Mr Spaceman
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External Fuel Tanks On Airliners - Ever Used?

Thu Jan 08, 2004 6:48 am

Hi guys.

I was looking at the 2 photos below of a South African Air Force B707-328C that has external fuel tanks between the outboard engines and the wingtips. This got me thinking .........

Has there ever been a commercial airliner anywhere in the world that used external fuel tanks?

It appears to me that no commercial version (and there are many!) of the 707 ever used external fuel tanks to extend it's range, but, perhaps there was a European, Asian, or Soviet, airliner that did.

Even though the 707-328C in the photos prove that it was a possibility. I wonder why the commercial version of this aircraft never utillized this feature? Was it an option?

Here's a military version of the 707-328 with external tanks.


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Photo © Thomas Johannesson
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Photo © Thomas Johannesson



The commercial version of the 707-328.


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Photo © Frank C. Duarte Jr.
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Photo © Rolf Wallner


I
wonder if the USA Air Force ever considered this option for "Air Force One" when the Presidential aircraft were 707s ?


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Photo © Pedro Aragão



PS, how many US gallons of Jet fuel do you think those external tanks can hold? I'd say around 400. Big grin

Chris  Smile


"Just a minute while I re-invent myself"
 
OPNLguy
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RE: External Fuel Tanks On Airliners - Ever Used?

Thu Jan 08, 2004 8:01 am

>>>I wonder why the commercial version of this aircraft never utillized this feature

Mainly because of the inevitable "ramp rash" incidents with ground service vehicles such as tugs, baggage carts, belt loaders, lav carts, and catering trucks. Ramp accidents happen every day, and most are minor, but if the aircraft had external tanks hanging off the wing, they'd just become additional vehicular targets. Hit one of those tanks, fuel leaks, and you could easily have a potential "boom" on the ramp.
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
L-188
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RE: External Fuel Tanks On Airliners - Ever Used?

Thu Jan 08, 2004 2:45 pm

Are those fuel tanks or refueling pods?

Fuel tanks are draggy.

I heard that the Herks with the drop tanks are significantly more draggy then those without them.

Of course that lowers efficency and airlines don't like that.


But that being said, I do recall reading somewhere that there was a proposal to "wet" the carrots on the trailing edge of the CV-990 wing.
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AJ
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RE: External Fuel Tanks On Airliners - Ever Used?

Thu Jan 08, 2004 4:21 pm

They are pods for the inflight refuelling drogue, not fuel tanks:

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Photo © Craig Murray

 
SlamClick
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 2:38 am

There used to be a Gulfstream II seen around LGB a few years ago that had Lear 23 tip tanks. The buzz around the airport was that the drag of the tanks actually shortened the range of the G II. Don't know if it is true, but "wetted area" does add drag.

When AF1 was a 707 it probably had all the range it needed. Remember that in its executive configuration it carried far fewer passengers and therefore a lot less luggage than its airline counterparts. There have always been aux fuel tank systems available that fit in the bag pits.
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DeltaGuy
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 3:34 am

Basically, those pods will let Hornets or other jets with an IFR (In Flight Refueling) probe, come up to the tanker simultaneously, instead of waitin for gas from one boom. On the Air Farce KC-135, it just has a boom, which has to have the hose and basket adapter to mate to a Navy jet...with capability for one jet at a time. This passes the gas faster (no pun intended lol)

DeltaGuy
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broke
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 4:35 am

The only commercial airliner that I know of that used external fuel tanks was the Lockheed L-1049G Super Constellation. It had provisions for external tanks under the wing tips and I only saw these installed once, on an airplane in Kuwait.
 
Mr Spaceman
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 5:19 am

Hi guys.

Thank You for your replies.

OK, so these are not external fuel tanks, they're refueling pods. The angle of the 2 photos that show these pods doesn't allow us to see the aft part of them (which would be verticaly flat instead of tappered), so my mind instantly thought of fuel tanks ........ like the kind used on the C-130 Hercules.

The thought of extra drag never entered my mind. I thinks that's because of all the fighter jets out there that use external fuel tanks. However, I understand that's a different situation.

I also never thought of the inevitable "ramp rash" that OPNLguy mentioned. If those were fuel tanks on that 707, they could very well be an "explosion" waiting to happen.

Last month wasn't to good for a few CRJ's in the USA. On December the 2, a COMAIR CRJ was struck by an unoccupied belt loader at JFK in New York. The operator of the loader fell off it as she was driving it towards the CRJ. The right side of the jet was substantially damaged.

On December the 14 at Miami, a WISCONSIN Airlines CRJ was struck by a tug after the driver jumped off of it after the tow bar shear pin broke. There were 9 ribs broke along the bottom of the fuselage!


Chris  Smile
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Mr Spaceman
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 6:22 am

Hi guys.

> Broke, here's a photo of a Lockheed Super Connie which just happens to be at my city's Intl Airport ....Toronto's Pearson Intl Airport (YYZ). I've taken many photo of it myself. It's located beside the entrance road for the corporate jet hangars on the north side of YYZ. It used to be located miles away near the south east corner of the airport where it stood on the front lawn of a hotel called The Constellation. When it was there, on the lawn, it had steps leading up to tail doors because there was a instant teller bank machine inside! ............ I hate what's been done to this beautiful aircraft.

