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Blenvid
12-03-2004, 01:32 PM
My X-45 just went bad on me. Apparently, Saitek tech. support is calling it a "hardware failure." http://forums.ubi.com/images/smilies/cry.gif Anyway, I had to get out the old trusty (or not so trusty) Logitech Wingman FF stick and try to fly that way. I couldn't believe how much more responsive the aircraft were in flight with the Logitech! I've gone from the tight centering stick of the X-45, to the no-centering properties of a FF stick. (although I can make the FF stick center if I want it to) This got me thinking about what happens to a stick/yoke in flight in a real plane? I'm not a real pilot so I don't know these things. Any real pilots out there please contribute to this thread.

So, when you're flying, what does the stick or Yoke want to do? Does it want to re-center itself if it's not centered? For example, if you do say like a left banking turn, does the stick stay in the left position if you were to take your hands off, or does the stick want to move into some other unspecified position? Does it want to move around if you're flying straight and level, or just move slowly to a certain position which occurs when your flight surfaces are equalized, or whatever? Thanks!

http://forums.ubi.com/images/smilies/353.gif

http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif It sure would be cool for a manufacturer to make a stick that has the actual movement properties of a real aircraft stick that would change dynamically as you fly, although I'm sure this would require software written for the stick which would have to sync up with the game/sim somehow.

Opiate364
12-03-2004, 03:32 PM
I am an avionics specialist on C-5 Galaxies and on that aircraft and with all others, the Yoke or Control Stick always returns to center.

Nimits
12-03-2004, 03:45 PM
In the T-41As (C-172Fs) that I have flown, the yoke returns to neutral (more or less) if you release it.

Blottogg
12-03-2004, 07:02 PM
Blenvid, mechanical flight controls like those of most of the aircraft in the game will center in flight due to the aerodynamic pressure (the elevators will usually droop on the ground, pushing the stick forward.) If they're trimmed off center with trim tabs, then they will return to that modified center (the little trim tabs will "fly" the controls up/down, left/right a bit.) Since the aerodynamic forces increase with velocity (V^2 actually), and the only control force is that of the pilot's muscles, there comes a point where he can't move the controls to their fully deflected point. Since many simmers don't have force feedback (and even FF sticks simulate only a small fraction of the actual 30-50 lbs or more of resistance felt at high speeds) the game translates stick movement into force applied instead of actual control deflection. Look at the stick in the cockpit view at high speed, and you'll see that full joystick deflection moves the in-game stick much less than at slow speeds.

Hydraulically powered and actuated controls (the ailerons for the P-38L in the game) provide no force feedback IRL, so if the controls are going to have an intuitive feel of increased weight at speed, springs and/or bob weights are attached to the pilot's controls.

Electronically actuated, hydraulically powered controls (F-16, Grippen) can have springs/weights to give artificial feel too, but there is more flexibility on what the control inputs actually command. The F-16's controls can command Angle of Attack per pound of stick pressure, or g for example, depending on what the plane is doing at the time. In the F-16, the only "feel" is provided by how many g's or degrees AoA the pilot gets per pound of stick pressure. The only reason the stick moves at all is because the screws that hold it to the aircraft have rubber washers that let it move about 1/4 inch in any direction.

TX-EcoDragon
12-03-2004, 07:31 PM
The previous posts pretty much covered it, but I will add that when in certain maneuvers that involve stalls, spins, tumbles, and tailslides the controls will find centers that are often far from the normal center. . . sometimes against the stops, and often moving as aerodynamic forces change. Other than these particular situations the stick generally has a pretty linear and smooth feeling of increasing forces as you move away from the trimmed center that you encounter in cruise.

I like the X-45 overall, as it has more travel than most sticks out there, and for aircraft that aren't fly by wire types that is generally a more realistic emulation of the way teh stick might feel.

And Blotto, while we are talking about aerodynamic counterbalances lets not forget spades and offset hinge points that reduce stick forces to featherweight loads in otherwise conventionally actuated controls. The Pitts S-2C uses ailerons that are hinged at about 20-30% of the distance from the leading to the trailing edge of the aileron such that the spades could be removed, the Extra 300 and the Edge type aircraft have this feature in addition to spades, this results in very light stick forces that respond to the pilot if he hiccups. The Extra has very little centering force, or what is known as breakout force, this makes returning the stick to neautral more a matter of muscle memory than feeling the center point.

