Flight Director Mode, why it is not used in real?

[ericinexile]

But couldn't you just turn the autopilots assisted stuff off then? Or am I missing the point entirely here? (Entirely likely!) Is it easier (or do you specifically choose) to fly with no assistance, other than attitude guidance from the HUD?

 

You could. In fact I did for about a week until someone on this forum pointed out that with the FD, you get some stability augmentation without the obtrusive autopilot interferance. I find this to be the perfect balance as it is still easy to fly. The helo is fun to fly with all blue buttons off but nearly impossible to fight effectively...at least at my skill level. I have both FD and Auto Hover buttons assigned which provides a quick ramp up to the automation level I need to fight.

[Reticuli]

Personally, I find the FD only useful at night. Otherwise it just seems pretty superfluous. Switching the heading diamond to heading or track usually seems enough...or just looking at the ARBIS in HUD only mode.

[Frederf]

If Grodin's post is right (#2) then FD is trying to behave like a poor man's fly-by-wire system, that keeps the attitude last commanded which would be rather different than the normal fixed wing FDs out there.

[ericinexile]

If Grodin's post is right (#2) then FD is trying to behave like a poor man's fly-by-wire system, that keeps the attitude last commanded which would be rather different than the normal fixed wing FDs out there.

 

I think you may have it backwards. NO FD, but Blue Buttons ON, is closer to what you describe. More accurately, this configuration is similar to the rarely used Control Wheel Steering (CWS) feature found in many non-FBW airliners. The Ka50's FD does the opposite and takes the autopilot OUT of the equation--except for dampening.

[aledmb]

this thread got my attention and i thought wikipedia could help:

"The flight director computes and displays the proper pitch and bank angles required in order for the aircraft to follow a selected path. A simple example: the aircraft is in level flight on a heading of 045 degrees and at an altitude of 15000 feet maintaining a speed of 260 kts, the FD bars are thus centered. Then the flight director is set to a new heading of 090 degrees and a new altitude of 20000 feet. The aircraft must thus turn to the right and climb. This is done by rolling to the right and pulling up. The roll bar will deflect to the right and the pitch bar will deflect upwards. The pilot will then pull back on the control column while rolling the aircraft to the right. Once he reaches the proper pitch and bank angle the FD bars will again center and remain centered until it is time to roll back to wings level (when the heading starts to approach 090). When the aircraft approaches 20000 feet the pitch bar will deflect downwards thus commanding the pilot to reduce pitch in order to level off at the new altitude.

 

The FD is generally used in direct connection with the Autopilot. Where the FD commands the AP to put the aircraft in the attitude necessary to follow a trajectory. The FD/AP combination is typically used in autopilot coupled low instrument approaches, (below 200 feet agl) or CAT II and CAT III ILS instrument approaches."

[ArchAngel]

After much trial and error I discovered that flying with fd on and altitude hold off allowed me to more accurately control the ka-50 while hardly trimming-retrimming. In addition, I could enter a stable and sustained hover quite effortlessly compared to doing so with the fd off.

 

So, try this. Fly with fd on and altitude hold off, go into a hover, trim once, disable fd and enable altitude control, trim once more and enable auto hover. You will be amazed at how simple and effortless it really is.

 

Of course it will help if you have the above mentioned keys mapped on the joy stick and collective.

Edited January 2, 2009 by ArchAngel

[Frederf]

I think you may have it backwards. NO FD, but Blue Buttons ON, is closer to what you describe. More accurately, this configuration is similar to the rarely used Control Wheel Steering (CWS) feature found in many non-FBW airliners. The Ka50's FD does the opposite and takes the autopilot OUT of the equation--except for dampening.

 

I didn't describe anything. I said if post #2 is true, then this. From what I can tell no mode, damped or FD-on, really works like fly by wire in the "point 'n' stay" sense.

 

Also that wiki entry is about the general flight director implementation mostly in Western airliners. The Ka-50's FD is similar only on the most basic conceptual level.

 

Is it even possible to get AP direction through the Ka-50's FD? I figure to get direction you'd need to turn RTE mode on which I don't think you can do until you turn FD off, right?

[EvilBivol-1]

I'm not sure it's a good idea to use a western definition of "Flight Director" for the Ka-50. The term is probably the closest thing ED could find in western avionics literature, but it may not necessarily be the same thing. I could be wrong about this, also.

Literally translated from Russian, the words would be "Directed Control" mode, i.e. the pilot is directed by the avionics on what to do with the helicopter to get where he needs to go.

[Prophet]

From what I can tell FD is almost the same as holding the trim button, and that may be why people are using it. Because it still dampens your inputs, but doesn't hold the bank/pitch/heading/alt. There is nothing to fight against. Holding the trim key will do the same.

