Demon cortex questions
 

Just got home from making the first two flights with a Cortex gyro installed in my Tam F-18. For the first flight I had cut back the expo on ail and elevator by approx half as instructed in you tube videos I had seen regarding the cortex install and setup. I had the gyro on a three position switch and had the gain set fairly low (20% with solid green light and about 28% with steady amber light). I took off with gyro turned off, flew around got airplane in trim and flying good. I then turned the gyro on to the steady green light position and flew a few circuts at a safe altitude. My aileron and elevator were quite desensitized. I found myself using much more stick travel than I am accustomed to and I felt like the gyro was fighting me some what. To keep the plane banked I had to hold constant stick deflection and the same with pitch. After 3 or 4 laps of the field I decided I needed less gain and less expo because I did not care for the feel as currently set up. I turned the gyro back to off and flew the rest of the flight with gyro off.

I made the next flight with expo turned down even more ( almost none) and turned the gain down to 12% green light and 18 % amber light. Flew it this way and it was better but still flighting me ( or maybe I was fighting it) . Again after a couple laps I turned it off and liked the way the plane flies better with out the gyro turned on. I did not turn the gyro on to the amber light position for either flight.

On the drive home I got to wondering if I was flying in the correct ( best or proper) gyro mode. I was of the impression that the steady green light on position with the lower gain was the mode to use for a jet. Clearly I dont have a very good grasp of the differences of these two modes.


I everybody who uses the Cortex gyro loves it, but I did not and it makes me think I am doing something wrong.

Can some one explain the mode differences and which one I should be using and why.


Thanks

At factory defaults, the green LED is "heading hold" and the orange LED is "rate mode". Most jet jocks prefer rate mode at all times. A few people seem to like heading hold. However, heading hold takes some getting used to and may require some setting changes via a computer.

For your next try, use rate mode only (orange LED).

...jim

As Jim stated you do not want to fly in hold mode (green LED). Please set 25% gain in the normal mode (amber LED) and reduce your expo 20% from what you normally use. I'm certain you will like the results. If you have any questions you can email me at: [email protected] or call: 407-687-3126.

Thanks guys. By the time I typed this and posted it I had pretty well decided I must have been flying in the r was the heading wrong mode. No wonder I didnt care for the way it felt. I;m not sure how or where I got it from but I was under the impression that the green light was the rate mode and the other was the heading hold mode. For one thing I was thinking a steady green light was the indication of the preferred mode, seems logical to me anyway. I will reset the gain to around 20 or 25 and try it that way. Not sure what to do with the gain in the heading hold mode, Tempted to go with 0 so if I get in the wrong (heading hold) mode I wont have to fight the gyro. Thanks for the help.

On some radios (Futaba) you can leave the Green setting (hold) out and only have the orange setting (stabilization) in an on and off switch so there is no chance of flying in the wrong mode. Once you learn the gyro and get it setup you can add in the green hold function.

TB

Also with the PC interface you can simply copy the rate mode bank over the hold mode bank so both banks operate in rate mode but at different gains or with nose wheel steering stabilzed in one bank, etc..

Gents this is a very good technique when fine tuning.

What I do after I have a basic gain setting.. (its usually 25-35%), I then set up the other bank with a little more stick priority and a little more rudder gain, and a little less aileron gain.. Then I switch back and forth to see which one I like.. It seems as though its always my ailerons that are hottest. some jets I set up on low rates aileron.

My technique.. FWIW..

Would love to know how you like it after you re-set it. I am using two on "rate" modes. One on my F-35 and the other on my F-16.
On the F-35 is more of a necessity, and I have noticed a significant improvement on how it flies. However on my F-16 I hate how sluggish my elevators have become, even with all the expo taken out, and if I go more than 20% gain.....I get elevator flutter (I don't blame it on the cortex, as the elevator linkage is of very poor design to being with on most F-16 models). So....on the F-16 I will take the elevator channel out, but leave rudder and ailerons, those seem to work well.

David

Do you have a Cortex USB cable? If so lower the elevator gain by 2 points and increase the elevator stick priority 10 points using the Cortex software. While you are in there you might as well set the servo type to digital if it is not already set.

I did a maiden a few weeks ago that had the cortex in heading hold and I had a real hard time flying it. It was a wrestling match lol. But after a few laps trying to trim it out and fighting it I figured it out and turned it off and finished trimming the model out and landed ok. I got in a hurry and forgot to check this before the first flight. Normally I disable the heading hold when I first install the gyro since I will never used it.

Just curious, I see that the cortex has two outlets for JR or Spectrum remote sattlelites! What is the advantage or use for adding sattlelites to the cortex? I am using the AR20120 12ch reciver with 4 sattlelites.

Thanks

TB

Danny, can you provide and info about the relationship between stick priority and dual rate settings in the transmitter ? For example, lets assume I have an airplane where I have 50% dual rates for low rates which I will use for precision flying and high rates set to 100 percent which I will use for extreme aerobatics. I also want the Cortex to decay the gyro gain so that it is essentially off at full stick deflection in each mode so that it doesn't fight my control inputs at all.

I assume I would start by setting both bank 1 and bank 2 for rate mode (have no interest at all in hold mode) and then doing something like setting gains, etc for bank 1 for low rate / precision mode and bank 2 for high rate / 3D mode.
So is there a specific relation ship between stick priority and rates ? It seems there SHOULD be since with different rate settings the Cortex will see different stick deflections. For example, with the Aura 8 gyro which has the ability to set rates and expo internally, setting the stick priority to match the selected rate will cause the Aura to be off at full stick deflection and I would like to be able to understand how to accomplish the same thing with my Cortex. Any suggestions would be appreciated.

