posted 02-17- 01:45 PM               

Please don't say "they did this in real life". They didn't. Yes, they did have swing problems, but that was precession when the tail lifts. In the game this happens long before the tail lifts.

posted 02-17- 01:51 PM               

p.s dont slam the throttle open because it givees the same effect. ease the throttle open very slowly and you only get a bit of swing as the tail lifts up.

posted 02-17- 02:57 PM               

The tail will swing and the wings will dip due to engine torque. yes this is real and something not modeled very well if at all in most other WWII sims.

here's an example of part of the REAL takeoff checklist for a P-51B.
1. Rudder trim several degrees to the right,
I don't remember the exact amount.
2. Aileron trim set several nothches to counter the roll effect induced by engine torque.
3. NO FLAPS

Pilot keeps slight back pressure on the stick until enough speed is gained for the rudder to provide adequate control. Then he lets the tail lift. Allowing the tail to lift too early actually decreases the acceleration rate down the runway.

Using flaps actually makes controlling the fighters on the ground even harder and increases the roll effect of the engine torque. Flaps should only be used in the following situations. In some cases flaps can cause elevator blanking and prevent you from holding the tail down.

1. Landing
2. Carrier takeoff
3. All bombers
4. Fighter carrying a heavy loadout
5. Takeoff with a tail wind (sometimes)

I had this game for a year before I did some reading and learned that taking off in a hot rod like a Mustang is different from the process people use in a Cessna or other slower aircraft. (I can be pretty dense)

Last, A couple of planes are nearly impossible to take off in without seperate rudder control. This is not the builders fault, this came from making the flight model very realistic. The one that gives the most problem is the Corsair.

I'm working on some takeoff routines for the more torquey fighters I'll post in missions and on Fighter Squadron Central.

Also, depending on the plane, with no bombs or rockets, 45-70% throttle is plenty enough to get you off the ground. The Jug is one of the few planes you can really crank up but you still have to be careful.

Just remember, the higher the horsepower to weight ratio, the more more the effects of engine torque are felt by the airframe. This is what made the Mustang deadly to new pilots on takeoff. Many used too much power or were too fast on the throttle when first trying to takeoff in her.

Hope this helps.

posted 02-17- 03:05 PM               

quote:

---

Originally posted by Biggles3:
SWING befour the tail lifts?

---

Yes. Start engine, release breaks. With the tail still on the ground, the plane swings hard - typically to the left.

quote:

---

the reason why they do thatis the engine torque pulls the aircraft to 1 side.

---

That is incorrect, torque _cannot_ do this (I say that as a physicist and pilot). Torque, by definition, is a rolling force.

Gryoscopic prescesion _can_ make the plane swing like this, but only as the tail is rotating. I see this effect before the tail rotates, and after too. For instance, take a 190, pull full back, and then start up. In this case the plane swings to the _right_ as it rolls out.

P-factor might be one explaination for a left-swing, but I was under the impression that the game didn't model this.

So, what's causing it?

posted 02-17- 04:33 PM               

1) Prop wash is set too high for the tails control surface.

2) perhaps your controller is deflecting the tail a bit when you think it's dead-on straight.

posted 02-17- 05:01 PM               

There are/were known bugs having to do with this issue - aircraft bugs, not game bugs. It can be either the ground handling (CG, tires) or prop wash.

Who here has carefully set the airWash prop lists? I would like to know how to do this... I removed them from my WWI planes... I will add them back (or Pang) when I make sure they are close to correct.

My SE5a used to cruise very nice, but at idle it would stall - VERY tail heavy! It turns out that the CG was way off... very tail heavy. The prop wash was holding the nose down hard, very hard.

I admit I am way behind with the latest WW2 planes, but I found lots of back pressure on the stick helped me allot. Still, back in the old plane pack 5.3 days I remember the Mossie used to do this real bad... well, maybe another plane in another plane-pack, it is all a blur now

------------------
-Sv

Wings with Wires

posted 02-17- 07:41 PM               

I had this problem at one time- the rudder settings eres the cause. I set the rudder deadzone slider all the way to the left (-), and coupled the steering to the rudder- the problem went away.

BTW, sorry for the lecture, didn't know you were a pilot and though you were talking about the roll effect.

