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psyonic

I can't figure this out...

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Hi guys. I'm almost hesitant to post this, but I can't figure this out.About 45% of the times I initiate a TO roll, the plane deviates to either left or right of the centerline without reason, or at least no reason I can determine. That's why I decided to ask for imput. I have checked that:-There is absolutelly no input (keyboard, joystick, mouse, or whatever)-There is no wind affecting me- My rudder trim is centered-There is no autopilot input trying to control the plane.On the last point, sometimes I even leave the A/P on, with HDG for the runway heading, sometimes I don't.Seems to happen at random.Any ideas?Thanks!Armando Arjona R.

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Try calibrating your controls. Why do you have the autopilot on during takeoff? The only part of the autoflight system that should be on is the autothrottle.

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I have exactly the same problem as you, i'm pretty sure i found some forum ages ago saying that it was an fsx bug. It dosen't normaly happen after a fresh install of fsx however after a while i have this issue. The wind also seems to play a big part in it however what your talking about is a bug...I think.

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Hi. Thanks for answering.

Try calibrating your controls. Why do you have the autopilot on during takeoff? The only part of the autoflight system that should be on is the autothrottle.
I thought one could engage the different modes of the autoflight on the ground. That would only arm them so that they "kick in" when the appropiate conditions (xxx above ground level) are met. In any case, this is unrelated to the problem.As for the calibrating the controls, I did. I absolutelly make sure there is no control input whatsoever (i.e. neutral in all axes).
I have exactly the same problem as you, i'm pretty sure i found some forum ages ago saying that it was an fsx bug. It dosen't normaly happen after a fresh install of fsx however after a while i have this issue. The wind also seems to play a big part in it however what your talking about is a bug...I think.
Can anyone please confirm that is an fsx bug? And if so, any workarounds?Thanks!!!!Armando Arjona R.

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I have never seen this !Have you tried a TO/GA takeoff with no controls plugged in and use F3 to advance the throttles to 40% N1 ?I do not understand what you mean about the autopilot !!Fred.

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I have never seen this !Have you tried a TO/GA takeoff with no controls plugged in and use F3 to advance the throttles to 40% N1 ?I do not understand what you mean about the autopilot !!Fred.
Hi. Yes, that's the way I usually do my TOs anyway. It doesn't matter wether I do them that way, or I advance the throttles manually to N1, the aircraft still deviates from the centerline about 4 out of 10 times, even without any control plugged in.About the autopilot: What I meant is that you can arm VNAV, LNAV on the ground (white text anunciated). When you reach a certain altitude above ground level (I think it's 1,000), they automatically engage (green text on the anunciator).

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Do you mean centerline on the runway while taking off ? Yes it always happen to me too and I use the keyboard only + mouse.I thought one engine was overpowered than the other one , but, cause it happens each take off, I dropped that theory.BTW 45% of TOs ? Do you keep a so precise statistic ? smile.pngI think that there are no silly questions to be reluctant of, while posting about such a sophisticated simulator.-

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How badly is it deviating? Just a degree or two off centerline, or is it wildly turning to one direction or the other? A couple ideas...One, when you line up on the runway, do you let the aircraft roll for a short distance in a straight line, or do you have the nosewheel turned when you come to a stop? If it's the latter, that could be your problem, as the nosewheel may not recenter while the aircraft is stopped. If it's only a slight deviation left or right, then this is one point where the simulator may be accurate. Most airplanes don't go straight as an arrow without control inputs.Hope this helped at least a little bit.

