Setting stab compensation for Crow

[john ensoll]

Hi All,
Great to see such interest in the F3X group.
I have just upgraded from a JR 3810 to a 9XII and am having lots of trouble setting the stab compensation for landing flap
I would be very interested in reading about how all you other people do it.
I suppose that we will be talking about what the computer graph looks like on the Tx
Model is a Lubos ERASER Xtail full Carbon.
Regards,
John E.

[chetosmachine]

Every plane will need a different compensation.
In my planes, with the same tx as yours, in buttefly submenu, i set butt->elev at -20%
With this %, i got my elevator to go down about 2mm, which is all that i need with my plane at full brakes.

At first, i put a -30%, when i tried it while i was high, i saw it excessive, so i had a buddy control the stick while i opened the menu and changed the value input.
If i had to do that alone, i would let the menu open, launch, then when at safe height, try it.

If the compensation needed is not lineal, then go to mix #1, and adjust it as the manual says. If you have a friend who can either control the sticks, either change the parameters while you fly, it will at least twice easier.

Chets

[craignzcd]

hi john.....in the butterfly/crow sentings you can set your values there.....have been flying with the 9303 which is pretty much the same as a 9X 2 ...i first go for a fly and test the crow in the air and then alter it after i land then try it again till i am happy with the percentage i have put in.....you can run less in breezier conditions and more in still air to your likings......cheers craig

[Tuomo]

It takes time to set up the mixer and it never becomes perfect. Needed mix value depends on flying speed. I look for neutral behaviour when flying slow. This gives slight nose down tendency when lowering flaps at high speed.

Somehow all my v-tail planes seem to be ok with linear mix, with x-tails I use curve mix.

[john ensoll]

Hi All,
Thanks for the responses, I have been out this last wednesday for some more adjustments, in calm conditions and have decided that the exponential I had on the elevator was restricting my pitch corrections during crow aplications.
I now have 30% exponential in lieu of 40% and there is a marked improvement in Handleability during landing.
Any further comments would be appreciated

Regards,
John E

[Wing-span]

I'm glad that you seem to be happy with your settings now John.

Generally it is a good idea to start off with a linear mix. After this you will be able to fine tune, so the plane will do what you want it to do.

[davidjensen]

In the 9303 Mix No 1 is a dedicated Flap to Elev mix that allows a 7 point curve. It is designed to allow you to fine tune the amount of compensation for any given amount of flap deployment. I do not use the butterfly settings to give any flap to elev comp. With the 7 point curve you can (and this is most common) add more comp (usually down elev) in the first 25 degrees of deployment (when its most needed) and the last 50% of the flap movement usually only gets about 30% of the end comp +-><. On the screen you will see a curve. Testing the set up is easy. Deploy 1/4 flaps and adjust the numbers in the mix to make the ship fly flat. Next fly with 1/2 flaps and adjust the numbers and then again at full flaps. This type of fine tuning really helps keep your ship on track to the hunsky.

[F3X]

Hi John,
Try this: Copy your existing program to a new location. Put a standard length servo arm on the elevator servo (10mm from the screw to the hole) and remove all differential from the program for elevator. See if she flies a lot better? If not its a easy change back to what you had before. 30% expo is a LOT on elevator.

[Rich Speroni]

Hi John,

Does the 9xII have a delay feature for the elevator? On the Stylus we use the elevator delay to compensate for the fast return to neutral elevator compared slower return of the flaps.

So no matter how fast or how much flap is deployed in landing mode no pitch change will happen. Not enough delay and the nose will rise up.
Rich

[Wing-span]

With the 9xII you can delay the introduction or change of a flight mode. The delay will affect all flying surfaces.

[shoe]

Hi John,

Does the 9xII have a delay feature for the elevator? On the Stylus we use the elevator delay to compensate for the fast return to neutral elevator compared slower return of the flaps.

So no matter how fast or how much flap is deployed in landing mode no pitch change will happen. Not enough delay and the nose will rise up.
Rich

This is something we've been trying to figure out at our flying field as well. Does anybody have the answer?

[Rich Speroni]

Shoe,
When you drop your flaps down elevator is needed to compensate for ballooning. This down elevator Mix is called in the Stylus Transmitter: SP (spoiler) > EL (elevator) .

In the sub-mix the "delay" actually is a mix between FL.SP (as stated above) > EL.

So maybe you could configure a sub program to mix with another sub program to solve the problem.

Rich

[shoe]

Shoe,

In the sub-mix the "delay" actually is a mix between FL.SP (as stated above) > EL.
So maybe you could configure a sub program to mix with another sub program to solve the problem.

Rich

This is an interesting idea.
Can you expand this description a little? I'm having difficulty making the mental jump of mixing the flap>spoil to develop a delay. Wouldn't this just be able to affect the travel?