But- I do know the mustang and Corsair were reported to swing around one wheel if the rudder trim wasn't set prior to takeoff. I think this has to do with the prop wash and the pressure placed on the wheel strut on one side. The torque effect will cause some compression on the one strut, increasing bearing friction on the wheel and making it harder for the wheel on that side to start to roll.

Since there's no toe brake setting for SDOE, tying steering to the rudder is how you can get really good control on the ground.

posted 02-18- 01:49 AM               

One is the engine torque. This will try to roll the aircraft, compressing one strut, and turning the plane much like a skateboard is steered.

Another is p-factor. The wind blast coming from one side of the prop will be greater than the other any time the aircraft is at a positive angle of attack due to the difference in angle of attack between the blades on each side of the plane. This produces more lift on one wing than the other, again rolling the aircraft, and inducing some yaw moment as well.

The higher speed airflow over one wing will also move the effective center of pressure to that side, introducing another rolling moment.

The propwash is the only thing that will induce a "true" yaw moment, due to the way it hits the vertical stab and rudder.

If the prop spins the opposite direction, these forces will all act in the opposite direction as well.

It's a bit difficult to know how much propwash effect to add to the model, but I just used the same setting as the stock models. I varied it a bit during testing, but it really didn't have as much effect as you might think, as long as the changes were kept small. The aircraft's center of gravity and the size of the rudder are FAR more important IMO than any propwash effect, with the exception that the rudder becomes VERY effective with propwash added. Another factor is that the ground is modeled like wet clay rather than dirt or concrete. There appears to be almost NO "friction" between the wheels and the ground.

The current Corsair is set up to require significant use of rudder, based on reams of anecdotal evidence which suggest it was not well-behaved at all on the ground. The nickname "Hog" comes from "Hog on Ice," which was how its pilots described its ground handling characteristics That said, I did make it a bit more forgiving in the current beta version (available now at simfiles!)

posted 02-18- 11:06 AM               

quote:

---

Originally posted by Michael Harrison:
1) Prop wash is set too high for the tails control surface.

---

Well this would definitely explain it. Is there some easy way to check this?

Is there some sort of prop wash blanking effect based on AoA so that on the ground the wash is different than in flight?

quote:

---

2) perhaps your controller is deflecting the tail a bit when you think it's dead-on straight.

---

Possible, but I'd think this isn't it off the top of my head simply because the plane runs straight for some time and then *pow*.

posted 02-18- 11:13 AM               

quote:

---

Originally posted by jedi:
One is the engine torque. This will try to roll the aircraft, compressing one strut, and turning the plane much like a skateboard is steered.

---

Ahhh, that's a torque effect I hadn't considered.

quote:

---

Another is p-factor.

---

Yes, but I was under the impression that the game did not model this.

Also I should point out that many of the planes swing back to the right after the swing to the left - although typically not as strongly.

quote:

---

The wind blast coming from one side of the prop will be greater than the other any time the aircraft is at a positive angle of attack due to the difference in angle of attack between the blades on each side of the plane. This produces more lift on one wing than the other

---

Actually that's not p-factor. p-factor is simply that the right side of the prop has a higher angle of attack, and thus more thrust (up to a stall point, which tends to break the prop). That means there's a net force to the left.

The wings are not involved in p-factor, although there are a number of slipstream effects involved of course.

quote:

---

The propwash is the only thing that will induce a "true" yaw moment, due to the way it hits the vertical stab and rudder.

---

Which implies all the more than this is a propwash setting problem.

quote:

---

It's a bit difficult to know how much propwash effect to add to the model, but I just used the same setting as the stock models. I varied it a bit during testing, but it really didn't have as much effect as you might think, as long as the changes were kept small.

---

Hmmm.

quote:

---

The current Corsair is set up to require significant use of rudder, based on reams of anecdotal evidence which suggest it was not well-behaved at all on the ground. The nickname "Hog" comes from "Hog on Ice," which was how its pilots described its ground handling characteristics That said, I did make it a bit more forgiving in the current beta version (available now at simfiles!)

---

I have no problem with the system doing what it's supposed to do, let me assure you. I just get the feeling that this isn't doing what it's supposed to do - or is doing too much of it.

The long and short of it is that once the tail comes up into the slipstream (during rotation) there should be plenty of rudder authority to counteract this. Yet in the game I find that many of the planes are simply uncontrollable in this regard - tail up or down.

