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PostPosted: Fri Dec 16, 2016 3:27 pm 
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Hey guys,

Ever since a Couple of Core updates My P51 wont respond properly to steering on the ground.

It Taxies properly but once powering up even at segments or even low power it just goes left and i am mashing full right rudder and brake. As Soon as I lift the tail it darts right toward the control input. Somehow the physics got swapped or something.

what should I do.

Thanks.

JDW


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PostPosted: Sat Dec 17, 2016 1:01 pm 
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Hi,

Since the last core updates, the Mustang become more hard and realistic to handle. I have the civilian version and can confirm, that there is a difference in the behaviour. The plane should be handled by the manual. Check the rudder trim before take off and try to apply graduate power.

Make sure have applied the latest updater and check her also in the hanger.

Cheerz,
Will

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PostPosted: Sat Dec 24, 2016 2:41 pm 
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Hey Thanks for the Reply.


I have tried everythinf in the arsenal. Even if I have just a little bit of power when it gets higher speed than a taxi it starts going left full brake and full right right. But it will magically dart to the opposite direction if the tail is off of the ground. That is not realistic at all. If anything it should turn even harder left due to the lack of the traction of the tailwheel is lost and there isnt enough air going over the rudder.

Dunno. Just seems funky.


I have checked all updates are on the latest update. Not sure if I am missing something on the installation dunno. And it is also the civ p51


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PostPosted: Sun Dec 25, 2016 7:19 am 
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If I am not mistaken, during rotation to a two-point attitude in a tailwheel aircraft like the Mustang, P-factor is initially and briefly reversed (with an effective shift from a high angle of attack in the three point attitude to near-zero once up on the mains), then resumes the expected left turning tendency once the mains lift off the ground and the positive angle of attack (and accompanying change in propeller blade angle relative to the relative wind) is reestablished. Granted, engine torque is going to be applying a normal left turning tendency this whole time, but during rotation the net forces rapidly and briefly change quite a bit.

The latest update did change things for me, too, but not to an unreasonable extent. I am a chicken though and rarely use anywhere near full power for takeoff in the 'Stang. ;-)

-Ian C

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PostPosted: Mon Dec 26, 2016 5:03 pm 
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Yes best step is to not use full power to test things out, and slowly increase power settings each take off until you are use to it. You can also double check updates, via removing the p51 update folder and then re-running the updater to force an update just in case. Also in the sim make sure all the settings match the manual, esp auto rudder OFF and all flight modelling full real.

thanks,
Lewis

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PostPosted: Wed Jan 11, 2017 11:29 pm 
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Ok Lewis. Ill check the updates because I have full right trim all three wheels on the ground and 20 inches manifold and im still having to sit on the roght rudder at full deflection plus full right brakes.


Ill check tomorrow and get back to you guys. I appreciate it.

I know I take a long time to reply but my internet is limited where i Live.


JDW


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PostPosted: Wed Jan 11, 2017 11:31 pm 
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Pistonpilot wrote:
If I am not mistaken, during rotation to a two-point attitude in a tailwheel aircraft like the Mustang, P-factor is initially and briefly reversed (with an effective shift from a high angle of attack in the three point attitude to near-zero once up on the mains), then resumes the expected left turning tendency once the mains lift off the ground and the positive angle of attack (and accompanying change in propeller blade angle relative to the relative wind) is reestablished. Granted, engine torque is going to be applying a normal left turning tendency this whole time, but during rotation the net forces rapidly and briefly change quite a bit.

The latest update did change things for me, too, but not to an unreasonable extent. I am a chicken though and rarely use anywhere near full power for takeoff in the 'Stang. ;-)

-Ian C



Thats interesting! I had never heard of that. Im gonna do some more research on it. Lesrn something new everyday. Thanks for the info!


Jdw


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PostPosted: Thu Jan 12, 2017 12:12 am 
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Read Dudley's post of take off again. Trim is set to 6 degrees right and this is the optimum setting for just after take off which is progressively reduced as speed is increased in the air. Trim has no effect prior to this point.
The majority of problems people experienced is because of too much power introduced too early. From a standing start on a very long runway (to remove fear of running out of runway), very slowly feed in throttle working up to 30" prior to tail lifting. Initially there will be a small swing to the right and then as speed starts to increase the swing will be to the left. Power can only be added up to the point that the rudder can overcome. Any further swing left after full rudder is applied means too much power at this point. The quickest you can get off the ground is dependant on balancing power against rudder to maintain centreline.
I just checked the other night for the other post about take off with full fuselage tank and spinning into the ground. Applying the same logic above described in Dudley's thread the acceleration will be slower and more speed will be required prior to lift off. A successful take off can accomplished at full load.
With practice the centreline can be held quite smoothly using the above method.

