Official Freewing JAS 39 Gripen 80mm EDF Jet

[Airguardian]

Don't quite agree. I felt it lacking even without the TV. Flight time was great but the plane was lackluster as it came stock.

[kallend]

I really think the stock fan choice for this bird is really not great. FW should work harder on that aspect of their models IMO.
Still a fantastic jet though, made three flights just the other day in absolute 0-wind conditions and I had an absolute blast!

FMS PRO makes a difference.

[Airguardian]

It does on the Su-35, bet it will too on the Gripen ;)

[flightaddict]

On another subject regarding the canards. From Airguardians earlier posts on the subject, the canards should be on a gyro set to stability in pitch to modify the flow over the main wing. Does that mean that there should be no input from the elevator stick into the canards? I have mine set to run off the gyro in stability mode but the elevator mix still overrides the gyro in that I can go to the limits in canard pitch. I think the canards should be high manual rates when taking off but maybe more gyro controlled when the gear is up and in normal flight. Does that sound right?

[Evan D]

I don't use gyros on either of my Gripens...

[Airguardian]

On another subject regarding the canards. From Airguardians earlier posts on the subject, the canards should be on a gyro set to stability in pitch to modify the flow over the main wing. Does that mean that there should be no input from the elevator stick into the canards? I have mine set to run off the gyro in stability mode but the elevator mix still overrides the gyro in that I can go to the limits in canard pitch. I think the canards should be high manual rates when taking off but maybe more gyro controlled when the gear is up and in normal flight. Does that sound right?

I don't cut the pitch feedback from the radio to the canards, there's no need to. You can do it though and test it out. I did it back in the day for the Eurofighter. I would run canards on pitch only with a gyro and the pitch output of the receiver could be toggled on and off with an easy transmitter mix. For the most part, I feel more comfortable flying with the pitch being on. Otherwise, the canards will actually fight your inputs. It's usually not a big deal because elevons still have more authority but it may be less than ideal in a number of conditions so, my recommendation is: set it up as if there was no gyro in between with pitch being fed to canards, but put the gyro in between because it works really well IME.

Plane can fly without it too, but I like it better with the gyro.

And then, if you feel like experimenting, have the 'no-pitch' mix on a switch so you can turn it on and off to notice the difference. The jet will suddenly act more 'sluggish' but it will also likely look as if it carries through the air with a bit more inertia. So up to personal preference I guess. It also depends on gyro gain and throws. If you give the canards/gyro too much authority and cut the pitch input feedback, then they may fight your elevons too badly, and you don't want that.

The beauty of using the gyro is precisely that it will usually adapt the canard deflection according to pilot input to maintain pitch rate, and for a well balanced plane (neutral CG or close to), this translates to the canards pitching slightly down through many maneuvers, similar to what you see on the full scale jet.

On that topic, I recently gave a talk on Extreme Aerobatics as performed by fighter jets and the physics behind and there's a section in there talking about canards precisely, so that may be of interest to you ;)

[flightaddict]

Thanks for the info. I too was feeding my pitch through to the canards from my S8R to a Hobby Eagle A3 Pro and mixing them. I wasn't sure if the manual pitch was just swamping the gyro effect with high stick input,
In one of the previous posts, one of the guys here has a set up for landing he called virtual flaps since the model has no physical flaps. The way he described it, it seems like he had the canards not working on pitch, just on the gyro and pitch down about 5mm. Sometimes I have noticed when landing, the plane seems to want to pitch up a bit and keep flying and I have to reduce pitch and increase power. On my field, the slower the landing, the longer the gear last. I was thinking of a landing mode that would set the canards on gyro pitch with a slight down angle so that it would smooth out the landings. I have set it up on a three position switch for my gear that sets normal pitch feedthrough on gyro in gear up position, gyro only in the center position with gear down and normal pitch feedthrough and gyro in the third position with gear down. . All have a slight down pitch on the canards in the neutral state. I wanted to maintain the option of full up canard deflection to help with rotation on take off but I am not sure if the canards help much for that. I have no numbers on the gyro gain but I have it set on a slider to give about 1cm down deflection on a fairly sharp pull up by hand on the nose. So far it flies ok but seems to be a little pitch sensitive although it doesn't stall or do anything bad. Thanks for the video, it is fascinating and very informative.

