MC setting?

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Fingers
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MC setting?

Post by Fingers » Fri Sep 17, 2021 11:24 am

Hi Folks

Just wondering what the MC setting is doing and what it is used for? Is it possibly calibrating the vario for desired sink indication.

Steve

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OXO
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Re: MC setting?

Post by OXO » Fri Sep 17, 2021 11:27 am

Chris Wedgwood,
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Fingers
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Re: MC setting?

Post by Fingers » Fri Sep 17, 2021 12:15 pm

OXO wrote:
Fri Sep 17, 2021 11:27 am
https://en.wikipedia.org/wiki/Speed_to_fly
Ahh, that's great thanks. So its based on the expected climb of the thermals which can be edited on the fly to suit.

"We can switch from vario to “speed command” with the default RIGHT CTRL key."

Sorry if I am missing something obvious and repeating questions asked previously but where on the dash is it pointing to the best speed to fly?

The vario needle will then show if we are flying too fast or too slow. If the needle shows up, we are flying too fast and vice versa. To relieve the pilot from watching the vario all the time, the sound signal is also emitted. If we are too fast, the tone is high, if we are too slow, the tone is low and if we have the right speed, the vario becomes quiet.

This sounds like its doing the opposite that I would expect from the vario, if I am going too fast I would expect to be loosing height and the vario going negative.?

Maybe its about time I looked through the manual. :-)

Advanced – MC theory

When trying to maximize your cross-country average speed, you come to the question of how fast to fly between thermals. You can fly fast to reach the next thermal as quick as possible, but you will lose a lot of height that will have to be gained back in the next thermal. On the other hand, you can fly slowly and preserve your height, but you will loose too much time to reach the thermal.
The problem was solved by Paul McCready and his theory is called MC theory. It says that the optimal speed to fly between the thermals is the same as the speed of best glide when flying trough sinking air with vertical speed that is equal to the rate of climb in the next thermal. Sounds complicated?
Today we luckily have computer instruments on board of every modern glider that show us how fast to fly. There is one important thing that the pilot must estimate himself though: the expected rate of climb in the next thermal. This rate of climb is usually called MC setting. If we expect 2 m/s climb, we set the MC to 2.0 and the computer will output the optimal speed to fly.
One would expect that the optimal speed to fly remains constant till we change the MC setting. It is indeed the case in still air. But if we fly through the air that moves either vertically or horizontally, then the optimal speed will change. But the pilot has nothing to worry about as the computer does the job – the pilot only follows the given speed.
We can switch from vario to “speed command” with the default RIGHT CTRL key. The vario needle will then show if we are flying too fast or too slow. If the needle shows up, we are flying too fast and vice versa. To relieve the pilot from watching the vario all the time, the sound signal is also emitted. If we are too fast, the tone is high, if we are too slow, the tone is low and if we have the right speed, the vario becomes quiet.

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wickid
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Re: MC setting?

Post by wickid » Fri Sep 17, 2021 12:41 pm

Fingers wrote:
Fri Sep 17, 2021 12:15 pm
This sounds like its doing the opposite that I would expect from the vario, if I am going too fast I would expect to be loosing height and the vario going negative.?

Maybe its about time I looked through the manual. :-)
Try it, it makes sense when you fly. If you have it on speed command and you fly into a thermal you will be going too fast for the actual conditions. The needle will in this case show fly slower which is pointing positive. So it will show positive when entering a thermal and negative when in sinking air unless you are doing the correct speed for the conditions and your MC setting.

Don't try to chase it too much. Pulling up too strongly and then diving again usually doesn't gain you much more energy than just gently bleeding some speed off and gently going back to cruise speed. But it will cost you a lot of Cross Country speed. See the speed to fly as a guide. Only when you plan on turning bleed the speed off to thermalling speed. Also G-loading increases your lift requirement and therefor the Drag. So pulling up into a thermal with a lot of G's isn't very efficient either.
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Re: MC setting?

Post by Fingers » Fri Sep 17, 2021 5:09 pm

If we expect 2 m/s climb, we set the MC to 2.0 and the computer will output the optimal speed to fly.

Thanks for helping here folks, sorry if I am being a bit thick, but I just cant find where the output for best speed is indicated. This is in the JS3-18, is it on the dash somewhere or PDA?

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Re: MC setting?

Post by wickid » Fri Sep 17, 2021 5:12 pm

No worries, that is what the forum is for.

You can see it on the E-vario. Blue and red arrows on the left side of the dial. And if you have it in "speed command" the vario needle also shows you what to do combined with the audio tone. High pitch is slow down (needle shows climb), low pitch is speed up (needle shows sink) No sound is good speed.
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Re: MC setting?

Post by 6266 » Fri Sep 17, 2021 5:29 pm

To change from E-Vario to speed command and back you use the right CTRL-Key, if you doesn't have changed it in the setup

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Re: MC setting?

Post by Fingers » Fri Sep 17, 2021 6:00 pm

I think I have it, is it the little coin stack thing to the right in the vario!!!... Tried the audio option, cant get away with it, love the old vario sound toooooo much. But this is a great little tool.

Cheers Folks. Took a while but got there in the end. :)

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Re: MC setting?

Post by wickid » Fri Sep 17, 2021 6:28 pm

Fingers wrote:
Fri Sep 17, 2021 6:00 pm
I think I have it, is it the little coin stack thing to the right in the vario!!!... Tried the audio option, cant get away with it, love the old vario sound toooooo much. But this is a great little tool.

Cheers Folks. Took a while but got there in the end. :)
Yes indeed. Small square stacks or arrows depending how you look at it. Red is too fast and blue is too slow. Don't worry, there is no right way. I do it the same as you. I leave it on vario and use that indicator as a rough guide as to what speed to fly. Only for final glide I go to speed command
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Re: MC setting?

Post by Fingers » Fri Sep 17, 2021 8:36 pm

Just tried this Mc tool for the first time on a download of a flight with 10 ghosts. I am still like the Sheriff from Blazzing Saddles when he's a child going west being part of a waggon trail, "Well, we were bringing up the rear".

Took a couple of goes, bombed out in the little village twice just before turn 2 yesterday. Hats off to all who just jumped onto this task first time and nailed it! I've much to learn. But this little tool deff made a difference and I was not so back from the rest of the settlers :)

1:22 in the JS3-18

https://www.condor.club/ftrrank/0/?fpl= ... 8275c42942

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Re: MC setting?

Post by congo » Sat Sep 18, 2021 3:40 am

Hi Fingers,

I just read through this thread and realised you don't fully understand the Evario when it is in "Speed to Fly" mode.

It's not just the "coin stack" indicator that you use. The Evario needle is the indicator! When the needle is nuetral (zero),
that is the correct speed to fly. If the needle goes positive, slow down, if the needle goes negative, speed up.

The Evario and ALL it's indicators switch modes (Thermal/Speed), so just as "coin stack" reads lift ot sink in Variometer
mode, it also switches to speed mode with Right Control key.
The Evario's audio tone also switches mode, the same as the other indicators.

Think of the Evario as two different instruments, one for each mode selection.
Actually, the Evario is three instruments when you include the Altimeter.

I also like the vario sound when cruising Fingers, but you can quickly change modes to cross check your cruise or final glide.
Final glide calculations and glide speeds are particularly useful when using speed to fly mode.
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