 

People 'should' (IRL) be holding the trim button, but it is hard to get used to. Even I just use the FD mode. I can easily trim it out, turn FD off and put it into a hover.

[EvilBivol-1]

In real life, you should not be holding the trim button. Not on the Ka-50 anyway. However, if that helps you in the simulation, I would say more power to you, as long as you understand the difference.

[Reticuli]

^^^^^^^^

 

I fly airliners as well. And although everything you stated is true, the

FD has a completely different purpose here. I use it exclusively. Not for command guidance (which is it's ONLY use in our environment) but rather to get the autopilot out of my way.

 

Smokin' Hole

 

AAAHHHH...o.k. That's what I've been wondering. Why are people using FD all the time in DCS:BS. O.k. So most of you are using it just to turn the autopilot-proper (course flying, not the FCS) off with a single button, so you don't have to worry about that 3-way switch on the collective? That makes sense, but it's a lot of clutter in the HUD for my taste. I don't need anything telling me how to maneuver the aircraft to get the diamond on the heading tape into the right spot...assuming the heading switch isn't in the middle.

Edited January 3, 2009 by Reticuli

[Reticuli]

I think you may have it backwards. NO FD, but Blue Buttons ON, is closer to what you describe. More accurately, this configuration is similar to the rarely used Control Wheel Steering (CWS) feature found in many non-FBW airliners. The Ka50's FD does the opposite and takes the autopilot OUT of the equation--except for dampening.

 

Right, you hold CWS on the yoke so you can take control momentarily without the system fighting you. When you release it, the AP takes over again. I see from some of the other posts, though, that there are airliners using Flight Director pretty much like the Kamov...allowing the cueing symbology to be used with the AP-proper turned off. I can definitely see where that would come in handy with civilian air transportation. You want the flight to be as error free, smooth, and predictable as possible. Just for curiosity's sake, do these airliners name the primary, automated nav computer "Flight Director", like a lot of light aircraft do? Is that what it's called on the Nav source switch, or is FD the mode you go into to send the selected nav source to the AP? Is there an FD button that disengages the autopilot course flying, or do you instead have to directly (no pun intended) turn off the autopilot but keep in FD mode?

Edited January 3, 2009 by Reticuli

[Frederf]

In all the Western jet airliners I've seen flight director and autopilot are 100% independent. You can have both off, both on, or any combination.

[ThunderChief]

When I started flying the Ka-50 the autopilot was very disturbing for me, especially because you can't change heading without retrimming.

But after a while I realized that the autopilot is the only way to fight effectivly (in most situations). For example when attacking a convoy from behind you can simply set pitch to +4° and you will close in very slowly AND you don't have to care about flying till you finished your attack. Your not to fast so you can kill all vehicles in one approach, but you're not a sitting duck like in a hover, which means you can descend and manouver much faster in case you need too.

When flying with FD I will have to check fligth parameters ever 2-3 seconds and correct it, which means I have to take my eyes away from target. Also you can't use "automatic turn to target" which can make live even more easier.

But when flying just for fun or fast egress, I will still switch to FD :)

[Reticuli]

But when flying just for fun or fast egress, I will still switch to FD :)

 

I don't get why you've got FD on if you're flying just for fun. Why don't you just keep route following autopilot AND flight director both Off? What's fun about having all this HUD cueing telling you exactly what to do with the aircraft? I still get the sense my sim is not doing something your sims are doing, like it's a forcefeedback thing that's causing some significant difference in experience. You guys are just hitting FD to turn off the autopilot flying your route without having to touch the route switch and also give you manual route-flying information in the HUD, right?

[ericinexile]

Right, you hold CWS on the yoke so you can take control momentarily without the system fighting you. When you release it, the AP takes over again. I see from some of the other posts, though, that there are airliners using Flight Director pretty much like the Kamov...allowing the cueing symbology to be used with the AP-proper turned off. I can definitely see where that would come in handy with civilian air transportation. You want the flight to be as error free, smooth, and predictable as possible. Just for curiosity's sake, do these airliners name the primary, automated nav computer "Flight Director", like a lot of light aircraft do? Is that what it's called on the Nav source switch, or is FD the mode you go into to send the selected nav source to the AP? Is there an FD button that disengages the autopilot course flying, or do you instead have to directly (no pun intended) turn off the autopilot but keep in FD mode?

 

I don't think many (read: ANY) users of the FD feature are doing so for the cueing. They do it for the single reason that gets stated every other post on this thread: to bypass the middle-man. Yes, that may also be done by holding the trim but that is far more cumbersome and once the trim is released you then must react to the autopilot's re-intrusion to your flying.

