Spiral of Death

[drummaker]

I posted in the Beginners Forum the other day.

Rockin Robbins mentioned to me that the T6 Texan I am going to build was anything but a beginners plane, and that it had a tendancy to stall and go into the Death Spiral.

I will be a much better pilot by the time I fly the Texan, but.

I watched a bunch of videos on youtube yesterday about T6 Texans, and Many of them showed the Stall then Spiral.
Most of these were high enough that they surely would have been able to recover had they done the right thing...

So.....

How DO you recover from this spiral of death?
here is a prime example
I think this guy was using too much rudder.
right?
how would he recovered? about 5:40 in

HobbyKing FunFighter AT6 Texan - RC Plane of the week (part 1)

here is one that probably didn't have enough time. But I am wondering. Would a little washout in the wing help on this?

T6 Texan Stall and Crash

This guy stalled dived and could never come out of it? What did he do wrong? 3:40 or thereabouts

E-Flite RC AT-6 Texan - Crash

ground loop: at 3:40

Fatal AT-6 Maiden Flight.wmv

[Chucksolo69]

You will never know until you are in that situation; a spiral of that type is probably unrecoverable. RR was spot on. Most ANY warbird, not just the AT6, are NOT beginner's planes. I know they look cool and all, but too many newies want to go directly to them after flying a sim a few times. It is always better to err on the side of caution and start off with some type of "beginner" type RC aircraft. Most of us did. I did, and am now enjoying flying my warbirds every chance I get. It took me almost a year, but I did it with the help of my trainer RC aircraft.

[dahawk]

First thing I do is chop the throttle if I'm high enough. Had the AT-6 JPowers mini and she was a tip staller, especially, if it was too slow in the turns. Had no rudder. In that case, I would apply power. Never got into the full death spiral mode.

[fhhuber]

Originally Posted by dahawk

First thing I do is chop the throttle if I'm high enough. Had the AT-6 JPowers mini and she was a tip staller, especially, if it was too slow in the turns. Had no rudder. In that case, I would apply power. Never got into the full death spiral mode.

I have 5 models that require power OFF to recover from a spin. The torque of the electric power system and the relatively large props just hold the planes in the spin regardless of other control inputs.

There are a few aircraft that DO NOT EVER recover from a spin. This is usually from a combination of the CG being back (for improved maneuverability) and lack of effective rudder/in area when the aircraft spins.

The F-4-U Corsair (full scale) had this issue. The Navy waived the stall/spin testing requirement for type acceptance because of the aircraft's speed and ability to survive battle damage.
Moving the CG forward will cure the issue... so RC models tend to be able to recover because of CG and "fudging" the vertical tail-surfaces oversize a bit.

************

So...

Keep CG forward a bit (25% to 30% "MAC"*) and be ready to kill power in order to recover from a spin.

If CG is far enough forward you can't keep the aircraft in a spin regardless of how hard you try. It will recover and you can force it back into a spin again though.
For some planes when the CG is that far forward they can barely take off at full throttle... if they can take off at all.

*Ajaer explains MAC better than I do (I know him from other forums)... I think he has the explanation in a doc to copy-paste.

*******

Another thing that can help with spin issues is tweaking the ailerons' centering just a bit to give wash-out (or cure wash-in). I have seen cases where one turn on each aileron clevice (you just about can't see that the aileron center is different) cured bad stall-spin characteristics.

*********

Finding what is the real issue is 90% of the problem in curing a plane of bad spin "habits".

[JetPlaneFlyer]

It's just a type of stall. All stalls are due to exceeding the critical angle of attack of the wing and there is pretty much only one way to do that, that's by applying too much up elevator.

The way to avoid the stall is not give too much up elevator and the way to recover is to get the nose down by relaxing the up elevator or adding down elevator.

[drummaker]

Originally Posted by JetPlaneFlyer

It's just a type of stall. All stalls are due to exceeding the critical angle of attack of the wing and there is pretty much only one way to do that, that's by applying too much up elevator.

The way to avoid the stall is not give too much up elevator and the way to recover is to get the nose down by relaxing the up elevator or adding down elevator.

Please note.. I am presently learning on a 3 ch foamie..I use the sim. and I have joined an RC club... The instructor tells me they have a Spectrum trainer radio, so they will be able to train me on my own J3cub.

The texan is my Next project.


anyway

so the right way to get out of this is to level the elevator build speed then re apply?

