Faro From Egypt, joined Aug 2007, 1327 posts, RR: 0 Posted (4 years 6 months 2 weeks 1 day 5 hours ago) and read 3437 times:
Why do airliners not reinforce and/or bladderize the space in their wing-to-fuselage fairings in order to carry fuel? On certain airliners like the A380, this can afford some handy useable volume, even after the space occupied by the landing gear:
Same goes for the excess overhead space in 777's between the pax cabin roof and the upper fuselage skin; maybe that would make the 772LR a London-Sydney regularity?...
Futureualpilot From United States of America, joined exactly 12 years ago today! , 2445 posts, RR: 8 Reply 1, posted (4 years 6 months 2 weeks 1 day 4 hours ago) and read 3424 times:
I would imagine some of it has to do with the weight of the installed tanks, and the necessary components needed to make them usable (pumps, lines, gauges, fueling points, etc) the ease of installation/Mx and so on would negate any potential money to be made.
Avt007 From Canada, joined Jul 2000, 2131 posts, RR: 6 Reply 4, posted (4 years 6 months 2 weeks 1 day ago) and read 3330 times:
I'll wager the space above the "ceiling" is substantial. On a 747, it's huge. On a related note, on the Shorts 360, all the fuel is stored above the cabin on top of the fuselage.
FredT From United Kingdom, joined Feb 2002, 2180 posts, RR: 29 Reply 5, posted (4 years 6 months 2 weeks 21 hours ago) and read 3283 times:
Mass in the top of the fuselage means having to reinforce the fuselage to prevent that mass from crushing the fuselage in case of a crash. Not good, steep weight penalty. Still wouldn't want to sit under the wing in a high wing design in a crash...
Ditto for reinforcing a fairing to make it an integral fuel tank. It would not be weight efficient. Besides, you will find most fairings crammed full of equipment.
The space above the inner ceiling of some aircraft is indeed substantial. It has been suggested to add crew bunks or even passenger sleeping cabins in that space. Much lower density than fuel.
Cheers,
/Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
Starlionblue From Greenland, joined Feb 2004, 15102 posts, RR: 69 Reply 8, posted (4 years 6 months 2 weeks 17 hours ago) and read 3224 times:
I'm sure if the airframers really wanted to put in more tanks they could. But there aren't a lot of aircraft today that actually need more range. Sure, you could build a LHR-SYD airliner, but adding a few extra tanks to small recesses wouldn't solve the problem, at least cheaply.
IIRC the 346 and others do not have tanks in the horizontal stabilizer like the 744. That would be the first place to bladderize.
Tact Is For People Who Aren't Witty Enough To Be Sarcastic
2H4 From United States of America, joined Oct 2004, 8937 posts, RR: 65 Reply 9, posted (4 years 6 months 2 weeks 16 hours ago) and read 3207 times:
AIRLINERS.NET CREW HEAD DATABASE EDITOR
Supposing 1000 pounds of extra fuel was loaded onto an already full 747-400.....how much additional fuel would be burned carrying that 1000 pounds all the way to the point at which it would be used?
JetMech From Australia, joined Mar 2006, 2446 posts, RR: 54 Reply 10, posted (4 years 6 months 2 weeks 16 hours ago) and read 3206 times:
Quoting Starlionblue (Reply 8): IIRC the 346 and others do not have tanks in the horizontal stabilizer like the 744. That would be the first place to bladderize.
I'm quite sure that the A346 does have fuel in the horizontal stab. The A330 and A342 / A343 definitely do. The Airbus system is actually a fair bit more sophisticated than the Boeing system on the 744. Airbus pumps fuel to and from the stab tank to actively control the longitudinally trim the aircraft.
The beauty of the system is that it reduces trim drag, and hence in theory at least, allows more range to be achieved for a given amount of fuel. The 744 stab tank is for additional capacity only, and cannot be used to actively trim the aircraft. The 744 stab tank does not have bladders, it is a normal tank like the ones in the wing, where the joins between the various wing components are sealed with fuel proof sealant.
