SEVERE take off issue

[Tomas Linnet]

Also remember these birds were not designed to land with a big fuel load. They must have more or less on fumes when returning from Berlin

[cessna lover]

if they can land with all the bullet holes they had. also do I need the update for the Cessna that I have for it? or do I understand the one post made that the updates take care of all of those? cause I had one for the b17 as well.

[Jacques]

Hi Cessna,
There is now, for Accusim aircraft, just the one update. At the top of each forum, in the announcements section. The current update is 1-26-2015. That will change when they release a new update and it will be labeled by the date of the release.

Run the updater. It automatically moves through your files and updates all relevant aircraft. As the program runs, it will tell you which aircraft it is looking for and whether it was found or not and then when the update is complete.. Very nice and easy!

The update post outlines at the top all aircraft affected, and then all the changes made for each aircraft.

[cessna lover]

oh ok. well then I can get rid of the separate update I have for the Cessna 172 then as well. less work for me means more time to bore some holes in the sky

[Stephan]

I just want to raise the question that maybe there's a different behavior that has been introduced with a certain update. I keep hearing people telling me I don't understand the p51 and that's why I crash on take off, rolling to the left, but I used to take off dozens of times without issue. I know you have to apply power slowly and counter the torque with the rudder. I was able to take off every single time.
Since an update both a year ago, I saw that behavior.
I did the experiment of reinstalling the aircraft and I can take off no problem. If I apply the latest accusim update, it makes the aircraft behave in a completely different way, meaning the left wing systematically drops and I can never take off.
Had anyone experienced a change in his p51? What I don't understand is the major difference between a clean install and a latest update. Has the aircraft behavior changed so much that it makes it so incredibly hard to take off?

Another clue if that may help but I've noticed that the horizon doesn't seem to be perfectly flat when I load the aircraft, almost like if it was tilted to the left. That is on a cold and dark, clean load of the aircraft. All my other planes in the same spot show a flat horizon.
I know this all sounds like I'm crazy but I swear my p51 acts up if I update it to the latest accusim.

[TreeTops]

I have just update mine and took the P51 civ for a quick spin. I see no problems with the handling.
Sound like you are stalling after liftoff if its the left wing dropping. What is your speed at lift off and your fuel loadout?
Just an example, get a really long runway so length is no factor. Hold the plane on the ground for at least another 20 knots past what you would normally consider and what happens with the behaviour after lift off?

[Dominique]

I it makes the aircraft behave in a completely different way, meaning the left wing systematically drops and I can never take off.
Had anyone experienced a change in his p51? .

Hi Stephan

You may keep the joystick aft a tad too long during the roll, inducing a 3-point take off below required TO speed thus a stall few feet above ground. I did lot of take off since the last update without much problem.

[Stephan]

I do my tests on KWYS which is a very long runway. I can keep rolling until I have enough speed to lift off even without elevator, and the aircraft will bank left and crash. Basically the right wheel will lift off faster. I'm sure I have plenty of speed. Please note also that other behavior if by miracle I manage to take off: After a minute of level flight (seems random), gear up, no flaps, full power, no touching of the controls except maintaining ailerons straight, the left wing drops suddenly and I go into a spin. No buffeting, no slow down, no stall, plenty of power, but still a sudden left spin.

Also how do you guys explain that I can take off every single time on a clean install, but never on the update? It's not like I was never able to take off. I took off dozens of times, nice and straight, and I just did it twice on my clean install a minute ago. That's the one thing that I can't understand.

[Dominique]

I assure you that the 51 flies the takeoff and climbout as she used to do before the upgrade, on my side at least. The engine startup is now a little more sensitive to flooding, that's all.

Three comments :

- WYS is a high altitude airport (I just did a pattern there with Glamorous Gal to get a feeling), at 7000 feet the air is thin and that impacts the take off. Not enough speed, not the proper AoA , you stall. The 51 is pretty unforgiving, that's why she is such a great aircraft to fly.

- "plenty of speed" is not what you need, you need the proper speed and the proper attitude ! Do you take off horizontal with the tail raised (good) or with the tail wheel still on the ground (bad ) ?

- About the "full power" part , you don't stay at full power, you need to reduce the power twice, after take off and after leveling up but you need to have your speedometer needle always in the green. Again at Yellowstone, you are quite high very fast, so not enough speed and you stall.

Now, if you fly her at the proper MP/RPM/Speed as instructed in the SHIFT 2 menu, you may have a controller spiking problem.

I fly the civ. with the Thrustmaster combo the CH pedals, in P3D and W7.

[Stephan]

I appreciate you taking all the time to try and help me in detail but I'm afraid you're missing the point.
I don't doubt the aircraft flies exactly the same as it used FOR YOU.
You can always try and find a fault in my way of describing what I do wrong, but again then why CAN I take off every single time, on the very same airport, in the same exact conditions, doing exactly the same thing, with a clean install? I know about the bad three point take off and the thinner air and all that. High altitude airport, improper piloting, wouldn't that affect me EQUALLY in both a clean install and the latest update?
I think what happens is that the update has a dramatic change on the aircraft for maybe a limited number or people, who have a specific combinations of things in their setup.
The fact is that the forum sees quite a number of posts describing exactly the same thing from a number of users, right around the same time, and they describe a change in the aircraft after a certain update. I couldn't find anyone describing that around the time the aircraft was released. Isn't that something worth investigating from a software/hardware standpoint rather than systematically assuming the pilot is in cause?

