Auto-Rudder and Take-Off Assist Issue

[Flatch]

I have noticed that the Spitfire will not roll down the runway straight with Auto-Rudder and Take-Off Assistance set to 100%  If I have the same settings on the P-47 or P-51 or TF-51 they will go straight down the runway until take-off.  The Spitfire will veer off to the left of the runway as soon as it starts rolling.  From an external view I see the rudder wiggling from side to side, but not making a strong enough correction.   I notice that it will veer to the left even if you only have the throttle set just above idle, around 1,200 RPM and no boost.  The mission I am running is the Caucus Region Take-Off.

 

I can provide a track of this if needed.  I am running the 2.7 Open Beta with the Game Mode Flight Model Enabled.  I am a very new player and my old rudder pedals broke so I am forced to this option until my new pedals arrive.  Is there something I am overlooking on the Spit?  It was the first module that I bought and I am extremely found of it, once I am in the air.  I am very curious why my other Warbirds will perform acceptable on take-off and the Spit does not.

[Terry Dactil]

I suggest you turn off auto-rudder and take-off assistance so you get only the effects of your control inputs.

You will quickly learn that you need to apply some right rudder and a smidgin of right aileron to counteract the torque and p-effect to get a straight and stable take-off run.

It is quite easy once you get the idea, but it is a lot harder if you have "assistance" banging the rudder about.

The Spitfire is an aircraft that generally responds best to small and precise control inputs.

 Check this forum for advice on control setup as the default values are way too savage.

[Art-J]

Also, check what happens with game flight mode disabled. This feature is quite glitchy and poorly supported anyway (devs are even considering removing it in future versions because it seems to be causing more harm than good).

[Yo-Yo]

19 hours ago, Jimmer said:

I have noticed that the Spitfire will not roll down the runway straight with Auto-Rudder and Take-Off Assistance set to 100%  If I have the same settings on the P-47 or P-51 or TF-51 they will go straight down the runway until take-off.  The Spitfire will veer off to the left of the runway as soon as it starts rolling.  From an external view I see the rudder wiggling from side to side, but not making a strong enough correction.   I notice that it will veer to the left even if you only have the throttle set just above idle, around 1,200 RPM and no boost.  The mission I am running is the Caucus Region Take-Off.

 

I can provide a track of this if needed.  I am running the 2.7 Open Beta with the Game Mode Flight Model Enabled.  I am a very new player and my old rudder pedals broke so I am forced to this option until my new pedals arrive.  Is there something I am overlooking on the Spit?  It was the first module that I bought and I am extremely found of it, once I am in the air.  I am very curious why my other Warbirds will perform acceptable on take-off and the Spit does not.

TO assistant like auto-rudder do not maintain straight path but rather eliminate side accelerations requiring fast reaction. Anyway, they have limited authority and the player under some circumstances has to help applying, for example, steady and slow right rudder input at the start of takeoff run to correct the path.
By the way, the authority of the rudder (and, thus, of TO assistant) depends on how fast you apply power and what MP it is. To start takeoff run in Spitfire you need to apply not more than 12 lb in 1-2-3 count. and it is the best way.
Gradual power is great for the planes with the locked tailwheel and, especially, for steerable tailwheel.

 

[Flatch]

Yo-Yo,

 

I understand.  But with the Spitfire I can set at the end of the runway, set the RPM to 1200 and the Boost at 0 psig and it will veer to the left and the TO Assist cannot keep up even with that small amount of movement.  Whereas with the P-51 and P-47 I can go to military power with the 1, 2, 3, count and it will stay on the runway.  Can you duplicate this or am I doing something wrong?  Fortunately my new rudder pedals should arrive by Monday.

 

Thanks,

 

Jimmer

[grafspee]

Spitfire case is a bit different,  Spitfire does not have lockable tail wheel, so taxing is asisted with differential braking. Taxing = any low power setting.

Take off  assist is influencing only rudder inputs, so when you set 1200rpm in spitfire you re in taxing mode let say, so you need to use differential braking to keep this plane rolling straight.

If not plane will drift off the straight line.

In order to utilize spitfire take off assist, you need to set higher power setting something like +8lbs or higher, so rudder inputs due to sufficient prop wash  will be enough to keep plane straight.

Planes with lockable tail wheel will roll straight at very low rpm w/o need of using differential braking, like p-51 p-47 bf109 or fw190, spitfire is just unique in that regard.

Edited June 10, 2021 by grafspee

[Yo-Yo]

11 hours ago, Jimmer said:

Yo-Yo,

 

I understand.  But with the Spitfire I can set at the end of the runway, set the RPM to 1200 and the Boost at 0 psig and it will veer to the left and the TO Assist cannot keep up even with that small amount of movement.  Whereas with the P-51 and P-47 I can go to military power with the 1, 2, 3, count and it will stay on the runway.  Can you duplicate this or am I doing something wrong?  Fortunately my new rudder pedals should arrive by Monday.

 

Thanks,

 

Jimmer

1200 rpm and zero boost??? At the start? It is the best direct way to veer left.

 

9 hours ago, grafspee said:

Spitfire case is a bit different,  Spitfire does not have lockable tail wheel, so taxing is asisted with differential braking. Taxing = any low power setting.

Take off  assist is influencing only rudder inputs, so when you set 1200rpm in spitfire you re in taxing mode let say, so you need to use differential braking to keep this plane rolling straight.

