Hi

I was wondering if anyone (off the top of my head, LOU :D ? ) had an idea how to distribute the fuel between the tanks on the 707 ? Up until now I've been trying to keep everything in the wings (L/R Main and Aux) for short/medium range flights, but while I haven't snapped a wing yet, I get the feeling it has to be more complex than that.

Is it like the 727 where you have to divide the total fuel equally between tanks ? Do the wingtip tanks need to be filled or are they just there to counter-balance the Center tank when it exceeds a certain weight ?

Cheers

Nico

Nico,

This should keep you busy for a while.  ;D

Lou

http://img819.imageshack.us/img819/2168/707fuel.png

http://img225.imageshack.us/img225/10/707fuel2.png

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Wow! that is a great explanation of fuel usage for the 707.
That means I need to revise my fuel tank usage during a flight. I've been doing it wrong. :(

me too. But one thing at a time. i was busy with navigation and landings recently. now it time to understand how to work with fuel ;)

Thanks LOU, but I've known that schematic for a while now, and been trying to stick to it as closely as I can, but what I'm still looking for is the "Recommendations and Limitations, Chapters 1 4 and 15" mentionned in the top left hand corner. Would you happen to have those handy or know where I could find them ?

Cheers

Nico

I found what I was looking for !  Turns out I wasn't far off with my method... up to a certain amount of fuel anyway :D

Here's the chart for those interested :

http://i737.photobucket.com/albums/xx14/allaboutpics/Boeing707-300-FuelDistribution.jpg

Cheers

Nico

Lou, Barb. - thanks guys!

That table shows that you can fill different density fuel into the 707. What's the difference in that types of fuel? And what we using now?

That is another good question I do not have the answer too. I'm guessing it's either :

- The standard density for Jet A, Jet A1 and Jet B fuels with error margins (Jet A1 is usually 0.800 Kg/L standard density, Jet A is 0.820) I do not know the density of Jet B, but its freezing point is significantly lower than the Jet A fuels, could that be because of a lower density (0.73) ?

- Ground temperature. 0.80 being density a 15°C, 0.73 would be 30°C and 0.82 0°C or something similar...

FSX uses Jet A-1 fuel at  6.7lbs/US. Gal and 0.8Kg/L.

Cheers

Nico

Fuel density for a given fuel is temperature related.

Hot fuel is less dense.

This was always a problem with long range flying out of hot places. Flying out of Cairo or Tel Aviv in the summer at hot temps - always - would limit the number of gallons of fuel you could put in the tanks. Fueling from underground storage helped a lot to get more fuel on the plane since the fuel was cooler.

Airlines use only Jet-A or A-1 which on a standard day (15 degrees C ) yields around 6.7 pounds/gal. The difference in Jet-A or A-1 is the amount of antifreeze in the mix. Never saw other fuels like Jet-B at the airports we flew into.

Lou  

Now you know why there was a flight engineer station for these birds!

Lou's point about fuel temps is an interesting reminder of some of the more arcane problems of real life aviating. A Pan Am 707 ran off the runway in Sydney in the 60's after a bird ingestion into one of the fans led to an abort before Vr, couldnt stop and ended up with its nose on a nearby road. Turned out the fuel density calcs were wrong, and the aircraft was way over weight, they were very lucky as they went through some of the HIALs and managed to not damage fuel lines or tanks with engines running and shut her down and every one got out unharmed.

Would be interesting if some one inserted a fuel density algorithm into the TOW calculator in the program in FSX.

LOU, you gave us a nice, complete and technical explanation about the REAL B707 refueling. Congrats. But for me as a mere FS user, if not asking much, could you tell us in a simple and not so complex form how to deal with refueling and tank usage for simulation purpose?

As Mark said above (reply # 2), I need to revise my fuel tank usage during my flights, too. I'm pretty sure I'm doing it in the wrong way.

Thanks,

Pinatubo.

http://www.skybrary.aero/bookshelf/books/552.pdf - thats the 707 accident report. Guys measured density with defective meter, and estimated baggage weight wrong. Also looks like they aborted takeoff above v1. As usual in accidents - many factors summarized.

