Why does the Ju-88 pull right on takeoff?

[SCG_Limboski]

Many of the aircraft in IL-2 realistically require significant rudder input to counteract physical forces forces of the  propeller like torque during takeoff.  For example, both the Bf-110 G2 and the BF-109 K4 have clockwise spinning props causing a  natural tendency to veer off to the left and right rudder input is required to keep the airplane centered on the runway.  However, I recently noticed that the Ju--88, despite two clockwise rotating propellers like the aircraft above, unexpectedly veers off to the RIGHT requiring a bit of left rudder to counteract,  This seems completely backwards to me. I have the rudder trim set at default or neutral according to the indicator.

 

Is this an oversight in the modelling of the Ju-88 in IL-2 or am I missing something else here? (The He-111 also does not veer off to the left despite two clockwise spinning props too.)

 

Edit:  The Ju-88 does NOT pull to the right as I originally posted.  Instead, its prop effects are very minimal compared to other planes in IL-2 and can pull hard in the direction originally pointed as the beginning of the roll.  See below for more commentary.

Edited October 19, 2020 by SCG_Limbo

[J2_Oelmann]

Tje Ju88 engines turn both into the same direction. Maybe the overall construction of the He prevents that to a certain degree. I might be wrong, but I remembering using a bit rudder for the he during take off aswell.

[Fritz_X]

What Oelmann said.

 

Plus, you basically answered the question yourself: As you wrote in your initial post, both props rotate into the same direction, causing the plane to drag to the left.

 

To eliminate the torgue on a two-engined plane, the props have to rotate into opposite directions, just like it's done with the P-38 Lightning.

[Guest deleted@50488]

I don't have IL2 installed to test now, but to the OP I should ask:

 

- are you sure you weren't taking off with a starboard wind component ?

 

Other hypothesis: The aircraft loads with too high rudder trim compensation. You could try hitting the key / button assigned to neutralize all trim settings, and see if it still has that right  / veering tendency ?

[Hanu]

Yes, it should veer to left and that is why real pilots pushed the left throttle ahead to compensate. Actually Ju-88 does veer to left if you initially center the controls and push the throttle at the same time without touching the rudder or brakes. However Ju-88 starts to twist and turn right after correcting that so I usually start my pedal-dance to keep the ball in the center and see no noticeable veering focused on either side.

 

I think that effect in Ju-88 is not the most successful one in this sim. Ju-88 would benefit a lot from another look from the developers, if they could spare the time.

[SCG_Limboski]

Thanks for the careful consideration on this issue guys.

 

I planned to make a video to prove to @Hanu that the Ju-88 does immediately start to pull right initially on takeoff but mysteriously I am unable to replicate this today.  (Argh!)  I have no idea why I had the Ju-88 pulling pretty hard right on my previous two seperate testing sessions because I was very careful to make sure my trims were neutral, had no wind, etc.

 

What I did notice in my last round of testing does confirm Hanu's general observation.  If you have neutral rudder and aileron trims and keep the rudder pedals perfectly centered the airplane initially shoots very straight down the runway followed by a very gradual pull to the left requiring a small amount of right rudder to correct.  I think the prop effect should be more pronounced for this aircraft just like you see for almost all of the other aircraft in the game (sans the He-111 variants which operate similarly to the Ju-88 and the P-38).

 

In addition, if you are initially turning to the right slightly and slam full throttle at the beginning of the takeoff, the 88 does pull very hard to the right.  It is very easy to overcorrect for this and you can start creating bad yaw oscillations where the nose wildly pulls from side to side, and this is the effect that make many people struggle to takeoff in the Ju-88 successfully.  Yes, a "pedal dance" is often needed for this plane on takeoff.

 

I agree with Hanu that the devs could revisit the flight modelling of this plane--there should be more of a torque effect and I think it is too easy to get into pilot induced yaw oscillations on this plane as a result.

 

Edit: As a side note, the Ju-88 A5 in Cliffs of Dover performs similarly on takeoff to  the one in BoX.

 

Edited October 17, 2020 by SCG_Limbo

[Blitzen]

...and then there's the Hs-129....another aircraft I haven't been able to master in takeoff ...sigh...

[AndyJWest]

I've not got time to check this in-game right now, but could the issue be down to the tailwheel not being straight when you apply power? There's no airflow over the fin/rudder when you power up, meaning that any initial turning tendency will have nothing to counteract it.

 

Pilots manuals for tailwheel-equipped aircraft frequently seem to advise taxiing directly forward at slow speed a little before starting the takeoff run, for this very reason.

Edited October 17, 2020 by AndyJWest

[SCG_Limboski]

Yes, if you do not have the tail straightened out completely then the 88 will pull pretty hard in one direction.  I thought this might be a primary culprit but I don't see how I was doing that originally.

[SCG_Limboski]

@Blitzen I had not tested the HS-129 to see what prop effects it had on takeoff.  It has two propellers that rotate in opposite directions so the effects should cancel each other out.  Despite this, the plane behaves similarly to the 88 in that it is very easy to get into pilot induced nose oscillations.

 

In general, my casual observation is that the later modelled aircraft (e.g., Bodenplatte planes) do a better job of modelling propeller effects than the earlier modelled ones in IL-2 BoX.  Does anybody agree or disagree?

[Catfish2]

I recently read two books of JU 88 deployment in WW2, and both state it tried to veer off to the left during start, though not as hard as one would have had difficulties to counter this. It was said that this happened when you lifted the rear too early. Do not remember though whether it was explained why it did that .. torque? not enough speed for rudder authority?

Edited October 18, 2020 by Catfish2

[Blackhawk_FR]

On 10/16/2020 at 11:46 PM, SCG_Limbo said:

I recently noticed that the Ju--88, despite two clockwise rotating propellers like the aircraft above, unexpectedly veers off to the RIGHT requiring a bit of left rudder to counteract, 

 

It's not the torque effect but the "spinning blast" of propellers. 

My Ju88 pull to the left, requiring rigth rudder.

[JG1_Vonrd]

I'm not in the game right now but I recall that the Ju-88 requires LEFT rudder trim in climb. This is, I believe, incorrect. Every twin that I've flown with engines rotating in the same direction as the 88 required RIGHT rudder trim in climb. I think this is the same situation for several planes in the game but maybe I'm mis-remembering and ultimately it doesn't really matter as I just trim as needed for coordinated flight...