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Is Tank 11 Limit 10,500Kg?


Ray Proudfoot

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Ray Proudfoot

It appears the maximum amount of fuel that can be pumped into Tank 11 is 10,500Kg. Despite setting the Load Limiter to 11,300Kg once 10,500 had been reached the fuel was then diverted to tanks 5 and 7.

I'm assuming this is hard-coded in Concorde-X but confirmation would be appreciated. The reason I ask is because according to a BA Fuel Management document provided by Frazz it can in theory take up to 13,200Kg.

However that document has a note underneath the table...

Due to fuel density variations and the Volumetric Capacity of Tank 11 the required contents shown above the broken line may not be achieved. In these cases Tank 11 high level shut off will occur and the initial cruise CG will be forward of 59% Co.

The amount of fuel in each cell immediately above the broken line is 10.5 or 10.6. Confirmation from Andrew or Lefteris would be appreciated. This is associated with beta-testing of CPS-X.

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36 minutes ago, Ray Proudfoot said:

I'm assuming this is hard-coded in Concorde-X but confirmation would be appreciated. The reason I ask is because according to a BA Fuel Management document provided by Frazz it can in theory take up to 13,200Kg.

Ray, this may be a stupid question, but are you sure the document is using Kg and not litres? The only reason I ask as 13,200 litres gets you pretty darn close to 10,500 kg using Jet A/ A1.

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Ray Proudfoot

Thanks for your reply but purely coincidental. All Concorde fuel amounts in the FS Labs version are definitely measured in Kg. :)

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I think that the limit must be set at 10,500kg as I have never been able to go above that. I assume (could be wrong) that FS and Concorde X must have standard limits set that do not vary, as the sim has no knowledge of density and therefore it cannot vary. Now whether all limits are set using the same density may be another matter...

Frazz

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Ray Proudfoot

Thanks Frazz. I imagine other limits may not be as noticeable. As long as the CG is within 0.3 of 59 then I suppose it's not too important.

There are others such as Andrew and yourself that are far more knowledgeable than I.

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The reason the chart shows a higher capacity is because each refuel depended upon the density of the fuel on that day. The fluid replenishment manual contained different charts for different density ranges. With more kilograms per litre, the weight of the fuel (which is what the gauges read) would be greater therefore capacity on the gauges would be greater. With less kilos per litre the opposite would occur.

For example, the total fuel capacity for all tanks full with a density of 0.735 kg/L would be 88040 kg, but with a density of 0.850 the capacity would be up to 101780 kg! 

When the Washington route first began, the winter upper winds meant it was often difficult to achieve the range from London to arrive without a technical stop - this was before the intake modifications which reduced fuel burn by around 2% on most sectors. As a temporary fix, BA acquired a special fuel called "Nigerian Heavy" which I think had a much higher density than normal jet A1 allowing them to have a greater capacity in the tanks. This gave the range required but apparently caused an issue with the readings on the fuel gauges as its dielectric properties were different, giving an under read on the gauges with full tanks. 

Basically, the "capacity" of the tank doesn't change in volume (litres) it's just that the fuel has different densities. 

I hope this makes sense...

Frazz

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Ray Proudfoot

Thanks a Frazz. It makes the mind boggle how they worked all this out. I get the gist of your explanation. I can understand why Andrew decided on a limit of 10500Kg because of the simplistic nature of FSX and P3D.

It requires quite an odd combination of pax loading and flight distance to require more than 10.5T of fuel in tank 11 so the situation is unlikely to cause a major issue.

What is important is Pierre now has the info to calculate how much fuel needs to be in tank 11 for the majority of flights. This will make CPS-X even better than CPS not withstanding all the other improvements he has made.

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Is that because of the chart I gave you? I thought he had access to all the AF stuff I seem to remember reading a while back?

In BAs case everything was laid out in useable form in the manuals so in fact there wasn't much to work out, more knowing where to look.

Frazz

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Ray Proudfoot

He may well have. I haven't asked. But as the tank 11 loading wasn't covered in CPS I thought it worth mentioning so we could make CPS-X as good as possible.

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If you did pass on the chart I gave you to assist in development of CPS, it would have been polite to have mentioned it to me before passing it on bearing in mind I have paid a lot of money to collect all the manuals, but never mind.

The issues with maximum range/fuel that I have seen mentioned occasionally on here with regard to CPS would only be rectified by the implementation of the High Level Incremental fuel loading that was used primarily on the Barbados route. As Concorde X has (as you have discovered) it's fuel tank limits set a little mire rigidly than the real thing, I don't think it would be possible to model this even if CPS could handle it.

Frazz

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Ray Proudfoot

Sorry. I wasn't aware you have paid a lot of money for them. Pierre is already a Concorde expert and it was only that Tank 11 chart that is relevant to CPS-X development.

I will direct him to this topic.

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On 2/6/2017 at 11:15 AM, Ray Proudfoot said:

Thanks for your reply but purely coincidental. All Concorde fuel amounts in the FS Labs version are definitely measured in Kg. :)

Thanks Ray. It is obviously difficult to interpret a table I can't see :). And yes fuel in planes Concorde included is typically measured as a weight in kg (or pounds on my side of the pond) in the cockpit. The weight or mass is what determines how far you are going to go and is obviously important in CG and MTOW calculations.

However, at the fuel truck where it tends to be volume based litres or gallons. And as Frazz noted the capacity of the fuel tank itself is a fixed volume. For tank 11, the F-BTSC bea report notes the tank 11 capacity is 13,150 litres and the following "The capacity of the thirteen tanks is shown in the table below. These represent maximum capacities, without exceeding the upper level sensors, corresponding to real fill of around95% (94% for tank 5)." You will see fuel capacities often mentioned in pounds or litres, but it is always based on an assumed fuel density.

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On 2/6/2017 at 11:47 AM, Frazz said:

 I assume (could be wrong) that FS and Concorde X must have standard limits set that do not vary, as the sim has no knowledge of density and therefore it cannot vary. Now whether all limits are set using the same density may be another matter...

That would be my assumption as well. It looks like a different developer that just released a certain 4 engine plane is attempting to model it though.

Quote

- Accurate refueling during Ground Operations (real-time refueling.)

- Accurate fuel temperature based upon aircraft wing skin heat transfer characteristics

- Accurate fuel density/temperature effects during real time refueling. (including volume limitations in the event of low density levels.)

- Fuel density during refueling based upon actual global/regional variations in fuel density.

- Fuel density during refueling adjusted for expected fuel temperature during fueling.

- Accurate fuel density/temperature mixing as fuel moves between tanks during operation and refueling.

 

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It isn't a major issue Ray so don't worry about it.  It has taken me years to get a complete set of manuals and I am lucky that a retired flight engineer that lives near me saw how interested I was and sold me the ones I didn't have already at a reasonable price as he knew they were going to a good home where they would be used and enjoyed for many years to come. Thankfully, they were also the last and most up to date editions. 

Frazz

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1 hour ago, MrNuke said:

You will see fuel capacities often mentioned in pounds or litres, but it is always based on an assumed fuel density.

Yes, and it tends to be the 0.799/0.800 density, which is why there is a table in the load and balance manual giving the maximum quantities for the range of densities. 

In some ways I wish Concorde X could be revisited and some of the techniques that have been put into the A320 (which is excellent) used in order to make some of the things even more accurate. Maybe then we could have density modelling like the aircraft you have quoted. I understand that they are a business however and that they are busy with the modern "buses" now. 

Frazz

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