Blottogg
12-03-2004, 08:05 PM
EcoDragon, you're right about the extreme maneuvering and the spades. I should have thought to mention them (the Decathalon I briefly owned had them, and it needed all the roll help it could get compared to the T-38 I was getting paid to fly at the time.)
Both spades and repositioning the hinge relative to the control surfaces aerodynamic center will affect aerodynamic load tranferred to the pilot, with the intent of both to reduce forces and allow full control movement at higher speeds (and lighter forces in general.)

You're right too that reversing the airflow over the plane can smack the controls against the stops hard enough to bend things. I hadn't thought to mention that, either (see what happens when you get old?) I remember being warned to keep firm contact with the stick and rudder pedals during tail-slides in my even more brief aerobatic instruction.

My understanding of breakout force is that it's actually the force required to overcome friction in the control systems hinges, bellcranks, etc. (interesting trivia: SpaceShipOne had a pretty nasty pitch breakout force of ~12-17 lb, which may have contributed to the hard landing it suffered before winning the X prize.) The game equivilent would be the force required to get the X45's inverted cone thingie to start sliding over the ring mounted to the stick's base.

Good point about centering force too. While low forces add agility to aerobatic airplanes, there is less stability, and more active flying is required of the pilot. Good for aerobatic planes (or fighters), bad for 747's (too many spilled drinks.) Just another of many engineering tradeoffs to consider when building/modifying aircraft.

Blenvid
12-03-2004, 08:10 PM
http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif Wow!! Thanks so much for sharing your expertise and/or experience guys/gals. It's apparent that there is a lot of experience in these forums and playing this sim. That is just great. Thanks again.

-Blenvid

TX-EcoDragon
12-04-2004, 03:21 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Blottogg:
. . .You're right too that reversing the airflow over the plane can smack the controls against the stops hard enough to bend things. I hadn't thought to mention that, either (see what happens when you get old?) I remember being warned to keep firm contact with the stick and rudder pedals during tail-slides in my even more brief aerobatic instruction.

My understanding of breakout force is that it's actually the force required to overcome friction in the control systems hinges, bellcranks, etc. . . <HR></BLOCKQUOTE>

Lol. . nah, I doubt it's anything to do with your age. . . I think that's just what happens when some members of the community paint their 190s to look like SU-31s and start doing torque rolls (err, sorta) and tail-slides in them and are then deprived of the sim so they instead compose long winded posts in the forums that really don't apply to WWII aerodynamics or WWII flying much at all simply to nitpick out of some sorta of desire to be thinking about acro. ;-)


My appologies. . . hehe

But while we are on the subject. . .
The Breakout force is what you mention, but in many cases it is also engineered in or out of the designs using aerodynamic means. The Edge for example has an aileron that sits somewhat nested/protected by the wing when the surface is at neutral, which you can feel when moving the aileron form this position, the Extra doesnt have much of this, thusly the Edge or One Designs are a bit easier to fly with precise stops in point rolls for example despite the 480 degree/second roll rates simply because as you bring the stick back through neutral and start moving it to deflect the aileron to the opposite very briefly you feel the force start to increase and can feel where the center point is even in an aircraft that have very light centering forces.

And yeah, in something like the SuperD you want to pull the rudder and elevator to the stops before the reversed airflow slams them against the stops. Most modern (ish) aerobatic aircraft are approved for tailslides though as they are built to withstand the reversed airflow. My 190 has no trouble though, I guess that Suke paint is doing something!

:-D

Fliger747
12-04-2004, 09:39 PM
I have mentioned this source several times, but it is a good one: "1944 Joint Fighter Conf.". Desireable and existing control inputs and feedbacks are discussed. Breakout force is in a real aircraft, the friction (mostly) that one has to overcome to move the surfaces without any aerodynamic load. It is not a desireable factor as it interfears with a light touch as might be usefull in formation flying. It also disrupts feedback of the minor inputs that allow you tofly smoothly. A little like flying with a joystick! I sat in a P47 cockpit once and was amazed at how smooth the elevator and aileron circuits were!

The Supercub I fly is much like this, good aerodynamic feel. The 747-400, which I fly more, is a hydraulic system, with artificially generated feel, you get used to it and can fly it well. However not much applicable to how WWII planes fly!

I am currently using the X-45 and find it satisfactory, though one has to stay in good trim. Light lubrication of the plastic sliding rings is of some aid (vasalene etc.) The FFB sticks (I've had three) are nice for a light touch. I went withthe X-45 because of the throttle unit.

