chevy43

I lost another plane last night This one was a .40 size trainer with the diheadral taken out and and a K&B .65 and 4oz of lead in the tail to get it to balance.
It was a bit on the heavy side but pretty sporty. It would fly straight up as long as you wanted. It didn't float anymore like a trainer I guess due to the weight. If you got it too slow it would stall a wing tip and drop that wing quick!

Last night I was flying upsidown patterns for practice about 60' up. All was going well for a long while. I was getting ready to quit for the day and gave up elevator to half loop out of inverted and when it came around it dropped a wing tip and began to spin nose down. I gave up elevator but it didn't do much and it slamed in. I have seen it do that onece before but I was up high and it recovered.

It had the nose down and the plane was sort of wobbeling around following the nose down. Is this called a spin? Does up elevator make it worse? What is the best way to recover? I didn't seem to have any chance at 60'. It was in the ground really quick!

RCKen

My Feedback: (9)

Chevy,
Sorry to hear about that. Even though it happens to all of us it's still hard when it does happen. Anyway, from what you have said and described it sounds like you snapped it into a flat spin. The way to get out of a flat spin is different for every airplane, but usually how you will get out of them is to give the plane power, rudder opposite the spin, and sometimes down elevator. Some planes are nearly impossible to recover from a flat spin no matter what you try to do.

If it helps any, I did the same thing on an Ultra Sport 40 about a month or so ago. It was exactly as you described... inverted, pull out of inverted, roll over into a spin, and spin right into the ground. It can be a helpless feeling, especially when you don't have much altitude to make your recovery in.

Ken

chevy43

The nose was definetly down at least 45 deg and probably more. Is that still a flat spin? Is there something about comming out of inverted slowly in a half loop that would make this more likely?

I just want to know how to avoid it. I had done the same thing several times earlier with no problem but I could have been going slower the last time.

Thanks,
Treven.

skiman762

flat spins are different for different planes and it also depends on your cg
I had a stock magic 3d that would flat spin like it had a rod down through the wing the prop would chase the tail all the way down.
Pulling out of inverted flight 60 feet off the deck with up elevator is risky enough with a aerobatic plane let alone a heavy trainer type and if you snap like you did your pretty much done for theres just no room to recover when your that low it's best to roll out or try down elevator save the up elevator stunts for when you have safe altitude

Montague

It doesn't sound like a flat spin to me at all.

It does sound like either a spin or a spiral dive. More likely a spiral dive. They are slightly differnet, but you can get there in basically the same way. Spiral dives kill more models than just about anything else I've seen. The plane spirals down in a nose-down attitude at a pretty good speed, while the pilot holds up elevator and wonders why the plane doesn't pull out.

What's happening is that the wing is stalled, and holding the up elevator is keeping it stalled. The way out of it is to let go of the elevator, wait a moment, then gradually pull out.

Releasing the elevator all by itself will cause the nose to drop a little, and the rotation should stop as the angle attack of the wing goes down and the wing resumes flying. The rate of descent will increase as the rotation stops. That increase in speed is your cue that you have flying speed again, and can start the pull out, since you've transitioned in to a normal dive.

Note that if you do this too close to the ground, you're doomed, no matter what you do. Recovery takes altitude. From 60' up, you were doomed the moment the wing stalled, everything after that will just affect where the crash happens and how deep the crater is.

I've also seen guys get into a "panic" after snapping out of a maneuver with plenty of altitude. They sprial dive, then let off the elevator a little, then pull hard, and go right back in to another spiral dive. (For some reason, 99% of the time, the 2nd one rotates the opposite direction from the first. I think because the pilot is probably holding some aileron in an effort to "correct" the first spin/spiral dive, which makes things worse).

chevy43

Well I might have been 80' up but your right there was no time to recover. Sure it helps to recover when flying high but it is hard to see the plane and learn to fly. Then again it is really hard to learn to fly a bag full of balsa pieces.

I want to fly where I can stand on the edge of a cliff and learn to do stuff at eye level and have a lot of room to recover.

So is it still a flat spin with the nose down?