[Airguardian]

Glad to be helpful!

I have my canard gain gyro maxed out. No oscillation problems with the stock gear setup. Your experience with other gyros may differ though.
As for offset, mine is permanently trimmed a bit down for the entire flight, typically between 3 and 7mm pitch down (I use to experiment).
This is very CG dependent, the more aft CG, the more down canard trim you usually want. If you overdo it though, the plane will feel like it wants to drop the nose.

[flightaddict]

Thanks again. I will try this setup. This plane seems to be very tolerant of CG and control surface experiments. Do you think the canards help with rotation on take off?

[xviper]

Thanks again. I will try this setup. This plane seems to be very tolerant of CG and control surface experiments. Do you think the canards help with rotation on take off?

If you set them up the way they are set up like the FMS Rafale, the canards move very little. If you set them up aggressively like you have described, then they can help with take off rotation BUT then, if you don't turn them down during flight, your pitch response will make the plane act like a roller coaster and difficult to fly smoothly.
I have very little movement in my canards during flight and I use them on high rates for speed brakes (full down) on the landing roll. I've also had the canards tied into the elevons and gyro control. Then I removed the canards from the gyro. Flight characteristics didn't change much. I now fly the Gripen with the gyro only controlling the elevons and rudder and the plane is solid. There is no need to complicate things even further by putting the canards on the gyro. There are two other Gripens at my field. One has no gyro and the guy flies it really well, no complaints. The other fellow started off flying with no gyro and was about to give up on the plane until he decided to put a gyro on it. The plane used to wing rock and waddle all the time. He hated that. After the gyro was put on, it become very smooth and steady and it is one of his favorite planes now. It guess it depends on how you fly and how you set it up.
PS. When you have the gyro ON, stick movements over-ride the gyro in that axis. The gyro intervenes primarily when the sticks are still and neutral. If you dial in gain to just before the point of oscillation, initial stick movement will still allow "some" gyro intervention. Lower gain, the gyro is defeated easily when the sticks are moved. Otherwise, the gyro will think stick movement is no different than a gust of wind and will fight the stick - resulting in nothing happening when you try to control the plane.

[Airguardian]

Thanks again. I will try this setup. This plane seems to be very tolerant of CG and control surface experiments. Do you think the canards help with rotation on take off?

I guarantee you they do! ;)
And yes, it is very CG tolerant, can be flown safely within quite a large CG range.
Still, be always careful and perform CG changes in small increments.

[Airguardian]

If you set them up aggressively like you have described, then they can help with take off rotation BUT then, if you don't turn them down during flight, your pitch response will make the plane act like a roller coaster and difficult to fly smoothly.

Not necessarily.

There is no need to complicate things even further by putting the canards on the gyro.

Need?
There's no need. No need to use a gyro at all. No need to even fly RC planes to begin with.
But a gyro on canards can do things for you when set up appropriately, that's the point I think you are missing.
I'm not saying one can't fly without the gyro, that's ridiculous. Almost as ridiculous as suggesting the gyro won't do anything for you ;)

It guess it depends on how you fly and how you set it up.

Aye, to an extent.

PS. When you have the gyro ON, stick movements over-ride the gyro in that axis. The gyro intervenes primarily when the sticks are still and neutral.

That's essentially false.

Of course different gyro brands and algorithms operate differently and one must account for that but the main operation of a gyro is not a total stick override whenever the sticks are not center, that is NOT how gyros work.

If that was so, my canards wouldn't be pointing down through turns when I am pulling pitch-up on the stick.

You can make a quick test, hold your pitch stick slightly in a pull up position and then ask a friend to wiggle the airplane in the pitch axis. You will see the gyro still does control the canards actively despite you giving a direct pitch command.

