[29SEP18] PMDG 747 QOTSII Update 3.00.9019 Released via OC

[JRBarrett 3,034]

11 minutes ago, Captain Kevin said:

Right, and I get that. I guess I wasn't understanding why Wilhelm responded to by post the way he did. The issue I outlined in my post was if I am requesting 248,000 pounds of fuel to be loaded, I should NOT get only 230,000 pounds of fuel loaded. That's an 18,000-pound difference.

I haven’t tried putting that much fuel on board yet, and when I have loaded before, I just entered the total on the fuel page of the FS Actions menu, and have gotten the correct amount. (Biggest load so far was 150,000 pounds).

I’m about to install the new update via OC. Hopefully that will have fixed any mid-loading issues.

[Captain Kevin 586]

10 minutes ago, JRBarrett said:

I haven’t tried putting that much fuel on board yet, and when I have loaded before, I just entered the total on the fuel page of the FS Actions menu, and have gotten the correct amount. (Biggest load so far was 150,000 pounds).

Hmm....interesting....although to be fair, that was at one extreme with the fuel density at 6.30, but even at 7.20, I could never get it to be exact, it would always be slightly less than what I asked for.

[JRBarrett 3,034]

13 minutes ago, Captain Kevin said:

Hmm....interesting....although to be fair, that was at one extreme with the fuel density at 6.30, but even at 7.20, I could never get it to be exact, it would always be slightly less than what I asked for.

I didn’t realize you could specify the fuel density in refueling.  I usually just do an instantaneous refueling through the FS Actions fuel page, though I know you can do a real-time gradual refueling for more realism, but I haven’t explored that option. 

With extremely low-density fuel, it’s possible that you might run out of fuel tank physical capacity (in gallons) before reaching a requested fuel load (in pounds) when requesting a tank to be filled completely full.

During refueling, when the level sensor in a given tank detects that it is completely full, the fuel computer will close the tank inlet valve to prevent any more fuel from being added. Otherwise the fuel would likely overflow out of the tank vents onto the ground.

[vc10man 732]

Makes sense what you state, Jim re: gallons, as the latest GSX fuel bowser shows a gallons and Kg figures(in parenthesis) when asking for that particular GSX service

Edited September 30, 2018 by vc10man

[killairbus 3]

4 hours ago, Cocobellomann said:

Correct!

 

 

Josef K

I can't find a lot of real life bird eye views of the 747-8's wing. How do you know they're supposed to be longer?

-Angelo Busato

[anden145 2,282]

5 minutes ago, killairbus said:

I can't find a lot of real life bird eye views of the 747-8's wing. How do you know they're supposed to be longer?

-Angelo Busato

I'm actually kinda curious about that too...

And please, don't present evidence as eye-witness accounts, random YouTube videos and/or pictures found on the Internet. Please present actual verifiable empiric evidence, such as data references or similar. 

[downscc 1,327]

5 hours ago, JRBarrett said:

Each aircraft fuel tank contains at least one compensator probe that measures the actual fuel density and applies a correction factor to the quantity displayed on the aircraft fuel gauges.

This caught my eye.  I've used Coriolis flow meters in applications where I need mass flow rather than volume flow and they make excellent transfer of custody instruments.  I've never ran into a "probe" that would measure a fluids density.  How does it work?

[vin747 316]

I downloaded the new update and tested the 747-8.. 

1. panel state issue seems to be fixed... was able to connect/disconnect devices multiple times

2. panel lighting issue is fixed.. even during daytime, the integral panel lighting is bright and makes everything readable.. 

3. When I turn the battery & Ext.Power ON, and when all the displays power up, the FPS drops by 7-8.. so at cold and dark, the FPS is 34 and when displays are powered up, its around 27-28.. and remains that way all the way until engine start.. anybody else observed this?

[killairbus 3]

7 hours ago, Cocobellomann said:

Let‘s play

what is wrong here?

 

 

 

How has he done that? 😜

Such an engine weighs tons.

 

 

Josef K

Would you kindly take a screen shot of the -8 from the same angle as the link?

https://www.google.com/amp/s/www.pinterest.co.uk/amp/pin/47287864810005667/?source=images

 

-Angelo Busato

[Wise87 1,275]

From looking up 747-8 diagram on google, the Pylons on the PMDG look as they should be. There are tons of top down views and drawings to show it's correct. Do you honestly think that PMDG would make that big of mistake?

Edited September 30, 2018 by Wise87

[Julean 12]

 

The installations declined because it could not find the 747-8 exe file?

Awesom plane

Jens

[Captain Kevin 586]

6 hours ago, JRBarrett said:

I didn’t realize you could specify the fuel density in refueling.  I usually just do an instantaneous refueling through the FS Actions fuel page, though I know you can do a real-time gradual refueling for more realism, but I haven’t explored that option. 

With extremely low-density fuel, it’s possible that you might run out of fuel tank physical capacity (in gallons) before reaching a requested fuel load (in pounds) when requesting a tank to be filled completely full.

During refueling, when the level sensor in a given tank detects that it is completely full, the fuel computer will close the tank inlet valve to prevent any more fuel from being added. Otherwise the fuel would likely overflow out of the tank vents onto the ground.