 

And that's another little issue that hasn't been brought up. With the FD, the use of trim is far easier. You can do some fairly aggressive manuevering, push/release the trim, neutralize the stick and never miss a beat. With "otto" this seems true in theory more than in practice. I find that even when I release to neutral immediately after trimming, the helo still exagerates the intended pitch command. This never happens with the FD on--at least not for me.

 

Smokin' Hole

[Reticuli]

I don't think many (read: ANY) users of the FD feature are doing so for the cueing. They do it for the single reason that gets stated every other post on this thread: to bypass the middle-man. Yes, that may also be done by holding the trim but that is far more cumbersome and once the trim is released you then must react to the autopilot's re-intrusion to your flying.

 

And that's another little issue that hasn't been brought up. With the FD, the use of trim is far easier. You can do some fairly aggressive manuevering, push/release the trim, neutralize the stick and never miss a beat. With "otto" this seems true in theory more than in practice. I find that even when I release to neutral immediately after trimming, the helo still exagerates the intended pitch command. This never happens with the FD on--at least not for me.

 

Smokin' Hole

 

Now I understand.

[Niehorst]

As long as you are maneuvering, hold the trimmer down. Release it as you reach your desired altitude/direction/speed AND the helicopter is

NOT CHANGING his flight position at the moment.

As some guys above said, it can result in real hard touchdown, to release the trimmer in a moment you better should not. For this case its important to have the "center trim" on a stick key. But be ready to push the stick down fast, when centering the trim. If you do not compensate the nose raising in a fast flight, it can result in a rotor clash!

 

In my first days flying the Ka-50, I used the FD too. But only until I understood how the trimmer hast to be used.

After that I never used it again.

 

Right now Im using the older Saiteks. Trimmer button is on the

"Pinky Switch". So very comfortable to hold it down while flying.

 

KEEP in MIND:

That the AP's try to "fix" the helicopters movement on the last trimmed point. During a manual hover the heli will spin back if you kick the pedal without holding down the trim!

When using the autohover, deactivate it, turn in the desired direction and reactivate it.

 

I think I mentioned the most important considerations which helped me a lot in the past!

[Prophet]

In real life, you should not be holding the trim button. Not on the Ka-50 anyway. However, if that helps you in the simulation, I would say more power to you, as long as you understand the difference.

 

I believe that is what we were told in the beginning when people were asking about trim.

 

In the trimming thread. http://forums.eagle.ru/showpost.php?p=571432&postcount=13

 

Hold trim

Make input

Release trim

Release controls

[Prophet]

I don't get why you've got FD on if you're flying just for fun. Why don't you just keep route following autopilot AND flight director both Off? What's fun about having all this HUD cueing telling you exactly what to do with the aircraft? I still get the sense my sim is not doing something your sims are doing, like it's a forcefeedback thing that's causing some significant difference in experience. You guys are just hitting FD to turn off the autopilot flying your route without having to touch the route switch and also give you manual route-flying information in the HUD, right?

 

With Route and FD off, but the 3 AP buttons on, you will still be fighting the bank/pitch/heading that the AP is trying to hold. That is why you should hold the trim key.

[AlphaOneSix]

I believe that is what we were told in the beginning when people were asking about trim.

 

In the trimming thread. http://forums.eagle.ru/showpost.php?p=571432&postcount=13

 

Hold trim

Make input

Release trim

Release controls

 

That was my suggestion, and it's what I am used t doing in other helicopters. AirTito has said that this is not normally done this way in Kamov aircraft, and that the usual method would be to move the controls first, then press and release the trimmer button.

[Prophet]

Although I can see it being easier IRL to not have to hold the trim, it still makes little sense. You would still be fighting the control the AP has.

 

Being in auto-hover and trying to change heading is a perfect example. If you try and yaw, you are fighting the heading that the AP is trying to hold. If you hold the trim, then you just yaw over and release trim. You yaw faster and more precisely.

[Reticuli]

With Route and FD off, but the 3 AP buttons on, you will still be fighting the bank/pitch/heading that the AP is trying to hold. That is why you should hold the trim key.

 

Well Route's on. Yeah, of course.

 

When both Route and FD are off, you're in a head hold/pitch/wings-leveling state (the orientation set by trim). Head Hold is following the middle postion of the DH/DT switch's heading tape diamond, whether you've selected it or not.

 

When Route's on but FD is off, AP is following the nav system's course...assuming the DH/DT switch is on the right setting.

 

When FD is on, regardless of anything else, you're in a purely axis rate dampening state, but with the weak 20% authority on each channel (that can't cross-assist) unable to stabilize the helicopter's inherent tendency to pitch up and bank right. A little raw trim will fix this, but...