Maury

posted 02-18- 03:26 PM               

quote:

---

Originally posted by Maury Markowitz:

The long and short of it is that once the tail comes up into the slipstream (during rotation) there should be plenty of rudder authority to counteract this. Yet in the game I find that many of the planes are simply uncontrollable in this regard - tail up or down.

Maury

---

This points more to joystick / controller issues in my opinion. Although some minor swinging will occur, it can be countered by gentle rudder application. Are you using a Microsoft joystick? They are notorious for being twitchy and oversensitive in SDOE.

Try this in the corsair, it seems to be the trickiest ground handler in SDOE. (I actually put this plane into an almost sideways skid a few times - I can see where the "HOG on ice" came from)
If you can't get her off the ground, you more than likely have stick issues. This will be a good way to test this.

No flaps, brakes on, stick hard back. Start the engine and ease the throttle forward to approx 40%. Apply gentle right rudder/steering. Release the brakes once the engine is revved. As she starts, keep the tail on the ground and steer her until you're 40- 50 mph, then let the tail lift. When the tail is up, ramp the power to 50%. She'll start to swing to the right and the back to the left if you correct too much because of stick problems.

She still a major handful, but I can usually get her off in half of the runway length, and if I anticipate the effects at each stage, I can keep her on the runway until she's airborne.

Take several tries to see what she does at each stage. Once you know what she'll do and can anticipate her moves, if you can't get her off the ground with some practice, you definitely have controller issues.

Also, when the tail lifts and pressure is eased on the struts, she'll often start to swing back, this bird is so powerful and has so much rudder control surface it's way too easy to overcorrect if your joystick is over sensitive. When this happens you'll wind up going in circles. If you don't have it, I'd downoad the calibration utility from stickworks that works with all joysticks. You can set a custom non-linear cal curve to compensate for any joystick induced oscillations due to oversensitivity.

The other thing that makes me think it's a controller issue is this. Without this utility, taking off in a Corsair or mustang is nigh near impossible on one of my machines with a MS Sidewinder 3D PP. The Spit is a cranky witch on the ground because of the narrow undercarraige. With this utility, they are much more manageable. On my other machine with the Top Gun Afterburner, the Spit is subject to roll from the torque because of her undercarraige but is far and away the easiest of the three to take off in. The Mustang is manageable, and the Corsair still a handful.

The 109 is a total pain when using the MS stick without the utility because of the narrowness and height of the undercarraige. With the utility, or on the Top Gun stick, it's a fairly well behaved plane as long as you apply no more than 50% throttle on the ground.

Go here for the utility http://home.att.net/~stickworks/swdownld.html
Download the CJFTV320.ZIP file

Again- watch your deadzone settings- I tried out several sticks and found on some, the deadzone setting prevents the rudder from returning to the center position. Definitely NOT a good thing. I verified this problem by doing a preflight check using the F2 key for an outside view.

Hope this helps.

------------------
"Where'd he GO!?!?"
thunk-thunk-thunk-zing-OUCH
That answered my question

posted 02-18- 08:33 PM               

For instance, try a takeoff in the P-47. Very docile, easy to keep tracking straight. Then try the Mustang or Corsair. A handful, to say the least. Now look at the numbers used for propwash on the tailfeathers Almost the same numbers used. Then try a takeoff in the 109K, and look at those propwash numbers (some weird numbers there).

I literally tried ALL the combinations when I was tweaking the Corsair. I finally set them to the same numbers as the P-47, and instead changed the vertical stab size. Voila! Stability! (Try the beta Corsair and you'll see what I mean).

The one thing that seems odd is that the plane will initially veer left (what I'd expect from the engine and slipstream effects) and then (sometimes violently) swing back to the right when the tail comes up. Initially, of course, the tailWHEEL is what's keeping you straight, but IMO the rudder wouldn't just "suddenly" become effective at speed X. You shouldn't need right rudder initially and then "suddenly" need hard left rudder.

Not sure what the answer here is. I DO wish I had picked the FW-190 as the "starter" for the Corsair tho, instead of the Mustang

------------------
--jedi--

posted 02-18- 10:06 PM               

quote:

---

Originally posted by Da Jug head:
This points more to joystick / controller issues in my opinion. Although some minor swinging will occur, it can be countered by gentle rudder application. Are you using a Microsoft joystick?

