Official Freewing JAS 39 Gripen 80mm EDF Jet

[xviper]

I have the opposite experience with prop planes. They seem to be much more powerful and faster at sea level than at my altitude of 3500'. I've not flown any of my EDFs at sea level so can't say much about that but here's another view on the matter:

https://www.motionrc.com/blogs/motion-rc-blog/having-trouble-flying-your-jet-at-higher-altitudes

I don't think you can use a jet (real or model) that runs on liquid fuel as an example of what it will do at altitude vs at sea level. The expansion factor of burning fuel is huge. You get way more out than what air goes in.

[kallend]

Ah of course. Completely agreed.

While a top speed record will probably be better at higher altitudes than lower, there are factors working in both directions though. While air density adds drag, it also adds thrust. Lower density hurts both, although drag surely is a far more significant factor here.

Taking my Mooney as an example (although it is a non-turbocharged piston plane and not a jet) the speed increases with altitude up to approx. 7,500ft,
at which point the engine starts to run out of breath and the speed steadily decreases above that. The turbocharged models get steadily faster and faster as they go higher, up to about 25,000ft when even the turbo runs out of breath. Electric motors, of course, do not run out of breath.

[kallend]

I have the opposite experience with prop planes. They seem to be much more powerful and faster at sea level than at my altitude of 3500'. I've not flown any of my EDFs at sea level so can't say much about that but here's another view on the matter:

https://www.motionrc.com/blogs/motio...gher-altitudes

I don't think you can use a jet (real or model) that runs on liquid fuel as an example of what it will do at altitude vs at sea level. The expansion factor of burning fuel is huge. You get way more out than what air goes in.

The piston engined Mooney M20S Acclaim tops out at 242 knots at 25,000ft.

[Airguardian]

Never seen the fascination with speed in something as inherently sluggish as an EDF. Even the most powerful EDFs in the world ultimately are not particularly fast.

Add to that that too-fast flying EDFs don't really look scale...

I don't particularly care about top speed per se, but kinetic can be converted to stored energy and a jet that can't climb can't replicate the real thing very well and also isn't that fun to fly in my opinion.

Agree with that, though.

[kallend]

Add to that that too-fast flying EDFs don't really look scale...



Agree with that, though.

I'm willing to trade a few mph/kph of top speed for better acceleration and climb.

Flying on Sunday I saw a very experienced guy only just avoid putting his buddy's Gripen in the weeds because it was so slow to pull out of a high alpha pass.

[FlyBoy90803]

Been flying my Jas-39 with no gyro and felt it would fly better with one. Just purchased the AR8360T 8 Channel with AS3X. I wanted to have gyro on my normal 3 axis's. Also trying to figure out how to get my canards (pitch only) set with gyro. Can anyone give me some suggestions on how to do so?

[kallend]

Been flying my Jas-39 with no gyro and felt it would fly better with one. Just purchased the AR8360T 8 Channel with AS3X. I wanted to have gyro on my normal 3 axis's. Also trying to figure out how to get my canards (pitch only) set with gyro. Can anyone give me some suggestions on how to do so?

That is a very good question.

I have an 8360T in mine (iX20 Tx) but the gyro is only on the elevons and rudder. I *think* I know how to apply the AS3X to the canards, but only if the pitch trim also operates on the canards, which I don't want. I sent a suggestion to Spektrum suggesting uncoupling the canard trim from the elevon trim but I doubt it is high on their list of priorities.

It might be easier just to add a separate Hobbyeagle A3L on the canards!

If you figure it out, perhaps you'll report back.

[Airguardian]

Using two separate gyros is the easy and most straightforward way to solve this and what I did on mine. ;)

Flying on Sunday I saw a very experienced guy only just avoid putting his buddy's Gripen in the weeds because it was so slow to pull out of a high alpha pass.

I did that already! (shame on me, right?)
Walked up to the crash site, unclogged the fan, extended LG, put the jet back on the runway and took off again as if nothing.