I also seem to remember that the VC-10 had a vertical stabiliser fuel tank as well Â
Regards, JetMech
[Edited 2007-11-13 16:56:15]
JetMech split the back of his pants. He can feel the wind in his hair.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 11 Reply 11, posted (4 years 6 months 2 weeks 16 hours ago) and read 3196 times:
Quoting Faro (Thread starter): Why do airliners not reinforce and/or bladderize the space in their wing-to-fuselage fairings in order to carry fuel? On certain airliners like the A380, this can afford some handy useable volume, even after the space occupied by the landing gear:
The porpoise of the wing to fuselage fairing is to smooth the are flow around the junction of the wing/fuselage. They are made from lightweight composite and their supporting structure is not designed to carry the weight of things like fuel tanks.
Quoting Faro (Thread starter): Same goes for the excess overhead space in 777's between the pax cabin roof and the upper fuselage skin; maybe that would make the 772LR a London-Sydney regularity?...
The area above the cabin is not really empty, there are air conditioning ducts, entertainment system, communication wiring, etc, up there.
RoseFlyer From United States of America, joined Feb 2004, 7619 posts, RR: 51 Reply 12, posted (4 years 6 months 2 weeks 15 hours ago) and read 3181 times:
Airplanes don't really desperately need more space for fuel. It's the weight of the fuel that is the problem. For example, some airplanes can store fuel in the tail. The 747 had an optional tank in the vertical stabalizor. There are places to put fuel, but the weight is a bigger concern. Volume isn't the only problem. Rarely do planes fill completely up with fuel.
If you have never designed an airplane part before, let the real designers do the work!
WingedMigrator From United States of America, joined Oct 2005, 1944 posts, RR: 57 Reply 13, posted (4 years 6 months 2 weeks 11 hours ago) and read 3131 times:
Quoting 2H4 (Reply 9): Supposing 1000 pounds of extra fuel was loaded onto an already full 747-400.....how much additional fuel would be burned carrying that 1000 pounds all the way to the point at which it would be used?
That depends on how far you wish to fly before using your extra 1000 pounds.
If you assume say 5000 nm, it would take about 480 pounds additional fuel to carry the 1000 pounds that far on a 744, and once you get to 5000 nm, the 1000 pounds would take you about 18 nautical miles further.
(By the way, this illustrates why ULR flights, which use lots of fuel to carry more fuel, will never be anything but a niche operation in an age when fuel is expensive and CO2 emissions are frowned upon... no matter how capable the airplane!)
Quoting 474218 (Reply 11): The porpoise of the wing to fuselage fairing
I didn't know they put whales in there... is that why they call it WhaleJet?
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 11 Reply 15, posted (4 years 6 months 2 weeks 4 hours ago) and read 3066 times:
Quoting WingedMigrator (Reply 13): I didn't know they put whales in there... is that why they call it WhaleJet?
I know, spell check doesn't work well when you use the wrong word. I saw it after the edit time had expired, so I was just waiting for someone point it out.
OldAeroGuy From United States of America, joined Dec 2004, 3141 posts, RR: 66 Reply 16, posted (4 years 6 months 1 week 6 days 22 hours ago) and read 3011 times:
Quoting Starlionblue (Reply 8): IIRC the 346 and others do not have tanks in the horizontal stabilizer like the 744.
It does.
Quoting JetMech (Reply 10): I'm quite sure that the A346 does have fuel in the horizontal stab.
You are correct.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
Tdscanuck From Canada, joined Jan 2006, 11033 posts, RR: 72 Reply 18, posted (4 years 6 months 1 week 6 days 14 hours ago) and read 2916 times:
Quoting Faro (Thread starter): Why do airliners not reinforce and/or bladderize the space in their wing-to-fuselage fairings in order to carry fuel? On certain airliners like the A380, this can afford some handy useable volume, even after the space occupied by the landing gear:
The landing gear are actually in the body, mostly, not in the fairing. The fairing is, however, stuffed with ECS equipment.
Quoting Faro (Thread starter): Same goes for the excess overhead space in 777's between the pax cabin roof and the upper fuselage skin
There's a lot of room up there (it's roughly equivalent to a 737's worth of space), but having fuel inside the passenger compartment is a huge hassle.
Quoting Airfoilsguy (Reply 17): I think I remember reading somewhere that it is prohibited to store fuel above passengers in planes that fly in the USA. I could be wrong though.
