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Old Aug 31, 2009, 10:57 AM
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Wichita Falls, TX
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Is the F22 a plank?

Rwilkinson and I had an discussion last Saturday with an military Instructor Pilot who explained in some detail the flight controls on the F22. The wing works like a PLANK! The tail feathers are secondary in normal flight mode. The wing trailing edge controls the normal up/down/right/left. The elevator seems to move enough to keep the combined airflow efficient. The elevator is only really needed in landing mode when the main wing is configured for maximum low speed lift at a high angle of attack.

As an experiment, we have configured a 4 servo 2 meter plank wing on a conventional fuse from a trashed 60" slope plane. Programming was done on a new Airtronics 10-G 2.4 radio. We hope to test fly the plane at Wilson Lake, KS, later in September.

We programmed three major flight modes to test: 1) conventional elevator and conventional wing; 2) conventional elevator with the inboard 1/2 span of the wing (the flaps) acting as a plank elevator; 3) no conventional elevator with full-span wing plank style elevator function. Landing mode on left stick activates crow with conventional elevator.

We can switch the conventional elevator on and off in the two plank style modes, and we can switch full span wing functions on and off in all three modes. We have a trim function on both the conventional elevator and the wing-flap elevator servos. We plan to add full span camber control to the wing in order to remove the plank's PW-51 airfoil 'duck-tail'.

This should be interesting.

Frank
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Old Aug 31, 2009, 05:01 PM
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Frank,

Any dates firmed up for Lake Wilson? Would like to see the test in action and fly with you guys again. How is the Airtronics 10 working out? Looks like a slick radio!

Chance
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Old Aug 31, 2009, 05:24 PM
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Sounds interesting. In flight mode 3 won't the TE elevator function be the reverse of a plank? ie dropping the TE will make it pitch up. Kinda like a pitcheron. Or snap flap without the elevator.

Jordan
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Old Aug 31, 2009, 05:56 PM
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I'd be interested to see how far back the CG is on the F22.
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Old Aug 31, 2009, 05:59 PM
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Wichita Falls, TX
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Quote:
Originally Posted by wavebuff
Any dates firmed up for Lake Wilson? Would like to see the test in action and fly with you guys again. How is the Airtronics 10 working out? Looks like a slick radio!

Chance
I hope we will be able to drive up Saturday the 19th. It all depends on the winds. I do not know how much time Rick will be able to take from work. Paul wants to come if he is not out somewhere on a job, and another friend wants to drive up to the Lake for the first time to fly with us.

About the radio: I will try to get Rick to comment since its his radio, but I am very impressed. Airtronics seems to have learned from all the radios that came out ahead of it: assignable output channels, an abundance of mixes and switch assignment options, plus a USB PC link for future firmware updates. We have beat on the radio a fair amount to get this plane programmed, and have not run into any bugs or limitations. There have to be some, but we have yet to see them.

Frank
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Old Aug 31, 2009, 06:37 PM
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Quote:
Originally Posted by slopemeno
I'd be interested to see how far back the CG is on the F22.
That is an pressing question for our plane. I ran the numbers in the spreadsheets (http://www.tailwindgliders.com/Files.html#Files), both as a Flying Wing and as a Cruciform Tail. The starting CG results are almost identical!!! (Let me know and I will post copies of the two files.) We seem to be good to go at 2.5" on the root cord. That gives a 9.3% Static Margin as a Cruciform Tail, and 12.1% Static Margin as a Flying Wing. (12.25" root cord, 6.75 tip cord, and 1" LE sweep.The fuse is from a 60" that had been DSed into the ground.)

Amazing to me.

My pure plank version of the identical wing (http://www.rcgroups.com/forums/showthread.php?t=1046882) flies very well at 2.5". I will move the CG back toward 2.75" as I get more stick time with that plane in better conditions.

Frank
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Old Aug 31, 2009, 06:43 PM
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Quote:
Originally Posted by Hamburglar
Sounds interesting. In flight mode 3 won't the TE elevator function be the reverse of a plank? ie dropping the TE will make it pitch up. Kinda like a pitcheron. Or snap flap without the elevator.

Jordan
Wing TE elevator function in each of its modes is just a plank: up to go up. The conventional elevator in the joint flight modes will also go up to go up. Its not Snap Flaps.

At least that is the way we have it programmed for the first test flight.

Frank
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Old Aug 31, 2009, 06:46 PM
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Quote:
Originally Posted by Hamburglar
Sounds interesting. In flight mode 3 won't the TE elevator function be the reverse of a plank? ie dropping the TE will make it pitch up. Kinda like a pitcheron. Or snap flap without the elevator.

Jordan
I have been wondering the same thing, but believe the TE will be plank-like but just not quite as effective with the Horizontal stablizer behind the wing. If any have flown a plank you quickly realize it does not take much elevons to get the job done.

That is why we have spent so much time programming the different flight modes, one of them should work..... we hope.

Flight test will tell it all, if the wind will just blow.

And the 10G radio is a keeper.
Rick
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Old Aug 31, 2009, 08:24 PM
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Wichita Falls, TX
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What would be a better airfoil?

The PW-51 is an issue for me. We are just working with the parts we have on hand at the shop. What would be a better airfoil for such a (slope) beast?

Frank
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Old Aug 31, 2009, 08:52 PM
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I totally believe what the pilot told you guys. But, here's a video showing extreme horizontal tail surface deflections. But, I'd guess that this little bit of light 3d style aerobatics is not exactly a "normal" flight mode :-)

http://www.defencetalk.com/f22-rapto...ce-base-20986/

Totally awesome aircraft. Look forward to hearing how your experiments go.
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Old Aug 31, 2009, 09:03 PM
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Quote:
Originally Posted by cavande
Wow!
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Old Aug 31, 2009, 09:13 PM
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Quote:
Originally Posted by cavande
I totally believe what the pilot told you guys.
I don't

Nauga,
who thinks there's a misunderstanding in there somewhere
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Old Aug 31, 2009, 09:53 PM
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First of all, The F-22 is a tailed delta configuration, not a "plank"

And here is another video that shows the constant use of the horizontal tail in both pitch and roll in aerobatic flight...the F-22 demo at Farnsborough in 2008.

F-22 Raptor at Farnborough Airshow 2008 (2 min 25 sec)


So much for the plank theory.

In cruise, the F-22 can likely do a lot just by camber adjustment to the wings. However, no slope glider spends much more than a couple of seconds cruising...it is all about the hard turning and aerobatics.
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Old Aug 31, 2009, 09:54 PM
Jim in San Diego
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I'm sort of with Nauga on this one. I'll give the pilot the benifit and just say maybe he's trying to explain something in a different way and there's something missing.

Jim
Trying to think hard about planks and vectored thrust
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Old Aug 31, 2009, 10:04 PM
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...

Nauga,
MOTO.
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