P-51 and Tip Stalls

Hi,

Stalling is loss of lift. It can happens when airspeed is too low and/or attak angle is too high. When it happens at wing tips before roots you loose also aileron control. At safe altitude you can usualy recover. Not so at 2' over track. If you add (ugly) triangle balsa pieces as you describe or slightly raise both ailerons than tip stalls is retarded but not eliminated. If you scratch build you can add some tip washout (less angle at tip than root). For an ARF check if that washout is not readily present.

Happy landings, Daniel

eliminate so

Doesn't really make sense, and it's ugly, too. Washout helps prevent tip stalls. This is angling the tip of the wing down at the leading edge. This keeps the tip flying when the root stalls. Keeping the plane above stall speed also helps. :) If you fly too slowly, and/or at too high of a AOA, ANY plane will stall. Keep the weight low, too. A lighter plane has less wing loading, and will fly more slowly before stalling that a heavier plane will.

I've never heard that the P-51 is prone to tip stalling. What makes you think you'll have a problem?

Tip stalling is when the wing tips stall before the root. Usually one side stalls first and the plane flips over...crash. This usually happens on landing approach where the AOA is too great or airspeed too small. I happens more frequently with higher wing loading.

That said, a P-51 is nore prone to tip stalling than any other model. A heavily loaded Extra or Sukhoi will do exactly the same thing.

Which ARF are you assembling? I have flown several of the EZ 40 size and they are a dream to fly with no bad habits. Some of the others which are near clones are the same.

"I'm going to build a ARF plane" ????!!! Have we come that far????

The most effective way to eliminate tip stalls (I hate that term) with any aircraft is to land at the proper airspeed.

TAS

If you could absolutely determine the airspeed of your plane, Seisy, then that will be valid. When you gonna put that pitot tube on all your planes? How about the downlink, or are you just gonna run along beside it and look at the dial?

Prior to the first landing, the "proper airspeed" for landing is totally unknown. In fact, until the first tip stall (which may be the last) it's unknown. Gotta hit the edge of the envelope to determine the limits, ya know.

Dr1

If you could absolutely determine the airspeed of your plane, Seisy, then that will be valid. When you gonna put that pitot tube on all your planes? How about the downlink, or are you just gonna run along beside it and look at the dial?

Prior to the first landing, the "proper airspeed" for landing is totally unknown. In fact, until the first tip stall (which may be the last) it's unknown. Gotta hit the edge of the envelope to determine the limits, ya know.

Dr1

Sorry DR this is one of those rare occasions when I disagree with you ;-) You don't have to "absolutely" determine the speed of your bird. Prior to any first landing you practice slow flight and power off stalls at a safe altitude. During this practice you get a good feel for your bird and also establish some visual cues that give you a fairly decent picture of the attitude (actually AoA) of the bird when it stalls. *Then* you begin shooting low approaches and go arounds. If your bird is still intact you go for your first landing and you don't attempt a full stall landing until you are thoroughly familiar with your baby. During all these shenanigans you always carry power to touchdown ad err on the high side when it comes to airspeed. Watch the pros - I have never seen a really good pilot attempt the first landing with a new bird before feeling it out at altitude. BTW, I too

*hate* the term "tip stall." Too often it is used to whine away a badly executed approach and flare. . That's my story and I'm stickin' to it! ;-0

I once saw a large very nicely built and flown P-51 pick up one wing and barrel into the ground on landing. It was going painfully slow into the wind. It seemed it had to be 'flown' onto the ground rather than harrier in. It got real wobbly before it flipped. No calm winds either.

Ed Forsythe wrote: BTW, I too

In a club I used to belong to, there was a guy named Ed Barton. He earned the nickname "Third-order" Barton. Sidenote: For those of you who remember "third order" interference, don't tell your ages. :) Anytime ANYTHING happened to his plane, the first words out of Ed's mouth were, "I got hit! Who's turned on? Yup, that's a third order combination." One day, he was dragging his Sweet Stik down the runway; about 6 feet up, and at about 1/4 throttle with a standard .40. Well, the plane got slower and slower, and the nose went higher and higher as altitude was maintained - for a while. You guessed it...sure enough, it rolled over and played dead. CRUNCH! "I was hit! Third order!" Several of us sitting under the shed almost had heart attacks from laughing so hard!

The other way around. Aileron without rudder will cause a slip, which is relatively safe. Rudder only causes a skid, which is asking for a wing drop at low speed. Flight should be coordinated to avoid slip or skid. Of course, using aileron to pick up a wing when it's dropping in a stall can often deepen the stall and make it drop faster. Depends on the airplane.