Blottogg
12-04-2004, 11:52 PM
Thanks EcoDragon. I didn't know about that aspect of the Extra 300's ailerons. It makes sense though, providing both light controls and precise off-center feedback to the pilot. I'm not too old to still learn a thing or two.

Thanks too to Fliger747. Vasaline, candle wax, or glossy finish cardboard are all good ways of reducing breakout force on the X-45 (and presumably the X-52) to avoid a face-plant in the flare, along with good pitch trim discipline like you also mentioned.

Blenvid
12-05-2004, 08:52 AM
It wasn't really until a year ago that I learned the value of trim. I showed my father, a private pilot and former mechanic of C-130s in Alaska, Forgotten Battles about 6 months ago. He'd never seen me fly before so that was nice. But during my flight, he said, "aren't you gonna trim the wings"? I didn't really know what that meant; it was just another key sequence on the keyboard chart that I didn't use. http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif Now, anytime I'm flying straight for a given period of time, I'm trimming. Thanks for emphasizing the importance of this with the X-45.

I've been flying, well, since CFS2 and WWII Fighters came out. I've always been a fan of helicopters too, so Jane's Apache Longbow and Enemy Engaged have been a great challenge. I also chose the X-45 for its throttle unit Fliger747, but it was for use as a collective.

It's good to know that real pilots are using the X-45 and find it capable. I'd never greased mine before, so that may be something to consider if/when I repurchase a stick/throttle combo. Right now, I'm considering the CH products. There's probably many threads here about which stick/throttle to use so.....

Just to sum up what's been said for the less experienced here, http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif it sounds safe to say that in most real planes, the stick wants to return to center or neutral. (or trim setting, if that happens to be offcenter) There are exceptions though. "In certain maneuvers that involve stalls, spins, tumbles, and tailslides the controls will find centers that are often far from the normal center. . . sometimes against the stops, and often moving as aerodynamic forces change," to quote TX-EcoDragon.

And lastly, depending on the type of engineering that has gone into the control surfaces (fly by wire, etc.), the pilot will feel resistance to his input just to move the controls. This is called the "Breakout force." For some aircrafts, this resistance is less friendly to the pilot, and for others, the resistance is actually desirable. To quote Blotogg, a 747 with a low Breakout force would make it too manueverable, and thus spill drinks. But, a low Breakout force is important for fighters and for acrobatic flying because it makes it easier to do maneuvers and formation fly.

Please correct me if my assumptions aren't correct.

Fliger747
12-05-2004, 11:24 AM
Actually the 747 is surprisingly manuverable, it's just the speeds we fly that uses up a lot of realestate! At a heavy weight takeoff (396,000kg) V2 is at about 186 KNOTS! Landing V ref at max landing weight (302,000 kg) is 156 knots. Breakout force isn't desireable in the Whale, or any other plane and we donn'a have much, though the control forces are in keeping with a large aircraft. If we had much breakout, it would be hard to be SMOOTH. Many of the WWII fighters had much higher control forces, especially in the rudder.

One technique to use to deal with a notchy stick, even in a real plane, is to use a trim setting that is SLIGHTLY off, so that you are making fine control inputs just off of the center. Many Real) pilots flying an ILS will have just a snitch of up trim, and be adjusting the pressure against their hand for maximum feedback. I land the 747 that way, with a little up trim against my hands and it works very well. With the Saitek that seems to work well against the notchiness on a carrier approach. Just a LITTLE though! This works well with the (especially) notchy CH pedals as well, have the pedals trimmed a bit off and work the sweet spot on one side.

The CH setup, pedals, combat stick and throttle is highly regarded, if expensive for the whole setup. If you go that way you would not be dissapointed in it's performance.

Blottogg
12-05-2004, 06:26 PM
Blenvid, my comment about spilled drinks was actually directed at overall control forces, not breakout force. Like Fliger747 said, breakout force makes any aircraft "notchy" or difficult to fly smoothly (his technique for keeping the controls slightly off-center to avoid or reduce breakout is good, too. I'll have to remember that.)

Light control forces allow rapid control movements (just as it's easier to change the direction of a billiard ball more quickly than a bowling ball.) This low force is good for rapid contol inputs (aerobatics), but can make overcontrol easier, since there is less resistance to control movement. By weighting the control force per unit AoA, or degree/sec roll or yaw rate higher, large aircraft have a type of damping that helps smooth out inputs (just as it's harder to violently shake said bowling ball than the billiard ball.)

