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Re: Navy 6th Generation Fighter

Unread postPosted: 03 May 2021, 21:49
by ricnunes
mixelflick wrote:It's interesting to see how US combat aircraft internal fuel volumes have flunctuated over the years. Yes, I know drag is another big one when figuring range, but consider the following..

F-14D 16,200lbs
F-15C 13,500lbs
F-16C 7,000lbs
F/A-18E 14,700lbs

F-35A 18,250lbs
F-35B 13,500lbs
F-35C 19,700lbs




I kinda disagree with your assessment that the internal fuel volumes/capacity of US combat aircraft have 'fluctuated' over the years since I believe you can't reach the conclusion that the internal fuel of US aircraft lowered (fluctuated on the low side) by comparing the F-14 with the F-15 and later with the F-16 because:
- While the F-14 and F-15 have similar sizes and the F-14 carries more 'internal fuel' than the F-15, the F-15 was designed from the very beginning to carry FAST fuel packs/tanks (CFTs) with which the F-15 will carry even more fuel than the F-14 without both aircraft carrying External Fuel Tanks (EFTs).
- The F-16 can't simply be compared to the F-15 since the former was designed to be much smaller and thus a cheaper complement to the later which of course means that the F-16 would always carry much less internal fuel than the F-15 (and the F-14).

Re: Navy 6th Generation Fighter

Unread postPosted: 03 May 2021, 21:52
by zhangmdev
The thrust increased with increase in bypass ratio while the specific fuel consumption decreased with increase in bypass ratio. For those very high bypass ratio turbofan on airliners, most of the thrust is generated by the fan. The extreme example is a turboprop. The propeller is good at moving a large amount of air, although the operating speed and altitude is limited. The other extreme is a turbojet. Good at high speed and high altitude, but performs very poorly at low speed and low altitude.

The point of the adaptive cycle engine is to decrease fuel comsuption during cruise, by increasing bypass ratio, while increase thrust in combat situations, by micmicing a straight turbojet. The following is a paper about some computer simulation of the adaptive cycle engine. It shows the the adaptive cycle engine has a much better fuel economy than the F-119 engine, while having higher thrust at high altitude and high speed.

https://rc.library.uta.edu/uta-ir/bitst ... sequence=1

Re: Navy 6th Generation Fighter

Unread postPosted: 05 May 2021, 17:28
by sferrin
ricnunes wrote:the F-15 was designed from the very beginning to carry FAST fuel packs/tanks (CFTs)


The F-15 didn't get FAST packs until the F-15C. The A/B did not have them and they also had less internal fuel than the C/D.

Re: Navy 6th Generation Fighter

Unread postPosted: 05 May 2021, 19:04
by strykerxo
The F-35 has double and nearly triple the amount of fuel of the legacy F-16/18, with all the characteristics of a 5th gen. AC. The Su-35/57 have 25k of fuel in a heavy fighter, with ranges +1000k combat radius, and extremely maneuverable.

6th gen AC will be a blended wing delta, cranked arrow, minimum 25k lbs. worth of fuel and whatever else they want to cram inside, ie EW, Laser, Fuel, Weapons?????

Re: Navy 6th Generation Fighter

Unread postPosted: 05 May 2021, 19:46
by ricnunes
sferrin wrote:
ricnunes wrote:the F-15 was designed from the very beginning to carry FAST fuel packs/tanks (CFTs)


The F-15 didn't get FAST packs until the F-15C. The A/B did not have them and they also had less internal fuel than the C/D.


The FAST fuel packs were first tested on the F-15B in 1974, two (2) years before the F-15A/B entered in service and only two (2) years after the F-15 first flight.

Re: Navy 6th Generation Fighter

Unread postPosted: 05 May 2021, 22:41
by eagle3000
They were tested but not introduced. The F-15A/B unmodified could not carry CFTs.
Not sure if the CFTs on the F-15B test aircraft were plumbed.