[Rich Speroni]

Well does the 9x2 haveany delay sub mixes? Or any slave>master mixes with delay option?

What's needed is the delay function in relation to the elevator (Master).
Then the flaps function could be the (Slave)

I don't know the 9x2 features, I was just suggesting ways I use with the Stylus.

People like Wurts, Hoopes, or Jennings are the ones who could help out here.

[john ensoll]

Thanks Guys for the responses
The 9xII is the version that is sold in NZ and Australia and Japan where as the 9303 is the version sold in the US of A.
I am learning how to drive the 9XII having moved on from X347/388/3810 and have yet to discover all the features I have been out to our club field today for more testing and have removed more exponential, now at 20%. The dive test shows thar I have been flying at pretty well neutral pitch stability so hae started to add a little nose weight. The set up i was using on the 3810 was to allow participation in F3b and now have decided to fly less F3b and more thermal events
Regards
John
(granddad)

[Rich Speroni]

After looking at the Manual Glider Part 1, I found the solution on page 20. It explains how to add elevator delay in landing mode.
http://www.modelflight.com.au/manuals/pdf/jr/9X%20v2%20Instruction%20Manual_Glider.pdf

Buenos Dias

[becsta]

John,

I have the 9XII, and have recently been through setting up the compensation curve as you're now doing.

My best suggestion to you would be to do a search on the Internet for Sherman Knight's excellent JR 9303 programming guide. It's more tuned for the US 9303 than the 9XII, but the concepts, and programming, is essentially the same.

In Sherman Knight's guide, he discusses the exact steps required to tune the flap->elevator compensation curve (located in Programmable Mixer 1). Follow those steps, and you can't go wrong.

I found that my compensation curve was a 180 degree mirror of his curve, so you need to check that you're getting lots of elevator travel at the start of the flap movement, rather than at the end...

Anyway, I eventually worked out a rough curve, based on the observing the plane during landings, and taking mental notes during landing approach "mid-stick/more down, full stick/less down", to a point where I was happy with the attitude of the plane on approach.

Cheers,
- bec

[becsta]

With regards to "elevator delay", I've heard of the opposite being desired some times - start to move the flap stick, you get just elevator movement, to a point where the aircraft is nose down, and able to take flap without immediately nosing-up. Basically, preparing the plane's attitude for lots of flap. It's also to keep the plane from stalling, especially if it's already quite slow on approach.

- bec

[Mike the Snake]

I think that's because when the flaps are JUST dropped, they are closer to camber (deflection and making lift), until after 45 degrees where they stop deflecting and they instead scoop, creating less or no lift.

So the plane experiences BIG extra lift at first and then less lift as the flaps reach their max throw.

Flaps that go to 90 degrees also need less elevator deflection at full throw.


For slope, I fly in high winds, I want my plane ON the Ground, so I mix in a LOT of down elevator so the plane dives with flaps deployed.
Down elevator input is to be totally avoided always unless you're inverted IMHO, it Always results in a downward dip (during landings that spells SPLAT).

Keeping in mind that the only time the flaps are deployed is when you want to go down, it is MUCH easier for me to land in difficult situations with a BUNCH of down mix, so to go down I simply let go of the stick, pull to maintain level, the plane can be slowly lowered without fear of getting blown back or splat from a down push on the stick.

[Rich Speroni]

Ok, lets say your at the SLOt , wind blowing 40 mph in the LZ.
Most pilots come in hot and at the last moment flash flaps to decrease speed.
Then land using no flaps or in and out flaps.

If your elevator returns to neutral before your flaps in that "type of situation" you will balloon and have good chance of a broken plane. All it takes is a few seconds of brain fayed and no matter how much down elevator you put in your going BACKWARDS.

So this is why I have elevator delay mixed in with the flaps. The elevator returns with the flaps at the same speed. The nose never raises it's ugly head to do you harm.

No matter how fast, slow,how much or in and out the flaps deploy pitch does not change.

The nose stays down and I can control decent throttling the flaps and over-riding the elevator with my thumbs.

If for a sudden wind gust or sudden lift comes in with the nose DECLINED the plane is at a proper attitude so I can clean up the control surfaces, let it fall, pickup airspeed and do a go around.

[jcosta]

tsk, tsk, tsk...


Get a Royal Evo. Setup elevator compensation at 15% for half crow and 25% for full crow.
Set the full throw setting on a digiadjuster.

Go fly, try full crow and turn the digiadjuster (no need to take your eyes off the plane) until the compensation is just right.

Land and set the half crow setting according to the full crow setting.

It does not get easier than that.


BTW, I like the plane's nose slightly down when in full crow.