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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henshao

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Unread post01 Dec 2022, 00:47

Yes, I pointed it out on page 51 that the "air superiority" Eagle is carrying bomber CFTs, however the EX does have notably more powerful engines than the E
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f119doctor

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Unread post01 Dec 2022, 00:51

henshao wrote:Yes, I pointed it out on page 51 that the "air superiority" Eagle is carrying bomber CFTs, however the EX does have notably more powerful engines than the E

Compared to the early F-15E with the -220 engine, yes. But there is not that much difference between the later F-15E with the -229 engines and the EX with the GE-129 engines.
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viperzerof-2

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Unread post01 Dec 2022, 01:00

I was under the impression the 229 was better suited to the Eagles traditional high altitude mission while the 129 was better at the lower altitudes the Viper traditionally liked. But I don’t even really remember what I based that on.
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weasel1962

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Unread post01 Dec 2022, 01:47

f119doctor wrote:
henshao wrote:Yes, I pointed it out on page 51 that the "air superiority" Eagle is carrying bomber CFTs, however the EX does have notably more powerful engines than the E

Compared to the early F-15E with the -220 engine, yes. But there is not that much difference between the later F-15E with the -229 engines and the EX with the GE-129 engines.


F110s had an original growth plan to reach 36k lb thrust. Supposed to get to 32k lb thrust for the EFE, then 34k/36k lb for the EFE+/++. Today its 129E. Consider the age of the F-15Es and therefore the engines, the thrust difference today between EX & E could be as great as that of a E vs C.

F110.jpg
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viperzerof-2

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Unread post01 Dec 2022, 01:51

weasel1962 wrote:
f119doctor wrote:
henshao wrote:Yes, I pointed it out on page 51 that the "air superiority" Eagle is carrying bomber CFTs, however the EX does have notably more powerful engines than the E

Compared to the early F-15E with the -220 engine, yes. But there is not that much difference between the later F-15E with the -229 engines and the EX with the GE-129 engines.


F110s had an original growth plan to reach 36k lb thrust. Supposed to get to 32k lb thrust for the EFE, then 34k/36k lb for the EFE+/++. Today its 129E. Consider the age of the F-15Es and therefore the engines, the thrust difference today between EX & E could be as great as that of a E vs C.

As I understand it the f110-ge-132 as mentioned by members of this site and some flight articles I’ve read over the years is actually closer to the 340000 static thrust rating. The 36500 version would have used a common core with the CFM56. It’s really a shame the UAE turned out to be the only operator, lots of interest from other users but I guess none with out the USAF. Same with the Pratt equivalent.
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henshao

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Unread post01 Dec 2022, 08:31

Well I know Pratt and Whitney's gang won't like to hear this but, though the GE -129 and PW -229 are roughly equal in static thrust, there is a somewhat significant acceleration difference between an -229 viper and a -129, the latter being quicker. this hints at greater thrust in flight for the GE engine
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Unread post01 Dec 2022, 12:24

I had a rare chance to talk to an F-16 pilot who was involved in testing 129 vs 229 equipped fighters. his comment was they were both absolute monsters but at one point they had similarly configured F-16 and just put them through a drag race.

The 129 could be seen slowly but steadily inching away from the 229. TEG responded by saying that yes at some parts of the envelope the 129 does have some incremental advantages, but not all, there are areas where the 229 will win.

Anyway going back to why I ask, watching DCS simulations, there seems to be more turning involved when doing a BVR intercepts, a lot more than I expected. So with the F-15EX having the RCS that it has, it will be susceptible to these long range shots from R-37s and R-77s.

now with the performance of an F-15E thanks to those CFTs, I’m not confident that it can defend against multiple BVR shots from long range. So its mission may be limited to Mig-21 style intercepts in Vietnam. Ingress fast, shoot your load, Egress and hope something hits
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henshao

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Unread post01 Dec 2022, 13:37

zero-one wrote:I had a rare chance to talk to an F-16 pilot who was involved in testing 129 vs 229 equipped fighters. his comment was they were both absolute monsters but at one point they had similarly configured F-16 and just put them through a drag race.

The 129 could be seen slowly but steadily inching away from the 229. TEG responded by saying that yes at some parts of the envelope the 129 does have some incremental advantages, but not all, there are areas where the 229 will win.

Anyway going back to why I ask, watching DCS simulations, there seems to be more turning involved when doing a BVR intercepts, a lot more than I expected. So with the F-15EX having the RCS that it has, it will be susceptible to these long range shots from R-37s and R-77s.

now with the performance of an F-15E thanks to those CFTs, I’m not confident that it can defend against multiple BVR shots from long range. So its mission may be limited to Mig-21 style intercepts in Vietnam. Ingress fast, shoot your load, Egress and hope something hits


this will depend entirely on what is shooting at the eagle...there are only a handful of types on earth that will see an f-15 before it sees them, especially with the AESA. also the -229 engines are so powerful that in an air superiority configuration an E with cfts is about as quick or quicker than a C with a centerline tank. as mentioned the -129 engines are a little hotter still. the tragedy is always that a -229 C probably would be as quick or quicker than a eurofighter IMO
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Unread post01 Dec 2022, 15:49

Another thing is the F-15E CFT is very draggy because of all the extra pylons sticking out mainly for air to ground. The original F-15C CFT/FAST packs were way less draggy, with drag index that’s half of F-15E CFT drag index of 21.3. I get the argument for commonality but if the F-15EX is really meant only for air to air, then it should get the original F-15C CFT/FAST packs without all the additional pylons.

