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IDG MD-11 Development Archive - Closed

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Re: IDG MD-11 Development

Postby Isaak » Sun Jul 07, 2019 3:31 am

This looks genious. I'll definitly use your work as an example to improve the 777's fuel systems! Thanks so much for your work!
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Re: IDG MD-11 Development

Postby Octal450 » Sun Jul 07, 2019 4:52 am

Dear Isaak,
Thanks for the compliment but this system is 100% JSBsim specific and in fact uses no nasal whatsoever. It cannot be ported to YAsim. Sorry.

Kind Regards,
Josh
Waste of time. Goodbye forever.
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Re: IDG MD-11 Development

Postby WoodSTokk » Sun Jul 07, 2019 8:04 am

I think YAsim has no fuel system at all. You can define tanks so that YAsim calculates the weight on the right position and engines that consume the fuel.
But you can't define witch engine draw fuel from witch tank. I dont know how the fuel is calculated on YAsim aircrafts.
Does FG calculate anything about fuel? There are some properties but it looks that they do nothing.
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Re: IDG MD-11 Development

Postby Octal450 » Sun Jul 07, 2019 1:59 pm

Neither does JSB. You can assign an engine to feed from a tank and then cannot change it.

What I've come up with is using the external flow rate of each tank to transfer fuel properly (with a deadline for error too to make sure phantom fuel loss or gain doesn't happen) and then have each engine feed from a "pipe" which is just a really small tank placed at CG so it doesn't affect CG.

Kind Regards,
Josh
Waste of time. Goodbye forever.
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Re: IDG MD-11 Development

Postby LH-9920 » Fri Jul 19, 2019 6:02 am

Octal450 wrote in Sat Jul 06, 2019 11:01 pm:Hi "wrg" and "LH-9920",

I have just revisted all your comments about the fuel system. All behavior will be correctly shortly!

Kind Regards,
Josh


Hi Josh,

Thanks, that looks great. I look forward to trying it!

And thanks for the great job, I really enjoy flying your planes due to the level of detail in the aircraft systems!

Cheers!
LH-9920
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Re: IDG MD-11 Development

Postby Octal450 » Fri Jul 19, 2019 3:35 pm

Thank you!
I appreciate it.

Kind Regards,
Josh
Waste of time. Goodbye forever.
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Re: IDG MD-11 Development

Postby Octal450 » Mon Jul 22, 2019 5:26 pm

Hi "LH-9920" and others,
Maybe the following interested you:

Now the Tank 2 will feed Tank 1 and Tank 3 using the Transfer and Fill Valves when Tank 2 is greater than 1 or 3. This is done to keep the Tank 1 and Tank 3 full while Tank 2 is bigger than them, and once it becomes the same value as the tank, the feeding will stop, and the tanks will decrease at the same rate. Note that this balances Tanks 1 and 2, and Tanks 2 and 3. It does not yet balance Tank 1 and 3 - that will be added later.
Of course - all this assuming the SYSTEM switch is left in Auto (blank). Reversion to Manual does not continue this logic!

And lastly, did a big of housekeeping on the code.

Image

Kind Regards,
Josh
Waste of time. Goodbye forever.
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Re: IDG MD-11 Development

Postby LH-9920 » Thu Jul 25, 2019 4:55 am

Hi Josh,

the tanks now work as you said.

To keep you busy, I have a question regarding the autothrottle.

On ground, the default set value in the system seems to be 160 kts, even if I set a higher value on the panel. The higher value is only accepted by the system once the autopilot is active. Unfortunately it activates only at a certain altitude. Now the folllowing happens:

I take off and climb, typically accelerating above 160 kts before I can activate the autopilot. When I activate the autopilot, even if I quickly set a higher speed, autothrottle significantly reduces thrust because it tries to decelerate to 160. So I lose speed in initial climb.

Is that a bug or a MD11 feature? In case it is a feature, what would the pilot's recommendation?

