Gian Paulo

I recently bought a new fuselage for my SIG Somethin' Extra and I'm having this small problem: in order to keep the plane going in a straight line I need to trim the elevator up just a little bit, not much just a bit. If I don't the plane goes down.
Is this a CG problem? if so, is it nose heavy or tail heavy?

Thanks,

P-51B

My Feedback: (5)

Could be a couple of things. A few that come to mind:

-slightly nose heavy (you checked the balance though...right?)

-incidence on the wing or horizontal stabilizer is slightly off.

-a touch to much down thrust on the engine.

Gian Paulo

Thanks for your reply,
I checked the balance and it was a bit nose heavy, would that cause the problem I'm describing?.

I checked the incidence on the wing and horizontal stabilizer and they seem fine.
What is down thrust on the engine?, I don't think this could be it cause the problem happens even if the engine stops.

TailDraggin

My Feedback: (5)

It is not unusual at all for a plane to need slight trim on any control surface, including elevator.
There are many factors involved, including throttle setting, prop selection, incidence, engine thrust line and so on.
If it's just "a little bit" as you say, then it shouldn't be a problem.

Gian Paulo

Thanks again,
Do you think I could fix this problem by taking some weight of the front of the plane?...

My question is: will a slightly nose heavy plane need a bit of elevator up to keep a straight line?...

One more question... The guy who build this plane set up the engine pointing a bit to the right of the plane, he told me that is the way it should go, could anyone explain this to me?

MinnFlyer

My Feedback: (4)

The right thrust in the engine is there to counteract torque. So, yes, it should be there.

As far as removing nose weight goes, I would say take the plane up high, and try doing a spin. If the plane spins nicely, I wouldn't worry about the nose weight, but if it just sort of "Spirals" down, then yes, it probably is a little nose heavy.

Gian Paulo

Thanks MinnFlyer... I did all sort of maneuvers with my plane this last wekend and it performs great. I even landed on the beach on a 25 degree angle landing area with some wind coming from the side!.
As far as a spin, please excuse my ignorance, I don't know what it is... I do rolls, loops... but don't know about spins.

Live Wire

Did you balance plane with or without fuel? if with out fuel it will be nose heavy, which is normal trim should take care of it as you burn fuel it will go back to balance.

Live Wire

Correction If with out fuel Should balance full it will be nose heavy.

MinnFlyer

My Feedback: (4)

If you don't know what a spin is, I'm not going to tell you.

You would be better off having someone show you in person.

Montague

Get up really really high.
Put the engine to idle.
Keep feeding up elevator until the nose drops anwyay.
Hold the full up elevator, and add in full rudder (and sometimes aileron) in the same direction.

That should result in a spin.

To exit the spin, put all controls at neutral and wait. Sometimes a bit of rudder in the opposite direction or a bit of down elevator will help. The plane should stop rotateing and drop the nose in to a vertical dive. Now add throttle and pull out.

Here's why MinnFlyer didn't want to tell you this:

- Some planes will get in to really neat looking spins that they won't come out of. So you spin all the way to the ground. *splat*.
- It's really easy to under-estimate the height needed to get out of a spin. So you fly straight in to the ground. *splat*.
- It's common to see guys exit a spin, then yank the elevator too hard to get out of the vertical dive. The result is a stall, and sometimes another spin right to the ground. *splat*.

So, the odds of a spin resulting in a *splat* can be high if you aren't careful. I agree that you should talk to someone with experience, and maybe let them spin your plane before you do it.

Some planes won't spin at all until the CG is moved back, and the control rates are increased. This is especially true of trainers.

Here are a few manuvers to try before you spin, just to get the feel of things:
- vertical dives. Just go up high, cut the throttle, and push the nose down with the elevator. Let the plane dive vertically a little bit, then pull out. Some guys find this un-nerving. But it's the exit if a spin, so if you panic here, you aren't ready for spins
- straight ahead stalls. Go way up high, cut the throttle, and hold elevator to keep the nose level. Keep feeding elevator until the nose drops. Then add power and pull out. You'll want to get familar with how your plane stalls anyway, so this is good to do with any plane.