*EDIT* Drag number for F-15C CFT/FAST pack is 4.0, the F-15E CFT is 21.3.
Last edited by disconnectedradical on 01 Dec 2022, 19:58, edited 2 times in total.
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Unread post01 Dec 2022, 16:01

disconnectedradical wrote:Another thing is the F-15E CFT is very draggy because of all the extra pylons sticking out mainly for air to ground. The original F-15C CFT/FAST packs were way less draggy, with drag index of 6 rather than F-15E CFT drag index of 17. I get the argument for commonality but if the F-15EX is really meant only for air to air, then it should get the original F-15C CFT/FAST packs without all the additional pylons.


Probably this would be best for export customers who will rely on the F-15EX as their primary AA platform (i.e Indonesia, but then again they have Flankers, Rafales and F-16s that will probably be their front line fighters while their F-15EXs with their big radars, tons of missiles and fuel will be safe at the back)

Sadly this is the role that the F-15EX would probably fill out most, a bomb truck
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disconnectedradical

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Unread post01 Dec 2022, 21:15

Also, a question for f119doctor, why does the F-15 with the F100-PW-220 top out faster than the F100-PW-229? In the performance charts for a clean F-15E with no CFT, the -220 tops out at about Mach 2.4 while the -229 tops out at Mach 2.3, which isn’t a huge difference and the -229 ceiling is higher, but it’s still strange.
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Unread post01 Dec 2022, 21:30

disconnectedradical wrote:Also, a question for f119doctor, why does the F-15 with the F100-PW-220 top out faster than the F100-PW-229? In the performance charts for a clean F-15E with no CFT, the -220 tops out at about Mach 2.4 while the -229 tops out at Mach 2.3, which isn’t a huge difference and the -229 ceiling is higher, but it’s still strange.

Possibly because E is a two seater?
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Unread post01 Dec 2022, 21:44

viperzerof-2 wrote:
disconnectedradical wrote:Also, a question for f119doctor, why does the F-15 with the F100-PW-220 top out faster than the F100-PW-229? In the performance charts for a clean F-15E with no CFT, the -220 tops out at about Mach 2.4 while the -229 tops out at Mach 2.3, which isn’t a huge difference and the -229 ceiling is higher, but it’s still strange.

Possibly because E is a two seater?

This is for the 2 seat F-15E, the -220 tops out at Mach 2.4 and the -229 tops out at Mach 2.3. The single seat F-15C with -220 tops out at Mach 2.45.
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basher54321

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Unread post01 Dec 2022, 23:44

zero-one wrote:
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.
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f119doctor

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Unread post01 Dec 2022, 23:59

Whether it is M2.3 or 2.4 or 2.45, they are all speeds that are never reached this side of flight test where the extreme corners of the flight envelope are validated. You are out of fuel when you get there in a clean F-15.

Why is the -220 faster than the -229. I can only speculate:

1. The -220 is a higher bypass ratio than the -229, so the augmentation ratio is higher. Above M2, ram recovery pressure and AB performance begins to dominate the thrust production, so the higher bypass ratio may be an advantage.

2. The F100-100 was developed with a requirement to push the F-15 to M2.5. One of the hidden tricks employed was to run the high compressor variable vanes (RCVV) to a more axial schedule under high inlet temperature elevated Mach conditions. This effectively increased the core airflow when the core rotor speeds were limited by FTIT and mechanical speed limits. More core airflow increased power available to drive the fan airflow and pressure ratio, increasing high Mach thrust. The engine internal throttle is locked up at Mil power or above at these speeds, preventing any core RPM reduction that would immediately put the high compressor blades into axial flutter, breaking them within seconds. The -220 DEEC reproduces this RCVV schedule that was developed for the -100 Unified Fuel Control.

With -229 development, it is possible that the USAF relaxed the requirements to M2.3 maximum, and the -229 control schedules don’t include this RCVV high Mach bias, which reduces the risk of running this aggressive schedule but also reduces thrust M2+.

3. The USAF just reduced the requirement to M2.3, because anything beyond that point is unusable. Flight test cleared the -229 envelope to M2.3 and that is what is published in the Dash-1. Engine may still have excess thrust available at the M2.3 point. If you have the Ps charts for the F-15E, this would be indicated by the Ps = O lines being truncated at M2.3.

Enough speculation for one day
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