Warbirds and Tip Stalls

I have a World Models P-51 and on its second flight I experienced tip
stall and came down hard collapsing the retracts. I have since
repaired the gear but am now a little gun shy about flying it again.
Can anyone out there offer some suggestions on how to combat tip
stalling? I am flying on a hard runway but it is rather short at 270
feet so need to be careful on all approaches. I have heard adding
washout to the wings will help this but don't know how to do that on
an ARF wing. Suggestions there would also be helpful. Thanks
Ted
Reply to
Ted
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You could add 'washout' by setting the ailerons to sit up slightly. It's worth checking that the C of G isn't too far forward and that the wings are laterally balanced.
It may be stating the obvious to point out that you might need to fly the approach faster, or choose a windy day! CM
Reply to
CM
I will restate the obvious: A tip stall would break the nose of the airplane. Coming down hard on the gear sounds like a low speed stall and you need to come in hotter.
Those warbirds don't have much lift. Landing hot does not mean landing hard. You can come in fast but very gently and it looks like a work of art.
Reply to
M-M
Twisting washout into an ARF wing does indeed sound problematic at best. Perhaps you might do a bit of research on adding stall strips near the wing roots instead - eminently doable and at least your "tips" will be the last part that stall ;-)
Cheers
/daytripper
Reply to
daytripper
Stop thinking and blaming "tip" stall and start thinking "stall." If you stall the wing during the flare prior to touchdown mild to nasty things may happen. If the controls get sloppy to the point that you are about to lose control, add power. The key is *not* to allow the bird to stall until *you* are ready - as in a 3-point touchdown. Without getting involved in an aerodynamic discussion and the resultant intellectual flame war ;-) the solution to your problem is; 1. Practice power on and power off stalls at a safe altitude until you are familiar and comfortable with the stall characteristics of your aircraft. 2. Maintain airspeed above the stall speed until you are ready to let the bird touch down. Fly the aircraft - don't let it fly you. Control instead of react.
Reply to
Ed Forsythe
Practice, on your sim, with a 33% Cap 232. They are unsually unforgiving of sloppy landing techniques. No sim? Buy one. You'll save the cost ten times offer through the years. There are many good ones out there, but I favor the Aerofly Pro Deluxe. The Real Flight G2 and G3 has some snap happy Cap 232s Good luck!
Reply to
Ed Forsythe
" You could add 'washout' by setting the ailerons to sit up slightly. It's worth checking that the C of G isn't too far forward and that the wings are laterally balanced."
Agree 100% - For many years have heard fliers moan about tip stall with a P51 and similar models. In almost every instance have observed that the builder has eye balled the set up of the ailerons to follow the smooth flow of the top surface of the wing. When setting ailerons, suggest builder turns wing over and sighting from centre to tip, align ailerons for smooth airflow across bottom of the wing. Set model up and viewing square from behind tailplane, both ailerons should look slightly raised by 1.5 - 2.5 mm. [This suggestion was initially rebuffed but after testing was taken up and recommended by then largest UK kit mfg, especially noted with high wing trainers with semi symmetrical wings.] Double check CG, using "Vanessa" balance beam and sling method preferred, and enjoy smoother flying and landing. Much more under "Aircraft Design. Airfoils, Pull-Pull Systems, Flight Trim & Static Thrust Calculator." and "Calculators, Conversion, Center of Gravity, Electric Flight , MAC & Servo Torque calculation charts." on my web page.
Regards Alan T. Alan's Hobby Model & RC Web Links
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Reply to
A.T.
On 14 Mar 2007 10:25:29 -0700, "Ted" wrote in :
Land with more speed on the mains. Don't try to 3-point it. Coming down to stall speed makes tip stall more likely.
Use flaps if you have them. They add lift and increase drag. That should allow a slower, safer landing.
Depends on how the wing is built.
Here's a description of setting washout with a Robarts incidence meter:
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If you have a shrinkable covering, you can twist the wing very gently so that the trailing edge at the tip is about 1/4" higher than it used to be. Hold the wing in that position while re-shrinking the covering. That might do it.
If it is plastic or foam, you can attach stall strips to the inner leading edge of the wings:
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Seems to me that I remember triangle stock being recommended for stall strips. The pointy leading edge causes the air to separate from the wing causing that part of it to stall at higher speed that the rest of the wing (getting it to stall inboard is an antidote for having it stall first at the tip, you see?).
Marty -- Big-8 newsgroups: humanities.*, misc.*, news.*, rec.*, sci.*, soc.*, talk.* See
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for info on how to add or remove newsgroups.
Reply to
Martin X. Moleski, SJ
Excellent suggestion, Martin. Stall strips are easier to do than washout. The ol' T-33 had 'em. Nothing but angle iron strips attached to the leading edge of the wings at the roots. Worked for us Kaydets!
Reply to
Ed Forsythe
| Use flaps if you have them. They add lift and increase | drag. That should allow a slower, safer landing.
Don't use flaperons. They make tip stalls (if that's what is really happening) worse.
Flaps are OK (because they're inboard) but not flaperons.
Really, the key is to just stop landing so slow.
