Kougar inverted question

How much elevator does it take to keep your Kougar inverted? An old, tired, often rebuilt, and too heavy Kougar requires almost full down to keep it inverted. The wing incidence is zero relative to the stabilizer. Something seems wrong but I don’t know what.

Bill

too much downthrust or nose heavy ????

[:-]

If you move your center of gravity back it will require less elevator to keep it level unverted. It's all a process of trimming a plane for the flight characteristics you want. Experiment with moving things back but be aware that the farther back you move it the more sensitive the elevator will be come.

It's a fine flying airplane and it should be able to handle it well enough.

And check your wing incidence. The Koug should require very little elevator travel.

Before the inverted question was asked I put an incidence meter on the airplane and also checked the CG. The incidence was zero on the right and 1/4 degree positive on the left relative to the stab. I looked but did not find the incidence setting in the manual. The CG was 3/4 “back from the wing leading edge at the tip (a somewhat nebulous measuring point). I also flew the airplane the previous day to check the amount of down elevator required when inverted. On low rate there was not enough down to hold the plane inverted. On high rate the elevator seemed to require most of the throw. The airplane tracks level from half to full throttle i.e. it does not climb or sink with throttle setting from half to full.

Something is believed to be wrong but I don’t know what.

Bill

What is the amount of throw you have at high rate on the elevator up and down?

I looked online for the manual but could not find it.

I still stand by my suggestion; the Kougar is a low wing airplane so it is less neutral inverted than a midwing (like an extra) airplane would be. Thus moving the center of gravity (more appropriately the center of balance) towards the rear will help to neutralize it in an inverted position (that's how you measure the CG anyway right?). Move it back about a half inch at a time and be sure to use low rates because as I stated before as you move the CG back the elevator will become more effective. Again; the Kougar is a very stable model and should have no bad snap tendencies (I've had two and am planning my third).

Good luck and post pictures. =-)

What engine do you have in it?

Just finished double-checking the incidence after setting the aileron reflex and adjusting the servo center and aileron throw. Zero on the right and 1/16 degree (damn close to zero) on the left. Still cannot find incidence in the manual.

The elevator throw was 1/2” plus up and 3/8” down probably a result of a field setting too long ago to remember. The manual calls for 3/8” up and down and I just changed it. Also put the reflex back in the ailerons for further testing.

It is a great airplane and flies in any kind of wind. The airplane is 17 years old and no beauty queen and I have been flying it regularly since 1992. However it has gained weight as it aged and is now 6 1/2 pounds however it has a great sink rate. Several months ago the engine was changed to an OS 50. The pretty airplanes often stay home while the Kougar goes flying.

I have never been able to fly it upside down but for some stupid reason decided to rethink the trim issues and therefore the question. My flying skills are marginal so there has been some resistance to moving the CG rearward past 3/4".

Thanks for your help.

Bill

I have a King Kobra and it requires basically no elevator to fly inverted. Here's what I would do. Check the thrust lines by flying at a 45 degree and then vertical angle. See what the plane does and adjust the thrust accordingly. Also, those incidence readings don't mean too much because I'm sure the carved leading edge is not perfectly semmetrical so experiment with some shims. Finally, move the CG back a touch and also check to make sure those push rods aren't bending under load (maybe full elevator on the stick isn't really full elevator under load).

Mike

One thing I would certainly check if you're using the stock setup is the condition of those dowel based pushrods. That's how I lost my first one - the elevator pushrod busted in the down line of a loop.

What does the manual say for the CG?

Moving the CG back will make it more receptive to control inputs - i.e. touchier but you can dial that out by using less throw and exponetial rates in your radio if it has those. Lower high and low rates however should be enough to control the touchiness while still getting the minimal elevator input during inverted flight.

I went through this with my second one as it was my first pattern "trainer."

The manual says real bad things will happen if the balance is rearward and I believed them.

“Test fly with the balance point located anywhere between the leading edge of the wing tip and 1/2” back from the leading edge at the wing tip.

Sport Fly at 1/2” back from the Leading Edge at the wing tip.

Aerobatics – If your model will spin in both directions at 1/2” it need not be moved back any further. Some models need the balance point at 3/4” back for full response.

Flying with the balance point any further back than 1” from the tip is not recommended unless you are and expert flyer, with a purpose for doing so.”

And three more paragraphs of warnings.

As a reference point I still would like to know how much elevator it takes to keep a Kougar inverted?

Bill

I fly mine pretty radical with the cg at 1.5", and it still requires a good amount of down elevator to maintain level inverted flight. But once you get it in that "groove" its a piece of cake, it stays there without requiring a lot of correction.
I even bring it down on the deck inverted, hi speed...just rock solid...

I believe its just a characteristic of this plane, after all, it is a low winger with built-in washout.

I don't know how much down I'm using, I usually don't think about it....I too busy flying to worry about things like that...

Thanks it is good to know and to stop chasing rainbows.

Bill

Oh one more thing, while flying inverted, if you turn it by banking (instead of rudder) it tends to fall pretty hard and requires lots of aileron/elevator correction. Rudder turns are uneventful.