By default, it's set to 6.70. Supposedly, the fuel density changes on its own, but I've never seen it do that, and when I initially submitted the support ticket reporting the fuel loading discrepancy, they had said it might be related to the fuel density, and thus, a non-issue. I ended up testing the fuel density to the extremes, just to be sure. The end result was even with the highest possible fuel density, I could never get the exact amount of fuel I entered, it was always a little less. At a low fuel density, the differences between the input fuel request and the actual amount of fuel loaded was drastic.

I'm aware that with a low fuel density, it's possible to run out of fuel tank space before reaching the requested fuel load, as this was mentioned in the introduction manual. However, the highest you can load under idea conditions is somewhere close to 383,000 pounds for the 747-400. My loading of 248,000 pounds is certainly nowhere near that limit, which makes me wonder why it only loaded around 230,000 pounds in that instance with a low fuel density. Do keep in mind that all this is happening with the instantaneous refueling via the FS Actions fuel page. I never did test the real-time refueling option since I didn't have time to really play around with it much after the -8 came out (as it is, I still haven't even flown it yet).

[JRBarrett 3,034]

3 hours ago, downscc said:

This caught my eye.  I've used Coriolis flow meters in applications where I need mass flow rather than volume flow and they make excellent transfer of custody instruments.  I've never ran into a "probe" that would measure a fluids density.  How does it work?

Aircraft fuel quantity probes are basically capacitors. A small metallic cylinder nested inside of a larger cylinder by insulating standoffs. The probes are mounted vertically in the tanks, and are open at the top and bottom.

If you are familiar with the properties of capacitors, you will know that the capacitance is dependent on three factors: the area of the two plates (in this case the inner and outer cylinders), the distance between the plates (which is fixed), and the dielectric constant of the material between the plates. In this case, the dielectric is the fuel itself.

When the probe is fully immersed in fuel, it’s capacitance (measured in picofarads) will be at maximum. As the fuel level drops, air enters through the top of the cylinder, while fuel flows out the bottom, so that at anything less than “full” the dielectric is partially fuel, and partially air, which causes the capacitance to decrease. The lower the fuel level, the less the capacitance.

A very low voltage (1 volt peak-to-peak) AC waveform at several hundred hertz, which is generated by the fuel quantity computer, is applied to one plate (cylinder) of each fuel probe, and a signal return line goes back to the fuel computer from the other cylinder of each probe. The magnitude of the returning signal is directly proportional to the probe capacitance (less capacitance = less signal), and the capacitance is directly proportional to the amount of fuel between the two plates (cylinders) of the probe.

The fuel quantity computer determines current fuel quantity by measuring the magnitude of the AC signal returning from each probe, which decreases as fuel level drops. A specific voltage equates to a specific amount of fuel.

There are several types of compensator probes. Most are also capacitors, using fuel as the dielectric, but mounted lower in the tank so as to be always fully immersed in fuel. This probe has its own separate AC input and output line going to the fuel computer. The dielectric constant of the fuel varies with the density, which is dependent on the ratio of the various hydrocarbons in the mix, and also the temperature. For any given density, the return signal will be of a specific known magnitude. Lower density = less signal. That value is used by the fuel computer to apply a correction factor to the quantity measured by the standard probes.

TL:DR Each main fuel probe is a variable capacitor, which produce a specific output voltage directly proportional to how deeply the probe is immersed in fuel. The compensator probe is a fixed capacitor which produces a specific output voltage directly proportional to fuel density.

The fuel computer translates the voltages from all the various probes into quantity readouts by mathematical magic.

[JRBarrett 3,034]

50 minutes ago, Captain Kevin said:

By default, it's set to 6.70. Supposedly, the fuel density changes on its own, but I've never seen it do that, and when I initially submitted the support ticket reporting the fuel loading discrepancy, they had said it might be related to the fuel density, and thus, a non-issue. I ended up testing the fuel density to the extremes, just to be sure. The end result was even with the highest possible fuel density, I could never get the exact amount of fuel I entered, it was always a little less. At a low fuel density, the differences between the input fuel request and the actual amount of fuel loaded was drastic.

I'm aware that with a low fuel density, it's possible to run out of fuel tank space before reaching the requested fuel load, as this was mentioned in the introduction manual. However, the highest you can load under idea conditions is somewhere close to 383,000 pounds for the 747-400. My loading of 248,000 pounds is certainly nowhere near that limit, which makes me wonder why it only loaded around 230,000 pounds in that instance with a low fuel density. Do keep in mind that all this is happening with the instantaneous refueling via the FS Actions fuel page. I never did test the real-time refueling option since I didn't have time to really play around with it much after the -8 came out (as it is, I still haven't even flown it yet).

Yeah, The density setting is right there on the fuel loading page right in front of my nose. Just never noticed.

So far, my loads have been very accurate. I’m doing a 6-hour flight right now in the standard 400F. I requested 160,000 pounds, and got just a few pounds less - something like 159,980, which I assume is due to rounding.

I’ll try a full load on my next flight. I’m using the new update just released.

[downscc 1,327]

Thanks Jim,  being an EE and working around industrial instrumentation and control systems for 20 yrs I know exactly what you are talking about.  Similar capacitance probes are used in the tank farms at refineries, although level measurements using ultrasound or radar is more common.  I did some googling and found alot of vendors for magnetostrictive probes that seem to be more accurate than the capacitance probes.  In either case, the density is a derived value and not something measured directly as is the case for Coriolis flow meters.  I use those in cases where I need to measure say for example exactly 3.33 kg of water, and milk terminals use them to detect when the flowing liquid changes from milk to water wash.\

Interesting stuff.