GENTLEMEN, I WOULD LIKE TO KNOW IF ANYONE CAN EITHER VERIFY, OR DISCLAIM, THAT TOO MUCH ELEVATOR, CAN CAUSE A PLANE TO "SNAP ROLL" IN A HARD LOOP? I HAVE HAD AN ONGOING ARGUMENT WITH A FRIEND...I SAY THAT TOO MUCH ELEVATOR CAN CAUSE A PLANE TO "SNAP ROLL" AT THE TOP OF A LOOP,BECAUSE OF HIGH SPEED ELEVATOR STALL,... HE SAYS, THAT IT IS SOMETHING ELSE, LIKE, LATERAL BALANCE WILL CAUSE IT TO ROLL....YOUR THOUGHTS? THANKS, pAUL

Why are you shouting at us?

Too much elevator will cause a model to stall at any speed or attitude. What is happening is that the tail is generating enough lift (downforce) to move the wing to a high enough angle of attack that it will stall. The higher the wingloading, the more abrupt the stall will typically be. This type of stall is rarely symmetrical, so the aircraft will roll to one side or the other. The problem can be exacerbated by warps in the wing or tail.

I was at Morro Bay on Sunday... I had a very nice time there. I didn't see any models flying though.

You are both right
Too much elevator can snap a plane...
bad lateral balance can cause a plane to fall out of a loop too

(caps lock is considered yelling)

It doesn't just happen at the top of a loop. It can easily happen at any point in a loop or steeply banked turn if you have enough elevator travel and the balance point is such that there's enough control to force the wing to the stall point. It can happen at slow or high speeds depending on how the model reacts.

I had a model that would do the first loop fine with full elevator and after that it slowed down but the loop tightened up. At tlat point the model was "hiccuping" around the loops unless I opened it up by easing off the elevator.

Racing models sometimes need to be tuned for elevator throw to avoid pulling too much in the near vertical banked turn and having the wing stall and snap the model out of the turn.

Gentlemen, i thank you for you're input! And Tall Paul, Sorry about the cap lock capitols! Didn't mean to sound like i was shouting, but it certainly comes across that way, my mistake! Paul

Davidfee, glad you came to morro bay, our flying field is about 5 miles south of morro bay, near Questa college. thanks Paul

Some 3D type models with the oversized elevators and light wing loading will NOT have the snapping problem.

While you can stall the wing and get a snap in a loop or steep turn if the elevator travel's too much, you're not getting actual elevator stall. If the horizontal surface stalls, the model will pitch towards the belly. With a conventional setup, the center of lift is aft of the center of gravity, so the horizontal stabilizer makes a down force to counteract the nose-down pitching force that results. If the tailplane stalls, then there's no more downforce, and the airplane will pitch nose down.

Early Cessna 177 Cardinals had problems with stabilator stalls. On landing, the pilot would have the airplane nose high just above the runway trying to get a good, low-speed full-stall landing. At a certain point, the angle of attack of the stabilator would reach the stall angle and the airplane would sharply pitch down. This usually resulted in a damaged nose gear assembly and a bent firewall. Until Cessna cured the problem by adding a slot to the stabilator, landing speeds were restricted to keeping the aircraft above the speed where the stabilator would stall.

With almost all airplanes, though, it's very difficult, it at all possible, to get the horizontal stabilizer to stall.

How would you know if the wing is stalling first, or the elevator? I maidened a H9 1/4 scale CAP 232 last weekend. First inverted loop I tried, it snapped unexpectedly on me about 3/4s of the way through the loop. Scared the hell out of me as it was very quick and violent. I was being quite gentle on the elevator input, and compared to other large planes I've flown, I didn't think I was yanking it very hard. I strongly dislike having a plane unpredictable and unpleasant to fly. I'll move the C of G forward and play with reducing the control throw, but I sure don't like what I'm seeing here. There's a CAP 232 thread on the giant scale - I'll see if I can dig it up ans seek advice there too...

I have at 33% H9 Cap,
at high speeds and full elevator, it will snap roll out of the loop.

At slower speeds and full elevator, it will do really tight loops around the center of the nose of the plane. I have to goose the throttle at the right times to get it to rotate properly.

Guy’s, back a few years ago when Scale combat was hot here in NY I was flying it every chance I could. It gave me a real time chance to try a lot of the maneuvers I’ve always read about and seen performed with only one plane in the air. Well with 6 in the air and all looking to do you it puts a whole new light on maneuvers. We wanted the max elevator and aileron we could handle, while aileron was easy, elevator proved to be quite the illusive little bugger. We would start the elevator throw at double the manufacturers recommendation Then do the loop test if it snapped out reduce the throw and try again until it stopped snapping out. Once this point was found we noted it in the flight log and moved the movement down another 10 points. This usually left us at 150 to 170% of manufacturers suggested travel.

I personally had seven planes that failed the loop test initially two of which never flew the same again after failing it. So the point is be careful you do not bust your plane ding these snaps as they are very stressful for the airframe/wing. The first on stopped spinning as soon as I let up on the elevator, I aileroned it back to level made a descending turn to bring the plane in front of us at a good clip then gave just a smig of elevator to level off and it snapped. While I was able to stop the spinning by letting up on the elevator the closure angle with the ground had increase. I throttled back (not that I expected it to help) and tried elevator again. It rolled inverted as it hit the runway. Two years later I had another one that snapped out of a loop by the time I got it back to straight and level it was getting out there (for a 47in wing span plane) so I decided to do a split –s. The role inverted was uneventful but as soon as I hit the elevator it began to spin when I let up on the elevator it stopped. I rolled her back around with the throttle at 1/3 to ½ and she spun again with elevator. So quickly before she hit the ground I tried to get it into a flat spin and it went in off the runway in the tall grass.

The cowling was a total loss but nothing else was damaged. I took it home and looked it over for something that was out of place / different / broken and found nothing. The next time out the aileron and elevator trim settings had changed (6clicks of A and two of E) so I figured the mass of servos in the wing for the ailerons has twisted the main spar. I also had noticed that the tank was empty after the first crash so I wanted to see if the aft CG had anything to do with it so I figured I’ld run it to about five minutes at ½ throttle then land. Well just after the two minutes left beep I was making a gentile turn and 30 to 60 degrees of bank at less than ½ throttle and it snapped again. I stopped the spin and got it headed back to the field, with another expert right there with me who suggested going to full throttle (because we already know that less does not work, so I went to full throttle let it run on that line as long as possible before I had to start adding elevator. You guessed it, upon adding the elevator it snapped and went in. Having already used up my luck on this plane this time it strained through the trees.

So what do you think happened? I’ll bet the mass of servos out on the wing for the ailerons twisted the wing in the first loop test. Two ounce servos in each wing of a 38 oz airplane.

Joe

I cannot add any deep thoughts other than we call Caps 21 , 232, whatevers. SNAP 21's, 232, etc.

I have a WM 232 Cap and it too has a snap hiding inside. Go too slow or downwind, don't have the wing level and pull hard up it rolls the other way like I had commanded it.

Try to do the same loop the same way into the wind nice and easy till you can determne if it always goes to the same side or not.

If so then you maybe able to adjust the eleavators halfs or add a little tip weight to the opposite side and try again.

Try tapeing large coins to the underside of the wing at the tip. I use 2 quarters on the left wing tip of the red plane you see in my avator

I'm flying a GP YAK 55 3D right now.. full flying stabilizer.
At 50% travel, (about 45 degrees) with 50% expo, it "notches" around loops.. ministalls a lot like you see with a plank wing.