[JetPlaneFlyer]

Originally Posted by drummaker

so the right way to get out of this is to level the elevator build speed then re apply?

yes, relax the elevator (or add down elevator) and the model should stop spinning and enter a steep dive. Now gently pull out but be really careful not to pull in too much up elevator or you will cause another stall.

The problem of course is this recovery requires quite a bit of height, if you stall and drop into a spin without enough height then there really is no way out unless you have a model with so much thrust that you can haul your way out on prop thrust alone, 3D fashion.

[drummaker]

Originally Posted by JetPlaneFlyer

It's just a type of stall. All stalls are due to exceeding the critical angle of attack of the wing and there is pretty much only one way to do that, that's by applying too much up elevator.

The way to avoid the stall is not give too much up elevator and the way to recover is to get the nose down by relaxing the up elevator or adding down elevator.

Bang... I just had an epiphany,

The maximum up and down elevator and up and down aileron, etc on models are not to prevent the model from being twitchy.... it is to help prevent stalls etc.

Right?

[rreid7]

Originally Posted by drummaker

Bang... I just had an epiphany,

The maximum up and down elevator and up and down aileron, etc on models are not to prevent the model from being twitchy.... it is to help prevent stalls etc.

Right?

Not really. Elevator travel has to be pretty severely limited to prevent a stall. Then there is lack of pitch control for other phases of flight, like landing. A proper landing should be at or quite near the stall. Stalls don't need to be feared, just learned and controlled like any other maneuver.

[JetPlaneFlyer]

Originally Posted by rreid7

Not really. Elevator travel has to be pretty severely limited to prevent a stall.

yeah, I'd not usually recommend limiting elevator travel so severely that stalling was impossible, but for your first few flights it might be a good idea to set the throw quite low which along with a shade of nose heaviness does make the model a lot harder to stall by accident. Just dont go so far as make it impossible to flair for landing.

[rreid7]

Practice stalls and spins (and recovery from) on a regular basis, up high, just like any other maneuver. That way you won't be caught out as much when you get into one accidentally and near the ground. Usually just neutralizing the sticks is enough, then smoothly recover to level flight.

[pizzano]

I've only flown an electric Texan (38") twice....it was a handfull for me. The tip stall cannot be duplicated on a sim anything like real time (after many sim practices).......no matter how much you try.

Like stated above, although I did not experience a "death stall", I found out quickly, once at altitude, keeping the speed up, staying smooth and gradual on the rudder and not over-compensating (the instinctive 1st reaction) with the elevator, will prevent and smooth out most stalls not attributed to environmental conditions.

You can try to wrap your brain around the do's and dont's...but until youv'e actually experienced the heart beating/finger twitching event....you'll have trouble imagining it.........that's where a buddy pilot can be a real blessing....it'll be shame to hear about a handcrafted Texan meeting it's maker (after the first flight) face planted at his feet.

[flydiver]

Elevator (any control surface) effectiveness is dependent on speed. With limited movement you'll have limited control at slow speed. At high speed it might be just fine.
Once you are stalled you may need more movement, along with other corrective measures, to get yourself out of it.

This is a bit like riding a bike, you can't 'think' your way to success. You can prepare so action plans and fly to minimize the problem, but once you have the problem you need to have experience to deal with it effectively. As stated, practice HIGH up, maybe on a buddy box at first. Trouble with that is the instructor can't give you too much latitude for saving it or they don't have room to do so.

[Rockin Robbins]

Basically, in the real plane the procedure is like this. First, neutralize that elevator and let the plane dive. Then stop the spin with the rudder, not the aileron until you are in a non-spin dive. At that point you can apply elevator to recover level flight. That's why I said you need lots of altitude to recover.

Now I expect a model to be a crankier beast than the real thing because airflow separation from wing surfaces happens much quicker on a model. This gives you less time to react.

In practice, I suppose you could do it at 300' altitude or so to practice, but your knowledge would be of very little value, as the monster is most likely to bite at low altitude.

Most warbird pilots content themselves with prevention, keeping airspeed high, making large diameter turns and wearing a rabbit's foot while they fly.

I suppose with a powerful enough motor you could just hit the throttle, make with the elevator and grab a lot of altitude. But you would need three times as much thrust as your plane weighs, and getting that thrust would mean a low pitched prop that would restrict your flying speed too much. Probably not a doable proposition.

