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Re: Wednesday evening session: sailplanes at Zell am See

Postby D-ECHO » Mon May 10, 2021 1:37 pm

There are multiple parts to making aerotow work out:
* Lag: Both pilots need good FPS and should be on the same mpserver in order to minimize network lag
* Tow parameters: These can be set by the glider pilot using the menu. Especially important for the experience are the elastic constant and also the rope length, as a longer rope can give more time to react before accidentally overtaking the towing aircraft
* Flying: The glider pilot should be very alert all the time during tow. Their position, once in the air, should be slightly above the towing aircraft, but never more than a few degrees. In turns, the glider's nose should point to the outer wing of the towing aircraft. When the glider gets too fast, thus loosening the tow rope and getting closer to the towing aircraft, they can use sideslip (more difficult) or the airbrakes *cautiously* to reduce their airspeed
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Re: Wednesday evening session: sailplanes at Zell am See

Postby benih » Mon May 10, 2021 1:40 pm

What elastic constant and rope length are you suggesting?
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Re: Wednesday evening session: sailplanes at Zell am See

Postby Ysop » Mon May 10, 2021 4:02 pm

Thanks D-Echo, for the airtow introduction!
Apparently we will have a lot of fun trying :-)

Assuming, the rope has 5% break elongation, it's length will vary between 60 and 63m. There is the impression, that it also transmits forces also at distances smaller 60m.
But as said it is possible with a lot of work with stick and rudder. I was told to steer in position just to see the top side of the towing craft.

We can talk with Jitsi again. Sorry for the Audio problems last times! At least I am zeroing on it it and have another idea to try out.
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Re: Wednesday evening session: sailplanes at Zell am See

Postby D-ECHO » Mon May 10, 2021 6:05 pm

benih wrote in Mon May 10, 2021 1:40 pm:What elastic constant and rope length are you suggesting?

Unfortunately, I don't remember what used to work, it's quite some time ago. I can try a bit around using the drag robot, even though of course that one doesn't behave just another pilot.
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Re: Wednesday evening session: sailplanes at Zell am See

Postby D-ECHO » Mon May 10, 2021 6:14 pm

Quick test showed that a lowered elastic constant (e.g. only 200N) resulted in a way smoother thus easier ride, but I think this also means less realism (don't know the elastic constant of irl used ropes off the top of my hand though). When you enter into oscillation (speeding up, almost hitting the tow rope and then no pull as the rope isn't tight, slowing down, ...), in my experience applying airbrakes anti-cyclical helps.
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Re: Wednesday evening session: sailplanes at Zell am See

Postby Johan G » Tue May 11, 2021 10:03 am

D-ECHO wrote in Mon May 10, 2021 1:37 pm:There are multiple parts to making aerotow work out:
* Lag: Both pilots need good FPS and should be on the same mpserver in order to minimize network lag
[...]

Regarding lag, there is a FlightGear feature that you can enable and tune that will help a lot with that.

This FlightGear wiki article should be of help: Real Time manual (permalink)
Low-level flying — It's all fun and games till someone looses an engine. (Paraphrased from a YouTube video)
Improving the Dassault Mirage F1 (Wiki, Forum, GitLab. Work in slow progress)
Some YouTube videos
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Re: Wednesday evening session: sailplanes at Zell am See

Postby benih » Tue May 11, 2021 2:03 pm

So i think we should at least all join the same mp server.
Should we take mp3?
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Re: Wednesday evening session: sailplanes at Zell am See

Postby Ysop » Tue May 11, 2021 8:19 pm

Thanks, Johan! As usual our wiki is full of valuable information!

20mm PP-rope 60 m could have 8000N/m elongation. So this is worth experimenting. And practicing, which might be root cause of the problem.

Wednesday evening we'll have ZERO wind by real weather and high pressure region with active thermals could work, but it is very hard to find and use thermals. Hence we should use 10kts wind from 180°, so there is the chance of ridge lift.

First try with mp3.

We are not too many, aren't we?
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Re: Wednesday evening session: sailplanes at Zell am See

Postby benih » Tue May 11, 2021 9:35 pm

Ysop, will you prepare a METAR string we should use in the launcher?
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Re: Wednesday evening session: sailplanes at Zell am See

Postby benih » Wed May 12, 2021 1:19 pm

I made a rough skyvector route for the Spaziergang. With winds from south we should be able to do this :)
-> https://skyvector.com/?ll=47.1942385361 ... 46E%20LOWZ

Jitsi: https://meet.jit.si/FlightgearSoaringZellAmSee

And i have read in the wiki, that all we need is advanced weather + Terrain Effects and Generate Thermals activated therein.

Also be sure to have the latest ASK21 glider and the c182s addon version ready for towing :).


We can use the old assigned starting positions again:
(just drop them in the launcher location input box and adjust heading in the location dialog):

Please tell which one you'll use, so we don't crash into each other :)

- P1 47.292474, 12.789991 @160° (i'll take this one)
- P2 47.292394, 12.789712 @160°
- P3 47.292333, 12.789034 @160°
- P4 47.292035, 12.789641 @345°
- P5 47.291897, 12.788799 @345°
- P6 47.291663, 12.787390 @345°
left of P6 are still some spots left, if needed.

Image
Last edited by benih on Wed May 12, 2021 5:03 pm, edited 1 time in total.
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Re: Wednesday evening session: sailplanes at Zell am See

Postby benih » Wed May 12, 2021 1:56 pm

Weather is overcast. I would suggest:
- Starting time = noon
- Weather = manual input: "XXXX 121100Z 18008KT 12SM SCT048 FEW300 25/08 Q1022 NOSIG" (QNH is 30.17 inHG)

(Max crosswind is 8KT or 15km/h!)


I try to join at about 17:30 UTC to start towing operations if someone is there already.
I added speed infos to the wiki entry, max towing speed is 180kmh for aerotow and 150 for the winch.
Last edited by benih on Wed May 12, 2021 6:04 pm, edited 2 times in total.
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Re: Wednesday evening session: sailplanes at Zell am See

Postby TheEagle » Wed May 12, 2021 3:17 pm

I take parking spot 6, 'cause it's the nearest to the airport RUNWAY ! :wink:
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Re: Wednesday evening session: sailplanes at Zell am See

Postby Ysop » Wed May 12, 2021 3:41 pm

Thanks for preparing!

Suggest as above to use rwy26 and just roll forward to make room for the next one. From the parking position it would by quite a long walk=taxi.

Is the trip feasible in 8kts? We will find out, this is part of the game!
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Re: Wednesday evening session: sailplanes at Zell am See

Postby benih » Wed May 12, 2021 4:59 pm

I just tried it, and 8kts gives ridge lift already. However the thermals are not so stable and small patched. I was not able to climb enough to make it to the Schmittsenhöhe, but this also was my third attempt at gliding, and the first success in gaining any lift at all.
If you have better weather ideas, please post 'em :)

As for the starting sports: You of course are right. Lets do it like this. I will start the cessna off-runway for safety reasons, however.
The gliders should however not roll forward: that will reduce the already short takeoff distance even further; please:
- after starting on the runway, roll back behind the latest plane. The first plane will go just one plane-length to the rear, so the start spot remains clear.
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Re: Wednesday evening session: sailplanes at Zell am See

Postby benih » Wed May 12, 2021 5:03 pm

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