DO FULL SIZE PLANES TRIM OUT PROPERLY

[3dubya]

Does anyone know if a full size Extra (any series) MX2 or Yak 54 if the horsepower is there when in knife-edge do they require any elevator aileron coupling from the pilot. Our models are based off these planes and when we go to trim them for IMAC they are way off. Mostly the stabs are way to friggen high in relation to wing. One of the few designs that trim out perfectly, are QQ designs cause he lowers the stab so much its almost in line with wing but not blanketed by it, but this is stretching the scale rule thing. I see some great full composite and wood models out there that look good but most trim out like a pig cause they do the right thing and keep close to scale lines. Allot of company’s produce lifting airframes as well which I don’t get in an aerobatic model. I want 0-0 incidence and create lift when I want it, which way I want it with elevator.

[excelpoint]

Providing it stayed within the 10% rule I would want a model that trimmed out well for IMAC. Also depending on what it looked like. I still would like it to look like the real thing.

[RustyTumbles]

	Quote: Originally Posted by excelpoint
	Providing it stayed within the 10% rule I would want a model that trimmed out well for IMAC. Also depending on what it looked like. I still would like it to look like the real thing.

I agree with matt. Not sure about the full size aircraft though.

[excelpoint]

TD maybe try sending Matt Chapman a PM he gets on the Giants a bit. Wouldnt be much better person to ask.

[krashmaster81]

I'm pretty sure that the real aircraft aren't perfect either. Full scale pilots have one advantage, and that is they are in the aircraft and can feel and see tiny changes in attitude and correct them before they get out of hand. It's another reason why it's good to start off in an aerobatic trainer such as a Decathalon. You learn all of the bad habits and how to correct them, then when you've got that mastered you jump in a high-performance plane such as an Extra, and viola, all the manuvers become easier to perform! That's the way i see it anyways...

-Matt

[sukhoi26mx]

	Quote: Originally Posted by 3dubya
	Does anyone know if a full size Extra (any series) MX2 or Yak 54 if the horsepower is there when in knife-edge do they require any elevator aileron coupling from the pilot. Our models are based off these planes and when we go to trim them for IMAC they are way off. Mostly the stabs are way to friggen high in relation to wing. One of the few designs that trim out perfectly, are QQ designs cause he lowers the stab so much its almost in line with wing but not blanketed by it, but this is stretching the scale rule thing. I see some great full composite and wood models out there that look good but most trim out like a pig cause they do the right thing and keep close to scale lines. Allot of company’s produce lifting airframes as well which I don’t get in an aerobatic model. I want 0-0 incidence and create lift when I want it, which way I want it with elevator.

Aerodynamics scale pretty much as expected. My full-scale Sukhoi 26, like the model, pitches to the gear and rolls against the rudder. The difference is that in full scale competition or airshow flying we don't fly extensive KE flight. The only time we pass through KE flight is during point rolls which only last for a second or less. Not an issue to compensate for that long.

So, in short, if your exact scale RC model couples - so does the full scale version.

FWIW, full-scale airplanes wing and stab positions are generally driven by structural concerns vs. aerodynamics concerns. Not generally an issue in competition aerobatics.

Scott

[dewet]

Kirby you reading this? I bet he'll know all about it!

[Mithrandir]

ugh... keeping the scale thing is SOOOOO 20th century....

[Tired Old Man]

I'm going to get a lot of heat over the following, but it's the cold, hard truth.

No full size aerobat is coupling neutral. That one of the things I find soooo amusing about IMAC. Everyone just has to have a plane that won't pitch, roll, or yaw with the application of another control input, and God help them if the plane yaws with power changes. There is no full size, propeller driven, aerobat that functions that way. The pilots have to fly them without benefit of a bunch of transmitter mixes to hide any coupling imperfections.

In other words, they are real pilots flying, real airplanes, and truly have to be good enough to fly them in the manner they were designed and intended without a computer assist. OTH, IMAC and pattern flyers need to have everything as perfect as possible for them to attempt to imitate the more capable full scale pilots.

[FastnLow]

	Quote: Originally Posted by Tired Old Man
	I'm going to get a lot of heat over the following, but it's the cold, hard truth. No full size aerobat is coupling neutral. That one of the things I find soooo amusing about IMAC. Everyone just has to have a plane that won't pitch, roll, or yaw with the application of another control input, and God help them if the plane yaws with power changes. There is no full size, propeller driven, aerobat that functions that way. The pilots have to fly them without benefit of a bunch of transmitter mixes to hide any coupling imperfections. In other words, they are real pilots flying, real airplanes, and truly have to be good enough to fly them in the manner they were designed and intended without a computer assist. OH, IMAC and pattern flyers need to have everything as perfect as possible for them to attempt to imitate the more capable full scale pilots.

You won't get flack from me on this one T.O.M.,you hit the nail on the head.

[flatspinjim]

Scott has already said that full scale planes have coupling. I believe him. I know he has TONS of experience in full scale aerobatics. Pretty good rc pilot as well!

[novemberalpha]

The trims on a full size planes are used to reduce manual labour of holding the aircraft's attitude in a paticular box of situation eg in a cross wind condition you would trim the aircraft optimal crabbing position to hold your track. The box always have variables Hence you trim best suited to your needs & as the variables change & yes you can achive 99.99% correct trims but how long this remains constant may vary for mere seconds to a entire section of your flight.

[Tired Old Man]

With a full scale, trims are correct for only one attitude and one airspeed. Everytime you change either of those you have to adjust the trim. So a full scale aerobatic pilot doesn't get to take a lot of advantage of trim offsets since they change everything constantly.

[BreadBowl]

	Quote: Originally Posted by kjkimball
	I can attest to the lack of coupling in the full scale model 12 Ti-12. In our test flights, the airplane was rigged for hands and feet free flight level and high cruise speed, say 190 mph. Knife edge flight left or right wing down had zero pitch coupling. It did not want to go to the canopy or to the wheels in level knife edge or in a knife edge climb. Wings level same speed hands off the stick and input full left or right rudder made a flat skidding turn, no roll, no pitch deviation. From 230mph 5 g pull to vertical, hands and feet off controls on the vertical line, the airplane continues straight up until stops and simply flops over pointing vertical down and did not deviate off the vertical downline as it gained speed. Pilot reported he felt it would drive straight in if he did not make control inputs. So, this is an example of an airplane that has a high stab and some of the arrangement issues pointed out above to allow pesky humans to ride in it that has near zero coupling. This shows that some full size airplanes can fly like a model and do not count on the pilot to "correct" the coupling issues. Some other notes on this airframe is that the wings and stab are all +2 deg incidence while the engine is zero down and 2 deg left thrust (russian backwards rotation engine). CG at about 27% MAC.

Posted by Kevin Kimball in another thread.

[Luispain]

For sure, IMAC airplanes are NOT the best airframes for precision flying, because their designs come from full-size ones. Full size aircraft are designed regarding the engine they will be mounting, the systems, structural requirements... and don't forget, a person will be flying in. These and more things determine what the final shape of the airplane will be.

Aerodynamically, the "perfect" design of a neutral airplane is something like a F3A airplane. This would be the perfect design also for a full-size aircraft... but they just don't do it because maybe a full size "F3A" aerobatic plane would be really difficoult or expensive to build, to make it strong, and light, and putting all the systems of the real aicraft in that design could be a challenge.

Me, particulary, I don't really know why all the people like that much scaled airframes... why don't we just go with completely original RC designs, like F3A? When you look for a big airframe, you only see scaled airframes, Extras, Edges, Sukhois, Yaks.... when we will stop trying to imitate our "big brothers"??

Greetings!!