Back on the origional question, a little up trim in the elevator is common. Before you mess with anything, fly the plane and roll inverted. How much down elevator does it take to stay level? If the answer is "very little", then you're good to go. If the answer is "lots, almost full stick", then you've got some stuff to adjust. As mentioned, the CG and wing-stab relitive incidences are good places to start.

Gian Paulo

Montage, thanks for the reply!... I've done all the maneuvers you have described, in fact I do them quite often, I just didn't know how it was called (I'm self taught, and english is my second language).

I think there is not much I haven't done with this plane. This is just a toy and I have fun with it, if it crash I really don't care that much(as long as nobody is in harms way)... I know it's all part of the game.

A spin, what I've done is rudder to the left, aileron to the left nose down no throtle or even full throtle... but no elevator.
I'll try it with some elevator later on today when I go to the field.

Thanks again.

jettstarblue

Gian,

Better test of correct CG- take the plane up, and put it into a 45 degree dive. Let go of all controls, if the dive steepens, you are tail heavy, if the plane pulls up out of the dive you are nose heavy, if it continues on the path you set it on, it's balance pretty close.
I know this may sound backwards, but it's not.

Also, for your spins, try (after you get it going) feed in OPPISITE aileron, and full throttle, this will flatten the spin considerably, and makes it more interesting.
Keep pushing the envelope!!!!!!!!!!



Jetts

john flynn

My method is similar to jettstarblue, however I idle back, put it into a dive then power up. If the plain steepens the dive then it's nose heavy and if it levels out a touch it's tail heavy. Actually that's the opposite of what jettstarblue stated, maybe Ive got it back the front? The method works for me anyhow.

MinnFlyer

My Feedback: (4)

Thanks Monty!

Another way is to fly straight and level, then bank the wings to a 45 or more (a sort of Knife Edge) and go to netural. The plane will lose altitude pretty fast so be ready to recover. If it drops nose down-noseheavy etc.

Montague

Gian,
Well, if english is your 2nd language, I sure couldn't tell. Man, that's one thing that sucks about being American, I can barely manage my own language, never mind some else's

If you don't apply the elevator, what you (usually) get is a spiraling dive, not a spin. There is a difference, but it's hard to explain. But, once you see it, you'll know it. In a true spin the rate of descent is very slow compared to a vertical dive.

Fly up high, go to idle, and point the nose at the ground. Note how fast the plane is coming down. Now try to do a spin. If the plane is coming down almost as fast, it may not be a true spin.

Another (very violent) way to get in to a spin is to do a snaproll and just hold it, most plane will drop in to a spin from that. Basically, fly level at pretty much any speed or throttle setting. Then, all at the same time, full up elevator, full aileron and rudder in the same direction. You should get a very abrubpt and violent roll, not a big corkscrew. If you do it at high speed and throttle settings, some planes will come apart, but most wont. (If yours does, it's not my fault, ok ). Anyway, just hold those controls and the plane will frequently just fall in to a spin.

Sometimes I like to do a snaproll on a vertical upline, just before I run out of airspeed, then just hold the controls there and let the plane fall back in to a spin the other way. It's very sloppy, but it's fun.

Gian Paulo

Montage, thank you once again for your reply and your complements on my english. I went to college in Washington D.C, Catholic University.
I'm heading out to the field today at 5:00PM right after work so I can get started on the spins... I don't think my plane will fall apart caus I've done some crazy stuff with it and has hold on pretty good... but if it does fall apart, don't worry cause I know it will be my fault.
I'll let you know how everything turns out.
GPV

CHassan

My Feedback: (13)

Gotta love them SE's

Gian Paulo

Montague, went to the field yesterday and did the spin and this is what happened: the plane goes down doing sort of a cone figure, where the tail spins in a circular motion, the nose does not and the plane rotates at the same time... hope I explained myself alright.

Montague

Sounds like a spin. It is hard to tell based on a description, but it does sound right.