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PostPosted: Thu Jan 12, 2017 12:17 am 
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Pistonpilot wrote:
If I am not mistaken, during rotation to a two-point attitude in a tailwheel aircraft like the Mustang, P-factor is initially and briefly reversed (with an effective shift from a high angle of attack in the three point attitude to near-zero once up on the mains), then resumes the expected left turning tendency once the mains lift off the ground and the positive angle of attack (and accompanying change in propeller blade angle relative to the relative wind) is reestablished. Granted, engine torque is going to be applying a normal left turning tendency this whole time, but during rotation the net forces rapidly and briefly change quite a bit.

The latest update did change things for me, too, but not to an unreasonable extent. I am a chicken though and rarely use anywhere near full power for takeoff in the 'Stang. ;-)

-Ian C


The forces acting on a Mustang takeoff (all tail wheels) vary both in affected axis and intensity.
Initially from a standing start the predominant forces are slipstream against the vertical stabilizer and rudder area and P Factor due to the angular difference between the prop arc and the relative wind. These two forces are in yaw and a right rudder correction.
As the takeoff continues and the tail comes up you get gyroscopic precession 90 degrees ahead of the prop disk which adds more yaw to the right rudder correction. There is an easing of the P Factor as the prop disk aligns more evenly with the relative wind. Now as speed increases you get dynamic pressure on the ailerons. Torque has been in effect since power came up but torque is a ROLL correction requiring right aileron. As speed comes on line and you have aileron authority you begin countering torque with right aileron.
As you rotate the airplane you again get gyroscopic precession but this time it's reversed. You also reacquire P Factor during the rotation until the prop disk again aligns with the relative wind. You have slipstream forces active throughout the takeoff and into the climb. The reverse gyroscopic precession at rotation isn't a prevailing force condition as the rotation of the axis is minor and the aircraft quickly stabilizes in climb. The left turning forces prevail even through rotation.
So all added up together what you have in control corrections in a tail wheel aircraft takeoff is a combination of right rudder and right aileron applied as dynamic pressure becomes available.
It's for this reason you should NEVER raise the tail on a tail wheel airplane EARLY in the run. Just let the tail come up naturally. This is ESPECIALLY important in an extremely powerful aircraft swinging a huge prop like a Mustang!
Dudley Henriques


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PostPosted: Thu Jan 12, 2017 9:58 am 
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Dudley,

Thabks for that reply. This is what I initially thought about tailwheel aircraft. I have a tailwheel endorsement although not anywhere enough experience to really comment about it.


This is why it seems odd to me that the p-51 has so much P factor at 20 inches manifold and even weirder to me is raising the tail early and getting reversed effects on the aircraft. Its not like the 51 its getting squirly because then I would understand it.

Would you say it is realistic to have dead wind full right trim 20 inches in the manifold holding full right rudder and brake and not be able to beat the forced on the P-51?


Thanks.

JDW


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PostPosted: Thu Jan 12, 2017 10:41 am 
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Thanks for the clarification, Dudley!

-Ian C

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PostPosted: Thu Jan 12, 2017 1:22 pm 
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Rarebear wrote:
Dudley,

Thabks for that reply. This is what I initially thought about tailwheel aircraft. I have a tailwheel endorsement although not anywhere enough experience to really comment about it.


This is why it seems odd to me that the p-51 has so much P factor at 20 inches manifold and even weirder to me is raising the tail early and getting reversed effects on the aircraft. Its not like the 51 its getting squirly because then I would understand it.

Would you say it is realistic to have dead wind full right trim 20 inches in the manifold holding full right rudder and brake and not be able to beat the forced on the P-51?


Thanks.

JDW


6 degrees right trim is normal for the 51 on takeoff and this is basically a METO setting anticipating the power reduction after rotation and into the climb. Rudder is prime for all yaw correction during the run.
20 inches isn't all that much torque. If you need all that counter control I would say something isn't right.

DH


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PostPosted: Fri Jan 13, 2017 7:09 pm 
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Thabks to all the replies guys.

Lewis. I did what you said. Deleted the update folder re updated the P-51 and everything is back to normal!!!


Thabks so much!

JDW


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PostPosted: Sun Jan 15, 2017 3:00 pm 
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Awesome stuff! Happy flying

thanks,
Lewis

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