F-104 Turbofan Performance

I've been lucky enough to see the F-4D a few times. What stuck with me was the sound in full burner. It sounded angry. It sound like the J79s were punishing the atmosphere for daring to get in the way of the flying brick.

B-58 was probably too easy to take her for too close to the performance curve that is acceptable around public displays.

The F-106 would have been nice to see kept flying at least a few times a year. But the F-4E, considering a few remain active, isn't as nostalgic IMHO.

There is a fake Me-262 that flies today. If some private entity could create a fake to scale remake specifically to fly demo at airshows, what in your choice would it be?

I'd pay good money to see Mig-31, SU-27 and especially the SU-35

Being in the US, I've been fortunate to see quite a few iconic planes..

1.) F-4D/E
2.) F-14A (piloted by none other than Dale Snodgrass)
3.) F-15C
4.) F-16C/D
5.) F-18 legacy hornet and Super Hornet
6.) F-22
7.) F-35 (nothing impressive though, mostly straight and level stuff. Can't wait for the 2019 demo!)
8.) F-101 Voodo
9.) F-104
10.) F-105
11.) F-106
12.) F-111
13.) F-117
14.) B-52, B-1 and B-2
15.) A-4, A-6, A-7, A-10, AV-8B

Plus the Blue's, Thunderbirds, Snowbirds and lots of others. Virtually none of the Russian stuff though, and I'd LOVE to see them. I did get a little late to an airshow in the early 90's where some German Tornado's apparently put on one hell of a show. Was told they tore up the sky...

F-15 is said to be Mach 2.5 "dash" capable, yet it has two turbofans. Discussion here is stating the turbofan is not a high Mach engine. This combined with the Eagle's "optimized for turn" wing design should have me question this dash capability?

Don't misunderstand. The F404 is not a high Mach engine. The F100, F110, F119, and EJ200 are all high Mach turbofans.

I am misunderstanding. I thought all turbofans are created equal.

What makes the F404 different than the F100, 110, 119 and EJ200?

Is the F414 also a high speed turbofan?

That Engine Guy explain away that misnomer if you look hard enough.

The long as short of it is that all engines have a design point. The F404 and F414 were designed for 1.8M aircraft and as such no money was spent on designing them to continue making excess thrust beyond that speed. The others I mentioned were all designed for aircraft that travel over Mach 2. Just like the F119 was designed to continue making excess thrust without afterburners beyond Mach 1.5.

The J79 was designed for Mach 2. As aircraft got bigger and draggier the J79 got more powerful to compensate. The ultimate service J79 was the J79-GE-19. This was the motor that would push an F-104A to 2.0M at 73,000ft with only 3/4 AB.

The long as short of it is that all engines have a design point. The F404 and F414 were designed for 1.8M aircraft and as such no money was spent on designing them to continue making excess thrust beyond that speed. The others I mentioned were all designed for aircraft that travel over Mach 2. Just like the F119 was designed to continue making excess thrust without afterburners beyond Mach 1.5.

The J79 was designed for Mach 2. As aircraft got bigger and draggier the J79 got more powerful to compensate. The ultimate service J79 was the J79-GE-19. This was the motor that would push an F-104A to 2.0M at 73,000ft with only 3/4 AB.

I am beginning to understand.

Air frame designed to meet engine design/thrust
Engine designed to meet air frame design and mission purpose


Engine design is actually quite specific to meet a particular goal or mission requirement. I did not know this. I thought you put the biggest (physically) engine you can in an air frame with the highest thrust to get maximum performance out of the jet (acceleration, speed, kinematics, etc...).

F-104 mission purpose: Interceptor. Get to altitude quickly and get out to intercept bogey ASAP. Air frame is designed and maximized for higher altitude and Mach 2.0

Tiny trapezoidal wing and elevator
Inlets to maximize speed above M1.4
Lightweight to maximize mission requirements
Engine: J79-19 Turbojet

Engine frontal area dictates drag i.e. F-135. F-35 is not meant to be a high Mach jet but rather, good performance at high subsonic speeds and good fuel consumption for its design envelope (bomber). F-22 has engines with smaller frontal area and less overall drag and it has a much different design and mission.

