Bf109-K4 control loads at higher speeds...

Sometime ago Yo-Yo commented that he would address the lightness of the K4 controls in pitch and roll at any speed / g load.

It's probably this lightness that accounts mostly for the broken wingtips, and I agree that there are many approaches to modeling "control stiffness" that do not suit the way the ED Team want's it modeled in DCS, so, and from someone who will not be able to have a FF joystick to play DCS, I am really curious about the approach Yo-Yo is going to take to this rather delicate matter.

One of my preferred sims - "Aerowinx PS series" - used, in the first version ( PS1 ) a model the forces required at different flight situations / configurations / regimes, based on increasing control travel required for the same control deflections ( in the absence of FBW or stability augmentation systems...), but in PSX he abandoned this approach because his PSX b744 is now even more than before meant to be used by full cockpit makers / owners or advanced mockup configurations, with rw yokes and columns, that wouldn't "like" that approach :-)

I'm really curious about it, and, although using fine tuning curves in the pitch and roll axis has helped a lot with unwanted wingtip breaking during my vlights, I still experience the effects of a way lighter than it certainly was IRL K4 control feel at higher speeds and G s...

the strange thing is...control stiffness was there in the very first release which was back then only available in the open beta for like two days...you couldnt pull out at like 700kph except using the trim wheel. then the first patch came for the open beta and it was gone....

the strange thing is...control stiffness was there in the very first release which was back then only available in the open beta for like two days...you couldnt pull out at like 700kph except using the trim wheel. then the first patch came for the open beta and it was gone....

:-( I never had the chance to try that one :-(((((

Now I have the DCS Beta installed... Well, let's hope Yo-Yo get's it back in good shape for the next update :-)

the strange thing is...control stiffness was there in the very first release which was back then only available in the open beta for like two days...you couldnt pull out at like 700kph except using the trim wheel. then the first patch came for the open beta and it was gone....

Yes, that was very strange. At my very first test flights i tought they got FM almost perfect in their first try, then couple days later it was changed to worse in this case. I actually started topic about this in bugs section back then but got no answer. Hopefully it will get better again in next update.

What's wrong in control loads for 109? We used two reports for 109 regarding the forces in roll and pitch.

The fact that the K4 can pull a lot G at high speed with ease seems nothing wrong to you?

Is this problem made worse by short gaming joysticks instead of the real life long stick?

Or does that not figure into it?

What's wrong in control loads for 109? We used two reports for 109 regarding the forces in roll and pitch.

The 109 feels like a plane with hydraulically boosted control surfaces.

Video of Bf109K4 in DCS rolling and pulling at high speed:

The plane has no stiffening at all. We can fly over 700kph and just pull to rip our wings off and the roll rate is simlilar to the Fw190. (Actually I just checked and it rolls better than 190 at high speed in game.)

IRL the 109 pilot couldn't pull more than 5G pulling with both hands using much strenght at speeds of 550kph and above. In DCS we can rip our wings no problem with one swing of the stick at over 700kph! From dives at speeds of 750kph the pilot could only get out with elevator trimm.

Alerion design was bad for high speed flight, but the alerion design is from 1940 prioritising low speed roll which was very good for just that. But at high speeds the 109 was hard to roll.

Main selling point of the FW190 was that it was a much better handling plane at all speeds. In DCS the 109 is superior at roll and has no problems with overcoming physical limitations breaking wings.

German ace Willi Reschke explains:

What's wrong in control loads for 109? We used two reports for 109 regarding the forces in roll and pitch.

Yo-yo, I believe in a post you said it would be addressed in upcoming patch?

Originally Posted by Solty

The Bf109 does not feel like the Bf109 I read about. Either the pilot is too strong or the plane is not modeled correctly.

 

The elevator and alerions are too powerful at speeds of 550kph+ The plane was reported to be stiff and both hands were used to perform any agressive maneuvers. That is not reflected in the sim. The pilot seems to be not affected by those

If you do not see ANY LIMITS would it be considered beta state?

http://forums.eagle.ru/showpost.php?p=2270700&postcount=15

What's wrong in control loads for 109? We used two reports for 109 regarding the forces in roll and pitch.

Now i'm getting bit worried. Do you think they are fine as they are now? Didn't you wrote about looking them later? It's way too easy to recover deep fast dive as it now, compared to what i've read many times from reports and memoirs. Now we can recover easily from 850+km/h dive only using stick and we can pull exessive amounts of G's at those speeds too. Barrel roll takes less than 4 seconds at 750km/h etc.