Fliger747, those speeds look close to our SFO (Simulated Flame-Out) approach speeds in F-16's, but then again, we didn't have nearly the same kinetic energy to absorb with our brakes, and we had a hook (not that it did me much good at Amori - civilian Japanese field without a cable.) The max weight abort tests of the 747-400 were impressive. Those disks glowed like they came from a forge.

edit: analogy

Blenvid
12-05-2004, 06:46 PM
Thanks for the correction Fliger747. I really want to understand this, and get it right.

I'm unfamiliar with some of your terminology Fliger747, like V2 and V ref. I'll have to look those up.

Quick question, if the goal of today's aeronautical engineers is to design planes with little or no Breakout Force, wouldn't this eventually result in an airplane which when you fly, you can't actually FEEL what is happening? Wouldn't it make you a better pilot to feel the responses of the plane? Just a thought....

Blenvid
12-05-2004, 07:03 PM
Thanks too for the correction Blottogg. Your post went up while I was writing the former response. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

I'm not sure that I understand the meaning of "control forces" Blottogg. Do you mean all forces combined, including the breakout force, results in control forces? Can you give me the layman's definition of control forces? http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

I think it's so cool that you guys are taking the time out to help me and other's (I'm sure) understand this. It's been a dream of mine, since I rode for the first time in my grandfather's Super Cub, to become a pilot. And, I can't help but get a little giggly knowing that pilots, with your many hours experience and with the great planes that you fly, are responding to these questions. http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif

Thanks again,
Blenvid

Fliger747
12-05-2004, 07:17 PM
Breakout force is the FRICTIONAL drag in the system that you have to overcome to move the stick anywhere. It's a bit like sliding the couch across the floor, the static friction takes a big push to 'breakout' and then moves along well.

Aerodynamic or generated stick forces are what you have after the breakout. In modern systems there is very little 'breakout force'. In WWII control forces were though of as # of pull per G generated. Somewhere around 10#/G was considered desireable in elevators.

Blottogg
12-05-2004, 07:38 PM
Blenvid, what Fliger747 said. "Feel" or resistance felt by the pilot through the controls, comes from several sources. Frictional resistance and aerodynamic resistance being the two players for mechanical (non-boosted) systems. Breakout force is just what it sounds like, the force required to overcome friction and get the controls moving initially. Further movement will require less force (just like moving the X45 further off center is easier once you've got it out of it's stationary center position.) For hydraulic systems, there is no doubt still some friction in the systm, but since most hydraulic controls are one-way (pilot inputs are magnified and sent to the controls, but control pressures aren't fed back to the pilot), artificial means are needed to approximate that feel (springs and bobweights are the most common.) These are calibrated to approximate the forces in earlier mechanical systems that pilots are familiar with (10 lb/g sounds like a good calibration.)

For fly-by-wire, there is also no breakout force transmitted back to the pilot's controls, and the electronic force sensors (transducers) are calibrated to give the force feedback passively. For the F-16 for example, full control input (not necessarily control deflection) was achieved at only 25 pounds of force. This could command maximum available AoA or g, depending on what the airplane was doing at the time, and 25 lb made for a fairly responsive aircraft, but with enough "feel" to avoid overcontrolling.

Blenvid
12-05-2004, 11:04 PM
Ok, thanks fellas. I think I'm getting it now. Breakout force is pretty easy to understand, but your posts cleared it up even more.

Control forces were the ones that I was uncertain about. Blottogg, your correction above said, "my comment about spilled drinks was actually directed at overall control forces, not breakout force." So the Control forces are the "Aerodynamic or generated stick forces" that "you have after the breakout" force? I'm using part of Fliger747's last post there just so I can make sure I'm properly defining "Control force(s)." Or is the breakout force included in the overall definition of Control Force(s)?

This is VERY cool about the F-16 by the way. "full control input (not necessarily control deflection) was achieved at only 25 pounds of force. This could command maximum available AoA or g, depending on what the airplane was doing at the time, and 25 lb made for a fairly responsive aircraft, but with enough "feel" to avoid overcontrolling) Wow!! http://forums.ubi.com/images/smilies/25.gif Is that a feature of all successive fighter fly-by-wire systems Blottogg?

