F-15EX

Hey F119doctor, whats your take on the 229 powered F-15E vs 129 powered EX? On paper their thrust levels are similar, they also carry the exact same CFTs, basically they should have identical performance, but do they?

There were early reports that EX models flew higher than the C models, but this could be just because they were now carrying the same payload. The E never did this because it always carried A-G ordnance

The 129 could be seen slowly but steadily inching away from the 229.

You would need to know the weight of both in those tests - the PW F-16s weights were often given about 800 lbs lighter.

The flight test data on the other hand compares at the same weight where the 129 does show a significant thrust advantage. However does that simply carry over to the F-15? - no idea.

here is what I saw on Quora

The 229 in Orange and the 129 in Green, they’re identical except for the far right of the envelope

Acceleration:

The 129 seems to have a 1 second advantage on most parts in acceleration, Im not sure how significant that is

You guys should go back to page 51 where some of this stuff was discussed

F119 doctor is correct; the F-15E simply wasn't asked to go faster than 2.3. Truncation at mach 2.3 on its sustained turn charts hints it still had acceleration available. Remember that mach 2.5 in the F-15 is nearly a paper capability only, extremely time limited and in the case of the sparrow maximum deployment speed was mach 2.3 anyway

As far as the acceleration charts posted, the difference is a bit more than 1 second to get to mach 1.45 for the same weight

Hey F119doctor, whats your take on the 229 powered F-15E vs 129 powered EX? On paper their thrust levels are similar, they also carry the exact same CFTs, basically they should have identical performance, but do they?

There were early reports that EX models flew higher than the C models, but this could be just because they were now carrying the same payload. The E never did this because it always carried A-G ordnance

When you are comparing the EX to the C, you are putting the -129 against the -220. I would expect 5k per engine thrust advantage to be significant. The -220 is around 750 lbs lighter per engine than the -129

The -129 vs -229 is very close. The -129 weighs 3920 lbs, flows 270 lbs/sec, fan pressure ratio 3.2, bypass ratio 0.76, Mil thrust 17,155 lbs, Max thrust 29,000. The -229 is lighter at 3820 lbs, flows 250 lbs/sec, fan pressure ratio 3.4 at Mil, 3.6 at Max AB, bypass ratio 0.36, Mil thrust 17,800 lbs, Max thrust 29,160.

Based on those figures, I would expect the -129 to have better accel at low speeds where mass flow dominates, better Mil SFC, possibly better high Mn thrust. The -229 probably has better transonic thrust in both Mil and Max due to the higher exhaust velocity, which is a function of fan pressure ratio and exhaust temp.

here is what I saw on Quora
The 229 in Orange and the 129 in Green, they’re identical except for the far right of the envelope

Acceleration:
The 129 seems to have a 1 second advantage on most parts in acceleration, Im not sure how significant that is

The first chart is actually for MIL power, Sea Level but they have at least compared the two at same conditions surprisingly. (The top has been cut off )
Change to Max AB, different altitudes you get different charts depending with differences between them depending.


The second chart is for MAX AB.
Subsonic acceleration is often pretty close on charts (few seconds), whereas often charts show a much bigger difference over M1 where you get a massive drag rise. Despite the GE F-16 having a bigger draggier air intake the charts show it to be significantly quicker transonic / supersonic as you can see.

The differences may change for different altitudes or if you use the MIL power charts but been years since I looked at them.

https://www.flightglobal.com/defence/ja ... 58.article

Seems like Indonesia is close to an F-15ID deal, which likely is identical to F-15EX except for mission systems.

About performance, I think regardless, any Mach 2.5 capability is really just on paper since the CFTs, whether the original low drag FAST pack or the air to ground CFTs, are limited to Mach 2.0 anyways. So in this regard, all the talk of a Mach 2.5 speed for F-15EX is quite pointless. And in the F-22 interview with Jim Brown who also flew the F-15, he noted the Eagle even when clean becomes very uncomfortable above Mach 2 and didn't handle well up there. The F-22 on the other hand has no problems there, and even though operationally it's limited to Mach 2, it thermally and aerodynamically go to Mach 2.4+, just as fast as a slick F-15, although again it won't because it's not worth wearing out the RAM.

The first chart is actually for MIL power, Sea Level but they have at least compared the two at same conditions surprisingly. (The top has been cut off )
Change to Max AB, different altitudes you get different charts depending with differences between them depending.

Would you happen to have a Max AB chart

It doesn't have stealth but it has plenty of what the orks in warhammer 40k call "dakka"

https://www.defensenews.com/air/2023/01 ... abilities/

Its not hard to understand the appeal of F-15 in 2023. Even without stealth it offers a lot of versatile loadouts, especially for a nation with large coastlines.