"IRL the 109 pilot couldn't pull more than 5G pulling with both hands using much strenght at speeds of 550kph and above." Do you have a source for this statement which specifically refers to a K4?

"Alerion design was bad for high speed flight, but the alerion design is from 1940.." Are you saying that aileron design was unchanged from 1940?

Do you know that the K4's wings and tail section were redesigned to address the problems of high stick forces, the addition of fletner tabs to control surfaces for example, and that stick gearing and linkages were probably also altered to aid in this objective as well. For an aircraft easily able to reach 750kph in a dive, you seriously entertain the thought that the Germans in a 1944 redesign left the ailerons unchanged?

We could discuss if DCS has correctly implemented the k4 flight model, but we'd both be guessing, unless you have actually flown one that is.

If Yoyo has used two contemporary reports about the K4 for the ingame stick forces, then I believe him unless you have some other documentation that has 1944 and K4 on it that contradicts his information. We would all like to read it if you have it.

 

Do you know that the K4's wings and tail section were redesigned to address the problems of high stick forces, the addition of fletner tabs to control surfaces for example, and that stick gearing and linkages were probably also altered to aid in this objective as well. For an aircraft easily able to reach 750kph in a dive, you seriously entertain the thought that the Germans in a 1944 redesign left the ailerons unchanged?

 

Actually there is no flettner tabs in DCS K4, because it use G-model ailerons like probably most of K4's did in real life too.

 

IRL the 109 pilot couldn't pull more than 5G pulling with both hands using much strenght at speeds of 550kph and above. In DCS we can rip our wings no problem with one swing of the stick at over 700kph! From dives at speeds of 750kph the pilot could only get out with elevator trimm.

 

Sorry but i think you are exaggerating a bit here. This old "no more than 5g's over 550km/h" is probably from that one well known british test flight with E-model, therefore not sutable with G or k models. Also, it was possible to recover even higher speed dives than 750km/h with using only stick, it was not easy tought and takes lots of altitude.

Kyösti Karhila's experience with G6:

"The maximum speed not to be exceeded was 750kmh. Once I was flying above Helsinki as I received a report of Russkies in the South. There was a big Cumulus cloud on my way there but I decided to fly right through. I centered the controls and then something extraordinary happened. I must have involuntarily entered into half-roll and dive. The planes had individual handling characteristics; even though I held the turning indicator in the middle, the plane kept going faster and faster, I pulled the stick, yet the plane went into an ever steeper dive.

In the same time she started rotating, and I came out of the cloud with less than one kilometer of altitude. I started pulling the stick, nothing happened, I checked the speed, it was about 850kmh. I tried to recover the plane but the stick was as if locked and nothing happened. I broke into a sweat of agony: now I am going into the sea and cannot help it. I pulled with both hands, groaning and by and by she started recovering, she recovered more, I pulled and pulled, but the surface of the sea approached, I thought I was going to crash. I kept pulling until I saw that I had survived. The distance between me and the sea may have been five meters. I pulled up and found myself on the coast of Estonia.

If I in that situation had used the vertical trim the wings would have been broken off. A minimal trim movement has a strong effect on wings when the speed limit has been exceded. I had 100kmh overspeed! It was out of all limits.

The Messerschmitt's wings were fastened with two bolts. When I saw the construction I had thought that they are strong enough but in this case I was thinking, when are they going to break

- What about the phenomenon called "buffeting" or vibration, was there any?

No, I did not encounter it even in the 850kmh speed."

- Kyösti Karhila, Finnish fighter ace. 32 victories. Source: Interview by Finnish Virtual Pilots Association.

Ok,

so, the way the K4 feels controlable at the full speed range in DCS has only to do with the fact that this latter ( latest ) Bf109 model incorporated all of the updates the German engineers designed to overcome previous limitiations / problems with the 109.

Fair enough, and I am glad to know that's the reason why I can easily control it and have exceptional roll rates even at 750 km/h, as well as recover from a high speed dive withou much efforts other than, not to break my wingtips.

Indeed the German aircraft must have been ahead of their time, I believe... and their pilots very careful about not breaking their wingtips easily when pulling from highspeed dives, or simply using abrupt roll inputs.

