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F-20 development

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Re: F-20 development

Postby swampthing » Fri Jul 17, 2020 5:57 pm

The window that opens up when you load the plane has the top cut off. O moved it to the side and it went away once I started the plane. Mu opinion the throttle detent sounds are extremely loud. You may want to lower volume for them. I got into a deep stall nearly hitting the ground could recover instantly with some throttle, that probably should not happen, I think I should have hit the ground. Its nose heavy even above 600 knots even trimming the elevators out quite a bit. I finally let it crash and thats when i see the ground reactions need a lot of work. It went crazy and locked up Flightgear, Ig you need help with that send me a PM. Other than that looking good.

All the best Steve
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Re: F-20 development

Postby Flying toaster » Fri Jul 17, 2020 8:28 pm

swampthing wrote in Fri Jul 17, 2020 5:57 pm:The window that opens up when you load the plane has the top cut off. O moved it to the side and it went away once I started the plane.

What is the resolution of your window ? I will see if I can move the window default position to improve
Mu opinion the throttle detent sounds are extremely loud. You may want to lower volume for them.

Agreed, I will put in the todo list
I got into a deep stall nearly hitting the ground could recover instantly with some throttle, that probably should not happen, I think I should have hit the ground. Its nose heavy even above 600 knots even trimming the elevators out quite a bit.

Now that is very weird. Once the gear is up, the aircraft should need no trimming at all. The fcs has a g-demand law so if you release the stick in level flight, it should remain around 1-g without any trim.

Also the behavior near stall is as expected. Actually if you yank the stick all the way back but without bleeding too much speed, it will remain stuck at around 30 degrees alpha and just stay there indefinitely. Straight wings have a lesser tendency to pitch up and deep stall than swept wing. This is why the f/a-18 (which configuration is similar to the F-5 family for obvious reasons ;) ) can do the famous "hornet walk" sticking its nose at very high alpha without losing control.
What you did looks actually like a hornet walk. You stuck the nose at alpha max and used power to keep altitude despite the massive drag from lerx lift. This is possible because a clean F-20 is kind of overpowered. It may even be possible to regain altitude in a deep stall at low altitude, but only at full afterburner and very reluctantly (basically, it is a rocket)
Your experience may differ with a full load.
If you want to deep stall the F-20, you will need to do a tail slide and even then, not all configurations will lead to the same results. The AOA will settle around 50 degrees, and the nose will bob up and down, until you get into denser atmosphere where you can try to power out of the stall. You may try to break the deep stall earlier by rolling the aircraft, though it will be difficult.
If you play with loads (fuel tanks mostly) and rudder, you can even start a semi stable spin ( though most of the time recoverable with some work)
Finally, if you really want some more excitement, this new version comes with the controls to switch off the FCS (CAS controls on the left console of the cockpit). You will have the "raw" aircraft, with the ability to pull incredible g's and a fairly nauseating Dutch roll.
I finally let it crash and thats when i see the ground reactions need a lot of work. It went crazy and locked up Flightgear, Ig you need help with that send me a PM. Other than that looking good.

All the best Steve

Yep I did not define body contact points in the FDM... Should go in the to-do list also

Thank you very much for the feedback

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Re: F-20 development

Postby swampthing » Fri Jul 17, 2020 11:25 pm

My resolution is 1600x900. For the stall I had power off and let it fall. yes the nose did bob up and down some, it would come back up after pitching down and gaining speed about 115 knots if i remember right. Gear was up so I;m not sure why the FCS did not kick in. I didn't do a low altitude, low speed high AOA pass. that something I like to do and yes the F-18 is great at that. I've seen them do it in person. Its a shame this plane was never put into production I'm a big fan of the F-5 and the F-20 that sadly never got its chance.
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Re: F-20 development

Postby Flying toaster » Sat Jul 18, 2020 6:17 am

On this simulation, if you have to keep the stick back to remain in stall, you are not in deep stall. If you push the nose down and it does not come back then you are in deep stall. The difference can also be spotted on AOA (around 30 vs 50).
To do a hornet walk, I usually put the engine at idle, bleed the speed off until the aircraft can't maintain altitude, then raise the nose until the stick is full aft back (in general you will be around 90kts and 27/30 degrees AOA). Then increase gradually thrust until the velocity vector on the HUD is just above the horizon, with the stick still full aft. With light loads you can keep there until you run out of fuel. To leave, release the stick, and to leave real fast release gradually as you go to full AB
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