F-15X: USAF Seems Interested

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mixelflick

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Unread post12 Mar 2020, 16:55

OK so let's start working from the premise of what we agree on. I think we can all agree that..

1.) The F-15 is a very flexible platform. It's been tweaked to carry everything from Israeli ballistic missiles to ASAT weapons to extremely large air to ground munitions. Since I think it'll be called upon to do a whole lot more than air defense, I vote it'll be the USAF's choice to carry large, hypersonic weapons. Or whatever they deem appropriate insofar as weapons carriage is confirmed.

In any case, I think we can agree - it's a very capable weapons carriage platform.

2.) The F-15EX buy is almost entirely political/corporate welfare for Boeing. Take the potential contract for 144 away, and Boeing's future looks dim. That, and it's pretty obvious USAF maintains a large and modern F-16 fleet. It's performing that mission NOW, so it's no stretch to imagine it being tweaked to even better perform it. And given they're newer, they should be cheaper to operate.

So here too, we should be able to agree that the F-15EX is being built under duress LOL. Politics is driving the buy, USAF/Feds don't want Boeing to shudder its doors

With respect to the EWP stuff, that's a good point about it providing some lift. I guess we'll have to see how it pans out, as EWP's are a relatively new phenomenon. Will they work as advertised? Will the missile shots go off without a hitch? Certainly hope so.

The EX will be a sight to behold. Flankers beware.... :)
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sprstdlyscottsmn

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Unread post12 Mar 2020, 17:34

madrat wrote:
sprstdlyscottsmn wrote:The Enclosed Weapons Pod (not CWB, that was the F-15 Silent Eagle EFT replacement) actually has a large drag profile. Quite large for something that carries four AMRAAMs. From the ASH brief the EWP has roughly the same drag as two JSOWs and a CL Tank

650+nm range listed for 17,000lb fuel internal and CL with 2xJSOW
650+nm range listed for 17,500lb fuel internal and CFT with single EWB
....
Centerline Tank, 19+1 (pylon)
JSOW, midboard 8+6.5 (pylon) x 2
EWP Drag Index 49 WITH pylon.

AIM-120 fuselage mount 4 x 2
AIM-120 wing mount 4 x 2
LAU-127 2 x 2
Low Drag Outboard Pylon 5 x 2
4x AIM-120 drag from four missiles, two pylons, and two launchers, 30


I was definitely adding up my pylon numbers incorrectly for a quad AIM-120 arrangement. I think I added in a second LAU-115 rather than identifying it as a twin. I was also equating the EWB's DI to be similar to a drop tank, which your DI of 49 completely throws the comparison out of line with. The centerline 480 gallon tank I figured was comparable at DI of 19-22 depending on carriage of other tanks.

Wouldn't the JSOW also require NAV/targeting pods adding DI 12 x2. The twin JSOW being around a DI of 33 (+19 for CL tank) should be higher to make the EWB number work out closer, but doesn't quite work out either. Is your DI 49 number not including NAV/targeting, too? I would assume EWB with that high of number to be all three.

Edit: I forgot to add CFT numbers. What is DI for them? Its not in NATOPS manual.

Alright *cracks knuckles*

I guess it's time to get fully detailed.

Starting with the following graphic,
ASH1.JPG

Let's look at the 2 JSOW config without CFTs (650+nm range)
And the bottom config, CFT and EWP (650+nm range) AHA! There is an IRST on that one! DI 12, so we can take that off the DI for the EWP, dropping it to 37.
And the CFT?
ASH2.JPG

zero to negative DI (it must improve the L/D), so it may not be unreasonable to say the CFT is -3 DI just to round the EWP up to 40.

How does this effect the use on an F-15? (gotta stay on topic)
First we need to calibrate a SHornet centerline EWP to a centerline or wing mounted SEagle EWP.
The trick is finding something the SHornet CAN carry on the centerline that the Eagle does too, which I am not seeing at first glance. So we are going to be tricky...

GBU-12 on SHornet is 5.8 plus 1 for the pylon for 6.8 centerline mount.
GBU-12 on Mudhen CFT with no bombs or tanks on wing is 3.9

Mk84 LDGP is 2.8 on CFT, 2.3 on wing, and 3.0 on centerline.

Taking DI 40 SHornet EWP would be DI 23 for theoretical CFT mount (Using GBU-12 ratios for translation purposes only) which means DI19 under a wing and DI 25 on centerline (using Mk84 ratios)

This would mean the EWPs, due to shape and size, have more drag than a 610gal tank, but would make some lift and could house a great deal of munitions.