---

Nope, mouse. I tried the MS stick, but as you note it was basically unusable.

Try this in the corsair, it seems to be the trickiest ground handler in SDOE. (I actually put this plane into an almost sideways skid a few times - I can see where the "HOG on ice" came from)
If you can't get her off the ground, you more than likely have stick issues. This will be a good way to test this.

quote:

---

No flaps, brakes on, stick hard back. Start the engine and ease the throttle forward to approx 40%.

---

Ok, but this is my sore point. You don't do this in real life, you go 100% and leave it there. You might push it forward slowly or slam it like you can in a 150, but one way or the other you go to the firewall and prey.

Sure, you can get the planes off the ground at 50% throttle, but that's simply wrong. If this is what you have to do it seems to suggest that the slipstream effect is twice as strong as it should be.

So, is this something that's easy to experiment with?

posted 02-19- 12:30 AM               

quote:

---

Originally posted by Maury Markowitz:
Ok, but this is my sore point. You don't do this in real life, you go 100% and leave it there. You might push it forward slowly or slam it like you can in a 150, but one way or the other you go to the firewall and prey.

Sure, you can get the planes off the ground at 50% throttle, but that's simply wrong
Maury

---

Here's where we need a copy of a pilots manual for that era. I understand what you're saying, but the training film clip I have on the P-51B is exactly the opposite of what you stated.

In the film they talk about NOT using full throttle to take off unless carrying external ordnance (bombs and rockets). The reasons given are a tendency to roll because of engine torque and to also ground loop when too much power is applied during takeoff.

Since I know you're a pilot, I'm trying to stick to only those issues I have documentation on for the real aircraft (but will offer opinions on computer issues like the joystick). The first post on the P-51B's takeoff routine was all quotes or paraphrases from the training clip.

The Warbirds were a totally different breed from what private planes are capable of. I know a couple of sites occasionally visited by Mustang pilots and some other Warbird flyers. I'll see if I can get an answer from them.

Biggles- didn't you say your dad has flown a Spit or knows someone does (besides the flyer that crashed recently)? Maybe you could get him to post a message on what taking off in these warbirds is like.

quote:

---

Nope, mouse.

---

I'll dig out the video and go through the training clip one more time to make sure I'm not remembering something wrong.

posted 02-21- 03:03 AM               

Seriously, in real life all the above arguments make sense. In OpenPlane, however, I think this tendency can be easily overcome by carefully setting up the CG, and the decalage of the airplane. Get the CG (actually the center of mass) close to the main gear on one of these models and see if that doesn't solve or reduce the takeoff problem. (If it's where it's supposed to be, and it's way aft of the main gear, all bets are off.) Once the CG is about right for takeoff, tweak the flight model by setting up the decalage.

Pang's .02

posted 02-21- 08:27 AM               

quote:

---

Originally posted by Pang:
I think this tendency can be easily overcome by carefully setting up the CG, and the decalage of the airplane. Get the CG (actually the center of mass) close to the main gear on one of these models

---

CoG is typically 1/3rd of the way back from the leading edge of the wing. Is this not the case for the models in the game?

It looks like we have a few things to try here...

1) I could just be full of crap and it was this bad

2) the slipstream numbers might need some tweaking

3) the CoG could be off

posted 02-21- 10:27 AM               

Center of Gravity: the way this is modeled in the sim, it's a bit of a crapshoot. IF you know the actual weights of component parts like the engine, each wing, the main fuselage section, etc, you can get "close" to positioning the CG "realistically." But if you don't, you're making educated guesses as to the "density" of the different parts. You can get the CG of each part right, but still screw up the "overall" CG because that is made up of the "aggregate" CG placement of all the parts, which depends on the weight of each part, which depends on the phyRelDensity--which you guessed at

Stability: like it or not, some of these planes WERE a handful on the ground. The Spitfire, Corsair, and Mustang were NOT trainers, and they were NOT Microsoft CFS planes or Aces of the Pacific planes. In most cases, these planes were built by finding the biggest, most powerful engine and prop combo in production, and mating that to the lightest airframe structure that would stay together under the stress. The plane went wherever that prop wanted to go, period--unless the pilot could prevent it.

