. This to have reliable input results every time again.

Note that this is a personal preference and most likely not done this way in reality.

Edited September 6, 2009 by Frazer

[Pogo]

Thank you Frazer. Can I ask if you use a force feedback stick?

 

I have an X52 Pro with Saitek Pro Pedals setup, but this was bugging me so much that I just went out and bought a Logitech Force 3D Force Feedback Stick so I could try out flying with a force feedback stick. After couple of quick flights I've found that the AP Heading Authority is not the issue with a FF stick that it is with a non FF stick. Even if you don't trim, I find that flying with the FF stick off center in both axis comes much more naturally than it does with a non FF stick.

 

Now I don't know that I would recommend the Logitech stick, I probably don't have it set up right but it is very sensitive and there is quite a bit of center slop in it, but at least it set my mind at ease that the aircraft is reacting as designed. :thumbup:

 

I am planning to build an A-10 cockpit so I'll probably be able to hack apart the Logitech for the force feedback circuitry and use it with stronger motors and a more precise gimbal setup for a custom A-10 stick.

 

Cheers,

Pogo

(Witty signature to follow.....)

[Frazer]

I think a FF stick will feel more natural because this is more like reality. I use a X52Pro + Saitek Rudders though and this is ok for me.

 

If you are going to build a pit, I advice you to make a stick with a long "arm" (long stick) aswell. With this you will get rid of the over sensitive stick feeling simply because you have a much longer range to move over.

[Conuk]

Just when I think about giving up I take a look at your demo frazer then I think I gotta do that!

Awesome flying. Great video - please make another when you have time!

[Frazer]

Thanks Conuk, I will fly a modified version of this demo at the Virtual Festival of Aerobatic Teams 2009. ;)

[Pogo]

You guys may already know this, but here is something interesting that I've just found.

 

If you are flying with rudder pedals or a twist stick, you can tap either the X or Z keys (the default keyboard mapping for rudder) and it will do two things.

 

1. It will re-center your rudder input independently of trim.

 

So if you rudder is trimmed off center and you want quickly center it just tap Z or X. I am still pondering this but I am thinking that you can use this in a macro or script to de-couple rudder from the trim.

 

2. It sets the Heading Autopilot to your current heading, again, independently of trim.

 

What this means is that if you are using a non-FF stick you don't have to trim just to change heading, just tap the Z or X key and the Autopilot will hold that heading.

 

This is actually quite a revelation for me. I wonder why using the keyboard rudder sets the Heading Autopilot to the new heading while using an Axis doesn't? This is a pretty significant difference in functionality between the two.

 

Cheers,

Pogo

Edited September 12, 2009 by Pogo
Lack of typing skill

[Conuk]

if i map a x or z to cougar this may work ? - i think this is the problem for me as on releasing my pedals they dont always go back to centre so I guess I trim in some of this rudder....

 

I was thinking this im my (I know not ideal) G25 pedals ?

[Pogo]

if i map a x or z to cougar this may work ? - i think this is the problem for me as on releasing my pedals they dont always go back to centre so I guess I trim in some of this rudder....

 

I was thinking this im my (I know not ideal) G25 pedals ?

 

Hey Conuk,

 

I just found this out. I'd love for someone to reproduce and verify it. To test it you can just tap the X or Z key on the keyboard and if that works for you, then maybe you can write a macro or script for it.

 

Cheers,

Pogo