Thanks for your patience gentleman. (and your tip on the CH products Fliger747) http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

-Blenvid

http://forums.ubi.com/images/smilies/353.gif
In my original post, I was talking about a manufacturer making a stick/yoke that has the movement charactistics of a real aircraft stick/yoke. In a former post Blottogg, you say "and even FF sticks simulate only a small fraction of the actual 30-50 lbs or more of resistance felt at high speeds." So, we don't have this stick/yoke yet. But, it occurred to me as I was reading everyone's posts that all aircraft have different amounts of forces that are felt in the stick/yoke by the pilot right? So, in the included software of this imaginary stick/yoke I'm dreaming about, you'd be able to select what aircraft you were going to fly, from what time period, etc., and it would send the appropriate feedback to the stick depending on this selection. Awww Yeah!!!! http://forums.ubi.com/groupee_common/emoticons/icon_razz.gif

ElAurens
12-06-2004, 05:08 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Blenvid:

In my original post, I was talking about a manufacturer making a stick/yoke that has the movement charactistics of a real aircraft stick/yoke. In a former post Blottogg, you say "and even FF sticks simulate only a small fraction of the actual 30-50 lbs or more of resistance felt at high speeds." So, we don't have this stick/yoke yet. But, it occurred to me as I was reading everyone's posts that all aircraft have different amounts of forces that are felt in the stick/yoke by the pilot right? So, in the included software of this imaginary stick/yoke I'm dreaming about, you'd be able to select what aircraft you were going to fly, from what time period, etc., and it would send the appropriate feedback to the stick depending on this selection. Awww Yeah!!!! http://forums.ubi.com/groupee_common/emoticons/icon_razz.gif <HR></BLOCKQUOTE>

You would need a second computer just to control all those variables, and still be able to run a sim with acceptable performance levels on your main rig.

Blenvid
12-06-2004, 10:03 AM
Yeah, you probably would need a second computer of sorts ElAurens. I say of sorts because we've really already got a second computer in our desktops/laptops: the video card. They have a processor and memory, and are just connected to the mainboard through a slot. So probably in the near future, many things will seem like connnecting just another computer to our computer/mainboard.

Fliger747
12-06-2004, 01:47 PM
Twice a year I get to (have to?) go down and fly a $50 million dollar full motion type sim. A lot of the big bux in these go to replicating the controlls and feel of inputs of the real plane. Because they are so specialized and CERTIFIED, everyhting on them is a pretty low production item. They use and modify as many of the real units and boxes from the plane for just this reason.

I do believe that Force Feedback technology has some potential here, but the setup to allow you to put realistic manuvering stick and rudder forces into play would have to be really befy and secured into a virtual cockpit. People have modified and constructed such things,but it's a real project!

The demand is probably too low to ever see this at your local game stop, or even produced at an affordable price!

I use my humble typical desktop setup to simulate and practice low visibility approaches in FS9 for the real plane I fly. It works well for the purpose intended, which is honeing the hand/eye/scan/thinking circuits.

These things have come a long way!

effte
12-09-2004, 08:10 AM
Where do you think current FF joysticks get their stick force information from? Yep, your desktop system. It€s not exactly advanced math to calculate stick forces. Il-2 already does it.

The problem with stick forces, when building full flight simulators, is that the update frequency has to be higher than for visual systems to fool our sensory system that it is real. It all has to run at 60Hz or so, which is mainly due to the force emulation.

At home, I happen to have an airliner yoke assy sitting in a corner. Hm... a hyd valve, a FF joystick, a hyd pump, some pistons... http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Fliger747
12-09-2004, 11:54 AM
The big 'sims': To control all of the 'real' stuff, a room full of mainframe computers is used. Generally the graphics are (ahem) poor.

TheGozr
12-09-2004, 12:48 PM
On the real stick of a plane YOU DO NOT HAVE THIS FORCE FEED BACK. the play on a real stick is anourmous, an example in teh yak9U when you pull the stick toward you it can touch you on the left and right sides it can touch your knees.
Force feed back stick is good in GAME but has nothing to do with the real thing , a stick with no feed back is the closest you can get from the real thing.

TX-EcoDragon
12-09-2004, 03:38 PM
We have 16 machines to boot to power the C-17 Full Motion Sim at Boeing's hangars at Long Beach. In the end the emulation is easier in a fly by wire system because similar systems can be used in the sim as in the real aircraft, this is not so in the case of conventional control articulation. Even if the sim coded for all aspects of the physics of flight at all sides of the envelope, in every flyable aircraft we still have the hurdle of finding hardware that can generate realistic forces.

Gozr, not all aircraft have very much play, and while I agree that FFB as it is today is not realistic, but this topic isn't about the shaking/pulse forces that FFB provides, but rather the forces that are smooth and constant in the stick. These are the forces that you feel in flight that resist your arm strength when the stick is moved away from it's trimmed neutral point. I am not sure of your flying experience, but if you have flown un trimmed, or done some basic aerobatics such as a loop you will feel that as you pull away from center on your way up to 4Gs the stick force may be around 40 lbs in some aircraft. Others it may be more, some much less. . .but in WWII aircraft the lbs./G can be rather high.

