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Old 09-16-2020, 09:35 AM   #41
freemind_fly
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Throughout the takeoff the yaw force provided by the trim set at 6 degrees will vary from zero up to the maximum force when the aircraft reaches its climb speed.
You mean when rudder effectiveness starts.
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Old 09-16-2020, 11:38 AM   #42
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A basic understanding of physics and trim tabs is required to understand what I am taking about.

A trim tab is a control surface that is deflected in order to deflect the control surface it is mounted on.

It relies on the air flowing past it to provide the force it uses to move the control surface it is mounted on.

If you deflect the trim tab to the left, air pressure on it will move the rudder to the right. Remember air pressure on the rudder is opposing this movement.

If you deflect the trim tab 6 degrees when the aircraft is parked, the rudder will not move. The same deflection at 400 mph will provide a great deal of force to deflect the rudder.

Throughout the takeoff the yaw force provided by the trim set at 6 degrees will vary from zero up to the maximum force when the aircraft reaches its climb speed. The 6 degrees of deflection is chosen so that the rudder is approximately properly trimmed when this speed is achieved. Before this speed, the pilot must do pilot stuff. He must input the appropriate rudder with his foot. This will vary as the speed and power changes throughout the takeoff.
You forgot the propwash that acts even at zero speed. And this pre-takeoff trim setting is useful either to lower right pedal force at takeoff run or it provides ready to climb configuration. After takeoff the pillot has a lot of things he has to take care of.
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Old 09-16-2020, 02:18 PM   #43
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Originally Posted by Yo-Yo View Post
You forgot the propwash that acts even at zero speed. And this pre-takeoff trim setting is useful either to lower right pedal force at takeoff run or it provides ready to climb configuration. After takeoff the pillot has a lot of things he has to take care of.
I didn't forget it.

DCS seems to have forgotten it in the prop FM, I will say. One should be able to blip the throttle and turn the aircraft without using inside brake and that isn't possible in DCS props.

However, the point is that the 6 degrees pre-takeoff trim setting is not something that is done to replace pilot manipulation of the rudder. It will reduce the force required on the rudder pedal once sufficient airflow is present but the pilot will still be required to "dance" on the rudders.

In DCS, one can forego the 6 degrees. This would be unpleasant in the real airplane because of the pedal force the pilot is required to maintain for an extended period in the climb but in DCS resting my foot on the rudder pedal is all that is required. This is a combination of no force feedback and some other things that are pointless to discuss.
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Old 09-16-2020, 06:42 PM   #44
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Originally Posted by pmiceli View Post
However, the point is that the 6 degrees pre-takeoff trim setting is not something that is done to replace pilot manipulation of the rudder. It will reduce the force required on the rudder pedal once sufficient airflow is present but the pilot will still be required to "dance" on the rudders.
So is this then why the pilot set his rudder trim 5 degrees before his taxoff? Just one less thing to worry about once airborne and climbing?
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Old 09-18-2020, 01:14 AM   #45
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Originally Posted by pmiceli View Post
I didn't forget it.

DCS seems to have forgotten it in the prop FM, I will say. One should be able to blip the throttle and turn the aircraft without using inside brake and that isn't possible in DCS props.
You mean you can’t turn without differential braking? Didn’t play for a while to remember.
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Old 09-18-2020, 07:05 AM   #46
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Originally Posted by pmiceli View Post
I didn't forget it.

DCS seems to have forgotten it in the prop FM, I will say. One should be able to blip the throttle and turn the aircraft without using inside brake and that isn't possible in DCS props.

However, the point is that the 6 degrees pre-takeoff trim setting is not something that is done to replace pilot manipulation of the rudder. It will reduce the force required on the rudder pedal once sufficient airflow is present but the pilot will still be required to "dance" on the rudders.

In DCS, one can forego the 6 degrees. This would be unpleasant in the real airplane because of the pedal force the pilot is required to maintain for an extended period in the climb but in DCS resting my foot on the rudder pedal is all that is required. This is a combination of no force feedback and some other things that are pointless to discuss.
DCS has the most complicated propwash model, by the way. You can see it easily if you are playing with controls. But I absolutely agree that 6 degree pre-trim is only to shift the neutral force point to right because all takeoff pedal dance is shifted to the right right.
And, additionally, as I said, this trim makes the plane ready to flight at low speed.
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Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me
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