I never thought that refueling aircraft is so "lots of calculations" thing  :o
I thought - you fill the gas and go  ;D

And the tables above is in kilograms, while we using pounds mostly. And max tank volume measured in gallons. So you'll need density in calculations....have something to calculate before flight (in addition to many other stuff)

As for FSX - i'll try to use all that calcs. FSX dont require it, but it looks interesting practice 8-) I guess fuel usage not depends on fuel density, so the mass of the fuel is main thing for engine.

And those figures above - they need to be thinked about, but i guess one flight can make it clear, and i guess that we'll have much more satisfaction if we'll figure it out ourselves ;) Right guys?

707 Fuel Use

As I've said so many times, I wish I had kept all my old handbooks including the special fuel slipsticks.

Here are 2 examples of weight & balance calculators.

http://img641.imageshack.us/img641/5343/trim.png

http://img256.imageshack.us/img256/1260/trim2.png

As you can see, it's a complicated business!

Let's say we are flying the 707 on a trip which requires around 100,000 pounds of fuel.

Simple fuel load...
I load my plane as follows:
Center = empty
TANK 2 & 3 get 32,000 each = 64,000 lbs
TANK 1 & 4 get full, or 15,500 each = 31,000 lbs
Reserve tanks full, or 2,900 each = 5,800 lbs
TOTAL = 100,800 lbs

Burn fuel from 2 & 3 to all engines until 2 & 3 = 1 & 4 + Reserve
Open reserve crossfeed ONLY when there is room in tanks 1 & 4

Above is a guess on my part since I don't have the old load charts.

Lou

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Hi Lou.

It is interesting to note that you say Open reserve crossfeed ONLY when there is room in tanks 1 & 4, yet the FUEL USAGE PROCEDURE chart, in your first reply, says to open them (if desired) when Tanks 2 & 3 = 1 & 4 + Reserve.

Why do you wait until there is room in Tanks 1 & 4 before opening them? I would just like to understand IF there is some special reason for this. After revising my fuel usage in the 707, I just opened the reserve crossfeed valves as soon as I was using fuel from tanks 1, 2, 3 & 4 + Reserve.

Mark

Here is some guidance...

http://img850.imageshack.us/img850/1843/xfeed.png

You notice that 12,000 lbs is just enough room to fit the reserve into the outboard main.

This is probably not that big a deal, but it is possible that if you opened the reserve with a full or almost full outboard main, you could risk having the fuel go overboard out the vent.  :(

Lou


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Thanks Lou.

I never thought about the fact that you could risk having the fuel go overboard out the vent! :o

Mark,

The small reserve tanks on each wing tip just gravity feed into their respective main tank.

The fact that they are just a bit higher due to wing dihedral is what makes that possible.

I often wondered if I opened the reserve crossfeed with a full main what would happen.

The handbook logic was that there needed to be enough room in the main for the fuel to fit into the tank.
Since the fuel vent is right at the wing tip it is logical that fuel could leak out, but I never tried it!  :o

Lou

LOU wrote on May 17^th, 2012 at 3:18pm:

Mark, The small reserve tanks on each wing tip just gravity feed into their respective main tank. The fact that they are just a bit higher due to wing dihedral is what makes that possible. I often wondered if I opened the reserve crossfeed with a full main what would happen. The handbook logic was that there needed to be enough room in the main for the fuel to fit into the tank. Since the fuel vent is right at the wing tip it is logical that fuel could leak out, but I never tried it!  :o Lou

That old saying of "It is better to be safe, than sorry" is a good way of looking at it! ;D

Great stuff.  I could listen to 707 specs all day... :D

Hi everybody,

I am just starting with CS707 and I'm still learning it.

I have written fuel system tutorial for the Historic Jetliners Group with many guidelines on how to manage the 707 fuel system.

It is avaliable at simviation.com/hjg/panels/boeing/707fueltut.zip

Great explanation. Thanks