I do believe luke352 is onto something!

It is only by careful (and occasionally skillful) manipulation of all of the aforementioned components that powered flight (at least in regards to what we are discussing) takes place and is maintained.

Jeez, if all I had to do get outta trouble and gain altitude was to goose the throttle, maybe that stupid, evil red J-5 Cub trainer would still be around! Heck, come to think of it, it WAS at full throttle when it executed a perfect one-pointer!

Happy Flying!

Originally Posted by Gerry__

Of course it controls altitude! The throttle is your altitude control. Without thrust, planes go down. With a lot of thrust, they go up. And with just the right amount, they fly level.

Don't tell that to the guy in the Schweizer 1-26 I saw climbing out in thermals this afternoon. His engine was left on the ground after he got off of the tow.

David

"Tip" stall is not a characteristic of a straight airframe. It's a term invented by modelers whose airplanes aren't straight and therefore when they stall, they drop a tip. It's just a STALL on a bad airframe. The PT-19's wings should be straight according to the USAAF rigging manual. I had the pleasure of restoring a PT-19 20 years ago. The lower wing should stall just before the upper wing, resulting in a straight forward stall with a quick and gentle recovery.

Have you tried re-rigging the entire airplane and going over EVERYTHING with the incidence meter including both sides of both wings, the thrust line (not likely part of this problem but worth checking anyway) and both sides of the H Stab? Also disconnect the servo linkages and make sure the control surfaces are all properly neutral with the servos centered? Is the dihedral equal on both lower wings? Is the top wing straight without dihedral? I don't own one of that particular model so can only offer thoughts. That's how the full sized one is built.

Good luck!

David

Take the throttle-altitude control as the way. I learned to fly inside full scale planes at the Beech Aero Center. When setting up to land, establish your approach airspeed with attitude. Now hold your approach speed with elevator and and use the throttle to control altitude, or more correctly, sink rate.

To prove it, start descending at very low throttle, then add more throttle. The first thing the plane will do is climb. The factors are somewhat interactive but the idea is at a certain attitude and thrust, the plane will climb or sink. At some point it will reach a balance and maintain altitude and speed.

It is harder to see and establish an approach like that with RC but that's how it works. The higher the wing loading, the easier it is to see the effect.

Originally Posted by luke352

Neither Thrust, elevator, or airspeed control altitude! It's combination of all three! Gliders don't have thrust in the traditional sense only airspeed which is mainly controlled by AoA which is adjusted by the elevator. You could say there thust is gravity.

I can have lots of thrust but it won't acheive much change in altitude without a change in AoA which is adjusted by the elevator, or for that matter airspeed.

You can't say one controls this and the other that, it's a relationship where in nearly all cases you need two of the three.

Originally Posted by David2011

Have you tried re-rigging the entire airplane and going over EVERYTHING with the incidence meter including both sides of both wings,...

The last I knew a PT-19 had only one wing.

Larry

Originally Posted by Chophop

Take the throttle-altitude control as the way. I learned to fly inside full scale planes at the Beech Aero Center. When setting up to land, establish your approach airspeed with attitude. Now hold your approach speed with elevator and and use the throttle to control altitude, or more correctly, sink rate.

To prove it, start descending at very low throttle, then add more throttle. The first thing the plane will do is climb. The factors are somewhat interactive but the idea is at a certain attitude and thrust, the plane will climb or sink. At some point it will reach a balance and maintain altitude and speed.

It is harder to see and establish an approach like that with RC but that's how it works. The higher the wing loading, the easier it is to see the effect.

And then we throw Speed brakes into the equation. Setup my approach angle with speed brakes out, now I reduce my deployment (same as increasing throttle) but if I don't change my elevator input my downward AoA won't change. Sure my initial sink rate has reduced but my airspeed has now increased so my sink rate is probably a wash. So if I want to reduce my sink rate I need to reduce my downward AoA through elevator input.

Originally Posted by David2011

Don't tell that to the guy in the Schweizer 1-26 I saw climbing out in thermals this afternoon. His engine was left on the ground after he got off of the tow.

David

The glider was descending, it's just that the thermal was rising faster then the glider's descent.

Originally Posted by luke352

And then we throw Speed brakes into the equation. Setup my approach angle with speed brakes out, now I reduce my deployment (same as increasing throttle) but if I don't change my elevator input my downward AoA won't change. Sure my initial sink rate has reduced but my airspeed has now increased so my sink rate is probably a wash. So if I want to reduce my sink rate I need to reduce my downward AoA through elevator input.

In a correctly trimmed aircraft, if you retract the speed brakes, the rate of descent will reduce, while the airspeed remains the same. You don't need to do anything.

Originally Posted by Gerry__

In a correctly trimmed aircraft, if you retract the speed brakes, the rate of descent will reduce, while the airspeed remains the same. You don't need to do anything.

