P-51 and Tip Stalls

I don't dispute anything you say. But keep this in mind: most of our language is made up of words that didn't always exist. Just because the FS text doesn't commonly use it yet does not mean it isn't a valid term for our usage. It perfectly describes what happens when the tip of one side of the wing stalls before the other side. It can happen with no aileron input at all and is usually associated with a lateral imbalance. Ever notice that if you try to induce the phenomenon at a safe altitude the plane usually drops the same wing?

As you can see below, it has become part of accepted terminology. RESISTANCE IS FUTILE! YOU WILL BE ASSIMILATED! ;^)

IMAA reference :

Aerotech: USA: members: , Magazine: Feb 1942 Aviation adds: Allison mounted amidships [as in P-39], four-blade contrarotating prop, high-taper Davis wing with modified tips to prevent tip stall. Scheduled armament: 4 cannon and 4 mgs; estimated v: 425 and range: 3,500 (the term predates many of us!)

Ed,

The last bit of your post would go a long way towards explaining the first part. If the planes were designed so that tip stalls were almost impossible, why would it be a topic of discussion?

A better way to do it is to introduce a little warp to strip ailerons so that the tip is a little higher than the root. You don't need much unless the wing is not designed or constructed straight to begin with.

Exactly Paul. That's why tip stalls are *not* a topic in full scale. It's only a topic in RC because of misunderstandings. Did I say "I'm out?"

Listen: the wing can drop without the tip stalling; all it takes is assymmetical stall pattern between the wings. Nearing the stall, the airflow over the wings near the roots is broken up and turbulwent, and this pattern works forward and outward. Some factor such as prop slipstream or a bit of yaw will aggravate the stall on one side or the other, making the stalled area bigger on that side, and the resulting lower lift on that side makes the wing drop. Simple as that. The tips may well still be operating normally. We demonstrate it all the time, and can prove it by lifting the wing with aileron, which would be imposible with the stall all the way out to the tip. Dan

I realize this isn't a flight sim newsgroup, but I frequent both and would like to inject a comment from the other to this. Just recently I bought the 3rd portion of IL-2 Forgotten Battles (called AceExpansion Pack) and installed it into IL-2 FB, and early on tried flying their P-51-D. If its flight modeling is even close to realistic to the full scale P-51-D, I'm surprised it became such a desirable fighter. Totally unlike their P-47 version in the same program, that P-51 was so stall sensitive, it whips into a spin with the least little bit of overcontrol, regardless of speed. I've had many R/C models that had tip stall tendencies, but nothing even approaching that flight sims' P-51's overall touchiness. Give that sim a try if you want to see the ultimate on this subject.

Olin McDaniel

We are not talking about controlled conditons but a catastrophic situation where ALL lift is lost on one side.

I'm "Wings" educated when it comes to the P-51 and certainly no expert.

The pilots that commented upon its handling characteristics on "Wings" indicated that the P-51 was a pleasure to fly, except when the 85 gallon fuel tank behind the pilot was full. It wanted to "swap ends" in a hurry at the slightest mistreatment.

Maybe someone that has flown one will comment, or someone with more knowledge than I on the topic (practically anyone).

Ed Cregger

:-)

Sorry Paul, *all* lift is *never* lost unless of course the AoA reaches 90°.

When applied to the wing it's called "washout" Paul :-0

Ok, get pissy about it.

I realize that. I was ONLY referring to the previous post. ;^)

;-)

So the airplane won't fall out of the sky as long as the tips are flying? What's the rest of the wing good for if the tips are the key to the whole thing?

Ever had any FS flight training? In a climbing turn stall the outside wing drops. In a level or descending turn the inside wing drops. The AOA is different between the wings in such attitudes due to the differences in helical paths. In a straight-ahead power-on stall the wing in the side of the upgoing prop blade usually drops first, if the flight is otherwise coordinated. Rotation of the prop slipstream does it, with a little torque rolled into the equation.

Such as when the wing breaks off, maybe. Does this mean that only a "catastrophic loss of lift" on one side will drop that wing? That the wings will stay level if one wing is 60% stalled and the other is only

30% stalled?

Dan

What is with you people having to be hyper-technical with everything on these boards? Just stick with the original queston. Tip stalling, as originally discussed, is not a desireable thing and is usually encountered at times when it is unrecoverable.

And since it does not exist, why are you all making such a big deal out of it? ;^)

encountered

Stalls aren't hypertechnical. They're easy enough to understand if you read the right stuff, and I'll bet there's a site somewhere on the 'net that has some animations of airflow at various AOA that make it really clear how and where the airflow breaks down. I just haven't found it yet. I have, in years past, seen videos of wind-tunnel tests, using smoke as a marker, that helped me understand it. Modelers have particularly hard time getting their minds around this stuff, as most of them haven't had the benefit of flight training. And even some of those that have had training have never been in anything worse than the "approach to a stall," which is all that is required in the US. In Canada full stall and recovery is required on the private flight test, and full spin on the commercial. The modeler has no airspeed indicator, either, and has to rely on a hot approach, or fool with various pitch attitudes and power settings to find a safe approach configuration. "Tipstall" is called "stall-spin" behavior. The wingtips are only one of many factors, and the idea that says if the tips could be kept from stalling the airplane would be OK is wrong. Sorry to harp on this, but as an instructor I strive to get my students to understand things properly so they don't go kill themselves. I only want fellow modelers to understand too, since it's to their benefit. Saves time, money and reputation if a modeler can keep his airplanes intact.

Dan

Correct..but my suggestion is only to use rudder momentarily to avoid a yaw into the turn due to adverse yaw produced by heavy application of aileron to roll out of the turn...

If

Exactly..

Yikes!

You did not mention anything about OPPOSITE AILERON! OR keeping the wing up! (until now)..

Agreed.. this would be a killer!

I understood your example to be rudder application only....

This is

Agreed...

I never feared steep turns at any altitude. Co-ordinated, and at adequate speed, they work just fine..

Dave

Build = construct, put up, erect, make, put together, manufacture, fabricate, (and the one I think you prefer) assemble. So yes, he is going to build an ARF. CH