The 129 could be seen slowly but steadily inching away from the 229.

You would need to know the weight of both in those tests - the PW F-16s weights were often given about 800 lbs lighter.

The flight test data on the other hand compares at the same weight where the 129 does show a significant thrust advantage. However does that simply carry over to the F-15? - no idea.

Apparently, the difference is substantial (at least in burner) - but I'm not sure which Pratt F-100 they used in the "old" F-15C. Direct quote from Retired USAF Gen. Paul Hester...
https://www.airandspaceforces.com/why-i ... fs-f-15ex/

“When I got to Eglin, I inherited a program integrating the (F110)-129 engines on the F-15,” Hester said. The upgrade added 4,500 pounds of rated thrust to each engine and unrestricted throttle movement. When Hester sat in the back seat of an F-15 with the old engines and flew alongside another F-15 equipped with the F110-129 engines, the difference was apparent.

The two planes were separated by just three or four aircraft lengths at 10,000 feet at an airspeed of roughly 350 knots. “Then came the order to approach military power”—maximum speed without afterburners.

“The GE-powered airplane steadily moved out front and accelerated away from the one I was flying in,” said Hester, who went on to command Pacific Air Forces. “The difference in military power was impressive. It just put a smile on my face.”

Then the two Eagles came around and lined up again. This time, the order called for full afterburner. “And here’s where you got to notice the real difference between the two airplanes, one powered at 25,000-pound thrust and the other at 29,500-pound thrust,” Hester said. It was a significant jump in capability, and seeing that, well, I wanted to be checked out on the F-15 again!”

No idea as to loadout, fuel etc. but one would assume if this comparison was made, they were similar. That, combined with the comments about the EX getting "higher and faster" during exercises is telling IMO. But who knows, lots of things usually play into these comparisons.

Either way, USAF got a great engine IMO...

The comparison is probably with a PW-220 F-15

F-15Cs fly with PW-220 (which replaced PW-100) both sometimes given a generic max rating of 25,000 max AB.

F-15Es used PW-220 (25,000 lb Max) and some were given PW-229 (29,100 lbs Max)

However PW-229 (29,100 lbs) and GE-129 (29,555 lbs) have always been close in Max thrust with data suggesting the GE-129 puts out more in flight in Max (regarding F-16s). So you need a comparison between F-15E-PW229 and F-15EX-GE129.

I always thought the F110 was better for low altitude applications like the F-16 and the F100 was better for the high altitude ones like the F-15, but maybe that’s over simplified?

Japan played around with Re engining the F-15J with the F110-ge-129 in the 90s but nothing came of it. Presumably it would have taken a lot of time and money.

The comparison is probably with a PW-220 F-15

F-15Cs fly with PW-220 (which replaced PW-100) both sometimes given a generic max rating of 25,000 max AB.

F-15Es used PW-220 (25,000 lb Max) and some were given PW-229 (29,100 lbs Max)

However PW-229 (29,100 lbs) and GE-129 (29,555 lbs) have always been close in Max thrust with data suggesting the GE-129 puts out more in flight in Max (regarding F-16s). So you need a comparison between F-15E-PW229 and F-15EX-GE129.

If it was a F-15C, it was equipped with -220 engines. You would certainly hope that an -EX with -129 engines would have higher performance at both Mil and Max, even with the increased weight of the -129 engines and the CFTs.

If you really wanted a hot rod, -229s are a straight bolt-in on the F-15C airframe (F110s won’t fit the F-15C). The only modification needed would be a few more Lbs of ballast in the nose for weight & balance. Light airframe and tons of thrust. Of course, the C airframes are out of life, so this is just a “what if”!

The last production C/D aircraft also have the common engine bay. The Saudi Peace Sun IV eagles and some Israeli attrition replacements in the 90s where built with some strike Eagle components and can basically take anything a strike Eagle can, at least the Two seaters, but I suspect all of them can.

I was unaware the last C/D had the common engine bay. Almost like they were really E’s without the air to ground features or the A/G CFTs. Wondering if they had the E cockpit displays and 1553 bus.

I was unaware the last C/D had the common engine bay. Almost like they were really E’s without the air to ground features or the A/G CFTs. Wondering if they had the E cockpit displays and 1553 bus.

From what I gather besides APG-70 they had D avonics. The D had E structure and the common engine bay, it seems what the C entailed was a matter of controversy. Apparently the C do have E style antenna on the tail boom.

https://www.key.aero/forum/modern-milit ... ace-sun-vi

This old Key topic is basically where most of what I know about it came from. Their is an old news article with some photos I have to remember where I found it.