rsrandazzo

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

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43 minutes ago, Cocobellomann said:

Let‘s play

what is wrong here?

6013CF47-646D-4434-92BD-D33E8DF5FFEB.jpg

 

 

 

How has he done that? 😜

Such an engine weighs tons.

 

 

Josef K

What's wrong, are the in board pylons supposed to be longer?

-Angelo Busato

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7 hours ago, Bluestar said:

You folks do realize that fuel is loaded in gallons and pounds? 🙂

I was loading it in pounds, so I'm not sure what the issue is. The PMDG fuel loader only gives you the option to load in either pounds or kilograms, so I don't know where gallons would come into play here.

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54 minutes ago, killairbus said:

What's wrong, are the in board pylons supposed to be longer?

-Angelo Busato

Correct!

 

 

Josef K

Edited by Cocobellomann

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56 minutes ago, Captain Kevin said:

I was loading it in pounds, so I'm not sure what the issue is. The PMDG fuel loader only gives you the option to load in either pounds or kilograms, so I don't know where gallons would come into play here.

The fuel order will be given in pounds or  kilograms. The aircraft refueling panel will have a digital preset for each tank also in pounds or kilograms. 

The refueling operator will annotate the amount of fuel dispensed on the aircraft load sheet (given to the captain at the conclusion of fueling) in either pounds or kilograms. This is done by noting the total fuel weight shown on the refueling panel at the beginning and end of refueling and subtracting the beginning reading from the final reading.

BUT the refueling truck (or bowser) meters will show the amount dispensed in either gallons or liters, and the final paperwork that the refueler turns in to his office (for billing purposes), will be in one of those two units of measurement.

The pilot’s fuel request is not given in gallons, because the weight per gallon is not exact. It varies with the temperature and the specific gravity of the fuel in the truck or underground tanks. That can vary from day to day depending on the supplier of the fuel.

In general, Jet-A weighs 6.7 pounds per gallon, but depending on the API index of a particular load of fuel in the truck, sometimes it may be a bit more than 6.7 pounds, and sometimes a bit less.

With high-density fuel, 10,000 pounds might equate to 1,470 gallons, while low-density fuel might equate to 1,515 gallons.

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.

Typically the only aircraft where the pilot would request fuel directly in gallons or liters would be on smaller biz jets without single point refueling - where fuel has to be dispensed directly into the tanks with overwing nozzles, much like refueling an automobile.

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29 minutes ago, JRBarrett said:

The fuel order will be given in pounds or  kilograms. The aircraft refueling panel will have a digital preset for each tank also in pounds or kilograms. 

The refueling operator will annotate the amount of fuel dispensed on the aircraft load sheet (given to the captain at the conclusion of fueling) in either pounds or kilograms. This is done by noting the total fuel weight shown on the refueling panel at the beginning and end of refueling and subtracting the beginning reading from the final reading.

BUT the refueling truck (or bowser) meters will show the amount dispensed in either gallons or liters, and the final paperwork that the refueler turns in to his office (for billing purposes), will be in one of those two units of measurement.

The pilot’s fuel request is not given in gallons, because the weight per gallon is not exact. It varies with the temperature and the specific gravity of the fuel in the truck or underground tanks. That can vary from day to day depending on the supplier of the fuel.

In general, Jet-A weighs 6.7 pounds per gallon, but depending on the API index of a particular load of fuel in the truck, sometimes it may be a bit more than 6.7 pounds, and sometimes a bit less.

With high-density fuel, 10,000 pounds might equate to 1,470 gallons, while low-density fuel might equate to 1,515 gallons.

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.

Typically the only aircraft where the pilot would request fuel directly in gallons or liters would be on smaller biz jets without single point refueling - where fuel has to be dispensed directly into the tanks with overwing nozzles, much like refueling an automobile.

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.

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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.

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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.

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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.

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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 by vc10man

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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

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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. 

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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?

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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?

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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 by Wise87
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The installations declined because it could not find the 747-8 exe file?

Awesom plane

Jens

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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).

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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.

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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.

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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.

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5 minutes ago, JRBarrett said:

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.

Right. What I'm saying is prior to the initial update to the -400 when the -8 got released, if I requested 40,000 pounds, I got 40,000 pounds rather than 39,994. Start lowering the fuel density, and the difference starts to become more noticeable at the higher fuel weights.

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10 minutes ago, downscc said:

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.

The capacitive system for aircraft fuel measurement has proven to be quite reliable over the years. It’s simple, and has no moving parts. The probes rarely fail - when they do it’s usually because they have been severely contaminated by water or biological growth in the fuel.

The probes are wired in series/parallel. The AC input to all the probes are wired In parallel from a common low impedence line coming from the FQMC, and the outputs are high Z with each probe having a discrete return line to the FQMC via coaxial cables.

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27 minutes ago, Captain Kevin said:

Right. What I'm saying is prior to the initial update to the -400 when the -8 got released, if I requested 40,000 pounds, I got 40,000 pounds rather than 39,994. Start lowering the fuel density, and the difference starts to become more noticeable at the higher fuel weights.

Gotcha. Didn’t think the difference was significant at mid-range loads like I have been using, but I haven’t tried high loads yet, or varying the density. Though, with low density fuel, you could definitely have a situation where you will end up with less than requested weight when filling tanks to the brim.

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1 minute ago, JRBarrett said:

The capacitive system for aircraft fuel measurement has proven to be quite reliable over the years. It’s simple, and has no moving parts. The probes rarely fail - when they do it’s usually because they have been severely contaminated by water or biological growth in the fuel

I suspect so.  The aircraft fuel tank is a much much cleaner environment that the product tanks in a refinery or truck terminal.  And you never know how much salt water you're going to get from an ocean tanker bringing you the crude.  It's nasty.  In fact when someone says they only use high octane I tell them about how refineries must trap the vapors that are released from tank trucks, barges or ships when they fill the tank.  Those vapors are compressed, cooled and condensed into a liquid and refiners will put that trash in the high octane product tanks because it will increase the volume of fuel without degrading the octane values.  Don't ever think that something is better because it's more expensive haha.

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46 minutes ago, JRBarrett said:

Though, with low density fuel, you could definitely have a situation where you will end up with less than requested weight when filling tanks to the brim.

Yes, I am aware of that, because you're limited to volume at that point. But 248,000 is nowhere near close to the fuel tank volume limit. I was wondering if there's something in the coding that's trying to convert the input into gallons, and then giving you an output with the fuel density being taken into consideration, but that doesn't really explain why there's still a slight discrepancy even with the highest possible density.

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