P-51 and Tip Stalls

Funny! I always plan a few stalls at altitude for every first flight of a new plane. That's how I KNOW what needs to be done for the landing. But of course, if you want to just throw the thing up there and see what happens...................................

By George Dan, I think you nailed it ;) Too much rudder = skid, too little = slip. A *little* over simplified cuz sometime you don't "step on the ball" you just release some/all rudder pressure. More of us RC types should learn that solo doesn't mean you are a pilot - it just means that the instructor thinks you know enough to get out of trouble. At least that's how it should be . Solo is the beginning of a new learning process that should last until they pry your hands off the stick .

A tip stall is a stall ( wing stops lifting) and plane yaws (rotates) and dives either to the right or left . Low wing heavily wing loaded planes such as WWII fighters tend to tip stall when taking off at too sharp of an angle for the airspeed of the plane, during that last turn before landing with insufficient airspeed, or during the final glide slope throttled back , nose up and insufficient airspeed especially when bucking a head wind. It's best to take off using right rudder as needed to counter engine torque, lift off at a shallow angle after airspeed is up and climb out at a shallow angle. When landing, keep sufficient airspeed for control, use rudder to keep wings level and land on the main gear then reduce throttle to lower the tail and then finish the roll out using the rudder to keep rolling straight.

A pilot should be using all the controls to keep wings level, not just the rudder. Using only rudder can and will induce a skid that can progress to an incipient spin (which is the proper term for the so-called bogus term "tip stall"). If he's afraid to use aileron in the approach because the down aileron might stall a wing and drop it, he's way too slow in the first place. Coordinated flight is the key here. The only time rudder-only should be used is to pick up a wing that has dropped into the incipient spin, but it also requires relaxing up-elevator to let the nose drop to unstall the thing. You don't want this to be happening near the ground.

Dan

Agreed!

Ummm.... it becomes a slip if you HOLD the rudder and not allow (or help) the low wing rise to level....initially it is a yawing rotation around the vertical axis that "speeds up" the low wing in this example.If one holds the rudder and completes a "flat" turn, (wings held leve)l, are you "skidding " around the turn? - or "slipping" around the turn? ....I gotta think about it... :)

we

Correct...Co-ordinated flight is the most important skill here... In my example, the use of the ailerons is avoided because it will drop a wing, and the rudder is gently used to turn. I was almost into the "reversed control" region of the flight envelope, WAY below what would be normal "slow flight". My instructor taught to use the rudder to keep wings level when approaching a stall, the ailerons don't work very well anyway at that speed... except to drop a wing tip.... Our 172 is the "M" model, with the larger leading edge radius..VERY difficult to spin, but will!

My friends Citabria will do as you describe, but seems to take a lot of rudder to spin from level.. takes a HARD shove of the rudder to drop a wing, but it has to be well below normal "slow flight" before the spin can be started this way.

Been a while, will try it next time up with him...

I have limited time in full size draggers, but most of my models are taildraggers....

What fun!

Dave

Hehe...

Conversation just after my 1st solo flight..... (full size)....

Instructor.. "How do you feel?

Me... "Great"

Instructor..... 'You should, 'cause you just earned the right to learn how to fly"

I never forgot that!

Dave

If you have to ask for a definition of "tip stall" the P51 may not be the plane for you. Someone has already said it but its worth repeating. Warbirds have a high wing loading and a high stall speed. I have seen a few Top Flite P51's bite the dust as a result of tip stalls caused by pulling them off prematurely i.e., before flying speed is reached or trying to float them in.They need lots of ground speed on take-off and have to be landed hot or you will be in deep doo doo. Grass fields are especially hazardous particularly if they are short. Find a nice paved runway and your chances of tip stall on takeoff are reduced. Beware of adverse yaw and be prepared to pump in right rudder since engine torque will pull the plane to the left. Correct with aileron at your peril. The Spitfire was notorious for this and if you tried to correct with aileron, you ended upside down. There are old pilots and bold pilots but no old bold pilots. Let uis know how you make out after this myriad of advice.

AFAIK, there is no definition for "tip stall." the term never crossed the lips of any pilot who learned theory before he learned to fly. A wing stalls for *one* reason and that is it's Critical Angle of Attack has been exceeded. The stall can occur at 40 kts or at Mach 2. The wing drop so many attribute to the so called tip stall can be caused by one or many factors. Check out books by Sammy Mason (Spins, Snaps, and Stalls (or something like that) or Wolfgang Langewiesche (Stick and Rudder). They are as old as hell but very good and written in language even us pilots can understand. *And* stop listening to the calls of the "I got hit," or "Tip stall" birds . Anyone like to discuss downwind turns? (troll, troll -).

Warbirds do NOT have a high wing loading unless they are built too heavily! Please don't continue to spread that myth. I don't think you would say that a Kaos or Ultrasport have a high wing loading. The GP P-51 is the same plane with a dressed up fuselage. Wing loading is nearly identical.

What is all this problem using a term that very adequately describes the phenomenon? If "tip stalling" doesn't actually happen, why is design effort expended to counteract it? Most colloquial terms don't appear in text before they are coined.

I did a Google search on "tip stall definition" and found many references to it in both model and full scale design discussion.

Ed Forsythe wrote: A wing stalls

Are you assuming that the entire wing stalls at the same time. Might not. I looked at the root area of a Mooney and it had some turbulators that caused that part to stall before the rest. So I was told. The tip has a bigger moment arm than the root so it would seem it is more sensitive.