TX-EcoDragon
12-09-2004, 04:27 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Fliger747:
Actually the 747 is surprisingly manuverable, it's just the speeds we fly that uses up a lot of realestate! At a heavy weight takeoff (396,000kg) V2 is at about 186 KNOTS! Landing V ref at max landing weight (302,000 kg) is 156 knots. Breakout force isn't desireable in the Whale, or any other plane and we donn'a have much, though the control forces are in keeping with a large aircraft. If we had much breakout, it would be hard to be SMOOTH. Many of the WWII fighters had much higher control forces, especially in the rudder.

One technique to use to deal with a notchy stick, even in a real plane, is to use a trim setting that is SLIGHTLY off, so that you are making fine control inputs just off of the center. Many Real) pilots flying an ILS will have just a snitch of up trim, and be adjusting the pressure against their hand for maximum feedback. I land the 747 that way, with a little up trim against my hands and it works very well. With the Saitek that seems to work well against the notchiness on a carrier approach. Just a LITTLE though! This works well with the (especially) notchy CH pedals as well, have the pedals trimmed a bit off and work the sweet spot on one side.

The CH setup, pedals, combat stick and throttle is highly regarded, if expensive for the whole setup. If you go that way you would not be dissapointed in it's performance. <HR></BLOCKQUOTE>

There is a balance with regard to breakout force, relative to stick force once defflected from center. . . as you've said this can be a real problem if breakout force is too high while offset forces are low relative to breakout. This was a factor in the A300-600 PIO that lead to loss of the vertical stab even though in the end this factor was minimized in the reports. Very high rudder breakout force, coupled with very light forces otherwise makes smooth and small inputs impossible.

That doesn't mean that breakout force is inherently bad however. In more modern aerobatic designs there can be so little breakout that it is taxing simply to fly level because it is impossible to isolate hand motions from the stick. The rudder also needs a fair amount of breakout force simply so that the large muscles used to actuate the pedals aren't accidentally moving it, and also so that the pilot can find neutral in the absensce of strong control surface centering forces. Adding breakout force is of course important in rather few aircraft becasue generally there is plenty. But in Fly by wire systems, aerobatic aircraft, and fighters their is art in getting it just right, not simply reducing it as much as possible. In these instances it may not be a very noticable force though, and certainly not "notchy" in the instances I was talking about. I've flown plenty of older WWII era aircraft, or transport/XC aircraft that notchy was the appropriate word. I gave a few examples before about how critical it can be in respect to unlimited class aerobatic aircraft that have next to no centering, very slight stick forces, extreme surface size and are being tossed about violently. In designs like the SuperCub, or even aerobatic trainers like the SuperDecathlon (spades and all) the stick forces are fairly high, and the centering is strong, so there can be no mistakes about center point. My points were not aimed at these types of aircraft, nor where they aimed at aircraft intended to be flwing straight and level.

As I said before, in unlimted aerobats there usually is no detectable friction in these aircraft's control systems when sitting on the ground. . .there are hardly any stick forces in flight, and again, no apparent friction, practically all in flight forces are aerodynamic
and when controls are boosted as much as they are in these aircraft finding center is a challenge, and again, if engineers don't want to enhance centering with higher stick forces (which most don't) then aerodynamic methods are employed to add a tad of breakout force to the center points of the ailerons in particular, no friction, no notchy feel, just a slight sensation that your at center.

Despite this most pilots (even veteran aerobatic pilots that fly older designs) that take their first flight in the Extra will still be rolling, pitching and yawing a few Gs worth untill they learn the tricks used to tone these things down.

effte
12-09-2004, 04:49 PM
That's what happens when you use antiquated (but proven) hardware. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

It is also a lot easier to have separate systems for different functions in real-time systems. You don't have to worry about having to interrupt the sound routines in order to get another update of the control forces calculated if they are on different systems. To give an idea about the complexity, one solution on one system is to have the update-critical functions are on top of an execution hierarchy. Every 60th of a second, everything is interrupted to go back to the top of the hierarchy. You have to mark all data potentially affected by the interrupted procedure, so the other functions won't act on or interfere with the half-processed state information. Oh, also make sure that no necessary state information is locked due to this synchronization. After the critical updates are over and done with, execution returns to where it was interrupted. If you then have a flight model which requires 45 Hz updating, control forces requiring 60 Hz, sound satisfied with a measly 15 Hz to enable it to feed the sound processor, seven different visuals each having to be updated at 40 Hz... let's just break them up, OK? Not to mention that the bugs on system 3 (motion) won't write over the memory on system 8 (top left view), causing a wonderfully purple sky and yellow dancing mooses above the lakes... makes troubleshooting a whole lot easier. http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif Need to add something, say a new prototype nav system? Write it into the code for the existing nav system? Nope, I don't think so. Put it on a separate system and hook it up to the data bus.

