Realistic tow height depending on cloud base

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Kekelekou
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Realistic tow height depending on cloud base

Post by Kekelekou » Mon Jan 23, 2023 2:46 pm

Hello!

I have been creating the Condor tasks depicting the 2014 33rd WGC in Räyskälä as a bonus to my scenery : viewtopic.php?f=37&t=21217&p=180841#p180841

As a little experienced virtual pilot, I am facing an unexpected issue, which is how to set the tow height in a realistic way.
I suppose that there is little use towing about 1500m AGL if the cloud base allows for it. But with lower cloud bases (from 1000 to 1500m), what would be a sensible figure : 200m below cloud base? 100m?

Thank you in advance, your input will be much appreciated!
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EDB
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Re: Realistic tow height depending on cloud base

Post by EDB » Mon Jan 23, 2023 3:09 pm

Realistic?

Towing is quiet expensive so a normal tow in NL is 500m AGL. You can go higher if you inform the tow pilot in advance. If cloudbase is high, it is more difficult to catch a thermal. In NL cloudbase is usually not very high. 1000 to 1200m on an avarage good day. 1800m on a very good day. 2300m is very rare. With cloudbase at 1800m, I would take a 600m tow (1/3).

In the east tows are less expensive so tows to 600m or 800m are more common. But cloudbase is usually higher too.

For Acro a tow often goes to 1000m AGL if I remember it correctly.

In Condor tows are free so usually higher... But not realistic.

If you go higher you have to indeed think about max start height (AMSL) and cloudbase (AGL in Condor/ AMSL in RL). A higher tow might give an advantage.

And you have to take into account that high tows will take longer to get every glider airborne. Especially when the start sector is further away from the airport. Something you need to do for other reasons.

In the documents of the 2014 33rd WGC in Räyskälä (600m) :

Local Procedures WGC2014 Ver E wrote:
7.3.2 Launch procedures for motor gliders
Motor gliders may self launch or launch by aero tow. For motor gliders taking off autonomously,
they must follow the designated launch pattern and the engine must be switched off in the release
zone, at or below the standard release height 600 m AGL or other height fixed at briefing.
The release areas and the designated launch patterns are indicated in the figure of Appendix F.

7.3.3 Release Areas and Release Heights
The standard release height is 600m AGL. Release areas and towing patterns will be described
during the daily briefing.
The release areas and the designated launch patterns are indicated in the figure of Appendix F.
Within the distance of 10 km from Räyskälä airfield only circling to left is allowed.
2023-01-23 18_14_12-Window - 50%.png
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Kekelekou
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Re: Realistic tow height depending on cloud base

Post by Kekelekou » Mon Jan 23, 2023 8:25 pm

Thanks EDB for your comprehensive input! Makes a lot of sense.
You have given the idea to check the release altitude on the IGC files from the competition (before you edited your post) and the average is 700/750m, EFRY lays at 122m MSL.
What matches the procedures of 600m AGL.
Could you point me to the site when you found the document by the way?
Thanks again. :D
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EDB
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Re: Realistic tow height depending on cloud base

Post by EDB » Tue Jan 24, 2023 1:53 am

Kekelekou wrote:
Mon Jan 23, 2023 8:25 pm
Could you point me to the site when you found the document by the way?

I think it was wgc2014.fi, but it doesn't exist anymore. I took the info from my personal archive.

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Kekelekou
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Re: Realistic tow height depending on cloud base

Post by Kekelekou » Tue Jan 24, 2023 8:57 am

Yes, the website is down, it would have been a goldmine :(
Any chance you could send the pdf file to me by email?
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Avelina
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Re: Realistic tow height depending on cloud base

Post by Avelina » Tue Jan 24, 2023 7:52 pm

https://web.archive.org/web/20161024143 ... gc2014.fi/ - Probably not all of the links will work, but there's a bit still around.

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Kekelekou
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Re: Realistic tow height depending on cloud base

Post by Kekelekou » Tue Jan 24, 2023 9:21 pm

Avelina wrote:
Tue Jan 24, 2023 7:52 pm
https://web.archive.org/web/20161024143 ... gc2014.fi/ - Probably not all of the links will work, but there's a bit still around.
Nailed it Avelina! Even the daily briefings are available! Thanks!
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DanD
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Re: Realistic tow height depending on cloud base

Post by DanD » Tue Feb 07, 2023 1:55 pm

I love the Wayback Machine - https://web.archive.org/ . A great link for old but useful information that has 'gone away'.

Dan
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