If not plane will drift off the straight line.

In order to utilize spitfire take off assist, you need to set higher power setting something like +8lbs or higher, so rudder inputs due to sufficient prop wash  will be enough to keep plane straight.

Planes with lockable tail wheel will roll straight at very low rpm w/o need of using differential braking, like p-51 p-47 bf109 or fw190, spitfire is just unique in that regard.

 

Take a look: 1200 rpm and ZERO BOOST. It's absolutely overloaded prop giving too much whirled propwash.

[grafspee]

I forgot one thing, don't forget to set full right rudder trim before take off. Helps a lot.

Edited June 11, 2021 by grafspee

[grafspee]

54 minutes ago, Yo-Yo said:

Take a look: 1200 rpm and ZERO BOOST. It's absolutely overloaded prop giving too much whirled propwash.

Yes, 0 boost and 1200rpm definitely something wrong here. 0 boost = 30 inch it should generate at least 2000rpm.

[Flatch]

Actually I did not check my boost gauge, I know that if I open the throttle enough to start the Spit rolling down the runway.  The same things happens with Auto Rudder set to off and TO Assistance set at 0%.   It is nice to see that someone else has duplicated what I am seeing.   The good news is my rudder pedals arrived early!  Still it is something to look at.

[Flatch]

I did repeat the experiment and watched more closely.  With Auto Rudder on and TO Assistance at 100% I can tap the throttle up until the Spit just starts to roll.  RPM is still at 1,000 and Boost is at 0 PSIG.   She will then roll off the runway to the left.  Very disturbing.  I think the Spit is overly sensitive to Torque Steer.  I had heard stories about the real P-51 having a lot of torque steer and even being able to flip on the runway if the throttle was shoved all the way forward instantly.   I didn't know the Spitfire was as bad as the P-51.  In either case I think the model needs a little tweak.

[DD_Fenrir]

19 minutes ago, Jimmer said:

I had heard stories about the real P-51 having a lot of torque steer and even being able to flip on the runway if the throttle was shoved all the way forward instantly.   I didn't know the Spitfire was as bad as the P-51.  In either case I think the model needs a little tweak.

 

Same horsepower + 2000lb lighter aeroplane.... of course she'll torque steer/roll with sudden power application, even more so than the Mustang.

[grafspee]

1 hour ago, Jimmer said:

I did repeat the experiment and watched more closely.  With Auto Rudder on and TO Assistance at 100% I can tap the throttle up until the Spit just starts to roll.  RPM is still at 1,000 and Boost is at 0 PSIG.   She will then roll off the runway to the left.  Very disturbing.  I think the Spit is overly sensitive to Torque Steer.  I had heard stories about the real P-51 having a lot of torque steer and even being able to flip on the runway if the throttle was shoved all the way forward instantly.   I didn't know the Spitfire was as bad as the P-51.  In either case I think the model needs a little tweak.

I don't know how exactly TO assistance work and when is triggered, Auto rudder is something like anti skid system.

For me take off assistance is what it is just helps assists take off run, it will not keep plane straight no matter what. 

Model don't need to be tweak imho, if anything should be tweaked is take off assistance in case of spitfire.

Anyway torque has very small effect in case you are describing.

When plane is stationary if you apply power only thing is that left landing gear is pushed a bit more then right in to the ground.

Main left tendency comes from asymmetric thrust, reason is that prop is at angle to the motion of the plane, so descending blade has higher angle of attack then ascending so it  produce more thrust. Rudder effectives comes in above certain rpm, it is expected that at very low rpm range plane could not be controlled by rudder alone, especially when tail wheel is free castering. 

In dcs you have to use rudder (even with rudder assign to keyboard is sufficient to take off or land ), there is no other way, if you unlock tail in P-51 or Bf109 or FW190 take off assistance will fail as in spitfire case.

It is just  Spitfire things.

This torque feels almost as mystical force responsible for all flying characteristics of planes,  there are 4 of the factors contributory to left tendencies .

1. P-factor (asymmetric thrust)

2. spiral slipstream

3. torque

4. gyroscopic precession 

 

Edited June 11, 2021 by grafspee

[VH-Rock]

1 hour ago, Jimmer said:

I had heard stories about the real P-51 having a lot of torque steer and even being able to flip on the runway if the throttle was shoved all the way forward instantly.   I didn't know the Spitfire was as bad as the P-51.  In either case I think the model needs a little tweak.

 

I would expect the Spitfire to be significantly worse than the P-51. Same power, much lighter airframe, narrower gear, smaller rudder and a none steerable tailwheel... You have to be on the ball with the Spitfire. Like the others say, turn the assists off and learn the aeroplane It's a very rewarding aircraft to handle in the circuit when you get used to it. Even if you don't have pedals, it's more than possible to take-off & land with keyboard inputs. 

[Flatch]

Thank you all for the explanations.  I especially like Grafspree's explanation of the reason for asymmetric thrust.  I was not aware of that.  Since I received my new rudder pedals last night I have turned off TO assistance on all planes and I am learning to dance on the rudder pedals and toe brakes during the take off run.  I gain more respect for the pilots of these aircraft from so long ago.

[Terry Dactil]

The big attraction to me is the realism of DCS.

Just learn to fly the aircraft like the real pilot has to.

That's the way to go.

Well done!