It's allowed, I believe, but you always have to have two barriers between the fuel and any pressurized compartment. If you run the fuel inside the fuselage, you need to add a second barrier which can be a significant hassle.
411A From United States of America, joined Nov 2001, 1826 posts, RR: 10 Reply 19, posted (4 years 6 months 1 week 6 days 13 hours ago) and read 2903 times:
Fuel in these areas is nothing new.
The DC-6B had fuel in the fairing area (saddle tanks....bladders) that provided a total of 5512 USGallon (ten tank) capacity which enabled non-stop SMO-ORY delivery flights to Air France.
And yes, I know all about these as my Dad was engineering project manager DC6/DC7 programs at Douglas.
Starlionblue From Greenland, joined Feb 2004, 15102 posts, RR: 69 Reply 20, posted (4 years 6 months 1 week 6 days 10 hours ago) and read 2882 times:
Quoting 411A (Reply 19): The DC-6B had fuel in the fairing area (saddle tanks....bladders) that provided a total of 5512 USGallon (ten tank) capacity which enabled non-stop SMO-ORY delivery flights to Air France.
Crikey. How long did that take?
Tact Is For People Who Aren't Witty Enough To Be Sarcastic
411A From United States of America, joined Nov 2001, 1826 posts, RR: 10 Reply 21, posted (4 years 6 months 1 week 6 days 1 hour ago) and read 2824 times:
16 hours.
A strong tailwind was absolutely required...and of couse, the airplane being empty, and cruised at an untimate range power setting (40%BHP), this proved to be adequate....just.
Avt007 From Canada, joined Jul 2000, 2131 posts, RR: 6 Reply 22, posted (4 years 6 months 1 week 6 days ago) and read 2806 times:
Quoting Airfoilsguy (Reply 17):
I think I remember reading somewhere that it is prohibited to store fuel above passengers in planes that fly in the USA. I could be wrong though.
In the case of the Shorts, the fuel is in 3 metal tanks outside the fuselage, so there are two barriers.
In the Twin Otter, the fuel is under the floor in 2 bladders.
Any fuel lines passing through a cabin usually have an inner and outer duct in case of leaks.
Abnormal From UK - England, joined Aug 2007, 66 posts, RR: 0 Reply 23, posted (4 years 6 months 1 week 5 days 13 hours ago) and read 2758 times:
Just a semi educated guess to add but there is also a load issue. More load in the middle means the wings have to to carry more weight which means a greater stress on the spar and a greater bending moment at the root.
One recent real world example that springs to mind - the A340 MEL lets you take off with outer to inner transfer valves latched open. This allows the outer fuel to freely flow into the inner cells much earlier in the flight than usual. You can't do this as part of the regular operation though because the fatigue loading and analysis of the wing is based on the assumption the valves will never be latched open more than 100 (?) times in the life of the aircraft. The weight has to be retained in the outer wing to help ease the wing loads.
You'll find quite a few aircraft with restrictions on the fuel loads for this reason and it's the main reason outer tank fuel is retained until much of the inner fuel has been burned off.
Another example that I just thought of (foggily) is the CRJ - I seem to recall you couldn't dispatch with X kgs in the wing tanks unless you had Y kgs in the ctr tank.
2H4 From United States of America, joined Oct 2004, 8937 posts, RR: 65 Reply 24, posted (4 years 6 months 1 week 5 days 13 hours ago) and read 2756 times:
AIRLINERS.NET CREW HEAD DATABASE EDITOR
Quoting Abnormal (Reply 23): the A340 MEL lets you take off with outer to inner transfer valves latched open. This allows the outer fuel to freely flow into the inner cells much earlier in the flight than usual.
I wonder if the resulting increase in wing flex during takeoff would be visually discernible...
2H4
Intentionally Left Blank
25 Abnormal: I prefaced my comment by saying "semi educated".
26 2H4: Oh, I didn't mean to suggest that you're wrong in any way....I hope it didn't come across as such. I was just wondering out loud. 2H4
27 Abnormal: It didn't. And I would't be surprised at all if I was. There are numerous reason for why things are the way they are on aircraft. Sometimes I just thr
28 Ex52tech: AH........an aircraft fuselage that would be structurally strong enough to support an overhead fuel tank would be very heavy. That is why they use th
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