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Do you mean centerline on the runway while taking off ? Yes it always happen to me too and I use the keyboard only + mouse.I thought one engine was overpowered than the other one , but, cause it happens each take off, I dropped that theory.BTW 45% of TOs ? Do you keep a so precise statistic ? smile.png
Exactly. I also tought that, but the thrust seems to be simmetrical.Its not that I keep statistics, in fact statistics was the only subject I ever flunked, but I'd say I experience the deviation roughly4 or 5 times out of every 10. Therefore 45% :)
How badly is it deviating? Just a degree or two off centerline, or is it wildly turning to one direction or the other? A couple ideas...One, when you line up on the runway, do you let the aircraft roll for a short distance in a straight line, or do you have the nosewheel turned when you come to a stop? If it's the latter, that could be your problem, as the nosewheel may not recenter while the aircraft is stopped. If it's only a slight deviation left or right, then this is one point where the simulator may be accurate. Most airplanes don't go straight as an arrow without control inputs.
The deviation grows as my speed does, so it starts with a few degrees and ends throwing me off the runway.Most of the time I start my flights on the runway already, so I'm (at least in theory) perfectly lined up and the nosewheel centered.
Only way to be sure is to unplug the controls and fly it with keyboard only.Are your thrusts symmetric?
I have tried disconnecting the joystick (and even keyboard sometimes) so there is absolutelly no control input whatsoever, and the thrust seems to be the same from both engines, or at least that's what's the display on both sides says.

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The deviation is pretty much a constant in each of mt takeoff but it deviates of 1-2-3 degrees only, it is enough to correct it a bit no major problem therefore.

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Assymetric thrust?Bert Van Bulck
It happens when you have controllers for seperate engines such as the GoFlight throttle quadrant. Set one up as Engine 1, another as engine 2, but when you apply thrust there's a differential causing one engine to have slightly more thrust than the other.
Try calibrating your controls. Why do you have the autopilot on during takeoff? The only part of the autoflight system that should be on is the autothrottle.
I think he referring to LNAV for the flight director.......

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... The deviation grows as my speed does, so it starts with a few degrees and ends throwing me off the runway.Most of the time I start my flights on the runway already, so I'm (at least in theory) perfectly lined up and the nosewheel centered.
Surely nobody aligns so perfectly with the centreline or expects such perfect conditions that they can simply turn up the power, take their feet off the rudder pedals and sit back? I've always had to make small rudder adjustments during takeoff as the aircraft picks up speed and it has never occurred to me that this might be unusual. It's also what I remember from my session in one of BA's real full-motion 737 simulators years ago. Tim

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Surely nobody aligns so perfectly with the centreline or expects such perfect conditions that they can simply turn up the power, take their feet off the rudder pedals and sit back? I've always had to make small rudder adjustments during takeoff as the aircraft picks up speed and it has never occurred to me that this might be unusual. It's also what I remember from my session in one of BA's real full-motion 737 simulators years ago. Tim
+1

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I repeat, I use mouse and keyboard only to fly NGX and despite that I have the deviation issue, even if it is really easy to correct it because it turns only 1-2-3 degrees right or left.

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I repeat, I use mouse and keyboard only to fly NGX and despite that I have the deviation issue, even if it is really easy to correct it because it turns only 1-2-3 degrees right or left.
I can only speak about my experience...Cessnas, Pipers, and Lear 35s, but I've never flown an aircraft that goes perfectly straight down a runway. In real life, you have to constantly correct left and right while on the takeoff roll, with or without winds etc. I would just make the small corrections, and chalk this one up to "realism".

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I can only speak about my experience...Cessnas, Pipers, and Lear 35s, but I've never flown an aircraft that goes perfectly straight down a runway. In real life, you have to constantly correct left and right while on the takeoff roll, with or without winds etc. I would just make the small corrections, and chalk this one up to "realism".
If it happens like that in the reality I feel better now but I still wonder if heavier 737s act the same or not.Please real 737 pilots could you please confirm ?Thx

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If it happens like that in the reality I feel better now but I still wonder if heavier 737s act the same or not.Please real 737 pilots could you please confirm ?Thx
Your feet are on the rudder pedals throughout the takeoff, making small corrections the whole way. This is just part of flying.

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Your feet are on the rudder pedals throughout the takeoff, making small corrections the whole way. This is just part of flying.
Thanks Spin for reporting that.Much appreciated indeed.

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