Thanks
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Re: IDG MD-11 Development

Postby Octal450 » Thu Jul 25, 2019 2:11 pm

Hi LH -
When in the T/O CLAMP or T/O THRUST modes, the speed cannot be modified. When the FMS is available, the speed will be set to V2 (or V2+10, don't remember right now). The A/P won't be available in these 2 modes of V2 speed is not confirmed (calc is auto).
As soon as another mode is selected (like CLB THRUST, which happens around 1500above takeoff altitude by default) the speed knob will then work. While in T/O CLAMP/THRUST you should follow the flight director to hold the speed.

Remember too that the knob just be pulled to change the speed at any time. However, when the set speed as not yet been captured the speed will be updated instantly and no pull is required.

Hope this help!

Kind Regards,
Josh
Waste of time. Goodbye forever.
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Re: IDG MD-11 Development

Postby LH-9920 » Fri Jul 26, 2019 8:20 am

Thanks, that works.

Regarding fuel, is it possible that in case tank 2 initial content is lower than tank 1 and/or tank 3, tank 2 runs empty? That's what it is looking like on my current flight. Will an empty tank 2 shut down engine #2? I won't see that this time, since I am going to land soon.
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Re: IDG MD-11 Development

Postby Octal450 » Fri Jul 26, 2019 1:28 pm

It shouldn't be... Can you tell me if you started with the aux tank bring used or not, and I will double check the scheduling.

It should be aux tank lower then upper, then tank 2 until it's equal to 1 and 3 then 1 2 and 3 at same time.

Remember that tank 2 is much bigger than 1 or 3, so the sliders won't line up when the quantity is the same.

Kind Regards,
Josh
Waste of time. Goodbye forever.
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Re: IDG MD-11 Development

Postby LH-9920 » Fri Jul 26, 2019 1:38 pm

I did not use the aux tanks.

I used Tank 1 (inboard and outboard), Tank 2, Tank 3 (inboard and outboard). And I started with tanks 1 and 3 equally filled and with tank 2 filled less (in absolute numbers, meaning lbs). Other than the case when tank 2 contains more lbs than each 1 and 3 at the beginning, in this case the numbers on the panel keep showing tank 2 lower than 1 and 3 and all tanks are emptying at the same speed (due to engine consumption). As a result, the number for tank 2 after landing was around 6000, while tank 1 and tank 3 each showed more than 20000. Can you follow?
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Re: IDG MD-11 Development

Postby Octal450 » Fri Jul 26, 2019 3:24 pm

Yes --- why did you do that? Unlike 2 engine aircraft, the MD-11 (and DC-10) feed each engine from each tank. Tank 2 is NOT used the way the "Center" tank is used on other aircraft. That would be Aux Tank, which is used like the Center tank on other planes. Here is why:

Tank 2 is actually NOT in the center fuselage. The left wing contains the Tank 1 Outer, Tank 1 Inner, and Left Tank 2. The right wing contains Tank 3 Outer, Tank 3 Inner, and Right Tank 2. Fuel can flow freely using tubes between the left and right Tank 2s. There are pumps to Engine 2 (tail) on each side so that in turns still the engine can be fed without problems. The fuselage contains the Aux tanks in the center.

Fuel is loaded equally in Tanks 1, 2, and 3 until Tanks 1 and 3 are full - then Tank 2 is filled until full. Then Upper Aux Tank is filled until full, then Lower Aux Tank is filled until full. The tail tank can be filled then last assuming that CG will not go out of range when doing so - as tail tank is usually used for balancing. But tail tank doesn't work yet in our model.

Hope that clears it up!

Kind Regards,
Josh
Waste of time. Goodbye forever.
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Re: IDG MD-11 Development

Postby LH-9920 » Fri Jul 26, 2019 3:42 pm

Octal450 wrote in Fri Jul 26, 2019 3:24 pm:Yes --- why did you do that?


Because it was possible :wink:

Alright, your explanation clears it up, thanks!

Kind regards
LH-9920
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Re: IDG MD-11 Development

Postby Octal450 » Fri Jul 26, 2019 3:52 pm

You're welcome! :)

I am not yet sure what the real airplane would do in such a situation - my guess would be to equally feed Tank 2 from 1 and 3 to balance. I will try to find out and simulate it!

Kind Regards,
Josh
Waste of time. Goodbye forever.
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