[BroncoSquid]

I watched the 4 videos here is my OPINION.
1st: Possibly rudder input, it is easy to try a knife edge type manuver in a turn to keep the nose up a little, but if you go the wrong way.....
It did seem that his speed was ok.
2nd: That was a dead stick landing. If you watch closely, the prop isn't turning. You basically have to dive to the ground and flare as late as possible.
3rd: Looks like a death spiral. He claims loss of control. Possibly something broke or came loose, camera man reported a rattling noise. But after a climbing spiral, a stall is likely.
4th: Sounds like alot of wind. A good crosswind could do that. Possibly had the alerions reversed, that is what happened to me in a simular situation. (Had raido set for wrong plane)

I guess you could say, don't over(or under) fly the plane. Have fun. If you are worried about crashing it before you evern start building it.....

[drummaker]

Originally Posted by BroncoSquid

I watched the 4 videos here is my OPINION.
1st: Possibly rudder input, it is easy to try a knife edge type manuver in a turn to keep the nose up a little, but if you go the wrong way.....
It did seem that his speed was ok.
2nd: That was a dead stick landing. If you watch closely, the prop isn't turning. You basically have to dive to the ground and flare as late as possible.
3rd: Looks like a death spiral. He claims loss of control. Possibly something broke or came loose, camera man reported a rattling noise. But after a climbing spiral, a stall is likely.
4th: Sounds like alot of wind. A good crosswind could do that. Possibly had the alerions reversed, that is what happened to me in a simular situation. (Had raido set for wrong plane)

I guess you could say, don't over(or under) fly the plane. Have fun. If you are worried about crashing it before you evern start building it.....

Good observations all.

On the 4th however I suspect he tried to use ailerons to react to the slight tipping of the wing and at 1st was not going fast enough.. then when he had the ailerons turned WAY to far. the speed came up and BAM

course what do I know I have never flow a plane yet

I am not worried as such. I just want to learn as much as I can before I go to far. All of these answers were enlightening. Yours maybe more so than others since you took the time to look.

Looks like after looking at your observations the reality is that these were all kind of Boneheaded mistakes.

Of course I am prone to those.

Looks like as far as the Texan is concerned. keeping up the speed is critical.

I bought Phoenix RC sim when I started this. I have some regrets now. I know that realflite has a Texan .

anyone want to make a recommendation as to what plane in Phoenix would be most similar to the Texan?

any of the war birds I suppose

[CNY_Dave]

Originally Posted by BroncoSquid

I watched the 4 videos here is my OPINION.
1st: Possibly rudder input, it is easy to try a knife edge type manuver in a turn to keep the nose up a little, but if you go the wrong way.....
It did seem that his speed was ok.
2nd: That was a dead stick landing. If you watch closely, the prop isn't turning. You basically have to dive to the ground and flare as late as possible.
3rd: Looks like a death spiral. He claims loss of control. Possibly something broke or came loose, camera man reported a rattling noise. But after a climbing spiral, a stall is likely.
4th: Sounds like alot of wind. A good crosswind could do that. Possibly had the alerions reversed, that is what happened to me in a simular situation. (Had raido set for wrong plane)

I guess you could say, don't over(or under) fly the plane. Have fun. If you are worried about crashing it before you evern start building it.....

Having a chance to watch the vids, only the 1st vid seems as though it wasn't total pilot frukruppery.

[CNY_Dave]

I have a 1970s vintage Texan that will be my next completion (it is partially built), I'll have to keep all this good news in mind.

Sounds worse than flying my WWI bipe...

[JetPlaneFlyer]

I know I keep banging on about over use op elevator but IMHO all those crashed were cause by too much back stick. Not helped by some of the planes probably being heavily loaded and having nasty stall characteristics.

• The first one he was flying quite slow and tried to do a 'bank and yank' turn and applied too much 'yank'.
• The second one he's dead stick and tried to stretch the approach with up elevator. There is no doubt at all, you can see that the elevator is full up as the plane heads toward the deck and even after impact.
• Third he pulled too much up trying to recover from the vertical dive, flick rolled it, then froze on the elevator.
• Third he yanked it off the ground with elevator while going too slow.

[drummaker]

Thanks you guys

[xmech2k]

I've seen a guy having a hard time with some balsa Texan, maybe the E-Flite. Don't know what it is about this model that gives it such a nasty bite. I always say never judge a model by it's full scale counterpart, or other models of the same plane, but in this case, I don't recall hearing about any T-6 model that's a nice gentle flier! I can say that in that 1st video, the funfighters don't even have rudder control. Looked like a classic tip stall.

CG is very important, of course, and a too far aft cg can have a hand in things like this. And like the OP mentioned, washout can certainly help. The whole idea with washout is to get the middle of the wing to stall before the wingtips, so the plane should just stall straight ahead, instead of what we saw in the videos.

