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The take off run is not that difficult with the Spitfire and the P47.

But it's true it's much more difficult with the P51 due to the strong left yaw tendancy that needs plenty of right rudder pedal to counteract it, even when applying power smoothly to reach a "moderate" 42hg manifold pressure. With such a MP it takes a long time to acquire sufficient speed to get the plane in "ligne de vol" = 2 points takeoff run with the fuselage nearly horizontal.

The rudder trim setting 6R and the elevator trim setting 0 or +1/+2 NU (fuselage tank empty) does not make much change, at least in FSX.

My question : what would be the correction(s) (if any) to make in the aircraft.cfg to get a normal yaw tendancy comparable to the Spit's and the P47's ones

To point out, just because the Spitfire and P-47 yaw differently does not mean the Mustang is incorrect or needs alteration. Altering the .cfg is not advised unless adding repaints. Of note, the Merlin in the Spitfire is significantly reduced compared to the Packard Merlin Mustang (roughly 1,175 horsepower on the MK.II compared to 1,720 horsepower at WEP on the Mustang). Further, the Thunderbolt is a significantly heavier aircraft.

You will find when taking off on the Mustang that keeping the tail on the ground and not forcing it up will result in better directional control on the takeoff run. I tend to make use of the full 61 inches (130 octane) on takeoff (only wing tanks full and no further weight) by doing the following:
1) Increase throttle slowly to 35 inches, keeping stick well back.
2) Apply rudder slowly and gradually as power comes online.
3) I don't apply rudder after the plane has already swung, but rather in anticipation of the yaw movement.
4) After forward movement has been achieved and I have control of the aircraft, I again smoothly and gradually increase to full 61 inches.
5) I keep the tail well down and allow it to come up on it's own by eventually bringing stick to neutral near roughly 80MPH or so indicated.
6) Liftoff requires very little if any upwards motion on the stick.
7) Upon liftoff, expect to put in a slight amount of right aileron to compensate for the torque.

If you are unable to achieve a stabilized takeoff, you might want to try different techniques and several touch and goes to help learn how the aircraft flies. I have also found that adjusting the sensitivity of the rudders can make a drastic difference in how the rudder lags and further is applied during the takeoff run. A very sensitive rudder can make things a bit squirrely but give you faster and more responsive control.

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"the Merlin in the Spitfire is significantly reduced compared to the Packard Merlin Mustang (roughly 1,175 horsepower on the MK.II compared to 1,720 horsepower at WEP on the Mustang. Further, the Thunderbolt is a significantly heavier aircraft"

True ! So let's compare similar a/c and particularly the take-off run between the wop3 P51 and the wop2 P51 (fix applied). Both of them are A2A simulations products but of course they are not exactly the same a/c !

The yaw tendancy on the wop2 P51 is not that big, making the take-off run much easier than the wop3 P51. I 'm not saying it's easy to take-off with the wop2 P51, I'm just saying it's just less difficult compared to the wop3 P51.

Have a look on the aircraft.cfg files of both of them.
There are 3 different lines in the flight-tuning section noted as follows (wop3/ wop2) :
- yaw_stability=-0.750 /yaw_stability=1.000
- induced_drag_scalar=1.075 /induced_drag_scalar=1.000
- rudder_trim_effectiveness=0.620 /rudder_trim_effectiveness=1.000

i'm not an expert of such things, that's why I'm asking : could that make the difference between the 2 a/c behavior during the take-off run ?

I'm thinking 'apples and oranges' here. WoP2 is not an Accu-Sim aircraft while the WoP3 is. I would
think that is the major difference.

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Paul


i5-2500K @4.3Ghz OC - GA-P67A-UD7-B3 - 8GB Corsair 1600mHz

Hi ontheair - the WoP2 P-51D FM was the start point for what you now see in the WoP3 P-51D. A number of changes were made to the older FM, mainly in the interest of enhancing the intangible feel of flight and facilitating interface with Accu-sim. These updates are found both in the .cfg file and the .air file. In many cases, changes in one file work in concert with changes in the other; as such, I would caution strongly against making changes in only the .cfg file for example.

In the case at hand, the revised yaw stability setting works hand-in-hand with changes in inertia modelling and yaw damping to provide the WoP 3 P-51D with a slightly "looser" feel about the yaw axis, while airborne. The downside, for some, is a somewhat more challenging takeoff than seen with the WoP2 Mustang. It is easily managed, and Cody has provided some excellent advice in that regard. Neither FM is "right" or "wrong" - they are just slightly different takes on the same thing.

Feel free to contact me by PM if you'd like to discuss in more detail.

I'm probably misunderstanding, but are you guys suggesting that users adopt some sort of custom, non-linear rudder profile for their rudder, adjusted for personal preference and ease of use? I'm not sure I'm following the logic there, because if we can forget about force feedback, it seems that the control response either mimics the real thing, linearly, or it doesn't. (Strictly talking about users with actual Pedals here,with a realistic throw, not users of twist handle joysticks)

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2)i7 2600k, Gigabyte z68x, gtx 285s sli

"the WoP2 P-51D FM was the start point for what you now see in the WoP3 P-51D..."

thanks blue six for the info provided above. Makes things more understandable, at least for me.

