I'm fairly new to RC, but have logged a lot of time over the past 8 mos on trainers such as the Sig Seniorita.

I read a lot about aircraft that tend to "spin" easily. Based on the posts, I've gathered that this is the airplane spinning while fairly flat (I think). And apparently, it is hard to get out of and often leads to crashes.

Can someone shed some light on exactly what a spin is, what causes them, and if you can or cannot get out of them? Can you spin a 3 channel trainer?

Thanks much.

A spin is a stall with rotation. It occurs when one wing stalls a little before the other. The way to enter one is to stall the airplane and at the moment the stall happens, apply full rudder deflection in the direction you want the rotation to occur. Airplanes with a cg near the rear limit tend to spin easily while those with the cg near or at the forward limit are difficult to spin and may not spin at all. Depending on the cg location, trainer types may be difficult to spin. The more aft the cg, the greater the tendency to spin "flat". To recover from a spin, stop the rotation with the rudder, and push the nose down, then recover to level flight.

If the airplane has ailerons, leave the ailerons in neutral for the first trials. The effect of ailerons is not very predictable, and depends on a number of factors. It may flatten the spin a little or make it steeper. The same goes for power. Normally spins are done with the engine at idle or very low power. If you use much power, you may not be able to stall the wing and no spin will occur.

Keep the elevators full up during the spin, unless you want to spin inverted, in which case move the elevators to full down, and keep them there until recovery.

Be sure to start the spin with enough altitude to allow recovery. It comes down pretty fast.

The Sig Kadet Seniorita will not spin well. The design of the plane is intended to prevent accidental spins, and to make recovery easy. Because of the wing shape, large tail surface area and the CG location, when it does spin, you have to hold the full rudder and full up elevator to get more than 1/2 rotation, and even then, its going to be a relatively wide corkscrew descent.

The Seniorita is an excellent initial trainer... but not great for learning aerobatics. (It will do some... and with practice you can fly it inverted though.)

Very good question. Very little is discussed in the R/C literature about spins, and I find most of my R/C friends know little about spins. I'm no expert of spins, but I did some spin training in full scale through an Emergency Maneuvers Training. There we learned spins mainly to get out of them or better yet avoid them. I'm sure there are lots of guy out there (mainly the fighter pilots and acrobatic pilots) who know a lot more than I do.

A good source for reading about it is in full scale training manuals. That's where I learned my stuff, but it can get quite technical. To get into a spin, as Lou W says, you must stall the plane, so you need to know what a stall is and how to avoid or recover from a stall. When rudder is applied during a stall, the plane yaws and thus one wing stalls before the other and the plane flips over and begins to descend spinning. If the stall is maintained with back elevator, the air speed remains low and the stall continues and the spinning continues.

To get out of a spin remember PARE - P= power- off A= ailerons - neutral R= rudder opposite the direction of the spin (abruptly deflect it opposite the spin to stop the rotation) and E= elevator - foreward elevator to break the stall Once the stall is broken, the plane will be pointed in a steep dive so all you have to do is allow the airspeed to increase a moment and then pull out of the dive. This is what I leaned with full scale and I practice it with my models to keep me current (I don't have a full scale acrobatic plane). What I find with models that they usually are difficult to stall with power on (they are so overpowered) and that it takes very little rudder to stop the rotation. That's why some modelers say neutralizing the controls stops the spin process.

I hope this is of help to you.

Roodester

One can spin a three channel trainer, and one can spin a two channel trainer. I regrded the Firebird XL as a trainer because that is what I have trained on. I used a spin on it to get down fast when I was so high I thought I'd loose it in the wind or range. I'd cut the motor, and turn . It would spin in less than a second, an descend rapidly. The Pull Out was opposite "turn" and then power. This is the only "aerobatic" I could do with the XL, other than porpoise through the air, and then return to straight and level flight. My grand kids thought That was cool too![img]i/expressions/face-icon-small-happy.gif[/img]