Drummaker, what I do with every plane's maiden, after trimming and such, includes taking it up really high, the cut the throttle and feed in elevator to keep it flying at a constant altitude until it stalls. I do it several times sometimes. This gives you an idea of how it behaves in a stall, and a sense of how slow you can safely go. Also, start with a CG in the forward range of the specs. It's always better to have a fwd cg rather than aft. (Well, not TOO far fwd!)

Those planes really went in quick! Knock on wood, I've never had an incident like that! But then I don't have Texan.

[drummaker]

Originally Posted by xmech2k

I've seen a guy having a hard time with some balsa Texan, maybe the E-Flite. Don't know what it is about this model that gives it such a nasty bite. I always say never judge a model by it's full scale counterpart, or other models of the same plane, but in this case, I don't recall hearing about any T-6 model that's a nice gentle flier! I can say that in that 1st video, the funfighters don't even have rudder control. Looked like a classic tip stall.

CG is very important, of course, and a too far aft cg can have a hand in things like this. And like the OP mentioned, washout can certainly help. The whole idea with washout is to get the middle of the wing to stall before the wingtips, so the plane should just stall straight ahead, instead of what we saw in the videos.

Drummaker, what I do with every plane's maiden, after trimming and such, includes taking it up really high, the cut the throttle and feed in elevator to keep it flying at a constant altitude until it stalls. I do it several times sometimes. This gives you an idea of how it behaves in a stall, and a sense of how slow you can safely go. Also, start with a CG in the forward range of the specs. It's always better to have a fwd cg rather than aft. (Well, not TOO far fwd!)

Those planes really went in quick! Knock on wood, I've never had an incident like that! But then I don't have Texan.

Ya I heard about Texans, but when I saw a couple of these videos It startled me. I think the most disturbing was the one where the camera guy says I hear something rattleing, cause It just seemed like he had lot of time to pull out and it just didn't come out of it. From my very limited experience, It looked like something I didn't want to experience.

I do think that JetPlaneFlyer is right though. air speed up.. no jerking on the elevator... just not that kind of plane.

[Rockin Robbins]

Yup, a healthy dose of fear makes EVERYBODY a better pilot!

It is possible that some washout might help. Some have trimmed both ailerons slightly up at neutral to achieve the same effect. I don't know how effective that is on this particular plane.

[rcers]

Yep I agree pilot error in the vids. Airspeed is your friend.

[CNY_Dave]

Here is some excellent reading on the full-size:

http://www.airbum.com/pireps/PirepT-6.html
"The Texan stalls clean somewhere in the neighborhood of 70 mph but the addition of G and/or bank angle can run that up rapidly. I love to show students that capability by pulling a bit too hard on the top of a loop. The airplane will gently stall and do a half-snap to right side up and will continue into a spin if you wait too long to release the back pressure.
You can see the same type of stall performance in a tight turn. I have the student pull into a tight turn to the left, increasing back pressure as the speed burns off. Somewhere along the line the airplane will decide it's had enough and do a half snap to the outside (if the ball is centered) in one of the prettiest vertical reverses you've ever seen. If the ball is shoved to the outside, however, the Six will snap to the inside and you'd better have a little altitude to recover."


"
Accompanying this ability to unload when you least expect it is a definite appetite for secondary stalls. If you spin the airplane or stall in any way, you absolutely have to allow time to accelerate and not put on any G until the Six has enough speed to support flight. It's really easy to accidentally spin the airplane while dog fighting and get anxious on the recovery, causing a secondary stall and a spin in the other direction. This has killed more than a few experienced pilots who are goofing around without the obligatory cushion of extra altitude. Don't construe these stall characteristics as being bad. Yes, the T-6 will bite you but it will do so the same way every time. It's totally predictable. You get slow and pull and the Texan lets you have it right now! Those areas where the Six tends to get fiesty are those areas where light handed flying is required. A little attention to the speed/G relationship will keep you out of trouble all together. In other words, you have to learn to fly the airplane . . . which is the true test of a trainer in the first place."
...


"Every time I get ready to land a Six I can feel my mouth start to turn to dust, a trait experienced Six drivers say is good. At least I'm not over-confident (an understatement), since most of the Six's reputation for being cantankerous comes from the landing phase."






http://www.aviation-history.com/north-american/at6.html
"Someone came up with the idea of twisting the tip of the leading edge of the wing down by 2°. This brought about better stall qualities. When combined with a modified rudder and a lengthened fuselage, the problem was brought somewhat under control, although it was never solved completely. "