In the gliders I flew if you were on finals and maintained your AoA and retracted your speed brakes Airspeed increased. If you keep the control stick in the same postion the aircraft will ballon a bit but there was still an increase in airspeed.

Originally Posted by luke352

In the gliders I flew if you were on finals and maintained your AoA and retracted your speed brakes Airspeed increased. If you keep the control stick in the same postion the aircraft will ballon a bit but there was still an increase in airspeed.

It takes time for any aircraft to settle after you change something, but settle they will.

Originally Posted by David2011

"Tip" stall is not a characteristic of a straight airframe. It's a term invented by modelers whose airplanes aren't straight and therefore when they stall, they drop a tip. It's just a STALL on a bad airframe.

David,

Sorry but that's BS.. tip stalls may not be what full size pilots usually call it but it's something that full size planes can suffer from and which full size plane designers do a lot to avoid. Heres a link to an old NACA technical paper titled "Tapered wings, tip stalling, and preliminary results from tests of the stall-control flap"

Tip stall (divergent stall, wing drop whatever you call it) doesnt necessarily mean that the plane is rigged wrong. One of the biggest factor effecting tip stall is wing planform shape. Sharply tapered wings for instance tend to suffer from tip stall unless the designer takes measures to avoid it, like washout.

Anyway.. The PT-19 really should not have a tip-stall problem so IMHO the OP needs to look for the cause of the problem rather than adding big ugly appendages to the wings.. but each to his own.

Steve

It's to bad the OP pulled out because of all the negativity, I would have done the same. No one here knows his true experience. A lot of the guys on this thread are newbies telling him what to do. He knew enough that the problem with the plane was washout. and knew how to do a quick fix to verify it. What he wanted was some suggestions for an easy fix, not a lesson in aerodynamics.
Had a plane or two with the same problem. With a built up wing like this, the box spar leading edge is too rigid to warp with steam or whatever. I slit the sheeting from the root leading edge to the outer rear of the spar. In other words, a diagonal slit from root to tip. Do this on top and bottom. Now you can actually twist the wing. On say, a 2 ft. wing panel, prop the wing level at the root on the workbench. Now prop the tip so it has about 1/2 an in. washout. Run a bead of CA down the slit and kick it. It will come back some when it's unloaded off the bench, hopefully with about a 1/4 in. washout. Now flip it over, prop it up and repeat. Cover it and your good to go.
When I was an apprentice mechanic in the 50s, on the high wing planes, we would rig the strut lengths to twist the wing with a couple of degrees washout.
Even changing the airfoil shape on a flat wing from root to tip can have drasic changes in tipstalling. Cap 10B is a good example. Nicknamed Snap 10 for good reason. The root airfoil is a good fat lifting airfoil, while the tip is almost flat. It's what makes it a great aerobatic plane.
Hope this at least helps the OP.

Gord.

Originally Posted by JetPlaneFlyer

David,

Sorry but that's BS.. tip stalls may not be what full size pilots usually call it but it's something that full size planes can suffer from and which full size plane designers do a lot to avoid. Heres a link to an old NACA technical paper titled "Tapered wings, tip stalling, and preliminary results from tests of the stall-control flap"

Tip stall (divergent stall, wing drop whatever you call it) does necessarily mean that the plane is rigged wrong. One of the biggest factor effecting tip stall is wing planform shape. Sharply tapered wings for instance tend to suffer from tip stall unless the designer takes measures to avoid it, like washout.

Anyway.. The PT-19 really should not have a tip-stall problem so IMHO the OP needs to look for the cause of the problem rather than adding big ugly appendages to the wings.. but each to his own.

Steve

Yep, in my aerodynamics class we addressed this specifically. You need either geometric twist or aerodynamic twist in order to combat bad stalling tendancies with certain wing plan forms. Geometric twist is what we are all familiar with, utilizing washout to combat tip stalls. Aerodynamic twist is when they change the airfoil across the wing to (in most cases) reduce the zero-lift angle of attack on the outboard panels of the wing so that the "tips" stall last.

Yep, sort of the reverse of the Cap 10B. Put a thin airfoil at the root with a sharp leading edge, and a fat tip with a blunt leading edge and you'll have a more mild mannered plane.
Another problem plane I have is a 35 in. scale Zero made from EPO foam. She's a beauty but on the first flight I was lucky to get it down in one piece as it would tipstall at about 25 to 30 mph. Had to wipe myself after that one.. This was a try to fix or fling it. I had to put washout in it so, somewhat like the one above, I slit the bottom of the wing, almost all the way through, from the root leading edge to the tip trailing edge. I kinda leaned the knife a second time to widen the slit without actually cutting the foam. CAed the slit and twisted the wing to close the slit, then kicked the CA. Luckily it's a great flying pussycat now.

Gord.

Originally Posted by flypaper 2

Another problem plane I have is a 35 in. scale Zero made from EPO foam.

Off topic but just curious to which Zero that was?