Oh yea, I need to have a dedicated body bag for my planes when I go to get the pieces

chevy43

Montague,

That sounds like it! It has happend to me more than once but this is the first plane I lost to it.

Thank you! Now I understand that holding up elevator just keeps it going. I wish I knew this before.

At first I didn't even know what happend and didn't know what the lesson was.

If I can just learn from each crash I at least will be knowledgable and broke intead of ignorant and broke!

Thanks again,
Treven.

2slow2matter

My Feedback: (1)

When you did the outside loop, you lost too much airspeed at the top, and your wing tip stalled--just as you said it does anytime you get too slow. It really doesn't matter what makes you go slow, if the plane has a tip stall tendency, it's going to snap on you when you get it too slow. If you used a lot of elevator (which I suspect you did), then you probably had close to zero airspeed at the top. Once in the spin, you apparently didn't have enough altitude to come out. A spin is really a type of stall condition, that is usually recoverable from, but sometimes not. To get out of it, some planes just require coming off of the control surfaces, and they will recover on their own. Some require opposite rudder and (as Ken said) down elevator. Down elevator gets the airspeed back up where the control surfaces are effective enough to fly the plane out of the spin. Some planes even require throttling down--to minimize the gyroscopic effect of the engine. Then opposite rudder, then down elevator, then reapply power as you pull out. It all depends upon the plane. This is why it's a good idea to be very high the first time you intentionally put a plane into a flat spin, so that you have time to try different techniques, should the plane not want to come out of the spin.
Anyway, yours wasn't intentional, and you were too low to do anything about it. Next time, make the loop a bit bigger so that you can keep the airspeed up all the way through the maneuver...

FWIW, I'd call what your plane did a spin. Maybe not a flat spin, but a spin none the less. It was induced by the snapping of a wing caused by too little airspeed. Some planes just don't play nice....

Montague

What is and isn't a flat spin is pretty relative, really. I'm not sure there is an offical description, but for most folks, "flat" means the plane is in a level or nearly level attitude, or just a hair nose-down, and the rate of descent should be noticeably slower than in a conventional spin.

I had a trainer that I could flat spin (CG was way way back and the control throws were really high). It would do a conventional spin with about 45 degree nose-down, and came down pretty quickly. When I popped in to a flat spin, it would be abotu 5 degrees down at the nose, and came down much much slower, while the rate of rotation went up quite a bit.

bruce88123

What Montigue was describing in post #5 is usually called a "secondary stall" and it requires discipline to do what instincts tell you is wrong. You MUST break the stall by letting the nose fall and recover so you may gently recover. Yes, you may not always have enough altitude but that is part of the game too. Trying to raise the nose simply aggravates the problem until impact. I've been guilty of this myself.

cjposada

After reading this thread, better describes what I thought was a radio malfunction (because of the non response situation), I even started a thread about this. Noe I call it LEARNING PROCESS!

This was the thread: http://www.rcuniverse.com/forum/m_4454592/tm.htm

skiman762

[quote]ORIGINAL: 2slow2matter

When you did the outside loop,

He did an inside loop from the inverted position if I read it correct he was inverted and and gave it up elevator to do a half loop out

da Rock

By his description, he was upside down and gave it up to half loop "out of inverted".

His plane would be rightside up at the bottom of that inside loop.

It would be pulling max Gs and probably had full elevator deflection. Ripe for a stall. As ripe as it's gonna get.

And when it stalled and spun, he gave it up to get out of it.

His wing was stalled and he pulled up.

yes
yes

da Rock

Chevy43,
A lot of guys get a new airplane trimmed on it's first flights to fly straight. Then they (we) spend the rest of that airplane's life trimming it to fly better and better. And one of the things we do often is to detune or de-sensitize the elevator.

A model only needs enough elevator deflection. More deflection than "enough" only puts the model at risk.

Once I got the CG pretty close to right, I work on either increasing or decreasing the elevator throw. I like to find out if it's too much by doing just what you stumbled into. Only I take her up high to do it. I do reverse immemalmans flat out. Fly inverted and PULL FULL UP. If the plane is going to highspeed stall, it'll do it for sure at the bottom of that half loop. If it does, I back the elevator throw some. When my jamming elevator won't stall it, I then try to get it to snap. If it will still snap, the elevator throw is good to go.