[Jacques]

Scott mentioned that the update does bring in behavior that they tweaked while working on the Texan. It is a more challenging aircraft. And, yes, the update is where all the new magic gets added, so the update will change hpw the aircraft behaves in comparison to the installation without the update.

You mention your aircraft seems to not "sit" level? Do you have any screenshots of that and does it also look strange from the exterioir?

When you re-installed and applied the updates, did you first delete the contents of the update folder, as a way of ruling out a possible corrupted install?

Do your controls activate the trim tabs fully and correctly?

Have you watched your aileron trim tab on takeoff to see if it is moving for some unknown reason?

What are your fuel loads, how do you set your trim tabs for takeoff?

[Stephan]

Hi Jacques,

Thanks for your help. Here's some answers:

First of all, to get this out of the way, here's me flying level a few minutes ago without problems, and then some screenshots of my successful landing. That was done with a clean install of the P51, no Accu sim update. As usual everything went fine, from take off to cruising to landing.

https://www.dropbox.com/s/c6gfcs9lm9zq7 ... k.jpg?dl=0

Now the answer to your questions.

Now all the following images show the aircraft on the same airport, same time, same conditions, after the latest accu sim update applied.

First of all a comparison of the view from inside the cockpit. On the left before the update, on the right after. You can see that the top of the canopy is not perfectly horizontal anymore. I don't know if that means anything but that's already a difference.

https://www.dropbox.com/s/y81i0s8cq1y57 ... t.jpg?dl=0

Yes I delete all folders before applying the update

I started cold and dark, then did the full check list, started the engine, warmed up. This is what I have:

46 gallons in each wing
pilot's weight 146 lbs
total payload 630 lbs
Brand new oil and coolant, garage shows no problems.
Oil temp 49

https://www.dropbox.com/s/ebfg3lp3sb8sc ... l.jpg?dl=0

My controls are not locked, as showing on the following picture. All my trims work, but I don't touch anything during take off anyway.
Here are the following trim tabs, which I have left at what you get by default on cold and dark. I believe:
Rudder : 6.1 right
elevator : 0
Aileron : 0
Flaps are up

https://www.dropbox.com/s/31izo7to9y7ll ... p.jpg?dl=0

Here's another image showing a test of the control surfaces from the outside. Everything works, flaps are up on both sides:

https://www.dropbox.com/s/oktf8l5wtg6hy ... t.jpg?dl=0

I managed to keep control of the aircraft at take off this time but as usual at a few hundred feet, while as I was flying level gear up, no flaps, throttle about 80%, not touching the controls, the left wing started to drop and I entered a fast spin. I captured the outside view. The ailerons seem fine, leveled. I tried to apply right aileron to counter the spin but it was like the aileron had no authority anymore, and I crashed. My feeling is that the left wing drop ALWAYS happens, regardless of what I do, sometimes very early, and that's why I can't even take off, sometimes after a minute airborne or so. So I think the problem has nothing to do with take off, it's more like a systematic behavior of the aircraft that I can't explain.

https://www.dropbox.com/s/upfo2elvo8agz ... n.jpg?dl=0

[Jacques]

I think the tilted cockpit is a depiction of the new torque physics added to the aircraft recently. As you start the engine, you can see the aircraft torque to the left.

I duplicated your fuel, weights and trim and did no less than four takeoff and landings from KWYS and another airport at lower elevation and had no issues- the aircraft was stable throughout. Perhaps it isn't fair for me to try to duplicate your issue because I only have the military version.

My best guess is a controller issue, but then why do your controllers work fine with the base model? Probably because it is pretty vanilla and needs the update to add the good stuff.

When this is happening, have you paused and moused over your trim settings to see if something has moved that should not have done so?

edit-- I just looked at your total weight and I'm still quite a bit heavier in the military version. The only way I could approximate your weight was by reducing fuel to nearly nothing, which then throws off the whole picture. I will say the only way I could ever get behavior like you describe is by taking with with too low airspeed at a high angle of attack, then I rolled over on the left side.

[Stephan]

Thanks Jacques,

Hopefully at this point you trust me for not being a complete noob and trying a three point take off at low speed. Like I said, i can take off if that left wing drop issue leaves me alone long enough. But then at level flight, 200 mph gear up, all trim tabs in proper position, the issue kicks in and the left wing drops suddenly.
There's no way in my mind this is "normal" behavior.
I had an idea though. I'll try to fly tonight with the AP on and see if the AP can maintain the plane from spinning down. That may tell me if my controls are in cause.

[ft]

Updates HAVE broken the flight dynamics on SOME installs before. In that instance which hit me, it was the unstoppable left turn on the t/o roll. IIRC, it onlu required an additional accu-sim reinstall that time around.

Chances are you are not going insane.

Good luck, hope you get it sorted soon!