Reply to
Doug McLaren
I have this bird and it does tend to stall rather suddenly, but not really a tip stall. Mine flew into the ground on short final when the radio stopped just after the gear came down, and no the gear had its own battery pack. Others have given you some suggestions about changes you can make in the aircraft but I will be different and suggest some changes in your flying style that may help you save aircraft in the future.
The first thing you need to do is make sure your engine will suddenly take full throttle after idling for 5 minutes. If it won't idle that long, or it won't take full throttle immediately get busy and fix it. This is critical to progress.
The second thing to do is to double check the CG with the fuel tank empty.
The third thing is to get 3 or 4 mistakes high and make sure you are trimmed out straight and level. Then while at full throttle suddenly pull and hold full elevator. If the plane will not do a full loop without snapping out, keep your speed up on final until you have the runway made because you need to adjust the elevator throw or add nose weight.
Once you can get past step 3 you can go to the next step which is learning how that particular aircraft responds to various speeds and controls. Most do not do this step so you will be different in that you will learn the low speed capabilities of your aircraft and probably be able to land almost anything because of your knowledge of what a plane about to snap looks and feels like.
The fourth step is to find out how slow your plane will go before it stalls. Notice I said nothing about tip stalling. Get 3 or 4 mistakes high again and set up a race track pattern. When on upwind, bring the throttle down to 25%. Do one or two circuits of the pattern and on the third pass, reduce the throttle several clicks. The goal here is to slow the aircraft down gently while you learn how to keep it at altitude during low power settings. As you reduce the throttle you will need to hold more elevator to maintain altitude. What we want to do is to keep lowering the throttle until the plane falls out in a stall, or your throttle will not go any lower. Remember the question is how slow can you go.
The fifth step is to practice flying as slow as you can go. Once you know how slow that is, add 2 or 3 clicks of throttle back in and fly some horizontal figure 8's with the crossover point right in front of you with the aircraft coming at you. Now you are getting a 3 for one deal. You learn low speed handling, you learn right turns, and you begin to recognize the limits of control available to you at that airspeed.
When you are somewhat comfortable in step 5, drop the gear down and try step 4 and 5 again.
I think you will find that much more productive than modifying a good airframe. Of course YMMV
- Jim B
Reply to
Six_O'Clock_High
I'll second that. If your plane is going all wobbly, just don't slow down so much. If you haven't flown very many planes of this type, then you're probably just getting used to the higher stall speed. I remember doing that when I first started flying symmetrical wings. My flat bottom wing planes were so forgiving, flying right through the stall, or never really stalling at all in some cases. When I first had a Super Sportster I was convinced that it must be out of balance because it would get wobbly and start flipping around when I tried to land. I finally figured out that it was just because I was trying to land it like a Telemaster.
Fly it all the way to the ground and you'll be fine.
Reply to
Robert Reynolds
Yes, landing at too slow airspeed on these warbirds can definitely wreck your landing gear. But also check your balance as some have mentioned: if nose heavy, it will tend to drop like a rock on landing.
Sure, you don't want it tail-heavy. That condition is a bear to handle. But nose-heavy airplanes will run out of lift real fast on landing
Reply to
M-M
"Six_O'Clock_High" > an ARF wing. Suggestions there would also be helpful. Thanks
I agree with what Six_O'Clock said. And to add to that fine advise, be sure to get lots of time using the rudder in slow situations. The rudder remains effective long after the ailerons have lost lateral control and can help you keep those wings level.
Chris
Reply to
Peavey_HP_Signature_Guy
"Six_O'Clock_High" > an ARF wing. Suggestions there would also be helpful. Thanks
My friend has one of these too and with a 50SX up front he says it's possibly his nicest flying aircraft - it certainly looks great doing a high speed pass - particularly due to the retracted gear.
He's not had any problems with tip-stalling or other stalls, but he's been flying for a few years now and has learned to deal with far more unstable planes such as the Blackhorse Sukhoi .
Given the high quality of the model, I'd suggest, as others have, that you check your CG and your flying technique first.
Reply to
Poxy
They don't run out of lift sooner when nose-heavy. The elevator runs out of authority so that the AOA can't be increased enough to properly flare.
Dan
Reply to
Dan_Thomas_nospam
On 15 Mar 2007 07:54:38 -0700, Dan_Thomas snipped-for-privacy@yahoo.com wrote in :
That is a great explanation!
I've never thought of it that way before ...
Marty
Reply to
Martin X. Moleski, SJ
If there is little or no adverse yaw (or even if there is) how is that going to cause an inverted landing? Perhaps you are talking about an over the top snap on base to final turn? Possible if you get too slow and pull too hard but definitely not a common occurrence, IMHO.
Reply to
Ed Forsythe
On Thu, 15 Mar 2007 23:57:04 -0400, "Ed Forsythe" wrote in :
It was a common occurrence with me and my first Fun One.
I had it set up in such a way that it would do very surprising (to me) snap rolls when I was turning to base or final.
For a long time, I thought it was radio glitches. I couldn't understand why LEFT aileron would make the plane snap to the RIGHT (or vice-versa).
I was guilty of trying to float it in like a trainer. Things that worked great with an LT-40 were diastrous with the Fun One.
I did better with my second Fun One, but I broke it several times, too. A friend has the pieces and says he's going to rebuild it some day.
Live and learn!
Marty
Reply to
Martin X. Moleski, SJ

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