You can use the Cortex without a 'main receiver' if you're using satellite receivers plugged directly into the unit. This is a great feature for smaller/lighter models but most jet users have bigger demands and tend to use a more sophisticated RX anyway. In which case you don't need to use the Cortex satellite remote inputs.

I bought the Cortex to be installed on my Ultra Flash , I start by using it on my Extra 300 .
It has been a few months now and no matter what I do I hate the thing .
My airplane flies better without the gyro .Good luck I will not install on my flash , cause my Flash flies like it is on rails . I do not a gyro for that .
I believe this Gryo is overrated .

It's all about the setup! I have found it to smooth out a great flying plane. To each his own!

TB

To say "My airplane flies better without the gyro" is rather meaningless without saying why you feel that way. I can't imagine you could have possibly set it up so badly that it isn't more stable with the gyro. Since you started with it in your Extra do you feel that it fights you during maneuvers or what ? That has been my experience with the Cortex, it made the airplane super stable but fought me during violent maneuvers making them impossible, which is why I asked Danny for some guidance on tuning stick priority, etc a couple of posts ago..
Just curios what issue you actually had with it. If you don't feel it made the model more stable then without a doubt, you failed to complete the setup properly. While I don't much care for the Cortex in an aerobatics airplane because I couldn't get it to not fight me during maneuvers, in a jet is an entirely different story unless possibly you are perhaps using thrust vectoring and are looking to perform violent maneuvers. For the types of maneuvers that a jet such as a Flash typically performs you shouldn't notice the Cortex fighting you at all if it is setup properly, it should simply be even more stable in the wind and require smaller corrections less often during crosswind landings, etc.

I have a Cortex in my Eurosport and I throw that plane around very tightly and violently in all 3 axes. I have never felt the Cortex is fighting me, but I had altered the stick priority by quite a lot before its first flight because I learned years ago that a gyro is only of use to me when sticks are at neutral and I see no point in it still having any effect once the stick is moved more than a small amount away from centre. That way the gyro gives me expo around centre but it fades out very rapidly as the stick is moved, and by 1/4 to 1/2 stick travel the gyro is disabled. I suspect that people finding the gyro is fighting them need to change stick priority a lot so that the gyro is quickly disabled.

It is easy to manually check the effect of stick priority. Turn the aileron gain up to max and rock the model from side to side noticing how the ailerons respond to the gyro, now start slowly moving your aileron stick until the ailerons stop responding to the gyro. If they are still responding almost to the end of stick travel, try altering the priority so that they stop responding to the gyro at a lot less stick travel.

i have a cortex in my ultra flash and it makes a very good plane fly significantly better and smoother. I don't fly aerobatic planes so can't comment on that. I have a cortex on a BobCat, Bandit mkII, and a turbine mini avanti. It makes all these jets fly much smoother. It's all about the setup.

Thanks for the suggestion. I had always tried making small changes to the stick priority and then test flying the airplane and never seemed to be able to get it the way I wanted it. I think your way of adjusting stick priority will help a lot to at least get it close..

If you do increase stick priority and fade out the gyro inputs when the stick is only displaced a small amount, be aware of my comments in the Cortex Pro thread.

If you teach the gyro its settings with flaps up, and have a significant flap-elevator trim adjustment required, then when you lower the flaps, the gyro inputs will be washed out, resulting in potentially very little gyro inputs in the landing config. The gyro doesn't know the difference between trim inputs and pilot stick inputs when determining stick priority wash-out of the gain.

My Ultra Flash requires 34% trim point adjustment between flaps up and landing flap (Jeti DS-16), and with the default rate mode stick priority setting I have minimal pitch gyro inputs with landing flap, even with the landing flap gain cranked all the way up. Each axis is independent in this regard.

According to Joachim (DemonJoe) in reply to my post on the Cortex Pro thread, decreasing the stick priority value will keep the gyro more 'in-the-loop' with these trim change effects. I have yet to try this yet, as waiting for a Pro s/w update before flying it. I may try this on the pitch axis only using the second gyro bank and switch to the second bank with landing flap.

Paul

Paul,
Sure, if you have a large flap to elevator compensation value and you have your elevator stick priority cranked up to the point it disables the elevator function beyond about 1/2 stick input that my be a problem. I wouldn't think that typical elevator compensation values would be a problem if you have the stick priority adjusted so that it fades out the gyro function between about 3/4 and full stick input. Again for an aerobatic plane it would probably be nice to have it go away quicker but for a jet or a war bird when landing, different stick priority settings would be appropriate. I would probably use different banks, both set to rate mode with differnt stiock priorities for landing vs normal, no flaps flight and aerobatics.

Also, it's my understanding that the regular Cortex, which we have been discussing has very different default stick priorities than the Cortex Pro but I could be wrong about that.

Hi Guys

I bought my Cortex after they'd stopped shipping it with the usb cable. I've not needed to set it up with my laptop, and haven't bothered yet about software updates.

For my next gyro which arrived yesterday I decided to buy a Powerbox iGyro3. I also bought the Powerbox usb lead.

Now for my question. Does anyone know if the Powerbox usb lead will work with the Cortex? I don't know anything about the wiring of a usb outlet, but it seems to me that the computer usb socket end must use the same pins, whilst the gyro end for both makes is just a JR-style plug.

Thanks in advance

Gordon

Gordon,

I believe that that question was asked previously and someone confirmed that the Powerbox USB lead will not work with a Cortex.

Paul

That's correct. They are not compatible.

Thanks guys. Sorry I missed the earlier confirmation :)

Gordon