[gooniac33]

I have a handful of flights on mine now and love it! Flown it with 6s 65c 5000 packs and didnt care for how heavy it felt. Switched to 6s 30c 5000 packs and much more to my liking!! Plane is fast stable and a joy to land! Added a little down on canards, evened out and lowered the elevon throws as well. No good video yet but here are some pix!

[FlyBoy90803]

That is a very good question.

I have an 8360T in mine (iX20 Tx) but the gyro is only on the elevons and rudder. I *think* I know how to apply the AS3X to the canards, but only if the pitch trim also operates on the canards, which I don't want. I sent a suggestion to Spektrum suggesting uncoupling the canard trim from the elevon trim but I doubt it is high on their list of priorities.

It might be easier just to add a separate Hobbyeagle A3L on the canards!

If you figure it out, perhaps you'll report back.

I set mine up on my DX9 with elevons and rudder as well. I was wondering if I could y the canards and plug them into an open channel and get them to work for pitch. I have an Hobbyeagle A3L so I might just do that and not worry about spending hours trying to get it to work with my 8360T.

If I can figure it out I will certainly let you know but sounds easier to just set up separate gyro for the Canards. Any suggestions on setting up canards with HobbyEagle A3L?

[FlyBoy90803]

Using two separate gyros is the easy and most straightforward way to solve this and what I did on mine. ;)



I did that already! (shame on me, right?)
Walked up to the crash site, unclogged the fan, extended LG, put the jet back on the runway and took off again as if nothing.

Thats what im going to do, Any suggestions on setting up canards with HobbyEagle A3L?

[xviper]

I set mine up on my DX9 with elevons and rudder as well. I was wondering if I could y the canards and plug them into an open channel and get them to work for pitch. I have an Hobbyeagle A3L so I might just do that and not worry about spending hours trying to get it to work with my 8360T.

If I can figure it out I will certainly let you know but sounds easier to just set up separate gyro for the Canards. Any suggestions on setting up canards with HobbyEagle A3L?

If you are going to "Y" the canards together, first you must make sure they both work in the same direction, so if they don't, then you'll need to reverse one with a reverser or rewire the servo's internals. Once they're going in the same direction (and the correct direction), you can plug that "Y" lead into the ELE output of the A3L. From the A3L to the RX, you'll need to plug that lead into whatever port you decide to use to make the canards work. Dial in the gain either conservatively to start with or hook up the master gain from the A3L to the knob or slider on your TX (a different one than what you are using for master gain on the main gyro).

[FlyBoy90803]

If you are going to "Y" the canards together, first you must make sure they both work in the same direction, so if they don't, then you'll need to reverse one with a reverser or rewire the servo's internals. Once they're going in the same direction (and the correct direction), you can plug that "Y" lead into the ELE output of the A3L. From the A3L to the RX, you'll need to plug that lead into whatever port you decide to use to make the canards work. Dial in the gain either conservatively to start with or hook up the master gain from the A3L to the knob or slider on your TX (a different one than what you are using for master gain on the main gyro).

That makes sense, what about just leaving them as separate leads? Would I just use elevator and aileron ports then plug those into two open spots on my receiver? Trying to figure out the easiest solution.

[xviper]

That makes sense, what about just leaving them as separate leads? Would I just use elevator and aileron ports then plug those into two open spots on my receiver? Trying to figure out the easiest solution.

Not sure how that would work. You could try it, but if you separate the channels on the A3L, now you've got one acting as elevator and the other as aileron (if the A3L is set as "normal wing"). You can't set the A3L as "elevon" for obvious reasons. Then comes the mixing in the TX if you use two open ports on the RX and tell them both to act as elevators, BUT, how does the A3L decipher two elevator signals when you've got them plugged into two different inputs and outputs (1 ELE and 1 AIL for each)?

[FlyBoy90803]

Not sure how that would work. You could try it, but if you separate the channels on the A3L, now you've got one acting as elevator and the other as aileron (if the A3L is set as "normal wing"). You can't set the A3L as "elevon" for obvious reasons. Then comes the mixing in the TX if you use two open ports on the RX and tell them both to act as elevators, BUT, how does the A3L decipher two elevator signals when you've got them plugged into two different inputs and outputs (1 ELE and 1 AIL for each)?