IF the plane is stalling on landing,put it in the air and get it trimmed out.Get it down in one piece and raise both ailerons up with two turns of the aileron clevis.It worked for me.

references to

It's not a commonly-used term in the real world. It implies that the wingtip had to stall before the wing dropped, and it leads to all sorts of misunderstandings about the functions of wings and airfoils and planforms and stall behavior. Misunderstandings do not make good pilots, and wreck a lot of airplanes, both models and FS. A wing can drop if it is a little more stalled than the other wing, creating assymetrical lift. Most wings begin to stall at the trailing edge near the root, and the stall progresses forward and outward. Any uncoodinated yawing introduced during the process will upset the balance of stall patterns between the wings and deepen the stall on one side, usually the wing on the side of yaw direction. It's how we make airplanes spin, for Pete's sake. Get it near the stall break, apply left rudder, say, and the left wing will stall more and drop and autorotation begins. In most straight-ahead stalls on most modern airplanes the tips are still flying when the nose drops; older aircraft designs sometimes have more abrupt stall behavior and the stall may reach the tip, but this is the LAST place the stall happens. Models built all crooked or with the aim of violent aerobatic behavior might tend to stall at the tip, but it's undesireable and can lead to unpredictable loss of control.

rotation

Watch the ball next time you recover from a turn using just rudder. It will swing toward the low wing, and therefore you have a slip. Sloppy flying. At really low airspeeds you could cause the outside wing to drop and roll over into a spin. Been there, demonstrated that. If you can't use the ailerons to recover from a turn, you are WAY too slow. Approach speed should be around 1.3 times stall speed, and on the base leg it should be about 10 knots higher. Nowhere near aileron-reversal speeds.

Nope. Get it into a 60 MPH glide, and start skidding it around a turn using rudder and opposite aileron to keep the wing up. Keep the nose up to keep the speed down. Tighten the turn some more and the wing will flick down and there you have it. Better have lots of altitude. This is the killer turn: base-to-final, a bit low, pilot has overshot runway centerline and wants to tighten the turn but he know steep turns near the ground are bad, so he holds the wing up with aileron and tries to get it around with just rudder, holding the nose up to stretch the glide, and one more Citabria and pilot are written off.

Dan

All of this points out why I try to land a bit hot.

Why? Because try as we might to assess the airspeed of the model, there are vortices constantly parading around on the airfield. This is not the exception, it is the rule.

Get the models nose into the wrong side of a vortice (wind rotating toward the nose of the aircraft) and you have just decreased your airspeed by the airspeed of the wind in the vortice. Generally, you cannot see its effect until it is too late, if you are a bit too slow. Keep the airspeed a bit above what is necessary and you will fly right through it before you can become aware of its existence.

Ever see those little burbles that your model displays on approach? Whoot - there it is...

I try to teach my student pilots to learn how to fly their models at speed near the ground. I then teach them to do low, flat approaches, field permitting, while carrying a bit of throttle. Yes, it makes them nervous at first, that is normal. But after a while they become used to flying with full control authority and they do not fear landing as much as they did when they were attempting to land with the throttle all the way back and the nose pointed downward, praying and hoping that the wind would not upset their approach. You make your own luck in this hobby.

Ed Cregger

Well, then the several hundred examples I found on one search for the term must represent all the people not in the real world! Some of those even in full scale tutorials.

Not everything on the 'net is authoritative. In my 32 years of FS aviation we have never come across the term. It might exist in the complex world of aircraft design, but never reaches those of us who teach flying or maintain airplanes. "Tipstall" will certainly be used on model sites, but that's folklore, not formal education. In any reputable text it might be referring to a very undesireable behavior caused by deficiencies in the tip profile, or a deliberately designed-in function for some experimental reason, but it's not going to be something any properly built airplane should exhibit.

See

It talks about stall behavior, and the loss of roll control as the stall progresses, but the term "tipstall" isn't used. It's an excellent site with a lot of good stuff.

Dan

Hi Jim, Nope, I am *not* assuming that the entire wing will stall at the same time but introducing another complexity into this discussion would not be productive . You're right (of course) about the Mooney and any other GA aircraft - AFAIK, they are all designed so that the stall begins at the root and progresses to the tip.The bottom line remains that when *any* part of a wing exceeds it's critical AoA it stalls (that part) - period. In over 3000 hours of flying (not much by airline standards ) I have never heard any pilot, instructor, accident investigator, or aero engineer refer to a "tip" stall. Ever heard an instructor tell a student he was going to demonstrate tip stalls? I don't think so. That figure 9 that happens when you honk a bird off on TO or when you get too slow on final is the result of a *stall*. When the wing stalls, torque, P-factor, gyroscopic precession, spiral slip stream, uneven weight distribution, the way you hold your mouth, etc., all conspire to roll/yaw the bird to the left (assuming clockwise rotation engine). BTW, I don't think that any civil aircraft would ever get past the FAA certification process (unless perhaps it was experimental) if it exhibited a tendency to stall at the wingtips first. That's still my story and I'm still stickin' to it ;-)) I'm out!

I could be wrong, but to me, this would be like using flaps in the wrong sense and reduce the lift properties of the wing thus needing a higher speed to keep airborne.

I don't understand how this alteration to the aileron "neutral" position would prevent a low speed stall.

I agree with Ed about keeping some speed on during landing to maintain control authority - it was standard practice to increase speed during the landing approach in full size gliders after the "airbrakes" were deployed when I was being taught many years ago.

I'm ready to be "shot down" by those who DO know.

Malcolm