1st. Boost tab like Flettner tab helped alleviating the stick force heaviness at high speed, but it did not it entirely eliminate the stick force like the way the K4 in game is currently behaving.

2nd. Boost tab actually make your roll rate at low speed lower than without boost tab? Does the K4 in game roll slower than it should without boost tab? I don't think so.

@DB605

Different pilots can pull different loads. Some are more fit than the others, some have more strenght than others. This one was able to pull more, maybe his plane was already trimmed a little up... we don't know. But you surely understand that we need some average numbers, and 5G is showing up in reports. But I can believe that one could pull more.

But the point still stands. The 109, not even K4 was able to have a roll better or even similar to FW190 and realy couldn't pull that much elevator to loose wings or even go out of 700kph dive like P-51 or Fw190 would. That is impossible.

Also, you said that the correct response was there at the BETA release... so what happened? Where are those correct 109 features that went missing!?

@jcomm

Are you trying to be facetious or are you conviced? I realy can't tell...

Just don't jump into conclusions and take verything for granted. The 109 should not be able to do that. It was an old design that never got changed to a degree that could compete with Fw190 at high speed maneuvering.

Also, I can't see anything that is "ahead of its time" in the 109.

1st. Boost tab like Flettner tab helped alleviating the stick force heaviness at high speed, but it did not it entirely eliminate the stick force like the way the K4 in game is currently behaving.

 

2nd. Boost tab actually make your roll rate at low speed lower than without boost tab? Does the K4 in game roll slower than it should without boost tab? I don't think so.

I was told before I bought it that it doesn't have Flettner tabs anyway... so. Yeah, they shouldn't have any effect. Because they are not there... right? Because it was based on the production model that didn't have those.

 

@jcomm

Are you trying to be facetious or are you conviced? I realy can't tell...

 

I'm being honest. It's a reply to yo-yo, and I believe he does his best to get the DCS ww2 warbirds as close as possible to their performance, so, since he answered my OP the way he did, I start to believe the K4 in DCS is indeed matching RW data, and because it was the final production and most advanced model of the Bf109 probably it really had this features ?

But!!! I still think that this being the case, then those wings breaking apart so easily still has to get some fine tuning.

Please bare in mind that my knowledge about ww2 or any type of war aircraft is rather limited, specially because they never were my focus of attention in aviation.

Regarding having wrote ( ahead of it's time ) what I mean is that, it outperforms the Fw190 and the P51d in turning flight. At least in DCS I can easily turn inside of a P51d opponent. Also, it climbs like the hell, and that looks to me as yet another advantage. Fire power is also very good, and it's a very stable but at the same time extremely light in controls platform. What more could a ww2 pilot ask for ?

What's wrong in control loads for 109? We used two reports for 109 regarding the forces in roll and pitch.

Yo-Yo, could you please answer these questions:

1) Are those forces reported at the control stick?

2) Does the simulation take controls position as input directly for non FF-sticks?

The problem we face here is complicated by the fact that those who fly this sim don't all use the same hardware.

Simulating the real control forces (and thus stiffening) requires a powerful haptic feedback system which we cannot assume to be present.

So either we can say OK control force simulation is not a realistic option and just equate joystick position to simulated control stick position,

OR:

we can filter the simulation input using a "force curve", i.e. a mapping of the stick force the simulated pilot is assumed to be capable of to the joystick range of motion. (The same holds for the rudder pedals btw.)

So that's what I mean with question 2: When FF is turned off, is there a force curve filtering in the simulation or not?

Thanks for being so present on these forums and taking time to explain the FM to us.

Cheers!

Mark

IRL the 109 pilot couldn't pull more than 5G pulling with both hands using much strenght at speeds of 550kph and above. In DCS we can rip our wings no problem with one swing of the stick at over 700kph! From dives at speeds of 750kph the pilot could only get out with elevator trimm.

This is not quite correct - if it was not possible to pull 5 gs, why were pilots reporting blacking out?

The stick force per g is fairly constant over the speed range until really high mach numbers are reached, meaning the pilot can pull the same amount of g up to very high speeds with the same force as he can at low speeds. The pilot will perceive it as a stick force increase, since the pressure on the surfaces will increase with airspeed, and he can move the surfaces less, but at the same time he will get more g per deflection for exactly the same reason.

