Forum: Modern Military Aircraft

Effect of EFT on fuel fraction, TWR, and wing loading



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shingen
PostPosted: Apr 14, 2012 - 07:08 PM Reply with quote Back to top
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I thought I'd put up some numbers because this issue comes up often.

I got the numbers from googling so feel free to correct them.


F-35:
Loaded weight: 22500kg
Fuel load: 8300kg
Wing area: 43m^2
Thrust: 43000lb

Rafale:
Loaded weight: 14000kg
Fuel load: 4700kg
Wing area: 46m^2
Thrust: 33,800lb

Typhoon:
Loaded weight: 15500kg
Fuel load: 4000kg
Wing area: 50?m^2
Thrust: 40,500lb

EFT:
Rafale: 3 1250l tanks carry 2925kg of fuel
Typhoon: 3 1000l tanks carry 2340kg of fuel

F-35:
Fuel fraction: .37
Wing loading: 523kg/m^2
TWR: .87

Rafale no tanks:
Fuel fraction: .34
Wing loading: 304
TWR: 1.1


Rafale tanks:
Fuel fraction: .45
Wing loading: 367kg/m^2
TWR: .91

Typhoon no tanks:
Fuel fraction: .26
Wing loading: 310
TWR: 1.2

Typhoon tanks:
Fuel fraction: .36
Wing loading: 357kg/m^2
TWR: 1.03


I couldn't find a weight for the EFT's themselves, so I left it off, assuming there's enough error in the weights so that it's insignificant. I just used liters*.78 (the density of Jet A) for the mass of fuel they carry.


I know that wing area is a rough measure but what matters is how the 4th gens change with tanks vs no tanks.

Also, what % of drag is from EFT's?

I'm wondering if the EFT's are that bad.
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sprstdlyscottsmn
PostPosted: Apr 16, 2012 - 01:29 AM Reply with quote Back to top
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in an F-16 two wing tanks, an ecm pod, and two 2,000 lbs bombs basically double the drag.

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shingen
PostPosted: Apr 16, 2012 - 01:47 AM Reply with quote Back to top
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Is that subsonic, supersonic, transonic...?

I find that hard to believe, no disrespect intended it's my own lack of understanding that makes it hard to believe, not anything with you.

The F-105 had an internal bay but it wasn't used, they just put everything external when the rubber hit the road.

So, it makes you wonder why 4th gen went for external carriage.

The only answer I can come up with is that they followed the WW2 lessons which is you take down the IADS, then bomb at will instead of trying to get through defenses. Maybe they thought they couldn't be fast and maneuverable carrying anything more than A2A missiles.

So, next question. Is the F-35 better used with internal carriage bombing everything, or is it better to kill the IADS with internal carriage, then use the external carriage to pulverize the actual targets once it's a more permissive environment? I would guess they do a mix of the 2 with some high priority non-IADS targets hit before the IADS is gone.

I think the idea that a plane can carry external stores and deal with modern IADS is wrong. Double the drag is ridiculous.
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sprstdlyscottsmn
PostPosted: Apr 16, 2012 - 04:38 AM Reply with quote Back to top
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keep in mind, the F-16 is a small plane, and a lot of the added drag comes from the interference of airflow between the tanks and bombs.

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