F-35 and external fuel?

F-35 Armament, fuel tanks, internal and external hardpoints, loadouts, and other stores.
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Corsair1963

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Unread post22 Dec 2008, 23:32

I've heard the F-35 was getting redesigned external fuel tanks? Which, I believe are around 426 Gals. Is this correct and how many can she carry??


Also, I believe Israel is developing even larger external fuel tanks and even CFT's! Does any one have any information regarding them???
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elp

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Unread post22 Dec 2008, 23:48

Corsair1963 wrote:I've heard the F-35 was getting redesigned external fuel tanks? Which, I believe are around 426 Gals. Is this correct and how many can she carry??


Also, I believe Israel is developing even larger external fuel tanks and even CFT's! Does any one have any information regarding them???


Blocks past 4 are notional. And yes the IDF have mentioned it in passing. However for SDD there won't be any drop tanks cleared. Funding was put out in a DOD contract in 2006 to cut WCMD (CBU-105 etc) and drop tanks from SDD stores clearance and add SDB to the SDD stores clearance list.

Maybe at a later date we will see drop tanks if someone coughs up the funds.
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energo

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Unread post23 Dec 2008, 01:18

Corsair1963 wrote:I've heard the F-35 was getting redesigned external fuel tanks? Which, I believe are around 426 Gals. Is this correct and how many can she carry??


Two, not sure if the 35' has additional wet stations.

Dakota 14 (C13) aeroshaped fueltank. Originally the 480 gal. from the Navy Hornets was to be used, but the 2003 Preliminary Design Review revealed unsafe store separation issues. Changing the toe-out of the pylons, a commonly used technique, didn't yield the required results so a redesign of the tank was done. I believe this is similar to the french Rafales external tank.

Good technical article on the projects CDF and wind tunnel testing:

http://pdf.aiaa.org/preview/CDReadyMASM ... 08_376.pdf


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B. Bolsøy
Oslo
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Corsair1963

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Unread post23 Dec 2008, 03:26

energo wrote:
Corsair1963 wrote:I've heard the F-35 was getting redesigned external fuel tanks? Which, I believe are around 426 Gals. Is this correct and how many can she carry??


Two, not sure if the 35' has additional wet stations.

Dakota 14 (C13) aeroshaped fueltank. Originally the 480 gal. from the Navy Hornets was to be used, but the 2003 Preliminary Design Review revealed unsafe store separation issues. Changing the toe-out of the pylons, a commonly used technique, didn't yield the required results so a redesign of the tank was done. I believe this is similar to the french Rafales external tank.

Good technical article on the projects CDF and wind tunnel testing:

http://pdf.aiaa.org/preview/CDReadyMASM ... 08_376.pdf


Regards,
B. Bolsøy
Oslo


Thanks, I believe I saw that site before. Do you have any idea on the size or the number that can be carried??
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energo

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Unread post23 Dec 2008, 12:47

Corsair1963 wrote:Thanks, I believe I saw that site before. Do you have any idea on the size or the number that can be carried??


426 gal. and AFAIK two tanks.


Regards,
B. Bolsøy
Oslo
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SnakeHandler

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Unread post23 Dec 2008, 12:51

It has 21000 pounds of internal gas. That's almost twice as much as a Viper. It doesn't need externals.
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cobzz

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Unread post23 Dec 2008, 13:51

The F-35 has a radius of 673 nautical miles on internal fuel alone and 728 nautical miles using external tanks. Not a big difference. Probably because externals are draggy and it already carries a massive amount of fuel. Assuming a 610nm mission, that is 220 nautical miles at Opt M/Alt Cruise, 390 nautical miles Ingress/Egress at 30K f/0.9M. Combat at 20,000 feet. Mission radius does not equal maximum radius.

http://norway.usembassy.gov/root/pdfs/v ... _dista.pdf

ELP. Didn't you say the F-35 cruises at 25,000 feet because of high wingloading that also happens to be similar to the F-16, F-18, superior to the F-14, and similar to the F-15 with twin bags on its wings? Or am I simply a 'defense chearleader' Lockmart PR guy?
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LowObservable

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Unread post23 Dec 2008, 14:51

If you look at the map in that document, you'll see that it shows a range of 728 nm on a maritime surveillance mission, with cruise altitudes between 5,000 feet and 25,000 feet.