You want enough deflection to fly the airplane into all the manuevers. More than that and all you've got is a harder to fly airplane that is also more apt for you to lose.

BTW, do the adjustments to the airplane's rigging. Leave your computer radio at 100% settings for the servo throws. That way, the servos will be working at their advertised speed and power, not slower and weaker.

CafeenMan

If it actually happened at about 60' and the plane was over-weight it would have taken a really skilled pilot to save it.

One thing I learned the hard way is that balancing a model by putting weight at the extremes is bad news. Imagine that you're holding a 2 x 2 about 6 feet long. Hold it so it balances in your hand. From that point use your wrist to rotate it. Now try to stop it. It doesn't stop instantly does it?

now imagine that you put a pound of weight on one end and a half pound at the other. Find where it balances and rotate it with your wrist. It takes a lot more effort to get it started and to stop it. Even though it "balances" there is a lot of inertia that does bad things.

Airplanes are exactly the same. If the extremes (nose, tail, wing tips) are heavy then it will be hard to stop it from rotating once it starts.

That being said, you should always balance your model but if you have to add weight to do it then know that you're adding bad inertia.

bruce88123

Correct, this is why we always say to shift your "required" weight, Recievers & batteries & servos, before adding dead weight. It can can help you avoid adding dead weight and it's also usually closer to the CG so it has less inertia.

Montague

CafeenMan,

Yep, I agree that it sounds like the plane was doomed the moment the wing stalled, given the altitude .

Fwiw, sometimes having a lot of weight in the ends can be a lot of fun. You've never seen a plane tumble and lomchvak (sp?) until you've seen one with a lot of rotational inertia do it. . (other than that, I agree with you though. Roll response, for example, can feel a lot more locked in if the wings are kept light especially out towards the tips).

skiman762

Also at that altitude once the nose points down and your not sure what just happened there's barely time to say oh $#!+ this anit good.

chevy43

Well I figured 4 oz of lead at the tail wasn't the greatest. I really don't know how overweigtht the plane was but it was alot heavier than with just a .40 engine in it.

Since it is a trainer and has small control surfaces I just maxed them out. They went to about a 45 degree angle. I did this to give myself more control but now I see how it might have led to me stalling in this situation. I probably gave it full up elevator to do the half loop figuring I would be gaining speed going down anyway. I might have even stalled slightly before the half loop started which really would have sent the airplane down fast.

cjposada

Well... you were right you did gain lots of speed going down! Same happened to me and completely distroyed my arrow Had to shovel the engine out of the dirt.

2slow2matter

My Feedback: (1)

[quote]ORIGINAL: skiman762


Sorry,
To me an outside loop puts the canopy to the outside of the loop--with negative G forces applied to any "pilot" onboard. An inside loop puts the canopy to the inside of the loop, with positive G forces applied to any "pilot" onboard. It doesn't matter if it's a half loop out or not, it's still an outside maneuver, with negative G forces. What he really did was to give "down" elevator--which in turn (being inverted) caused the plane to rise up into the loop, but all of that is trivial in trying to help him understand what he did wrong. It was an outside loop, by all definitions--nice try, though....

skiman762

[quote]ORIGINAL: 2slow2matter


No your discriptions sound right: Well he said he gave it up elevator to me meaning pulling the stick back so either right side up or as in his case inverted it's an inside loop well half loop in this case

chevy43

I was upsidown and gave up stick giving the imaginary pilot positive G for a half loop and heading twards the ground theorectically gaining speed and avoiding a stall. Obviously I didn't avoid the stall which makes me think It might have happend just at the moment I began the half loop but it could have still happend in the half loop I guess.

skiman762

Chevy I may be confused your saying you gave up elevator ? so did the plane loop toward the ground or the sky from it's inverted position ?

ok I was too slow on the post so it was an inside loop thanks

skiman762

[quote]ORIGINAL: 2slow2matter

Sorry I still say it was an inside loop even by your definition which is correct by the way