That makes sense, Y is the best way to go.

[xviper]

That makes sense, Y is the best way to go.

It may not be the only way. I suppose it's possible to use a fancier gyro. The A3L is the simplest of the HobbyEagle gyros and for almost all my applications, the more expensive gyros aren't needed.

[Airguardian]

Thats what im going to do, Any suggestions on setting up canards with HobbyEagle A3L?

Hope you were referring to the 2 gyros thing and not to crashing the jet by stalling it on high alpha!

I don't have personal experience with that gyro but, as I've said a few times in the thread, use rate (normal) mode rather than 'heading' hold or 'autolevel' functions, use a normal pitch-to-canards trim on the transmitter and experiment with it. With my particular gyro I can set maximum gain and I don't suffer any oscillations but that could be gyro specific so best praxis is to start with medium/low gain and slowly increase it until the jet starts oscilalting or until you like the feeling best.

Then the more aft you move your CG, the more 'scale' the canards will act while working with the gyro on.
Of course, there's a limit to that, if you set CG ridiculously aft, not even the gyro would keep the jet stable but doubt that's gonna be an issue here considering how hard it is to shift CG back on this bird.

And of course, if you manage to actually get a very-aft CG setup with gyro on, DO NOT turn it off.

If you are flying balanced and turn the gyro off, it wouldn't be a problem though, but if you got into 'slightly tail-heavy' realm, switching gyro off could be a handful to keep the aircraft under control.

My canards gyro is always on, both on this jet and on the Eurofighter.
The Eurofighter is 'permanently tail-heavy' and the Gripen, hopefully will soon join the ranks. :)

[FlyBoy90803]

Hope you were referring to the 2 gyros thing and not to crashing the jet by stalling it on high alpha!

I don't have personal experience with that gyro but, as I've said a few times in the thread, use rate (normal) mode rather than 'heading' hold or 'autolevel' functions, use a normal pitch-to-canards trim on the transmitter and experiment with it. With my particular gyro I can set maximum gain and I don't suffer any oscillations but that could be gyro specific so best praxis is to start with medium/low gain and slowly increase it until the jet starts oscilalting or until you like the feeling best.

Then the more aft you move your CG, the more 'scale' the canards will act while working with the gyro on.
Of course, there's a limit to that, if you set CG ridiculously aft, not even the gyro would keep the jet stable but doubt that's gonna be an issue here considering how hard it is to shift CG back on this bird.

And of course, if you manage to actually get a very-aft CG setup with gyro on, DO NOT turn it off.

If you are flying balanced and turn the gyro off, it wouldn't be a problem though, but if you got into 'slightly tail-heavy' realm, switching gyro off could be a handful to keep the aircraft under control.

My canards gyro is always on, both on this jet and on the Eurofighter.
The Eurofighter is 'permanently tail-heavy' and the Gripen, hopefully will soon join the ranks. :)

Haha yes I was talking about 2 gyros, its not worth the hassle trying to dial it in with just my Spektrum 8360T. Makes sense that if I am flying aft, turning off gyro will result in... money spent! I have made that mistake before. Thanks for the help.

[kallend]

Not sure how that would work. You could try it, but if you separate the channels on the A3L, now you've got one acting as elevator and the other as aileron (if the A3L is set as "normal wing"). You can't set the A3L as "elevon" for obvious reasons. Then comes the mixing in the TX if you use two open ports on the RX and tell them both to act as elevators, BUT, how does the A3L decipher two elevator signals when you've got them plugged into two different inputs and outputs (1 ELE and 1 AIL for each)?

I suspect you could set it up as "elevon" with the roll gains set to zero so it only stabilizes pitch. haven't tried it (yet).

[Airguardian]

Now that's an interesting idea!

Would solve the problem of needing to invert a servo direction.