My PT 40 when I take off will roll right very hard. Then I have to take the motor apart and clean out the dirt. I had this thing trimmed by a club member and it flew fine. I went back the next week and changed nothing. When i take off, it won't even get 5 feet off the ground and it's already upside down and in the grass. Ailerons are even with the wing, Rudder is centered, Plane is balanced,etc...Why would the characteristics take such a change from the first flights? It flew like a dream at first. I had so much confidence and now I, like my plane, am a broken man...
:drowning:
2 other guys have tried to fly it and it takes a digger before we get it figured out.
Thanks.
Derrick

Are you sure the wing mounting is really secure, and the aileron servo linkage is working properly?

-DC

Did you balance your plane laterally also ? (wing to wing )

Yes the Ailerons are going the correct directions and I did balance the plane side to side. The wing was the last thing I monokoted and I had to add about 1/2 oz to one side. It still is balanced when I pick it up by the spinner and the vert. stabilizer.
This thing rolls almost violently. The only thing keeping it from kindling is the fact that it don't get much over 4 or 5 feet in the air and not a ton of speed.
I check for control surface movement before every flight. (It's the most affordable thing in this hobby) As quick as this thing flips, I'd think it would need a lot more airspeed and a lot more aileron. I'm about ready to get an Avistar ARF and swap the guts.
This PT 40 was a kit and I double and triple checked every step before I did anything.(My first plane) The first guy at the airfield that flew it and such was Impressed by how well I had done and how well it flew and how little trim adjustment it took. The only suggestions were that I put my name inside and that I may have a bit too much elevator throw.
The lateral balance would need to be off a ton, I'd think for this to roll this quick. I don't know for sure though. I know it won't drop a side when I pick it up by the spinner and the tail.
After todays festivities now I need to re epoxy my vert. stabilizer. She's a bit floppy now.

Also, I use 16 rubber bands to hold the wing to the plane. The last 4 I criss cross. I'm trying to eliminate the variables. :-)

If all is as you say... I'd be guessing that something slid back into the tail
and made it excessively tail heavy, or that you have developed a warped wing.
After the first flights... did you reshrink any of the wing's covering?
Did the wing sit in a hot place, that wasn't flat? (tips resting on something)

There's not a whole lot of things that can cause what you describe.
If you honestly can't think of anything that has changed... recheck the CG,
and carefully inspect the wing itself for any warpage or wash-IN.
Make sure the leading edges are at the same incidence, as well as the trailing edges.
Make particularly careful inspection at the tips, when you're checking it out.

If it's not something like this... and your tail surfaces are tight, and the wing is tight,
then I'm at a total loss, unless you're just not getting enough airspeed before liftoff.
Either that... or you've got a stray mix in the radio, that you're not catching in your preflight.


Please report back, whenever you nail this one down

Yep we even checked the wing washout. The only thing I haven't rechecked is the center of gravity. Possibly something slid in the rear of the plane. I did glue tape a weights to balance it front to rear.(I cut out one of the windows in the balsa to balance it and re monokoted it when it was balanced to where the destructions specified) It wasn't crashed after the first evening but it seems to be making up for lost time and it always rolls to the right.
(One time I had another club member try and take off with it. It went towards the end of the field and right after it lifted,it hooked hard right towards another flier standing behind a fence. My plane tore through the plastic mesh and hit this poor guy in the leg. Bruised his leg good. Meanwhile this guys plane is still airborn and he has to land his plane. If my plane had more altitude, it could have hit him in the chest or head.
My plane got busted up a bit too. I had to rebuild the firewall and fuel tank floor. I still feel bad for the other guy though but he says he's OK. At least he's not scared to fly . I think I'd give up the hobby (I even thought about it. I don't want to hurt anyone.)

This may not be accurate. Try suspending the model using kevlar string or fine wire hooked to the middle landing gear mounting bolt and the tailwheel mounting bolt. I've done what you did before and what seems balanced using this method, is not using the suspension method. The spinner also has some rotational resistance from the engine mechanism. I'd also go with what Cwatkins said. Just my 2C

Just a thought. .

Are you allowing enough time on take off to get to a good airspeed? It's amazing how quick a snap happens of you don't get fast enough.

Also, when it's in the air, does it loop nice and square?

DC

When it was flying, it looped nice and straight. if not a little quick. The last time(Yesterday) I tried to fly it, I had plenty of speed before I hit elevator to take off. I gotta reattach the vert stabilizer and then I'm going to double and triple check balance and C of G.
If it is close, I may have to try and preload a bit of aileron differential in it.
My G2 sim is way easier and less spendy to crash. Maybe I should stick to that. :-)

check that the nose wheel is set to allow the wing to be at least level, sounds like it might be nose down & is not quite up to flying speed as david had sugested in his post. pulling up too quick & snapping is common in this case. if nose wheel cannot be lower'd (to raise the nose of the plane), then lower the back of the plane by bending the main's up a bit, till the wing's level, even a bit leading edge high. good luck bill