Great info. Thanks so much. I'm building an Ultimate Bipe right now, and I know these aren't as forgiving. Trying to learn all I can on the Seniorita. Thinking about installing ailerons and installing a 4 channel reciever. I'm sure it's a learning curve going from a 3 channel (only one stick, throttle on the back) to a 4 channel where the rudder is under your left thumb and doubles as the throttle. I'm assuming my right thumb won't have a lot to learn since you can technically steer the thing with only the ailerons and elevator similar to rudder and elevator. I flew a friends 4 channel once and didn't have much trouble, but steering on the ground with my left thumb was challenging.
I've learned how to install the servo in wing to make ailerons while building my biplane. I'm guessing that I use a similar setup to install elevators on the Seniorita. Anyone tried this? I'm one of those dummies who taught myself to fly (way out in unpopulated farmland) [img]i/expressions/face-icon-small-shocked.gif[/img] . I've rebuilt the seniorita a couple times as a result, so I'm not to concerned about learning the 4 channel on this one, but I REALLY don't want to crash the new biplane. This one will be flown at a "real" R/C airfield.

Thanks,

You need something else between the Seniorita and the Ultimate Bipe![img]i/expressions/face-icon-small-shocked.gif[/img]

That biplane will react MUCH faster to small control movments than the Seniorita could ever hope to maneuver at full deflection. Also, the biplanes tend to have a very high sink rate when the engine dies.

Adding the ailerons to the Seniorita isn't a bad idea. Just adding on full san strip ailerons appx 1 inch wide will make a big difference. It sill not properly prepare you for the biplane though...

Build a Four-Star or something similar for a second plane. Get used to the higher response rate of that... then you have a hope of being able to handle the biplane.

When building the biplane... get an incidence meter to set the wing angles up. a very minor deviation in wing alignment can mean a tremendous trim problem.

for what it's worth
I asked a full scale pilot from the club at the WACO museum site in Troy Ohio (8 miles from my house) how a bi-plane differed from flying a high or low wing. He said it is just as unstable as a full size bi-plane, has a lot of drag, reacts quickly to stick input. I have a Stearman PT 17 I was given (Stearling Kit) about 1984. I built it in year 2000. I still haven't flown it. It has ailerons only on bottom wings. It was a control line kit, so I think It will be a heavy flyer. Please take your time with the Bi-plane. I'm still all electric. I had to get used to 4 channel electric when a Pebble Creek Wisconsin Flyer let me fly his twin electric, with 4 channels. THRILLING!

The conversion from CL to R/C on the Stearman... use the smallest engine in the recomended range. It will be PLENTY.

The C/L planes tend to be lighter than R/C planes, and the control movements tend to be HUGE So make sure you reduce the elevator throw vs recommended for CL.

Not ALL biplanes are bad about stability... The Tiger Moth for example is just as good as a Piper Cub for use as a trainer.... maybe better. A Tiger is noted for being EASY to fly, but will show you your errors in a manner that doesn't tend to kill the pilot. Pilots trained in Tigers could move directly to a Spitfire (a notoriously touchy plane) with little to no problem. The scale models of Tiger Moths seem to have generally inherited ALL of these qualities from the full scale aircraft. (DeHaviland knew how to design GREAT aircraft.)

A quick power off stall with plenty of rudder will usually give you the spin you want. Depending on the airplane it may be gentle or dangerous. I too learned to stall and spin, or prefferably avoid a spin, in 1'=1' scale airplanes in 1941. Spin recovery is still ailerons level, elevators neutral, power off, full rudder opposite the direction of the spin. Reason - the rudder is the control surface that doesn't go into complete stall.
Spinning model aircraft still has the same entry requirements. Full stall + rudder, however, in the case of recovery there is usually a parting of the ways. Most sport models will recover into a near vertical dive without any control input. 3D airplanes need almost the same technique as full size aircraft. Obviously the need for life depends on altitude. No one ever bumped into the sky. The first spin with a model that I tried recovering using full scale techniques cost the airplane and radio. Since that time just releasing the sticks and closing the throttle has done the trick. There is always the need to avoid hi-G pullouts. Power off, gentle back pressure on the elevator will probably bring you home.
I feel so old when I talk about full scale techniques learned so long ago. Must have been good for me because I'm still alive and I don't have to have an endorsement for taildraggers.