An 3 x EWP equipped SEagle could have 24 AAMs with a DI of 133.6, max speed would be just a bit over 1.3M to 1.4M depending on fuel, with a total range of 881nm (440nm radius) given 15,000lb of cruise fuel (8,300lb use in ground ops, climb, descent, and reserves)
Last edited by sprstdlyscottsmn on 12 Mar 2020, 18:43, edited 1 time in total.
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disconnectedradical

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Unread post12 Mar 2020, 18:32

mixelflick wrote:2.) The F-15EX buy is almost entirely political/corporate welfare for Boeing.


You mean the St. Louis division, or former McDonnell Douglas. They're definitely wanting to make sure all fighter manufacturers are in business for PCA. Super Hornet, F-15EX, etc is all McDonnell Douglas, or St. Louis division of Boeing after merger.

McDonnell Douglas arguably did quite a lot of damage to Boeing after the merger especially in corporate culture.
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Unread post12 Mar 2020, 18:56

sprstdlyscottsmn wrote:Alright *cracks knuckles*

I guess it's time to get fully detailed.

Starting with the following graphic,
ASH1.JPG

Let's look at the 2 JSOW config without CFTs (650+nm range)
And the bottom config, CFT and EWP (650+nm range) AHA! There is an IRST on that one! DI 12, so we can take that off the DI for the EWP, dropping it to 37.
And the CFT?
ASH2.JPG

zero to negative DI (it must improve the L/D), so it may not be unreasonable to say the CFT is -3 DI just to round the EWP up to 40.

How does this effect the use on an F-15? (gotta stay on topic)
First we need to calibrate a SHornet centerline EWP to a centerline or wing mounted SEagle EWP.
The trick is finding something the SHornet CAN carry on the centerline that the Eagle does too, which I am not seeing at first glance. So we are going to be tricky...

GBU-12 on SHornet is 5.8 plus 1 for the pylon for 6.8 centerline mount.
GBU-12 on Mudhen CFT with no bombs or tanks on wing is 3.9

Mk84 LDGP is 2.8 on CFT, 2.3 on wing, and 3.0 on centerline.

Taking DI 40 SHornet EWP would be DI 23 for theoretical CFT mount (Using GBU-12 ratios for translation purposes only) which means DI19 under a wing and DI 25 on centerline (using Mk84 ratios)

This would mean the EWPs, due to shape and size, have more drag than a 610gal tank, but would make some lift and could house a great deal of munitions.

An 3 x EWP equipped SEagle could have 24 AAMs with a DI of 133.6, max speed would be just a bit over 1.3M to 1.4M depending on fuel, with a total range of 881nm (440nm radius) given 15,000lb of cruise fuel (8,300lb use in ground ops, climb, descent, and reserves)

I appreciate the explanation. This certainly sheds some light on the topic (DI impact on performance) that gets thrown around here quite a bit. This whole lesson really is interesting. Thank you for taking the time.
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Unread post12 Mar 2020, 19:27

It truly is my pleasure to get to explore the performance changes that go along with different loads.
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sferrin

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Unread post12 Mar 2020, 19:31

mixelflick wrote: The F-15EX buy is almost entirely political/corporate welfare for Boeing.


I felt like this from the get go and was fairly bent out of shape over it. Buuut if they're going to use it as a weapons truck that can fight back. . . :shrug:
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Unread post12 Mar 2020, 22:58

mixelflick wrote:1.) The F-15 is a very flexible platform. It's been tweaked to carry everything from Israeli ballistic missiles to ASAT weapons to extremely large air to ground munitions. Since I think it'll be called upon to do a whole lot more than air defense, I vote it'll be the USAF's choice to carry large, hypersonic weapons. Or whatever they deem appropriate insofar as weapons carriage is confirmed.


There's no way the Air Force would risk undermining the bomber vector by supplanting the bomber in the
hypersonic* delivery role. Even with the current standoff weapons (e.g. JASSM) the bomber has been
the primary delivery platform. The LRASM model of allocation/tasking is the more probable model.

Premising air-launched hypersonics on (new build) fighter delivery would be way too risky:

As we've seen, new build fighter quantities are the first thing on the chopping block; FY21 killed outyear
buys of the SH and cut back on the F-15EX and the F-35 relative to FY20.