Anyways, in this photo of it, you can see that it has wing tip tanks. I'll have to go and have a look at her some day to check if you can see where provisions have been made for external tanks that would hang under the wing tips.


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Photo © Paul Bulas
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Photo © Howard Chaloner



> Slamclick, did the "Air Force One" 707's ever have mid-air refueling capabilities, like the 747 does today?

You can see the refueling receptical in Air Force One's nose in this photo.


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Photo © Sam Chui



Chris  Smile
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Jan Mogren
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 6:26 am

Don't forget this beauty



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the Comet 4C
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jetstar
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 7:15 am

There used to be a Gulfstream II seen around LGB a few years ago that had Lear 23 tip tanks. The buzz around the airport was that the drag of the tanks actually shortened the range of the G II. Don't know if it is true, but "wetted area" does add drag.

They were not LearJet tip tanks, wing tip tanks were offered on G-II’s as a factory option. The original design concept was to make them removable in the field and install them when needed for additional range by carrying more fuel.

The removable tip tank idea concept never reached production and they were permanently installed on the wing tips. It was not a success and not many wing tip tank G-II’s were sold.

The additional drag from the tanks almost offset the additional fuel carried and the additional range was not that much more. This option was dropped when the G-III was introduced.

Gulfstream offered a G-II rewinging program where the original wings were replaced with the more efficient wings from the G-III, including the blended wingtips. This modified Gulfstream is known as a G-IIB.

Most of the wing tipped G-II’s were modified to G-IIB’s, so a wing tipped G-II is probably a rare sight.

 
OPNLguy
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 7:19 am

>>>I also never thought of the inevitable "ramp rash" that OPNLguy mentioned. If those were fuel tanks on that 707, they could very well be an "explosion" waiting to happen.

Although there are exceptions (which others have noted) you just won't see such tanks on an everyday-use airliner, as if they had them, you might as well paint "HIT ME" or bullseyes on them, because eventually someone would...  Big grin
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
LY744
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 8:07 am

With respect to fighter jets, it is said that roughly half the fuel in a drop tank will be used just to compensate for the drag added by the tank.


LY744.
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Mr Spaceman
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 9:00 am

Hi guys.

>> Jan Mogren, Thank You, for pointing out that the Comet 4C has external (bullet like) fuel tanks. She is a Beauty!

The reason it's taken so long for me to reply to you is because I've been searching the web while trying to find out the specific difference in fuel capacity between the Comet 4B (without external tanks) & the Comet 4C (with external tanks). Then I got all caught up in reading about the Comet and it's history. There's some really good info out there about it.  Big thumbs up

The Comet 4B had a fuel capacity of 9,150 gallons (35,460 L). The Comet 4C could carry 1,290 gallons more, with a capacity of 10,440 gallons (40,450 L).

The Comet 4B & 4C.
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Photo © Stephen John Rendle
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Photo © Eduard Marmet



http://www.neam.co.uk/comet.html
http://aerospaceweb.org/aircraft/jetliner/comet/index.shtml

>> JETSTAR, Thanks for all of that info. It sounds like spotting a wing tipped G-II would be a rare sight indeed.

>> OPNLguy, I agree with you. Eventually, there would be a lot of smoke in the air!

>> LY744, That's pretty interesting info to know. I guess the extra drag is worth the extra fuel/range though, or they wouldn't be used.


Chris  Smile
"Just a minute while I re-invent myself"
 
Guest

RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 9:54 am

There have been several other aircraft with slipper tanks (ala Comet) for example, the Lockheed Jetstar and even the Turbo Commander had them as an option.
 
Mr Spaceman
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RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 10:18 am

Hello Jetguy.

Thanks for letting me/us know that the tanks on the Comet & Jetstar are called "slipper tanks."

Fifteen years ago I worked on the ramp for a corporate FBO at Toronto Intl (YYZ), and there was only one Jetstar that I got to refuel a few times a month. I don't think I ever asked back then what those tanks were called.

It was neat to have a G IV or a Falcon 900 and the Jetstar on the ramp side by side ........ the old & the new! Big grin


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Chris  Smile


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Guest

RE: External Fuel Tanks On Airliners - Ever Used?

Fri Jan 09, 2004 12:18 pm

A lot of pilots called the Jetstar's slipper tanks "canoes"  Smile By the way Mr. Spaceman, I ate many meals in the Connie in Toronto - really crummy food, really great atmosphere.
Jetguy

[Edited 2004-01-09 04:21:32]
 
XXXX10
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RE: External Fuel Tanks On Airliners - Ever Used?

Sun Jan 11, 2004 10:37 pm

I know its not the same but some airliners -A310s and some L1011s could carry extra fuel in tanks stored in the rear cago hold.

This way there was no extra drag or safety issues
 
jetstar
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RE: External Fuel Tanks On Airliners - Ever Used?