Otherwise, if you pull, FULL PITCH UP stick, then, depending on gyro settings, the gyro may saturate and command full up deflection regardless, but that's an extreme case, not what is going on through most of the flight.

[kallend]

I have separate gyro on the elevons from the one on the canards and TV, so I can adjust the gains independently.

[kallend]

Not necessarily.




Need?
There's no need. No need to use a gyro at all. No need to even fly RC planes to begin with.
But a gyro on canards can do things for you when set up appropriately, that's the point I think you are missing.
I'm not saying one can't fly without the gyro, that's ridiculous. Almost as ridiculous as suggesting the gyro won't do anything for you ;)



Aye, to an extent.



That's essentially false.

Of course different gyro brands and algorithms operate differently and one must account for that but the main operation of a gyro is not a total stick override whenever the sticks are not center, that is NOT how gyros work.

If that was so, my canards wouldn't be pointing down through turns when I am pulling pitch-up on the stick.

You can make a quick test, hold your pitch stick slightly in a pull up position and then ask a friend to wiggle the airplane in the pitch axis. You will see the gyro still does control the canards actively despite you giving a direct pitch command.

Otherwise, if you pull, FULL PITCH UP stick, then, depending on gyro settings, the gyro may saturate and command full up deflection regardless, but that's an extreme case, not what is going on through most of the flight.

Stick priority is adjustable on all but the cheapest gyros. Gyro gain on an axis decreases as the stick moves away from center.

[flightaddict]

Thanks for the input guys. I tried it with reduced stick, full gyro gain on the canards and slight down angle at neutral and it did fly smoother and more locked in. I have it on a switch so I can switch back to full stick effect on landings and takeoffs. I have the Hobby Eagle A3 Pro. I will have to check if it has stick priority adjustment. I am loving the way this thing flies now that I put the 12 blade fan in. FW should have gone with it to begin with. Reinforcing the landing gear would have been good too for grass fields. Greased a landing today and as it was rolling out, it hit a lump of grass or dirt, bounced around and almost tipped over, but the reinforced gear held up.

[Airguardian]

Good to hear, now time to enjoy the bird! :)

[Beggsy]

Had around 80 flights with mine now and it’s my favourite ever edf! COG 40mm behind marked with VT unit and 3D printed nozzle design posted here, stock power, slight down angle on the canards(adjustable for high alpha), canards elevator only. I’d never have got the performance I did without all the info on here. Thanks everyone! 😊

it would be nice with a bit more poke out of the thrust but still a great model.

Here it is

https://youtu.be/8J7m8e5ezxw

[kallend]

it would be nice with a bit more poke out of the thrust but still a great model.

What edf unit are you running in it? A fairly inexpensive thrust increase without killing the flight time or needing a new ESC can be had by installing the FMS PRO 3280 2100kV unit.

[Beggsy]

What edf unit are you running in it? A fairly inexpensive thrust increase without killing the flight time or needing a new ESC can be had by installing the FMS PRO 3280 2100kV unit.

Running stock unit. I’ll have a look at that, thanks!

[Airguardian]

Had around 80 flights with mine now and it’s my favourite ever edf! COG 40mm behind marked with VT unit and 3D printed nozzle design posted here, stock power, slight down angle on the canards(adjustable for high alpha), canards elevator only. I’d never have got the performance I did without all the info on here. Thanks everyone! 😊

it would be nice with a bit more poke out of the thrust but still a great model.

Here it is

https://youtu.be/8J7m8e5ezxw

Love to hear that!
And cool flying too! That high alpha was pretty stable and well managed ;)

And as Kallend points out, the stock EDF power is not really impressive but you can upgrade it, I bet his FMS recomendation is a sound one.
I tried going 8S but it's a tricky setup because for all the extra thrust you get, you may often find flight times are not as great, but I've heard the FMS is a good compromise (and cheaper at that).
Did the likewise thing on my Su-35 recently and it provided fantastic results.

Hope Freewing reads this and ups their game in stock powerplants in the times to come!