Thanks also Cody for your advice regarding the P51 t/o run.

Actually things are now going better and better since I fully pull back on the stick and keep it in that position during the first meters of the t/o run while progressively applying 50hg MP power until the a/c reaches the speed where I can release the pressure on the stick. As soon as the a/c is in "ligne de vol" on its own, with the tail in the up position, there is no longer any problem to control the t/o run.

I do not use any trim setting : 000 (aft tank empty) instead of 600. I may be wrong but it seems to me they are not effective in the sim when not airborne.

That's the way it works for me : stick fully back during the first meters of the t/o run !

Agreed.

I don't think it's necessary to keep the stick back against the seat throughout the ground-roll, just an initial pull all the way back to ensure the tail-wheel is locked - thereafter it can be held slightly aft of neutral for the roll, just enough to keep the tail down, and providing steering until I see 50+ IAS

Of course this may be personal preference here, but I do this incase of a premature airborne moment, especially if on a bumpy strip; as I'd rather not have the stick all the way back like that, whilst possibly having a lot of rudder input, particularly at low speed - as I'd feel as if I'm asking for some ugly wing-drop into the scenery.

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~ Make love to the sky, don't shag it.

Agreed Rusty I don't find a lot of rear stick to be required. I put the MP at 12 o'clock and add power as the rudder effectiveness comes in with airspeed.
With the P-51 and the P-40 before it the secret to me is anticipating the yaw and staying on top of it early. In other words act not react to it

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[....] just an initial pull all the way back to ensure the tail-wheel is locked - thereafter it can be held slightly aft of neutral for the roll ...

I did not know an initial pull all the way back is enough to lock the tail-wheel.

It's true a premature t/o is not expected with the stick back against the seat, not to talk about the rudder deflection

Thanks Rusty. I'll make a try asap

When I say lock, I should add that it's locked from castoring, but not outright rigid - affording 6 degrees left or right steering of inline.

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~ Make love to the sky, don't shag it.

Hello...youre not alone on this one.... I cannot believe how I'm beaten by this mustang really badly before we begin to just to more ideas, what ever you guys do don't alter the realism...It's tough but it's the way it should be. All I keep saying is, thank God this is no real life because I would of gone through the hospital tenn's of times with bills over 1 million dollars. This mustang is by doubt the most realistic I have seen In my entire life and no one could do a better job than A2A. When I am on the runway and throttling up with respect, I kind of feel fear This is one heck of a plane, as I throttle up gently for me she takes too long to get off the ground then I kind of panic and add excessive power and pull up on the stick. When the plane starts to lift, it violently swifts to the right and crashes. It's a bout as far as I get but by doubt, there's no way I'm gonna quit.

Don't pull back on the stick too far in that way during the ground-run, especially not before rotation speed of at least ~100mph indicated, the P-51 will fly off the ground well enough without such input.

Pulling back too far - in a deliberate attempt to pull the aircraft into the air - especially at speeds well below rotation speed; may get you briefly airborne, but then will risk a power-on stall, and may result in a wing-drop to one side, which is probably what happened.

It's great when you can consistently nail it though, so persevere!

John.

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~ Make love to the sky, don't shag it.

[...] Don't pull back on the stick too far in that way during the ground-run

To Busty_Bomber : Do pull back fully on the stick during the first few meters of the roll while progressively applying 50hg MP power until the a/c reaches the speed where the stick can be moved forward to the neutral position

I did not say to keep the stick fully back during the whole roll (that may lead to unexpected and catastrophic situations) but only the first few meters that are needed to take control over the P51 yaw strong tendency

Believe me, I've been practising a lot and killed myself many times, not to talk about P51s total destruction, before being able to make satisfactory (not perfect) take-off rolls

and let us know what suits you best !

Bon courage !!

P.S. next time you post Busty_Bomber tell us about the way you fly loops with your P51. It took me some time before .....

ontheair, you've placed the quote you picked from my post out of context, I felt I was fairly transparent when writing about locking the tail-wheel prior to the ground-run, and had not suggested you had been flying stick-under-the-jumper all the way from the numbers.

I was not challenging you in my post, it was purely in reference to Busty_Bomber's experience of a violent swing to one side, after apparently attempting to encourage the aircraft off the ground too early, with excessive back-pressure on the stick - or at least that's how I've interpreted the incident.

Loops are good fun, sufficient entry speed is important, good look-out left-right for wings level, and throttle-back as you start the descent portion. There's a good explanation in the P-47 training film; on how much altitude can be lost if the throttle is not retarted when performing similar maneuvers, like the split-S.

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~ Make love to the sky, don't shag it.