Have been ignorant of this until now but the A-10 is a classic example of design and engine function to meet mission requirements.

I came across this site and if the author is correct, the F414 is the closest engine to a turbojet. The EJ200 is perhaps the best engine pound and inch per pound and inch into today's modern world of engines.

https://defenseissues.net/2014/12/06/fi ... mparision/

The F-119 is simply out of this world but only due to its overall larger size. Based on this link, it appears the F404 is actually quite a poor engine.

Engine frontal area dictates drag i.e. F-135. F-35 is not meant to be a high Mach jet but rather, good performance at high subsonic speeds and good fuel consumption for its design envelope (bomber). F-22 has engines with smaller frontal area and less overall drag and it has a much different design and mission.

Have been ignorant of this until now but the A-10 is a classic example of design and engine function to meet mission requirements.

I came across this site and if the author is correct, the F414 is the closest engine to a turbojet. The EJ200 is perhaps the best engine pound and inch per pound and inch into today's modern world of engines.

https://defenseissues.net/2014/12/06/fi ... mparision/

The F-119 is simply out of this world but only due to its overall larger size. Based on this link, it appears the F404 is actually quite a poor engine.

Inlet diameter is a poor method for determining frontal area, as the maximum diameter of the engine is usually larger than the inlet, and it is the maximum diameter of the engine that determines the frontal area constraints of the engine installation.


Aside from that, the figures in that link are just plain wrong. Eg, it gives F-119 frontal area as 6.136 cm^2 (author of that link got his units wrong, should be 6136 cm^2 or 0.6136 m^2), which means an inlet diameter of just 34.75 inches; that's similar to the 34.8" diameter inlet for the F-100: https://www.pw.utc.com/products-and-ser ... 00-Engine/

The F-119 would be similar to the F-135 (as the F-135 was developed from the F-119), which according to Pratt and Whitney, has an inlet diameter of 43 inches and maximum diameter of 46 inches: http://newsroom.pw.utc.com/download/me_ ... _pcard.pdf

Pratt doesn't give inlet or maximum diameter dimensions for the F-119, but other sources indicate it is around the same as the F-135:
45" diameter; https://www.forecastinternational.com/a ... _RECNO=901
46" diameter; http://www.deagel.com/Propulsion-System ... 20001.aspx
46" diameter; http://all-aero.com/index.php/contactus ... itney-f119


The link gives the EJ200 as having a a 3.848 cm^2 inlet area, which calculates to approximately 27.5" inlet diameter, yet MTU Aero Engines gives the fan diameter as 29" / 740mm https://www.mtu.de/fileadmin/DE/7_News_ ... /EJ200.pdf

Took a while to find the maximum diameter of the EJ200, but this article has it at 0.85 meters: https://www.flugrevue.de/flugzeugbau/tr ... 200/470931 which gives a frontal area of 5674.5 cm^2

The F404 has a maximum diameter of 35": https://www.geaviation.com/sites/defaul ... Family.pdf
As does the F414: https://www.geaviation.com/sites/defaul ... Family.pdf
Resulting in those engines having a frontal area of 6207.2 cm^2


And lol, the author of that link gave the AL-41 175 kN... which is the power rating of the izdeliye 30, not the 142 kN of the AL-41F-1S or 147 kN for the AL-41F1.


Here's better figures for maximum thrust / frontal area:

EJ200; 0.5674 m^2, 90 kN = 158.60 kN/m^2
F404; 0.6207 m^2, 78.7 kN = 126.79 kN/m^2
F414; 0.6207 m^2, 97.9 kN = 157.72 kN/m^2
F119; 1.0722 m^2, 156 kN = 145.50 kN/m^2
F135; 1.0722 m^2, 190 kN = 177.21 kN/m^2
AL-31F; 1.2868 m^2, 123 kN = 95.59 kN/m^2
AL-41F-1S; 1.2868 m^2, 142 kN = 110.35 kN/m^2

So the F414 is actually comparable in thrust/frontal area to the EJ200, while the F135 is clearly far better. And the Russian AL-41 is outclassed by the decades older F404.

