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Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 14 Jun 2019, 01:22
by weasel1962
sprstdlyscottsmn wrote:Well, there goes any discussion at all of a Strike Eagle going farther. It was already close. With a 70k MGTOW the F-35A with two internal AIM-120s and two internal GBU-31s and two external 600gal tanks still has nearly 9,000lb payload remaining. You could slap on two more external GBU-31s and a pair of Winders and not even be close to MGTOW. Meanwhile, the Mudhen cannot carry more than two GBU-31s if it triple bags without going over MGTOW. If it double bags it can carry 4.


1. Can't the Mudhen just take off carrying 4 GBU-31 but with less fuel then top up to max via tanker, if there is a need? The f-35A will need to burn more fuel before tanking i.e. tanker will need to be closer to the target.

2. F-35A carrying 2 external GBU-31s, 2 EFTs and 2 AIM-9L will generate drag and attendant max altitude restrictions i.e. impact range.

3. F-35A with 4 GBU-31s may not be close to the MTOW but its TWR is worse off than the Mudhen by virtue of the F-15EX's "fuel-guzzling" but more powerful twin engines. I don't think it would be realistic to assume the F-35A has a consistent performance across all weights. The heavier the loads, the higher the fuel consumption, the lower the altitude, the more fuel burn per nm, with a weaker engine pushing those loads. The F-15E suffers from it, same laws of physics apply for the F-35A.

The requirements of a dual-engine heavy fighter vs a single-engined cheap lightweight fighter is an established, well proven strategy. Much the same way as the F-16 is a fantastic plane but still better to leave it to the F-15 to deal with fighters, a dual engined PCA will be needed. That should be the priority compared to the beauty parade/sideshow of F-15 vs F-35. Once one agrees on the validity of the strategy, the F-15 becomes irrelevant because it is neither a single-engined LWF nor is it ideal as a dual engine HWF. That is where a cogent argument has not been made which has allowed the F-15 to sneak back in.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 14 Jun 2019, 06:29
by marauder2048
weasel1962 wrote:The requirements of a dual-engine heavy fighter vs a single-engined cheap lightweight fighter is an established, well proven strategy.


That was for an era before the advent of accurate munitions that can threaten fuel supply, storage and
distribution infrastructure on practically every US and allied airbase.

You can massively harden aircraft shelters and protect them with terminal defenses but no one has figured out,
short of mountain redoubt style bases with deeply buried pipelines, how to protect fuel supply, storage and
distribution to the same extent.

If you accept that the US and allies will be operating in a fuel limited environment then you don't want twins.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 14 Jun 2019, 07:54
by doge
I daydreaming...May I fantasize of a dreams match combination this "EFT" and the "ADVENT engine"? 8)

I try to play with numbers. 8)
With a current A's 18,000 lbs fuel, the radius is about 1,400 km. (Max radius currently revealed.)

If EFT increases fuel +40% by My roughly simple calculation, will be the radius about 2,000km further from there.

Furthermore+, ADVENT engine is advertised increase the radius by +30%, so by My sketchy simple calculation will be the radius about 2,600km further from there.
2,600km!! :doh: It's a crazy distance!! :doh: It's a long working hour, which make the pilot tired... :doh:
(This is my fantasize... 8) )

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 14 Jun 2019, 13:55
by sprstdlyscottsmn
40% more fuel will not mean 40% more range. Maybe 25%. 30% tops.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 15 Jun 2019, 15:00
by mixelflick
In for EFT's. Let's see some 600 gallon bags. Every other external store makes it look that much more deadly, hope these will too.

But really, why not just move to CFT's? That's where everything went on the legacy's. First the Eagle, then Viper and lately the Super Duper Hornet. And if anyone can come up with jettisonable CFT's, it's Lockheed..

Or Israel :)

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 15 Jun 2019, 15:25
by viper12
sprstdlyscottsmn wrote:40% more fuel will not mean 40% more range. Maybe 25%. 30% tops.


Fully concur. Using the range equation at fixed height, and assuming the 40% extra fuel doesn't create extra drag and the extra weight is only the extra fuel, I end up with a combat radius of 898.7nm for the mission profile with a 669nm combat radius on internal fuel, or a 34.3% range increase.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 15 Jun 2019, 15:37
by ricnunes
sprstdlyscottsmn wrote:40% more fuel will not mean 40% more range. Maybe 25%. 30% tops.


Absolutely! Now you just have to inform this to Saab :wink:

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 15 Jun 2019, 22:04
by wrightwing
viper12 wrote:
sprstdlyscottsmn wrote:40% more fuel will not mean 40% more range. Maybe 25%. 30% tops.


Fully concur. Using the range equation at fixed height, and assuming the 40% extra fuel doesn't create extra drag and the extra weight is only the extra fuel, I end up with a combat radius of 898.7nm for the mission profile with a 669nm combat radius on internal fuel, or a 34.3% range increase.

There's got to be some drag penalty, but the question is how much? If we're more conservative and stick with 25%, that's still 837.5nm. Of course when the next generation motors are available with a 30 to 35% range increase, then we're looking at numbers like 1088.75nm to 1130.63nm when using EFTs.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 15 Jun 2019, 22:39
by viper12
There's obviously some drag penalty, so a 34% range increase for 40% extra fuel is just impossible. The weight of the fuel tanks themselves isn't completely negligible either, as I guess 2 of them should weigh around 600 pounds, or roughly 2% of the F-35A's empty weight.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 16 Jun 2019, 21:48
by geforcerfx
I wanna say it was on this forum or from a family pilot friend that said the rule of thumb was EFTs usually only give 50-75% of there fuel, the rest is the drag and weight penalty.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 16 Jun 2019, 22:07
by spazsinbad
Rules of thumb generalisation? Some A4G profiles were better with two tanks rather than three - one had to do the math.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 17 Jun 2019, 08:26
by taog
Omg, LM also considers adding the CFT to F-35 lol

Image

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 17 Jun 2019, 13:52
by vilters
Simple economics.
If LM does not develop extra range, Israel will, because they are going to use it.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 17 Jun 2019, 19:27
by blain
So both Israel and LM are developing CFTs, or is this a joint venture. A key issue will be capacity. The shape of the top of the F-35 will limit capacity. The F-16I supposedly carries around 450 gallons per CFT. The SH's CFTs have a capacity of around 515 gallons. So the capacity of the CFTs might approach the capacity of the external tanks.

The other issue will be whether the CFTs would preserve the low observability of the F-35. Israel might not have the ability to test RCS. If the CFTs are not low observable then it might make tactical sense to carry external tanks on long range missions and then drop them once entering enemy territory.

Re: Lockheed Proposes 40% F-35A fuel increase with EFTs

Unread postPosted: 17 Jun 2019, 21:02
by spazsinbad
"So both Israel and LM are developing CFTs, or is this a joint venture...." Both are in a joint venture and have been for years. What has been developed so far for Israel is not clear. One may speculate until someone elaborates on EFTs/CFTs.