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Flat turn

Old 12-13-2010, 09:15 AM
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ytell
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Default Flat turn

How can a model turn flat with rudder only and not be affected by the greater speed of the outer wing?

Thanks,

Yoav
Old 12-13-2010, 09:24 AM
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exeter_acres
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Default RE: Flat turn

it is affected...

you need to either mix the aileron, or adjust for it
Old 12-13-2010, 09:40 AM
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Default RE: Flat turn

Not only that....Yoav.

Helping a roll into the turn:

1) The inner wing is partially blanked by the fuselage, as well as the inner stab.

2) Any dihedral will increase the AOA of the outer wing or stab and decreasing the AOA of the inner wing or stab (opposite for anhedral).

Helping a roll out of the turn:

1) The rudder deflection induces a roll towards the outer wing, since the main area is above the rolling axis.

The aileron compensation that is necessary to keep the wings flat and zero roll depends on the unbalance among those forces and moments.


Old 12-13-2010, 11:14 AM
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rmh
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Default RE: Flat turn

We played with flat foamy shapes to get a good flat turn model
Basically the models with well balanced fuselage side areas and short flat wings did the best These could and would at proper throttle setting do a nice twirl with a tiny bit of up elevator and selected rudder input - tricky but predictable They also did nice inverted flat turns
I don't know of any full sized craft which will even approach this type turn
Old 12-13-2010, 12:04 PM
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HighPlains
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Default RE: Flat turn

The Guardrail Common Sensor RC-12 aircraft have to do flat turns during operation. The RC-12 is a military variant of the Beechcraft Super King Air used for tactical reconnaissance of radio communications. The aircraft look like a porcupine.
Old 12-15-2010, 08:04 AM
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Bax
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Default RE: Flat turn

Wow! found a pic of the Beech RC-12: http://en.wikipedia.org/wiki/RC-12

It's really festooned with antennas!
Old 12-15-2010, 08:56 AM
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Tall Paul
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Default RE: Flat turn

ES-3A was another flying antenna farm.
Navy spent a bundle getting it in service, and then wasted it using it as a tanker.
Very short service life.
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Old 12-15-2010, 04:07 PM
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HighPlains
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Default RE: Flat turn

http://virtualglobetrotting.com/map/...nna-test-site/

Same airplane, well sort of. This is the half size model used to figure out where to place all the antenna. On a hill top far far away and a long time ago in another universe.

Old Crows never die.
Old 01-09-2011, 11:06 AM
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Ed_Moorman
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Default RE: Flat turn

Highplains-Your mention about recon planes doing flat turns reminded of a mission I had in Vietnam. I was leading a flight of 2 F4-Es carrying two 2000 lb bombs and some smaller ordnance each. We were to escort a single RF-4C on a recon mission in at low altitude in southern North Vietnam. We joined up on his wings and busted through some clouds and he leveled off and began shooting pictures. Our job was to bomb anything that attacked him.

Flying formation on a guy who is being nice and smooth is pretty easy. That is until we came to a bend in the road. He makes a flat turn toward me. What the F***!, I'm thinking, as I bank away and lose sight of him under my wing. It is not easy flying formation when the lead makes a flat turn. We loosened up a lot and dropped back and down some more.

When we got back to base, some of the guys who had flown recce escort before were in the squadron building. "How'd you like flying formation with a recce bird," they laughed? They had their laugh, that time.
Old 01-09-2011, 04:32 PM
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Rick.
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Default RE: Flat turn

progressively add more and more rudder, watching the angle of bank develop and countering it with opposite aileron - feed in some elevator too if the nose starts to drop. Trouble is the amount of control input and counter inputs needed vary hugely from model to model.  I got a sebart katana that turns nicely on rudder, but if given lots of rudder like you'd use in knife edge, she drops a wing and tucks her nose under.  I also have an ikarus foamy of the Pitts bipe - that can turn flat and tight (like 5 feet circles) with just lots of rudder and lots of oppposite aileron held at the same time.
Old 01-10-2011, 07:38 AM
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Default RE: Flat turn

It helps to have as much rudder area below the centre line as above as on this foamy, to stop from rolling with rudder input. Does excellent flat turns with no other input.
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