F-15 is said to be Mach 2.5 "dash" capable, yet it has two turbofans. Discussion here is stating the turbofan is not a high Mach engine. This combined with the Eagle's "optimized for turn" wing design should have me question this dash capability?

Military turbofans have very low bypass ratio, often much lower than 1.0, having a fan improves performance because it moves air more effeciently at low speed. At high speed, they are very close to pure turbojet. F-15 has variable geometry inlets can regulate air flow at different speed and altitude, aoa, etc. That helps.

viewtopic.php?t=53492&p=377552

Also not all turbofans are created equal. They are designed to meet specific requirements. High speed high altitude cruise needs lower bypass ratio. Largely subsonic mission profile with occasional supersonic excitement needs a bit higher bypass ratio. Boeing chose PW turbofan on the first 747 instread of GE engines chose by C-5 because PW has lower bypass ratio and 747 cruise a lot faster than C-5. F-119 is a generation away from where F-100 is. The design is very different.

F-15 is said to be Mach 2.5 "dash" capable, yet it has two turbofans. Discussion here is stating the turbofan is not a high Mach engine. This combined with the Eagle's "optimized for turn" wing design should have me question this dash capability?

It's not that black and white. A GE90 won't even get you supersonic for instance. As for the F100s they were going to be used in DARPA's RASCAL.

"The F100 has a mass injection pre-compressor cooling (MIPCC) system that injects water and liquid oxygen into the inlet, boosting thrust at altitude and improving thrust-to-weight ratio. Speaking at the International Symposium on Air Breathing Engines, Vladimir Balepin, an MIPCC developer for the New York-based GASL test facility, says: "It fools the engine into believing it is flying at M1.64 when it is actually at M4, and when it is at around 88,000ft (26,840m) the engine feels it is at 24,000ft."

Forget that it's got MPCC in this instance, that's just to get it enough oxygen to breath. The D30-F6 engines in the Mig-31 can push it to Mach 2.8. The F-15 was originally meant to have a maximum speed of Mach 2.7 (with the F100) which only got reduced to 2.5 so they could use an acrylic bubble canopy. The F-111F was good for Mach 2.5 with a TF30.

As for the Eagle's wing, the requirement was for Mach 2.5 during design. There's no reason whatsoever to believe they forgot to design the wing to take that into account.

There is a TAC F-111 pilot (I think it was Jeff Guinn) who interviewed on the Youtube channel "Aircrew Interview" who said that the F-111 (with the wings back) had instances where it hit above M 2.5 (around 2.6-2.7, I'd have to watch it again to make sure those figures are correct). But it is around that area.


At the 5 min mark and beyond he talks about F-111 speed and the countdown timer.
https://www.youtube.com/watch?v=IwPg_ai3U_I

However, he has 3 other interviews and I think he talks about it further in one or more of those.





I think the best to answer your question is TEG aka "That Engine Guy" he works on them so he knows the best-

There is a TAC F-111 pilot (I think it was Jeff Guinn) who interviewed on the Youtube channel "Aircrew Interview" who said that the F-111 (with the wings back) had instances where it hit above M 2.5 (around 2.6-2.7, I'd have to watch it again to make sure those figures are correct). But it is around that area.


At the 5 min mark and beyond he talks about F-111 speed and the countdown timer.
https://www.youtube.com/watch?v=IwPg_ai3U_I

However, he has 3 other interviews and I think he talks about it further in one or more of those.





I think the best to answer your question is TEG aka "That Engine Guy" he works on them so he knows the best-

Yep, I'd heard higher for the F-111F as well. (The F has 25,000lb thrust TF30s, the rest are around 20k.) Back in the day there was a guy on rec.aviation.military who'd claimed an F-111F hit Mach 2.8 on a check ride.

F-111 was as clean as could be.