WT Forums

I figured I'd go right to the source...I'm obviously new to this site. I am not in the military and am not a FS pilot but am an avid radio control aircraft enthusiast and have just recently completed and flown a 1/11 scale (60" Wingspan) A-10 powered with twin .25 prop engines mounted at the front of the nacelles. The first and only flight (to date) resulted in a "hunting" for pitch stability at high throttle which settled down when power was reduced for landing (by the way, the plane made it back OK without damage). This plane has large split flaps and they were deployed about 10 degrees during the first minute of the flight. When retracted, stability had improved but not completely. The CG seems to be within reason but will research it further. Colleagues suggested the thrust vectoring should be pointed "up" vs. the level or somewhat "down" which is where it currently is. Does the FS A-10 thrust vector (exhaust) point "up" to help lift the nose? And what is the degree of incidence on the stabilizer? Most plans call for 2 degrees positive - is that in the ball park? On my model, at speed the nose had a tendency to drop without inducement but became more docile as power was reduced.

Thanks for any suggestions you may offer. I have pics if you'd like to see it.

Sincerely,

Ted

Yup, you came to the right place, tdwise! Someone here will be able to help. By all means, post the pix! And welcome!<img src=icon_smile_big.gif border=0 align=middle>

King George II on Gen. James Wolfe: "Mad, is he? Then I wish he'd bite more of my other generals!"

_________________
\"Those who hammer their guns into plows
will plow for those who do not.\"
- Thomas Jefferson

If you look at a picture of an A-10 engine, you will see that the exhaust "nozzle," if you will, is pitched slightly upwards. I don't know any degree measures or anything, but I hope it helps.

--Raven

"Work Hard, Party Hard, Hardly Sleep"

Interesting I am an Avid R/C Enthusiest. It could be several things THrust Line VS Trim VS Incedence of the MAin and Horizontal Stab. Could also be that the Rate of airflow over the Main wing could be causeing some buffetting in the Elevator. DO you have Dual Rates? on your Radio? Most CPU radios can Program Mixes and setup a switch for Dual rates. SAy a 70% rate at high speed and 110% at slow speed.

Check the Deflection angle and adjust the ATV's to limit the amount of throw. It coulkd very well be Thrust Line Vs Angle of attack of the Wings with Trim Settings interfering.

Id be interested in seeing your Design.

I use washers under the engine mounts to trim the Thrust angle of the Motor.

The nozzles turn (vector) the thrust about 9 degrees relative to engine centerline, but I was told that it was that way to align the thrust through the c.g.. Then there would be no pitch change with thrust. I think the critical thing was on "go around" there would have been a lot of pitch trim adjustment required at a critical time when the engines spooled up and control power low. It is also difficult to rotate the aircraft for takeoff without the vector, requiring more runway to get to rotation speed. Does this sound rational, or have I been misinformed?
I don't have an A-10 three view but the incidence of the horizontal tail relative to the wing (Is it called decalage, or pitch dihedral or something?) is very large compared to anything else around. They even had to increase the nose down incidence of the horizontal tail during the prototype phase. You can tell on the prototypes that the vertical fins look rotated forward a smidge. The camber in the wing is like permanent flaps that always want to pitch the nose down. The horizontal tail load increases a lot with speed in order to trim the cambered wing. The tail incidence selected, I figure, is the best compromise that lets the elevator be neutral for normal cruise speeds.

Mc/I + P/A

_________________
????

I want to Thank You all for the replies...they've been most insightful! "Nine degrees up thrust to align with the CG"...I like that! I think what I'll do is re-vector the the thrustline for "up" thrust as well as do-diligence on making sure the CG is more accurately set. As far as radio settings go, the throws were set on low rate and weren't excessive. I've flown pitch sensitive planes before but this one behaved differently. It's not that it was sensitive...it's just that it wouldn't settle in to a groove until the power was pulled back.

Thanks again!

Ted