Mtthwacrss

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I have a Super Sportster I bought from my brother in law and love it, I just have one question. Last night while flying the plane I started to notice that when I was flying fast and input a lot of elevator the plane would not only pull up but also start rolling to the left like I was adding aileron. This seams only to happen when going fast and using a lot of up elevator. I have a few ideas, first I thought maybe I was not pulling straight back on the stick. I checked that out and I am sure that is not it. I did not check and see if one side of the elevator was loose which I guess could be the cause but will have to wait until tonight to check that out. If anyone out there has another idea I would be glad to hear them.

Dr1Driver

If you have one servo controlling the two elevator halves, that would be my first idea, too. You either have loose hinges or the torque rod between the elevator halves is loose in the balsa. Also, check if the elevator halves are lined up evenly. The rod may have twisted. Whenever I build a model with separate elevators, I try to run two servos, one to each half. IMO, the torque rod is a problem waiting to happen.

Good luck with it!

BMatthews

You may be pulling hard enough to get one wing to get close to the stall angle. Or if one of your ailerons is a little more sloppy than the other it may be reflexing due to the play in the pushrod or hinges or whatever. Or you may have gotten the trims crossed a little so that the ailerons are very slightly out and you are compensating with a bit of rudder trim. This would balance nicely for most flying but when you load on the G's in a pull up like this you will tend to notice the ailerons being a little out and the rudder won't be able to compensate.

Strat2003

My Feedback: (1)

If the stab is misaligned, either tilted or crooked in top view, it can cause the airplane to pull crooked. I had this condition on a Super Sportster .40 many years ago and ended up cutting the stab loose and straightening it.
That fixed the problem.

ndb8fxe

My Feedback: (1)

Sounds to me like accelerated stall. Many planes do this when yanking hard causing high G loads. This increases the stall speed and due to torque, p-factor, angled thrust, it doesn't stall straight ahead, but it falls off to one side.

Dr1Driver

Good point. In an accelerated or "high speed" stall, the plane almost immediately snap-rolls into a spin. It's quick and violent. At low altitude, recovery may be impossible.

Mtthwacrss

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Thanks. This seems to be the most likely cause as it only happened when I was at high speed, and the elevator is solid. My brother-in-law never noticed it when he flew the plane, but I have been really ripping it around. The last time it happened I was coming out of a diving spin and I almost lost the plane. I was lucky and recovered and was able to land. I guess I will just have to watch my speed at low altitude more. Thanks again.
Matt

BMatthews

It's amazing the things that can cause such a thing. A slightly heavy wing on one side or even a mis matching sanding job at shaping the leading edge. The two sides need to be pretty much identical and correctly shaped so that they perform identically. Any differences that may seem very small to a novice builder can actually be huge to the airflow.

ndb8fxe

My Feedback: (1)

Be carful. It is not the speed that is causing it to spin, but it is the elevator induced g-factor. If you can't be gentle with the elevator out of the down lines, what you need to do is limit the elevator throw. Without the elevator throw you will not be able to acheave the g-forces to cause the accelerated stall/spin.

One thing you should do is to practice the accleerated spin so you can anticipate the outcome. Get yourself to a safe altitude in straight and level flignt. Pull back on the elevator firmly and see what happenes. It should "roll or spin out of the climb the same way each time. You will get a feel for when it will happen. So just do them on purpose a bunch of time and practice the recovery and it will be second nature to recover when it happens on accident. Then, once again at a safe altitude, do the same thing while leveling out from a downline. These are the ones that will really hurt you if you are not expecting it. All in all you are just becoming more familair with the characteristics of your plane and this will make you a better pilot.

Good luck with it. I have really injoyed the sportsers I've owned in the past.

Mtthwacrss

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Well ithappened again last night and I was not going that fast. May be half speed. I was very high when it happened. I had just taken off and climbed high then pulled up harder and the plane started spinning to the left. When I landed checked out the plane again and noticed I have a slight warp in the left aileron. I am thinking may be the warp is enough to cause this. It is worse at the tip and if I remember right the further out on the wing the more it affects the flight. I will be trying to straighten it out and see how that works out.

ndb8fxe

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I don't recall the sportser having a problem with this as much as other planes, but it might be just a normal characteristic of your plane. Like I said before, the most dangerous time is when heading straight down and trying to level quickly close to the ground. No time to recover. Try to get a feel for when it will do it and you won't be supprised.

Bax

My Feedback: (11)

This is the most likely scenario. If you add "up" elevator and the model snaps, then you have an accelerated stall problem. If the model just roll, like you've added aileron, it's most likely one side of the elevator moving more than the other. You do need to check the interconnection between the elevator halves. You don't need to use two servos, as Dr1Driver said, if you have a well-made interconnection. Many times, though, the carry-through, be it wire or wood, is weak and allows the side with the control horn to move more than the other side. Sometimes, there's no connection at all because it's broken. You can get enough elevator control from one side to fly the plane, but try to do some aerobatics and you'll get a surprise.

Mtthwacrss

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Okay it is not the interconnector I have checked and it is tight. The only thing I see that might be causing it is the right aileron, which is more pronounced at the wing tip. I am going to work on that and fly it again this week end if the weather permits. The last flight I was flying slower and the plane still kind of rolled hard to the left when I pulled up hard at altitude. I will let you know how it goes this weekend if I get to fly.

da Rock

"kind of rolled hard" sounds like a high speed stall that is quite common with too much too quick elevator application when the wing isn't the same one side to the other. It's also common with tapered wings even when they're true. But straight wings will do it although they usually have to have a warp one side or such, like your warped aileron for example.