 

I've got a better solution I came up with last night for FD mode that does very slight auto-trimming of bank and a good amount of auto-loading of the pitch so you don't have to trim for speed or hold forward. Just trying to tweak it some more. I haven't been using FD long. It's interesting how with hover & nav modes off, the FD symbology is a harmless little arbitrary pitch/bank marker that can be reset even with the trim reset/clear button. For those doing manual trim, that might be a useful thing if control panel isn't up. I've just been putting it at the level horizon & zero pitch.

 

Oh, and turning the 3 channel hold buttons off of course is completely undampened and no AP orientation hold or route following. We all pick up on that pretty quickly. Gives your wrist a work out.

Edited January 4, 2009 by Reticuli

[Prophet]

Well Route's on. Yeah, of course.

 

When both Route and FD are off, you're in a head hold/pitch/wings-leveling state (the orientation set by trim). Head Hold is following the middle postion of the DH/DT switch's heading tape diamond, whether you've selected it or not.

 

When Route's on but FD is off, AP is following the nav system's course...assuming the DH/DT switch is on the right setting.

 

When FD is on, regardless of anything else, you're in a purely axis rate dampening state, but with the weak 20% authority on each channel (that can't cross-assist) unable to stabilize the helicopter's inherent tendency to pitch up and bank right. A little raw trim will fix this, but...

 

I've got a better solution I came up with last night for FD mode that does very slight auto-trimming of bank and a good amount of auto-loading of the pitch so you don't have to trim for speed or hold forward. Just trying to tweak it some more. I haven't been using FD long. It's interesting how with hover & nav modes off, the FD symbology is a harmless little arbitrary pitch/bank marker that can be reset even with the trim reset/clear button. For those doing manual trim, that might be a useful thing if control panel isn't up. I've just been putting it at the level horizon & zero pitch.

 

Oh, and turning the 3 channel hold buttons off of course is completely undampened and no AP orientation hold or route following. We all pick up on that pretty quickly. Gives your wrist a work out.

 

You didnt read what you quoted.

 

With Route and FD off... You are still fighting the AP channels. The reason people are flying with FD on is because it is easier than holding the trim key/button. It is doing the same thing. Most people are mapping trim to the cyclic. Try mapping to the collective and it is much easier, Ruggbutt found that out and most of us in 3SQN have been doing it that way since.

 

Like I have explained earlier. Say you are flying straight and level. Now you want to change direction, and change speed. You bank, but the AP is trying to hold the bank that the trim is set to. You add pitch, but the AP is trying to hold the trim pitch. You are changing heading, but the AP is trying to hold the trimmed heading. If you want an even more clear example, try to change your altitude when in auto-hover and leaving the altitude hold on by default. That is the same thing you are dealing with on the other channels.

 

If you have FD on, it wont hold the attitude of the channels that are on. If you hold trim, it wont hold the attitude.

 

The added advantage of holding the trim is that once you have your new course set, you release trim and it will hold that attitude, where FD wont. You are going to need to keep your hands on the controls with FD. With trim, I can change course and let go. I am not free to do other tasks.

 

Some are using turning the channels off as a solution. But this is just creating more workload and instability in the flight. Same with FD, it is just a workaround. The AP is supposed to decrease the workload so you dont have to worry about flying it all the time.

Edited January 4, 2009 by =Prophet=

[EvilBivol-1]

"Fighting" the AP is a term we used for explanation purposes and it's been very helpful. I don't think it's a helpful description once you have the basics down and are looking for a more precise understanding.

 

The pilot always has more authority than the AP. The AP is there to help the pilot, not the other way around.

 

Using your own example of auto-hover, as you pointed out yourself, the pilot has the authority over the AP to adjust heading/altitude/anything else he needs. He merely needs to trim again when he's done to "tell" the AP that's where he wants to keep the chopper.

 

The problem with holding trim is that, in real life, it releases the forces on your controls, which can easily lead to oversteering. IMHO, because we aren't dealing with this problem in our joysticks, it becomes an allowable practice in the simulation, especially if you find it helpful in flying. I just want to make sure we understand how it's done in reality and only then make whatever adjustments we need.

 

So, in reality, as far as we are able to ascertain from AirTito's experience as a Ka-32 crew chief and the advice given to me on the Russian forum by both a combat helicopter pilot and ED's lead FM programmer - you do not hold down the button. You press and release it. However, AlphaOneSix'es experience as an Mi-17 crew chief, also confirmed by AirTito's exposure to Mil helicopter pilots, is that Mil pilots do press and hold the button. It's possible the difference is sourced to the different helicopter types, although from what I understand, Russian pilots of Mil machines still press and release, but I haven't asked enough to really know.

Edited January 5, 2009 by EvilBivol-1