Link trainers were useful, and those had all the computing capacity of a simple calculator. Simulation is a rather scalable application. You don't need umpteen mainframes... but if you can have them, you bet you're going to find use for them! What's that law called, the one about the required work somehow always ending up equal to, or slightly exceeding, the available resources?

Cheers,
Fred

TX-EcoDragon
12-10-2004, 01:24 PM
What. . I thought those pink elephants and purple moose were only in my head!! Man, I've been keeping that a secret every time I renew my medical. . .man. . . what a relief that I can drop the act.

:-D

Blottogg
12-10-2004, 05:07 PM
Blenvid, to answer your question about fly-by-wire systems after the F-16, I'll dovetail with EcoDragon's comment about getting breakout forces just right with fly-by-wire systems. In the steam-driven first F-16's (the original Block 1's) the stick was bolted to the airframe, without any rubber washers. Pilots were trying to fly steady, and straining arm muscles attempting to avoid small inputs (the stick picked up ANY input, so the plane moved unless the pilots held their hands rigid.) By mounting the stick with the rubber washers, it allowed enough slop in the system to avoid overcontrolling, or so I've been told (I've only flown the Block 30 Vipers.)

I did get a chance to see what happens when a lot more than 25 lb of backstick pressure is applied, when one of our squadron pilots got distracted after "attacking" an Aussie destroyer and buried his nose. When he looked forward again, all he saw was water. We figured he pulled at least 75 lb of back-stick avoiding the ocean (we got to view his HUD tape after he landed.) We came to this figure because during his recovery, the F-16 had a slight wing rock, not because of aerodynamics, but because he was pulling so hard to save his life that he was having a tough time holding the stick centered in roll. The slight resistance in roll offered by the washers was overwhelmed by the large amount of force in his pull. The altimeter in the HUD tape bottomed out right at 0' MSL. The Aussie destroyer had quite a show.

I have flown the F-18C sims (at McDonnell Douglas, before it became Boeing.) It is fly-by-wire too, but it's stick moves much more like a hydraulically controlled aircraft, with several inches of throw, and higher maximum stick forces. Either setup was easy to get used to, and intuitive to use. I think the SAAB Gripen (also fly-by-wire) is somewhere between the F-16 and F-18 as far as control stick movement goes.

Saburo_0
12-11-2004, 09:45 AM
I flew a few times years ago & IIRC you could "feel" the stall approaching on the C172 I took lesons in. I like FFB because it gives a tactile sensation to the buffeting etc. Shaking screns just don't convey that as well IMO. For that reason alone I'll put up with fewer features on a joystick for FFB. Just a personal preference tho.
a bit OT:
Would any of you guys be so kind as to go to this thread http://forums.ubi.com/eve/forums?a=tpc&s=400102&f=26310365&m=8281056742&r=5481033152#5481033152

where we're discussing the Zero's roll rate read the bit on Servo tabs & offer some comments or explanations ?
It seems that the NACA charts & some Jpanese sources Oleg have differ by quite a bit-how much exactly is not clear since we don't have the Japanese sources at present. but i was wondering how much difference these servo tabs would make.
Thank you,
S!

Fliger747
12-11-2004, 11:50 AM
Servo tabs on ailerons 'serve' to reduce the aerodynamic forces hindering actuation of the control at higher speeds. Typically one was fitted on one wing, with the other wing having a trim tab. They work by moving against the airflow and helping push the control in the desired direction. Sort of a trim tab which moves in a ratio in opposite direction to the control.

The sizing and throw of these was quite critical, as was the overall size and ballance of the whole control surface. In the sliderule era of aircraft design, considerable experimentation, experience and intuition was necessary to obtain a satisfatory result.

Vought flew over 100 test flights working on this single issue for the F4U, with requisite aircraft modifications before each ocassion. Time consuming! With any highspeed control modifications,loss of the aircrft through development of control surface flutters was always a possibility.

