F-15EX

Military aircraft - Post cold war aircraft, including for example B-2, Gripen, F-18E/F Super Hornet, Rafale, and Typhoon.
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sprstdlyscottsmn

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Unread post25 Jan 2023, 03:08

That 100% depends on what the Saudis wanted/ordered/paid for. It's possible physically, CG range is 23-27% notionally IIRC on the Eagle and if that is WITH ballast in the nose on the A and the EX has 1,000lb more weight in the engines it could be shifted to maybe 30%. But again, did the Saudis pay for that when they got the FBW? We don't know.
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Unread post25 Jan 2023, 11:17

henshao wrote:
f119doctor wrote:
henshao wrote:Also the Full fly by wire of the EX may finally allow the jet to be weight and balanced tail heavy/negative stability, with according advantages in turn performance as those big stabilators start adding net lift in cooperation with the nodding intake quasi-canards

Do we know if the the EX (or earlier variants with digital flight controls) has or is allowed to have a more aft CG? I know there there is several hundred lbs of ballast on the front bulkhead that can be adjusted to get individual F-15C/D aircraft within the Weight & Balance limits. And the F110-129 engines are heavier than either the -220 or -229 engines. Are these weights sufficient to make the EX a relaxed static stability aircraft?


Technically, the F-15 is already "relaxed" stability, but as far as an outright aft-cg allowed I do not know, only hypothesize. As I mentioned the F-15 was partial fly by wire from the very first F-15A, only now is it full FBW (during testing one Eagle made it home with several mechanical control lines severed; the pilot never even noticed) It would be cool if this allowed negative stability but there may be other limiting factors

There is also the matter of the tremendous AESA weight in the nose


On the F-15ACTIVE where the two canards were applied, the center of the lifting force moved forward, even if the weight is also had to move a little bit forward as well. Because of this additional aerodynamic surface, the stability went to slightly negative, so all the flaps and airelons were acting as a single large flaps, like on the Hornet:

http://www.airvectors.net/avf15_1_10.jpg

On the Hornet, the large, full wingspan flaps incorporate with the really long LERX, to balancing with the forward moved lifting force by their own "nose-heavy" torque effect.
If the EX would have a lighter nose section, while the engines are still heavier than the P&W engined airframes, the strutcure is going to be rear-heavy, so the stability is negative. If so, both of the flaps and airelons are needed to generate a larger downward torque, where the benefit is a larger lifting force in the meantime. So it could be a win-win situation, even if we do not have any additional canards at the front section.
I think, this could be compensate the lack of the leading edge flaps a little bit, so add some AoA room for the aircraft.

To keep the current wing, avoinding the extra weight and complexity of the leading edge flaps, maybe a sharper LERX also would be helpful. But in this case the sharper surface will be more sensitive to the asymmiterical design, which cased be the right side mounted cannon slot.
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viperzerof-2

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Unread post28 Jan 2023, 02:38

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mixelflick

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Unread post30 Jan 2023, 18:32

viperzerof-2 wrote:https://www.thedrive.com/the-war-zone/f-15e-strike-eagles-now-flying-without-conformal-fuel-tanks-on-air-defense-missions

Look what made the news


Very odd...

Seems to imply the performance penalty of CFT's for the mission outweigh any benefits. They prefer wing tanks, being able to punch them off in the event of a merge. Still, strikes me as weird..

The Strike Eagle has been in the inventory for decades and is well known to be an absolute beast when not fitted with CFT's. They're just realizing that now? Bizarre.

Perhaps in the air to air swing role, they've now assumed it's far more likely they'll merge/see actual combat. Ukraine perhaps? It sure isn't getting any better...
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henshao

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Unread post30 Jan 2023, 21:10

The f15c has heretofore made the capability unnecessary just as the f15e has made the significant bomb payload of the f15c unnecessary however father time is calling on the light greys
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Unread post30 Jan 2023, 21:17

mixelflick wrote:
Very odd...

Seems to imply the performance penalty of CFT's for the mission outweigh any benefits. They prefer wing tanks, being able to punch them off in the event of a merge. Still, strikes me as weird..

The Strike Eagle has been in the inventory for decades and is well known to be an absolute beast when not fitted with CFT's. They're just realizing that now? Bizarre.

Perhaps in the air to air swing role, they've now assumed it's far more likely they'll merge/see actual combat. Ukraine perhaps? It sure isn't getting any better...


Not so much a realization, as a change in mission. For A2A, which is what it looks like the current focus is, the kinematic performance is a higher priority than range/payload.
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Unread post30 Jan 2023, 21:58

It depends greatly on the A2A mission. CAP, sure throw the CFTs on. QRF? No way.
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Unread post31 Jan 2023, 04:42

The F-15EX is in "no-win" situation...CFT's hurt performance. While, no CFT's hurt range! :?
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Unread post31 Jan 2023, 12:58

Time and time again there is the question of benefit for CFT. The air superiority load on F-15 is with EFT not CFT for good reason. For strike missions the CFT is the clear choice.

The South Koreans believe in this strategy enough to repeat it on KFX.
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Unread post31 Jan 2023, 19:20

Corsair1963 wrote:The F-15EX is in "no-win" situation...CFT's hurt performance. While, no CFT's hurt range! :?


Whats that old saying? You dont get something for nothing?

The Air National Guard will be (unfortunately) loosing their fleet of F-15Cs. To make up for this an F-15E or EX without their CFTs will be able to more than sufficiently fill that role left open. An Eagle 2 with those better GE engines without those CFTs will have some serious muscle in the air.
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Unread post02 Feb 2023, 22:58

I look forward to seeing this aircraft really put through its paces to see what it can do. With the GE 110's, no CFTs and with the new FBW control system, she should be quite the hot rod.
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Unread post05 Feb 2023, 15:35

Fox1 wrote:I look forward to seeing this aircraft really put through its paces to see what it can do. With the GE 110's, no CFTs and with the new FBW control system, she should be quite the hot rod.


This right here. Can't wait to see what the penultimate Eagle can really do.

The new radar and especially weapons (and engines) will give it extremely impressive BVR capability. Will likely cream anything at a distance, save for truly VLO airframes. I see it as best in the Homeland Security role, taking down everything from hijacked airliners to cruise missiles to balloons.

I wonder if the EX (being able to get higher and faster than an F-15C) would have been able to take down that Chinese spy balloon as easily as the F-22 did. An interesting question, IMO..
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Unread post05 Feb 2023, 21:36

well, the F-22 is a different breed, but a balloon at 60k feet is small potatoes for an F-15A let alone one with engines 3 generations newer
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Unread post07 Feb 2023, 18:06

Just listened to audio from the balloon shootdown, was recently posted on War Zone.

Really stunned, as to what a big role the F-15C's played in this. They apparently used their SNIPER targeting pods to visually ID the balloon and wreckage, then follow it all the way down. Not just that, but had the first F-22 missed the 2nd F-22 was right behind it ready to take a shot, followed by these two F-15C's from Barnes - with the same orders. So clearly, they had live AAM's in addition to SNIPER pods.

If this is any indication of how big a role the Eagle still plays, then why they want the F-15EX is no mystery. Yes, I know it was "just" a balloon but its clear shooting these things down is no easy task, at least with the given ROI's. 2 seat bird carrying a big payload high and fast, and clearly had the gas to stick around as needed.

To be totally honest, it sounded like these F-15's quarterbacked much of the operation (or at least key parts of it). Bravo to everyone involved. For once, I'm proud to be from MA, lol...
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