The stick force gradient (stick force per g) will increase at high Mach numbers (exact amounts are known, as this was tested during the war and available to devs). Curiously, even though the stick force per g is lower on the 190, it increases slower on the 109 compared to the 190 with the increase of Mach number, probably on account of the thinner tail airfols used.

Long story short, there should be no reduction in the 109s actual pitch maneuverability unless you reach very high speeds in the order of 0,75-,80 Mach and above - at these changes your stick for per g would increase and you may find some reduction in pitch maneuverability at the same stick forces. What you do not perceive in a sim as opposed to real aircraft is the increased physical resistance of the stick to generate the same control surface movements.

Barrel roll takes less than 4 seconds at 750km/h etc.

Smells fishy though.. still, we are in beta.

Long story short, there should be no reduction in the 109s actual pitch maneuverability unless you reach very high speeds in the order of 0,75-,80 Mach and above - at these changes your stick for per g would increase and you may find some reduction in pitch maneuverability at the same stick forces. What you do not perceive in a sim as opposed to real aircraft is the increased physical resistance of the stick to generate the same control surface movements.

Is that so?

http://www.eaf51.org/newweb/Documenti/Storia/Flying_%20109_ENG.pdf

Pitch tends to be heavy above 400km/h, but it

is still easy to manage up to 500km/h, and

the aircraft is perfectly happy carrying ou

t low-level looping manoeuvres from 550km/h

and below. Above 550km/h, on

e peculiarity is a slight no

se-down trim change as you

accelerate. This means that when you run in

for an airshow above

500km/h, the airplane

has a slight tucking sensation-a so

rt of desire to get down to

ground level. This is easily

held on the stick, or it can

be trimmed out, but it is s

lightly surprising initially.

 

When you maneuver above 500km/h, two hand

s are required for a more aggressive

performance. Either that or get on the trimmer

to help. Despite this he

avying up, it is still

quite easy to get 5G at these speeds.

Funny even WT(or every other flight sim) was able to model this effect very well, while DCS can't?

I believe that probably the most plausible approach to model control stiffness due

to aerodynamic forces, in the absence of FBW systems, and for users without a FF joystick,

would be to:

1) Apply a filter to the required axis that would imply increased travel to simulate

the need for a higher force applied to the control system ( stick, yoke, rudder, spoiler, etc... )

2) Complement the above effect with time lag. For instance, to give the player the sensation of force

required for a given control deflection at higher speed / g-load, the stick might have to travel to

the physical stop of the controller and stay there for some fraction of time in order to somehow model

the actual travel time of the control in the real aircraft and the force required to actuate it.

Is this a perfect solution ? certainly not!, but at least I would prefer it to be able to manouver an

Bf109 using the same effort and getting the same outcome no matter if I was flying at 220 km/h or 700 Km /h

from someone who will not be able to have a FF joystick to play DCS

I should point out that even a force-feedback joystick would not solve this problem, unless it had a hyper-strong mechanism greatly exceeding that of commercially-available FF gaming joysticks. With the forces that we're talking about at high speeds, you'd break the FF mechanism in the shoddy gaming sticks out there. Or the mechanism would stop providing force, if there was a safety of this nature. Either way, the stick would, when entering high speeds in the sim, fairly quickly stop providing force, effectively turning into a non-FF joystick whenever the high speeds came into play.

The feeling of the pilot not always corresponds the results of measurements. Trim curves for the 109G is available and there is no sign of such trim behavior in this curves.

That is pretty clear to me.

Yo-Yo is right. If you know how to read the measured trim curves of the design the forces do not get excessive unless the aircraft exceeds Vne.

There are some trim curves are posted in this thread:

http://forums.eagle.ru/showthread.php?t=136155

Let's not keep repeating the mistakes of William Green and the past. Measured data trumps pilot perception every-time.

Some of the NACA's lesson learned during their flying qualities development:

During this period some very important facts about flight research were uncovered.

Examples are:

1. Some results from flight research are only as good as the instrumentation involved.

2. That pilots in general are reliable, dedicated and usually informed people. In spite of

this be sure to measure everything.

3. It is easier to make a test pilot out of an engineer than an engineer out of a test pilot.

4. Test flying or flight research is a time consuming, frustrating and expensive business, but we can't do without it

Crumpp,

thx for your additional notes.

I am glad I'm wrong about this non-problem with the Bf109 K4 stick forces in DCS :-)