Dan

Ummmm... I respectfully disagree...

Gord's post was correct IMHO...

At too low airspeed, the AOA is necessarily high to compensate.

Applying aileron (only) in this situation, (usually recovering from the turn to final) causes an adverse yaw. This down going aileron on the wing that is already travelling slower on the inside of the turn is slowed even more by the adverse yaw, - the down aileron increases the (effective) AOA of this wing tip even more, and the inside wing tip stalls, rolling the aircraft OPPOSITE to the applied aileron command.

Soooo... the "I got hit" call is heard, - after all, it DID roll OPPOSITE to the stick movement ... right?

I believe what Gord is saying is correct. Applying aileron ONLY in this situation is a recipe for disaster, and is too often the result. Add this mishandling to a clean P-51 with tapered wings,or the eliptical wing of a Spit, and a (usually) higher wing loading of a warbird, and many end up in a pile because the pilots were never trained to fly properly.

LOTS of rudder is required in this situation, and if it skids the aircraft out of the turn, speeding up the inside wing tip (good) the aileron can be used (a bit to help) with greater safety.

One should LEAD (apply first)recovery rudder, BEFORE the aileron is moved.

Watch others fly, and observe how many fly around with their left thumb on the box, reaching the left stick only to adjust the throttle....

If this is you, please learn to use the rudder properly before you fly a critical aircraft.

Try a Cub/Citabria with barn door ailerons, you WILL learn about the rudder! :)

We played with an Aeronca Champ one day, (full size) whatta HOOT!

Shoving the stick hard to one side merely allowed you to view the direction ahead out the side window!

You have to LEAD rudder then aileron into the turn, and LEAD rudder to recover..... (with the Champ)

I was demonstrating slow flight to a friend in our 172 last week, 20 deg flap, airspeed (what we could read) was less than 40 knots, stall warning horn blaring, and doing gentle figure eights WITH THE RUDDER ONLY. Touching the ailerons would have dropped a wing instantly!

I observe 3 of 4 modellers not using the aileron and elevator correctly while taxing the aircraft in a wind.

If you are unfamiliar with the terms "dive away" or "climb into" , (the wind, while taxing) then find a pilot who does and have them show you , it can save an aircraft.

OK... rant off! :)

Gord, did I follow your thoughts correctly?

Cheers!

Dave

I agree 100%, Dave. When I flew my first Dr. 1, I had trouble keeping it straight on landings. It weathervanes terribly. I bought and installed a gyro on the rudder. It never would respond fast enough or with enough movement. After about 2 weeks, I took it off and learned to fly the rudder. To those of you who don't know how to do this, try it sometime. There's nothing prettier than a multi-wing plane sideslipping against a crosswind on final.

Dr1

Yup - Back in the days "I got hit" was the call of the dumb thumbs bird I recall using it once or twice ;-)

Absolutely keerect DR. Nothing gets their attention more than a beautifully executed slip to a perfect three pointer. Perfect way to put the bird on the numbers when you are too high on a dead stick.

Hi, Ed.

Well, since you are fessing up, I may as well too, "I got hit!"

TAS (Ed Cregger)

Coordination is the key. Whatever rudder is required to keep the airplane from skidding or slipping. Incidentally, using lots of rudder to speed up the inside wing is a SLIP, not a SKID.

That's strange. I'm an full-scale instructor, been flying 172s and

182s and 185 and Champs and Citabrias and homebuilts for years, and we teach coordinated turns in slow flight to avoid initiating a skid with rudder only and asking for that spin. Right out of the official Flight Training Manuals. We show students what happens in slow flight in a Citabria when you skid it with rudder: it spins. And a 172 is so forgiving you can pick up a dropping wing while in the stall.

I just landed a few minutes ago from a brief check flight in one of our Citabrias. Taildragger training is my specialty.

Dan

I must be missing quite a few replies/etc. Two newsgroups and neither is doing a proper job. Oh well.

I never had a problem flying Citabria/Decathlons because I always treated them as though they were very short coupled beasties that could be nasty if you let your guard down. Once that was taken into consideration, they were no more difficult to fly than anything else.

The trick to flying short coupled, conventional geared planes successfully is to anticipate the needed input before it is needed and apply a little by leading it just a little. Everything looks beautiful, proper and straight to the casual observer, which leads them to believe that it did not require a correction at all. Then when they try it - snap!

Ed Cregger