In the game.... the 'Zeke' rolls quite well, then appears to halve it's roll rate above 200 knots. Implimentation of this phenomon seems to be perhaps a little basic, but is a factor, as it should be.

I haven't 'test flown' all of the Zeke models so can't commentwith authority on this matter.

IL2-chuter
12-11-2004, 12:55 PM
Or . . . a trim tab could be a servo tab with an adjustable center . . . http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif . . . (Why the heck didn't Willi add a jackscrew to the forward arm of the 109's flettner (servo) tab??? A question for the ages.)

Boone Guyton's book is an interesting read on the development of the Corsair and its ailerons, et al. (One heck of a crash, too. http://forums.ubi.com/images/smilies/16x16_smiley-surprised.gif)

I like the MS FFB2 because of the feedback for trim and prestall buffeting (and the variable centering forces). I have to admit I removed the other FFB folders from the game. (The stick "kicking" on the ground . . . where did THAT come from? http://forums.ubi.com/images/smilies/blink.gif) I feel it's more like the planes I fly (7AC, C152, RV4, PA28-181 . . .) than a non-FFB stick.

And for driving (race sims, i.e. GTR) a force feedback wheel is essential (but an entirely different application).

Blenvid
12-12-2004, 02:14 PM
That's great information about the F-16 and a great story Blottogg; thanks for sharing that. I'm glad that your squadron pilot lived to see the day to tell about it, and for you to see and learn from his experience by watching his HUD tape. That's pretty amazing, 75 lb of back stick.

I'm reminded, in a silly most likely Hollywood exaggerated way, of the beginning of the movie "Forever Young." Mel Gibson is pulling a completely vertical dive in a B-17 bomber, and then is using every muscle in his body to pull back on the stick and pull out of the dive. Some of his gauges are popping out and various pieces of glass are cracking from the stress on the airframe.

TX-EcoDragon, your paragraph here:

Gozr, not all aircraft have very much play, and while I agree that FFB as it is today is not realistic, but this topic isn't about the shaking/pulse forces that FFB provides, but rather the forces that are smooth and constant in the stick. These are the forces that you feel in flight that resist your arm strength when the stick is moved away from it's trimmed neutral point. I am not sure of your flying experience, but if you have flown un trimmed, or done some basic aerobatics such as a loop you will feel that as you pull away from center on your way up to 4Gs the stick force may be around 40 lbs in some aircraft. Others it may be more, some much less. . .but in WWII aircraft the lbs./G can be rather high.

is exactly what I was wondering about in my original thread. So, when are we gonna see the WWII FFB stick/throttle combo that can generate those kind of forces? You'd definitely have to have the stick screwed into something solid, as it wouldn't be able to withstand the pulling and pushing otherwise, or at the very least would be very cumbersome. http://forums.ubi.com/images/smilies/59.gif

-Blenvid

IL2-chuter
12-12-2004, 04:42 PM
TX-EcoDragon, your paragraph here:

_Gozr, not all aircraft have very much play, and while I agree that FFB as it is today is not realistic, but this topic isn't about the shaking/pulse forces that FFB provides, but rather the forces that are smooth and constant in the stick. These are the forces that you feel in flight that resist your arm strength when the stick is moved away from it's trimmed neutral point. I am not sure of your flying experience, but if you have flown un trimmed, or done some basic aerobatics such as a loop you will feel that as you pull away from center on your way up to 4Gs the stick force may be around 40 lbs in some aircraft.



Ya! - after you eliminate the bogus force feedback folders (as I did) these are the forces that you're left with. http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif


Carry on. http://forums.ubi.com/images/smilies/16x16_smiley-indifferent.gif

CV8_Dudeness
12-12-2004, 04:54 PM
in FB , your Real Joystick doesnt control your Virtual Stick

it inputs commands to your Virtual Pilot

TX-EcoDragon
12-12-2004, 08:42 PM
I read that Chuter, and it piqued my interest. I have only tried two FFB sticks on the PC, and the last time was in early FB and FS2002. . . I had a hard time not being distracted by the random tugs, thumps and bumps, but what you've done might be the ticket! If I get my hands on one again I'll try what you said.

effte
12-13-2004, 06:42 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I think the SAAB Gripen (also fly-by-wire) is somewhere between the F-16 and F-18 as far as control stick movement goes. <HR></BLOCKQUOTE>

Affirm. It's a short center stick. It moves more than the stick in the F16, but not a lot.

Regards,
Fred