Unbelievable side slip

[Mar]

At a (relatively) low speed and the flaps out, I hit some right rudder and the plane slipped right and did not recover. I let go of the rudder before the nose went completely into the swing. I leveled my wings best I could and touched some left rudder as I always do in flight sims to recover from these slips, but it had no effect.

 

I thought this plane had a vertical stabilizer for a reason?:huh:

 

I know there's still some work to be done on the flight characteristics, but this just seems to be way off to me...

unbelievable side slip.trk

[PeterP]

@all

when you post a track to show something particular - please tell when it happens... (Preferable in minutes...;))- so the possibility is much greater that others will watch it/see it .

 

...you have to know: there is no possibility to tell how long a track is beforehand - and hitting "fast-forward" can corrupt a track replay when it is very complex and the possibility is also very high that you jump beyond this and miss it.

 

 

For all that don't want to watch the 24 min before it happens:

 

 

IMHO: I really don't see why this is so "Unbelivable"

just look at your speed and take the flaps into consideration.

Maybe others can tell more.

Edited July 28, 2012 by PeterP

[Mar]

Sorry, I forgot to mention it was at the end of the track, and I didn't know that fast forwarding can corrupt the replay.

 

Did some more testing, and found the flaps were indeed the problem. Why though? I've never seen a plane get this sluggish just because the flaps are out.

[PeterP]

You stalled = loose of lift and control authority.

The plane slipped so hard probably because of your movement momentum.

 

And when this happened you can only hope that gravity +movement momentum+drag will point you again into the right direction.

 

I bet if you would have 30 feet more air under your belly you could have recovered.

 

:)I'm confident that others will add a much better explanations.

edit:

Don't get me wrong - I don't want to tell that this is the absolute relativistic behaviour in your track.

I just want to give a possible explanation.

 

But:

 

Don't expect a real pilot to post here and say "that's 100% realistic ! I already did this one hundred times..." :)

 

 

BTW: What the Hack did you do in the cockpit the first 10 min before even starting the plane ?! :D Can you imagine that I thought that you are sitting at home like "Dr.Evil" and laughing manic a lot while rubbing your hands... just by knowing that others watch it and that you are wasting "our" time ...?!:D

Edited July 28, 2012 by PeterP

[Mar]

I was messing with the snap views. Turns out there isn't enough of them unfortunately, so I have to keep using TIR. I also noticed some weird audio problem with the canopy opening and closing. Sometimes, but not every time the simulator runs, the canopy sound is really loud and cuts out all other sound for a few seconds after it quits.

 

That track was the first time it happened, I know I should have made another shorter track but I'm really tired and not thinking clearly. I better come back tomorrow after a good night's sleep, I should be able to discuss this more effectively then.

[PeterP]

Have also a look at this thread:

P-51D Stall Speed

 

Great post.

Our real P51 pilot agrees with you all have said - but remember - we are still tuning the flight model before final release and hope to address these problems.

Both P51 and T6 can do a snap roll but should be avoided at all costs, as they are unpredictable. In fact a T6 pilot in the UK was killed not so long ago as he ended up in a vertical dive after an inadvertent snap roll.

Only exception is that he agrees that a wheelie landing in a T6 is not a good idea, but is relatively easy in a P51.

[Mar]

Aye, thanks for the link Peter. I knew at the time that they are still working on it, I guess I just kinda jumped the gun on this one. I'll keep my big mouth shut until it's out of beta. :)

[Bucic]

End of PeterP's video. It is possible an A/C would end up in such flight attitude for short period of time. It's impossible for such aircraft to stay in such flight attitude for so long.

 

If you need more details though:

1. (simplification) The arm of aerodynamic forces of the front of the fuselage would have to be equal to the arm of the rear part. There.

2. (additionally) Propeller gyroscopic effects are out of question here as during the stabilized flight we saw on the video there are no changes to A/C attitude (angular movement).

 

Edit:

another vid

Edited August 8, 2012 by Bucic

[sobek]

Note: The track replay discussion was split off and moved to here due to being off topic.

[aaron886]

Yo-Yo, when you see this topic... are fuselage-blanking effects modeled? (Is simulated airflow to the wing disrupted/blocked by the fuselage in a sideslip?) In this movie example as posted by Bucic above (http://youtu.be/9D05ej8u-gU,) that aircraft should almost definitely have snapped into a spin.

[MaverickF22]

Yo-Yo, when you see this topic... are fuselage-blanking effects modeled? (Is simulated airflow to the wing disrupted/blocked by the fuselage in a sideslip?) In this movie example as posted by Bucic above (http://youtu.be/9D05ej8u-gU,) that aircraft should almost definitely have snapped into a spin.

 

Exactly as you've said Aaron..., that was the same thing i was trying to point to as well!

 

The roll due to beta for positive lift values isn't right in the sim! Nor for negative lift values eighter.

 

Let's all remember how the first flight in the world took place with a plane heavier than air (the Wright brothers airplane), where the aircraft was only moving a wingtip in front of the other by moving the wings in a different position around the vertical axis (XoZ) just like in a gyration movement, thus making the airflow smoother and better on the wing which was ahead/leading wing (the wing that had a negative sweep angle) and so worsening the airflow on the trailing wing which was rotated backwards (positive sweep). This effect led to a lift differential between the wings, making it roll towards the trailing wing.

 

That's how they used to roll the airplane in the first moments historical moments.

 

Our example here from the above shown track: a positive overall lift, having the left wing forward (right rudder), should produce a given amount of right rolling momentum equivalent to that positive lift level, and so the lift differential between the wings, case in which the wing which is also shadowed by the fuselage (the right wing) should have much lower lift and also be almost completely stalled due to that given airflow separation from the fuselage's wake...! So WHERE is that?

 

I've found this thing for months (perhaps almost immediately after flying the P-51 a bit and trying a lot of crazy stuff), yet i forgot to tell so far...!

 

Let's just hope ED will take a look at the P-51's aero tables cause this doesn't look good!

 

To make it simple...: At some particular alpha values (somewhere below -7 and beyond +7), the roll due to beta doesn't correspond to realistic values anymore and goes asymptotically to 0, or at least that's the case we can see in flight, only for the P-51 so far...!

 

Yes, when at low alpha angles, let's say between 0..5 degrees, there is some roll due to beta (sideslip) yet it still doesn't look quite enough to be real..., it acts like it has a very low wingspan..., as for negative values of alpha and lift..., the roll is still on the same side as the yaw? That's just the opposite of what should happen. Negative lift should give you a roll opposite to the yawing/sideslip direction in reality..., but in the sim it goes in the same direction!

 

 

With honest respect,

Mav.

Edited August 9, 2013 by MaverickF22