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Trimming the P51


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In the real airplane, that 6 degrees is supposed to give you a properly trimmed rudder during the initial climb. It is in no way meant to provide adequate rudder deflection during takeoff.

 

In the DCS P-51 the 6 degrees is unnecessary and most probably counterproductive. A half toe of rudder is all you need once above 100 mph.

 

5 or 6 degree rudder lifts a lot of work from pilot during take off it is said in p-51 manual somewhere.

It is canceling majority of prop/engine left tendency, another factor is angle of incidence of vertical stabilizer which helps as well.

Similar in spitfire with full right rudder trim you have almost no work in rudder department during take off.


Edited by grafspee

System specs: I7 14700KF, Gigabyte Z690 Aorus Elite, 64GB DDR4 3600MHz, Gigabyte RTX 4090,Win 11, 48" OLED LG TV + 42" LG LED monitor

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5 or 6 degree rudder lifts a lot of work from pilot during take off it is said in p-51 manual somewhere.

It is canceling majority of prop/engine left tendency, another factor is angle of incidence of vertical stabilizer which helps as well.

Similar in spitfire with full right rudder trim you have almost no work in rudder department during take off.

 

Not really. And I got that straight from someone actually flying real P-51's currently. Its a post takeoff climb setting.

 

In DCS, P-51 rudder trim is completely unnecessary unless you are racing. I don't even have it mapped.

 

 

 

 

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Not really. And I got that straight from someone actually flying real P-51's currently. Its a post takeoff climb setting.

 

In DCS, P-51 rudder trim is completely unnecessary unless you are racing. I don't even have it mapped.

 

 

If you would, check out what he does/says at 3:56.

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If you would, check out what he does/says at 3:56.

 

I never said that moving the trim to 6 degrees didn’t happen during the pre-start check.

 

In the real airplane, that 6 degrees is supposed to give you a properly trimmed rudder during the initial climb. It is in no way meant to provide adequate rudder deflection during takeoff.

 

In the DCS P-51 the 6 degrees is unnecessary and most probably counterproductive. A half toe of rudder is all you need once above 100 mph.

 

 

 

 

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In the real airplane, that 6 degrees is supposed to give you a properly trimmed rudder during the initial climb. It is in no way meant to provide adequate rudder deflection during takeoff.

 

Eh, well you kind of did in a more eloquent way. What's interesting is during his part 3 (flight) he adjusts rudder trim several times.

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In the real airplane, that 6 degrees is supposed to give you a properly trimmed rudder during the initial climb. It is in no way meant to provide adequate rudder deflection during takeoff.

 

Why would the real P51 pilot then trim his aircraft 5 degrees BEFORE takeoff and keep it there until after he's airborne then? This would tell me that it absolutely is a means to provide adequate rudder deflection...:book:

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Why would the real P51 pilot then trim his aircraft 5 degrees BEFORE takeoff and keep it there until after he's airborne then? This would tell me that it absolutely is a means to provide adequate rudder deflection...:book:

 

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.

 

 

 

 

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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.

 

Very good, so given all that you just explained, again, why setting rudder trim at 5 degrees before takeoff and not wait until you reach a speed that would require you to make those adjustments? I'm not understanding why I see a pilot do that before he even leaves the ground and you mentioning how it's unnecessary..

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In the real airplane, absolutely.

 

DCS P-51 rudder trim is unnecessary.

 

In game as well, if you want to put any inputs like flying hands off :)

So answer is, you need elevator and rudder trim for hands off flying in DCS as well as in real life.

With constant needs of change.

This was an issue of OP.

No matter what hardware are you using, this plane require lots of trimming.

Flying this plane w/o constant trimming in DCS is against real life.But this is a game everyone fly in the way as he likes.


Edited by grafspee

System specs: I7 14700KF, Gigabyte Z690 Aorus Elite, 64GB DDR4 3600MHz, Gigabyte RTX 4090,Win 11, 48" OLED LG TV + 42" LG LED monitor

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A basic understanding of physics and trim tabs is required to understand what I am taking about.

 

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.

 

I would disagree with that, elevator and rudder trim tabs are effecting control surfaces from very begging of takeoff, as soon as power is applied ruder and elevator trimming system is affecting control surfaces, it is increasing with airspeed.

But there is no magic speed like 100 mph at which trim system starts to work, at 90 mph rudder will be deflected too.


Edited by grafspee

System specs: I7 14700KF, Gigabyte Z690 Aorus Elite, 64GB DDR4 3600MHz, Gigabyte RTX 4090,Win 11, 48" OLED LG TV + 42" LG LED monitor

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Pimicelli is right in principle - though perhaps would be better to rudder trim is useless in all sims not just DCS. This is because we have no air load that can be transmitted through our rudder pedals.

 

The most important thing to understand is that rudder trim has absolutely no effect on the total amount of rudder authority; this is restricted by the size, shape and limits of travel of the rudder. Trim cannot increase this.

 

Trim simply allows you to set a dynamic 0 foot force position for making flight comfortable or in the case of take-off, easing foot load and allowing better control.

 

As such, unless you own force feedback pedals, use of rudder trim would not be that beneficial.

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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.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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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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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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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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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.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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