Mon Jan 12, 2004 10:40 am

The JetStar “slipper” tanks are called Auxillary Fuel Tanks by Lockheed, each tank held 565 gallons and were used after takeoff during climb. Most pilots called them the “Aux” tanks.

The JetStar had 4 main wing tanks and with the 2 aux tanks there was a total of 6 fuel tanks on the airplane. Fueling was done using only the wing fuel ports, single point fueling was not available until the JetStar II. If the airplane was being fueled from one truck, care had to be taken to prevent the airplane from being unbalanced on the ground. First one inboard fuel tank was fueled, then the other inboard, then one outboard and then the other, and then the aux tanks were filled, if needed. On short flights, the aux tanks were never used unless fuel was being tankered for the return flight.

There is a STC available to install single point fueling on the earlier models and this was usually done if the JetStar was updated to the 731 engines.

One the earlier JetStars the tanks was split with half the tank above the wing and half below the wing.

On the reengined JetStars with the 731 engines and on production JetStar II’s the tank was lowered to below the wing, hence the nickname “canoes”. This was done because the 731 engines had a wider inlet and the airflow over the older aux tanks interfered with the airflow into the engines.
 
Spacepope
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RE: External Fuel Tanks On Airliners - Ever Used?

Mon Jan 12, 2004 12:36 pm

Some USAF KC-135s have the refuelling hose drum pods in addition to the flying boom. The problem with the -135 is that it can either give gas from the center by flying boom or by basket, but not both during the same flight. the basket and hose are fitted on the center position on the ground The wingtip pods have a slower flow rate than the center position, but they allow for both boom and probe & drogue refuelling on the same mission. The KC-10 can do both from the center position, but some have the wingtip pods added so that it can refuel 2 aircraft at once.

T.J.
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Mr Spaceman
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RE: External Fuel Tanks On Airliners - Ever Used?

Wed Jan 14, 2004 8:58 am

Hi guys.

> L-188, you said ...... "I do recall reading somewhere that there was a proposal to "wet" the carrots on the trailing edge of the CV-990 wing"

Here's some photos of the Convair CV-990 Coronado. In the first photo, you can clearly see what appears to be a red fuel cap. So I guess these canoe fairings (carrots) are "wet" on the CV-990. Unfortunately I couldn't find any hard facts about these fairings/tanks, so I don't know how much fuel they can hold.


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Notice that these fairings/fuel tanks are only on the top surface of the wing.

Chris  Smile

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L-188
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RE: External Fuel Tanks On Airliners - Ever Used?

Wed Jan 14, 2004 4:38 pm

Hi there spaceman.

I do agree that looks suspicously like a fuel port on that CV-990 carrot.

But that being said, I know that Modern Air did try and retrofit the carrot on one of their CV-990's with an APU. The only 990 that ended up with one.

Don't think they would have done that if they displaced fuel for it. Those 990's where thirsty enough as it was.
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Mr Spaceman
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RE: External Fuel Tanks On Airliners - Ever Used?

Thu Jan 15, 2004 5:08 am

Hi guys.

> L-188, if that isn't a red fuel cap, then what is it?

Also, if the idea that they might be canoe fairings for covering flap actuators is mentioned, well, why are they so big, and why are they located on top of the wing when most fairings for flaps actuators are located on the bottom surface of the wing and flaps?

> Spacepope, check out this photo of a UK Air Force Handley Page Victor K2. As you can see, the Victor can refuel 3 fighter jets  Big thumbs up (in this case Lightnings), although maybe not all three fuel lines can pump fuel at the same time. I don't know.


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Chris  Smile
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Spacepope
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RE: External Fuel Tanks On Airliners - Ever Used?

Thu Jan 15, 2004 10:04 am

Mr Spaceman: Correct you are! I count 3 Lightnings as well. From my understanding, with 2 aircraft (especially anything larger than a lightning) the center position is quite bumpy from the wakes of 3 aircraft. The center station does have a flow rate advantage compared to the wingtip pods. I strongly suspect that photo was taken of a manouvre done for display only.

T.J.
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MD-90
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RE: External Fuel Tanks On Airliners - Ever Used?

Mon Jan 19, 2004 6:54 pm

It is an impressive picture, though. Nice formation flying.
 
vc10
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RE: External Fuel Tanks On Airliners - Ever Used?

Tue Jan 20, 2004 4:01 am

Mr Spaceman,
Nice pictures, but just to remind everybody the basic Comet 4 as operated by BOAC also had fuel pod tanks. I spent hours in them during the comet major overhauls in the early 1960s

Regards little vc10
 
neil49
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RE: External Fuel Tanks On Airliners - Ever Used?

Tue Feb 03, 2004 2:22 pm

Re the fairings on upper wing surface of CV-990: These were called "anti-shock bodies" and were designed to delay the onset of the shock wave from the airflow over the upper surface of the wing, which increased drag; the reduction in drag afforded by the pods allowed for somewhat higher cruise speeds.

The pods were designed to carry extra fuel, and depending on the "dash" model of the aircraft, the total capacity varied from 1,144 USG to 1,606 USG.

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