* The airbreathing hypersonics are a different matter since they are lighter/smaller and would be the only way
the Navy (via the F-35C) could accommodate hypersonics on the carrier; a joint buy is probably
the only way to make them affordable.


mixelflick wrote:2.) The F-15EX buy is almost entirely political/corporate welfare for Boeing. Take the potential contract for 144 away, and Boeing's future looks dim.


MQ-25, T-X and they'd be busy with re-winging/upgrading the F-15C for a long time (assuming Boeing won..
the Air Force was going to compete it) under the original SLEP plan along with whatever they'd be doing on the -E.

Quite how buying new build, warmed over decades old designs helps position your design teams for the fighters of
the 2030s is really unclear.
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Unread post13 Mar 2020, 00:12

They are being more or less led through recreating all of LockMart's fancy kit attached to the F-35.

If Boeing cannot share the vision of the future then it really deserves to shrivel up and die. I don't feel any remorse if they do considering they were in bed with China not too long ago.
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Unread post13 Mar 2020, 03:15

Hey sprstdlyscottsmn, does the above Super Hornet graphic you posted showing one way range only or actual combat radius? Because if that is actual combat radius in any of those configurations, that is amazing what the CFTs add to the Super Bug's range capabilities.
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Unread post13 Mar 2020, 04:09

Radius, that would be 220nmfor 3500lb fuel. 0.064 nm/lbs is nothing to write home about.
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Unread post13 Mar 2020, 07:28

marauder2048 wrote:There's no way the Air Force would risk undermining the bomber vector by supplanting the bomber in the hypersonic* delivery role. Even with the current standoff weapons (e.g. JASSM) the bomber has been
the primary delivery platform. The LRASM model of allocation/tasking is the more probable model.


That may have to be seen in the context below. Not exactly enough bombers either...
https://www.defensenews.com/opinion/com ... g-smaller/
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sferrin

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Unread post13 Mar 2020, 12:35

marauder2048 wrote:
mixelflick wrote:There's no way the Air Force would risk undermining the bomber vector by supplanting the bomber in the
hypersonic* delivery role. Even with the current standoff weapons (e.g. JASSM) the bomber has been
the primary delivery platform. The LRASM model of allocation/tasking is the more probable model.


And yet, as you point out, bomber weapons are being used on fighters. If fact today the only bomber weapons that AREN'T used on fighters are the AGM-86 and the B83. Everything else used by bombers is used by fighters.
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Unread post13 Mar 2020, 14:11

disconnectedradical wrote:
mixelflick wrote:2.) The F-15EX buy is almost entirely political/corporate welfare for Boeing.


You mean the St. Louis division, or former McDonnell Douglas. They're definitely wanting to make sure all fighter manufacturers are in business for PCA. Super Hornet, F-15EX, etc is all McDonnell Douglas, or St. Louis division of Boeing after merger.

McDonnell Douglas arguably did quite a lot of damage to Boeing after the merger especially in corporate culture.


I don't know enough about how McDonnell's engineers/culture was rolled into Boeing to really comment. From the outside looking in, it's an odd pairing. You have a company that was known for building the best fighters in the world, merging with a company known for their big airframe, civil transport/bomber work.

I'm not sure how you meld the two, or don't as it were. Boeing did well keeping the SH line going until recently, and so these new build F-15's are a lease on life. Without them, I'm not sure the institutional knowledge exists to build a future fighter. They haven't worked on anything more than 4++ gen designs, so it'll be interesting what they throw up for PCA, assuming they bid.

Given where Boeing is today, that may or may not happen..
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Unread post13 Mar 2020, 14:22

If I recall, the main driver was to get rid of the MD-11. Defense was an after-thought back then.
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Unread post13 Mar 2020, 17:04

sferrin wrote:
marauder2048 wrote:
mixelflick wrote:There's no way the Air Force would risk undermining the bomber vector by supplanting the bomber in the
hypersonic* delivery role. Even with the current standoff weapons (e.g. JASSM) the bomber has been
the primary delivery platform. The LRASM model of allocation/tasking is the more probable model.


And yet, as you point out, bomber weapons are being used on fighters. If fact today the only bomber weapons that AREN'T used on fighters are the AGM-86 and the B83. Everything else used by bombers is used by fighters.

Exactly. The ability for fighters to carry munitions doesn't endanger bomber missions/necessity.
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