The "ground": our ground is way too "slippery." Even selecting "rubber" as the tire material doesn't really provide much of an approximation of the real frictional force between the wheels and the ground. In a real plane, if you land "sideways" in a crab, the plane will almost immediately straighten out (or the gear will fail). If you get the plane "sideways" on takeoff, it will ground loop or collapse the gear. In SDOE, the "ground" is perfectly happy to have your plane slide along sideways. Which means the brakes and tailwheel don't have the "bite" they should--and of course we don't really have "differential" braking capability either--a pretty useful tool for directional control.

Sim considerations: is it "reasonable" to expect everyone to have to have rudders or a twist stick? Probably not, but I suspect most of the guys building these planes DO have those things, so when I build a plane, it's going to be a "rudder" plane, because I'm building it to "feel right" on MY system, which has rudder pedals, and to conform to MY ideas of "realism" which, fortunately or unfortunately, are colored by many years of flying in real planes. Could we make planes with no propwash effect? Sure. SHOULD we? Why? IMO there are plenty of sims that "let you off easy." SDOE has options to couple up the ailerons and rudder, I think, and to use or not use the tailwheel separately from the rudder as a steering device. That said, obviously these planes WERE able to be flown, by young pilots with little experience, and it's rather silly to expect flight simmers to necessarily have the same skills a combat pilot would have just to get a plane in a GAME off the ground

Solution? Sorry, don't have one Personal opinion is that we should continue to try to get the most realism we can out of a somewhat flawed, but still fairly versatile flight modeling system, and let the "difficulty" chips fall where they may. There is no plane in the sim I can't get off the ground. But it does take practice, and, unfortunately I guess, also takes some sort of rudder control. I suspect some of the difficulty can be reduced by "pre-trimming" the aileron and rudder for these planes, and practicing the throttle technique.

It might also be interesting to look at adding Mace's "catapult" system to more of the planes. When used on "dry land," it serves as a "one-time" power booster for takeoff, and as such could be used as an "easy mode" takeoff tool for planes that are "too hard" without a rudder control. Along with that, one "quick and dirty" way to restore some stability comes from the simple definition of stability: either move the airPT for the vertical stab AFT on the model, or make the vertical stab airArea BIGGER. Either of these will produce a natural "straightening force" any time the plane is displaced from equilibrium, even without a separate rudder control. The penalty is that the plane won't spin as easily in flight. Nothing is free I guess...

Just my $1.02

------------------
--jedi--

posted 02-21- 12:13 PM               

quote:

---

Originally posted by jedi:
A lot of factors conspiring together here...

---

[snip]

Excellent letter Jedi.

The ground one is interesting. Is there anything we can do about this? I assume this is why I'll slide down slight hills and so forth when I do a belly landing?

posted 02-21- 01:16 PM               

quote:

---

CoG is typically 1/3rd of the way back from the leading edge of the wing. Is this not the case for the models in the game?

---

Are you guys using a version of the code with the debug features? This is essential in placing the CG. There is a puple 3D "cross" that shows the exact location of the center of mass on the A/C. Build 76d is great for this , but it has some peculiar ground handling traits.

Jedi, you're right about the tires being slippery and this points to an issue that I don't think we can resolve. Realism in a sim at this level can't be achieved because we don't have all the feedback in a sim that we have in real planes. Since you're a pilot, you know that there is a huge amount of data coming to you from your own body! You can feel when the plane is swinging down the runway and you can counter it with rudder. In the sim, it's almost too late on some planes when the tail has begun to swing, since you don't have enough airflow over the tail to counteract the inertia of the airframe, right? (Actually in thinking about this, it sounds like the problem may be a combination of Center of Mass and not *enough* airWash on the vstab.) In order to make it possible to even steer these planes on the ground, it seems like Eric or MH or whoever gave us a little less realism in traction for our lack of sensory input.

posted 02-21- 01:24 PM               

It is funny to note than most real pilots can not fly a sim at all, my grandfather mocked them for this reason- he told me that flying was nothing like that. Well, these games to simulate flight well, but you have to suspend your disbleif and let the game take you on the magic trip... in the end it can be quite accurate when viewed apart from the human experience.

Also, I have heard at least, that many sim pilots make pretty darn good first-time flyers (as do good RC pilots).

Let's all chip in and get as plane, we can keep in in my carriage house

posted 02-21- 04:13 PM               

Spit I, Spit V, FW190A4, P38