What does it mean when you add 31 per cent more fuel and get 8 per cent more range? It means that the added weight and drag is causing you to fly less efficiently - slower, at high alpha and low altitude.

If your primary sensors are radar and ESM, why are you flying at 5,000 feet? Because you can't get any higher, that's why.
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cobzz

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Unread post23 Dec 2008, 15:00

Because the search area includes FLIR and laser designation. :lol: 5000 ft? Is that a joke? Carlo Kopps beloved Cessna can fly higher than that. So, a supersonic fighter with a wingloading comparable to other jets, and a comparable t/w ratio, cannot fly higher than 5000 feet, and cruises at 'high alpha' while flying 'time critical' missions. Uhuh.

Try reading the previous page.

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SnakeHandler, would an F-16 with three fuel tanks on the wings be abled to fly higher than 5,000 feet?
Last edited by cobzz on 23 Dec 2008, 15:32, edited 2 times in total.
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gtg947h

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Unread post23 Dec 2008, 15:16

It's 5000ft because the weather's overcast, and they need a visual/EO search too :)
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energo

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Unread post23 Dec 2008, 17:42

LowObservable wrote:If you look at the map in that document, you'll see that it shows a range of 728 nm on a maritime surveillance mission, with cruise altitudes between 5,000 feet and 25,000 feet.

What does it mean when you add 31 per cent more fuel and get 8 per cent more range? It means that the added weight and drag is causing you to fly less efficiently - slower, at high alpha and low altitude.

If your primary sensors are radar and ESM, why are you flying at 5,000 feet? Because you can't get any higher, that's why.


Possibly an error in the brochure. On LMs last presentation here in Oslo a similar slide was used showing a normal cruise profile (30-40k feet) and 750 nm radius. As always this is a conservative figure because it hasn't been properly evaluated outside the simulator and statistical estimates.

The 8% range increase with external tanks is still unanswered, but again it seems a bit low and might be an error. That said, it has been suggested that external ordnance and fuel tanks impact the aerodynamic properties of the F-35 more than traditional figthers due to a wing optimised for a clean configuration. I have to emphasise that this is purely speculation as this point.


Regards,
B. Bolsøy
Oslo
Last edited by energo on 23 Dec 2008, 17:51, edited 1 time in total.
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SnakeHandler

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Unread post23 Dec 2008, 17:44

I know it was a rhetorical question Cobzz, but I can get a two bag, tgp, ecm pod jet up to 39k and 1.2M. Stores limits are 1.6M but you'll never see it. The whole 5000 feet thing is just one edge of the envelope.
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energo

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Unread post23 Dec 2008, 17:46

cobzz wrote:Because the search area includes FLIR and laser designation. :lol: 5000 ft? Is that a joke? Carlo Kopps beloved Cessna can fly higher than that. So, a supersonic fighter with a wingloading comparable to other jets, and a comparable t/w ratio, cannot fly higher than 5000 feet, and cruises at 'high alpha' while flying 'time critical' missions. Uhuh.


Working altitude for the EOTS is about 40k feet. Almost twice the LANTRIN AFAIR.


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B. Bolsøy
Oslo
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energo

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Unread post23 Dec 2008, 17:49

SnakeHandler wrote:I know it was a rhetorical question Cobzz, but I can get a two bag, tgp, ecm pod jet up to 39k and 1.2M. Stores limits are 1.6M but you'll never see it. The whole 5000 feet thing is just one edge of the envelope.


Let me guess for cruise at 0.9: 25k? No wait, what engine are you on?


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B. Bolsøy
Oslo
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Corsair1963

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Unread post23 Dec 2008, 17:52

SnakeHandler wrote:It has 21000 pounds of internal gas. That's almost twice as much as a Viper. It doesn't need externals.



I believe the F-35A hold 18,500 lbs and the F-35C about 20,000 lbs. I've never heard the figure of 21,000 lbs? (i.e. internally)
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