Re: Navy 6th Generation Fighter

Unread postPosted: 06 May 2021, 13:36
by ricnunes
eagle3000 wrote:They were tested but not introduced. The F-15A/B unmodified could not carry CFTs.
Not sure if the CFTs on the F-15B test aircraft were plumbed.


The FACT that CFTs (FAST fuel packs) were tested very early during the F-15 development (on a F-15B) or more precisely before the first F-15A entered in service is more than enough evidence that the F-15 was projected/planned from the very beginning to carry CFTs and that's my point above!

As to why the F-15As and F-15Bs never carried CFTs operationally, I'm sure there are several/myriad reasons or at least a few reasons for that but this is something which IMO should grant a thread of its own.

Re: Navy 6th Generation Fighter

Unread postPosted: 06 May 2021, 18:35
by basher54321
ricnunes wrote:As to why the F-15As and F-15Bs never carried CFTs operationally, I'm sure there are several/myriad reasons or at least a few reasons for that but this is something which IMO should grant a thread of its own.



Isreali F-15A/Bs used them from a certain time period - have several photos undated.

Israeli Historian Shlomo Alomi makes out they first got some CFTs in 1980 and were needed to make the Osirak raid trip in 1981. He mentions 2 of the F-15s were Bs with CFTs.

Unfortunately unlike the Osirak F-16s where photos and serial numbers exist have not seen the same for the F-15s used yet.


Part of a 1970s report on FAST Packs but not that much info:

FAST-PACK-Report-P1.jpg

Re: Navy 6th Generation Fighter

Unread postPosted: 06 May 2021, 18:45
by jetblast16

Re: Navy 6th Generation Fighter

Unread postPosted: 06 May 2021, 20:59
by ricnunes
Thanks for the reply basher (and also jetblast) :thumb:

That proves what I suspected but wasn't sure - that the F-15A/B were also able to carry FAST fuel packs (CFTs) and thus prove my point that the F-15 was designed from the very beginning to carry them.

Re: Navy 6th Generation Fighter

Unread postPosted: 07 May 2021, 16:06
by mixelflick
Given all they carry is fuel today (that we know of), the acronym move from FAST packs to CFT's was warranted. The extra fuel looks to be what the EX will carry them for as well, although I'd think USAF might re-visit the other payload options for special missions. Yes, I know $ is probably the issue but as an example...

If you're going to carry the Sniper or Legion pods, why not carry those in the FAST packs and then fill the rest with fuel? If you look at the "strike assist" configuration below, it seems to be what the engineers were building towards.

A bit less gas but a whole lot less drag might just yield some surprising numbers. I hope they were at least looked at..

Re: Navy 6th Generation Fighter

Unread postPosted: 07 May 2021, 17:38
by steve2267
mixelflick wrote:If you're going to carry the Sniper or Legion pods, why not carry those in the FAST packs and then fill the rest with fuel? If you look at the "strike assist" configuration below, it seems to be what the engineers were building towards.

A bit less gas but a whole lot less drag might just yield some surprising numbers. I hope they were at least looked at..


Becuzz engineering...

oh, and testing...

oh, and that all costs money. Last I hurd 'Murican engineers don't work for free.

Looked at? Nah. Why bother with trade studies?

Re: Navy 6th Generation Fighter

Unread postPosted: 08 May 2021, 16:17
by jetblast16
The "Augmented Thrust" one is intriguing :)

Re: Navy 6th Generation Fighter

Unread postPosted: 08 May 2021, 16:34
by ricnunes
jetblast16 wrote:The "Augmented Thrust" one is intriguing :)


That one would have its name changed from FAST changed to FART :mrgreen:

Re: Navy 6th Generation Fighter

Unread postPosted: 08 May 2021, 16:51
by strykerxo
Augmentation tank = rocket assist

Spray tanks?????????????

worlds most expensive "crop duster"

I like the imaginative effort.

Now, that's a "Super Eagle"