F-104 Turbofan Performance

[kdub104]

First post.

My father flew the CF-104 out of Cold Lake (G model - nuclear strike role), Class of 69-70. Been fascinated with this plane and thanks to the pilots on this board who flew the Zipper (A model with -19), my fascination has only increased. Father was a quiet man who never talked about his flying days. Also flew the RF-4C out of Shaw 75-77.

The prodigious performance of the Zipper with the light air frame of the A model and the power of the -19 engine is legendary. The numbers are hard to believe and today, when comparing numbers with our modern jets, nothing can "run" with the Zipper, except perhaps the F-22.

JR wondered what a good modern turbofan would do to the performance numbers of the Zipper. I am curious to know this as well and what performance increases we would see. If a comparable thrust engine such as the F404 (18,800 lbs) was installed, what would we see out of the Zipper?


The F404 is lighter by 1,550+ lbs. This gives a higher thrust to weight ratio so here is a performance increase.
The F404 is more fuel efficient.

Okay great, but how would this affect the numbers?

Could the Zipper fly at FL730 with the F404?
Could the Zipper put up the high Mach numbers (M2.3+) with the F404?
Could the Zipper accelerate as quickly out to Mach 2 from .9?
What increase in range would we see?
Would the Zipper be limited by high Compressor Inlet Temps?
Could the Zipper achieve higher speeds and for longer periods of time?
Etc...etc...etc...


Great board.

Cheers.

[sprstdlyscottsmn]

Could the Zipper fly at FL730 with the F404?
Could the Zipper put up the high Mach numbers (M2.3+) with the F404?
Could the Zipper accelerate as quickly out to Mach 2 from .9?
What increase in range would we see?
Would the Zipper be limited by high Compressor Inlet Temps?
Could the Zipper achieve higher speeds and for longer periods of time?

Welcome!

I too used to be fascinated by this idea. That said, the more I learned about turbofans vs turbojets, and the J79 in particular, the more I realized that subsonic accelerations/climb and range would be the only benefits.

The J79 was a high speed motor. By Mach 2 at 35,000ft they were making more thrust that they would sitting on a test stand at sea level. The -19 was the ultimate iteration of this philosophy. The J79 was also rated to 75,000ft provided sufficient forward velocity.

So the answer to your questions would be as follows:
Could the Zipper fly at FL730 with the F404? - No. The F404 was not designed to be a high alt engine.
Could the Zipper put up the high Mach numbers (M2.3+) with the F404? - No. The F404 was not designed to be a high speed engine.
Could the Zipper accelerate as quickly out to Mach 2 from .9? - No, you want to beat a -19 powered Zipper to Mach 2? You better bring a Raptor or Eurofighter to even have the smallest chance. from .5M to .9M? maybe.
What increase in range would we see? - From J79 to F404? 20-30% would not surprise me
Would the Zipper be limited by high Compressor Inlet Temps? - No, thrust would limit it.
Could the Zipper achieve higher speeds and for longer periods of time? - Not higher speeds, but it would sustain any supersonic speed it could obtain for a longer period of time.

[madrat]

But in turns below 36,000 feet and in metrics like climb to 30,000 feet from a standstill, I'd put my faith behind an F414 or EJ200 pushing an optimized F-104 airframe. Clearly the airframe would need some reshaping and intakes retuned to handle the latter two engines as everything about the Zipper design was built around the J79. By the time you get done you're flying something that resembles an F-104, but it would have been cheaper to just buy a Gripen.

[kdub104]

sprstdlyscottsmn thanks so much. Glad to be on board.

So the F404 would not enhance the 104 in terms of altitude and speed, only in range. But why in climb? Because there is less air flowing through the engine in climb (under .9) and the J79 needs more air?

What about speed on the deck? Would the J79 hold an advantage over the F404 in acceleration or top speed? M1.2-1.4?

That bit about the J79 making more thrust at 35K than on a test stand at sea level is incredible. The turbojet is a real wonder when used in its design envelope.

The intake cones were optimized for high Mach yet they were fixed. I recall reading pilots' accounts of it feeling like the 104 was in a "passing gear" at M1.4. Why weren't the cones movable? If I may bring the SR-71 into the discussion, I recall reading how the inlets were paramount for the performance of the J58 (yes it was a turbo-ramjet).

What could we expect if the inlets on the 104 were movable? Better low speed acceleration? Higher top speed? Better fuel economy? Lower CIT temps?

Acceleration with F414 or EJ200:
Would this be due to increased thrust of the F414 @ 22,000 lbs and EJ200 @ 20,000 lbs or, these engines are closer to a turbojet than a turbofan?

Eurofighter, with 40,000 lbs thrust would have better acceleration out to Mach 2, I assume not from an aerodynamic point but because of pure thrust?
Raptor, with what I guess to be 29-30K/43-45K thrust per F119 AND similar trapezoidal wing design (someone remembered and embraced the 104!), would surely out accelerate the 104 to Mach 2. Surely? Canopy design hinders outright top speed ala F-16?

[hornetfinn]

I'd think it would be somewhat like difference between F-4 Phantom with J79 and then with RR RB.163 Spey in British F-4K:

http://all-aero.com/index.php/64-engine ... 9-qin-ling

The British versions of the McDonnell Douglas F-4 Phantom II F-4K (designated Phantom FG.Mk.1) replaced the 16,000 lb thrust J79 turbojets with a pair of 12,250 lb thrust dry and 20,515 lb thrust with afterburning RB.168-15R Spey 201 turbofans. These provided extra thrust for operation from smaller British aircraft carriers, and provided additional bleed air for the boundary layer control system for slower landing speeds. The air intake area was increased by twenty percent, while the aft fuselage under the engines had to be redesigned. Compared to the original turbojets, the afterburning turbofans produced a ten and fifteen percent improvement in combat radius and ferry range, respectively, and improved take-off, initial climb, and acceleration, but a lower top speed.

Of course more modern engines would likely be quite a bit better than Speys, but still the basic differences would likely be similar.

[mixelflick]

The F-404 is an incredible engine, and lends itself well to these possibilities...

A-4 Skyhawk with an F-404, would have loved to see it!

A-7 Corsair with an F-404

F-8 Crusader with an F-404, or even 2!

A-10C with twin F-404's. Dare I say supersonic Hog? LOL

An F-4 Phantom with twin F-404's would be interesting. But you'd lose the brute force, smoke and noise the Phantom is coveted for. Plus, those F-404's would sure look wimpy on its airframe!

A-6 Intruder with twin F-404's. HUGE increase in capability, on an already hugely capable airframe.

SU-35 with twin F-404's. Miles ahead of the Mig-21 engines it currently flies with.

And of course, the still born F-20 Tigershark. Would love to have seen its performance with the higher thrust (22,000lbs) motor that powers the Super Hornet.

[knowan]

I've always liked theory games like giving old planes new engines (I've recently been playing around with the idea of a F119 or F135 in a F-16).

If a F404 wouldn't give much performance advantage, is there any other engines with significantly more thrust that would fit the F-104?

[sprstdlyscottsmn]

I've always liked theory games like giving old planes new engines (I've recently been playing around with the idea of a F119 or F135 in a F-16).

If a F404 wouldn't give much performance advantage, is there any other engines with significantly more thrust that would fit the F-104?

EJ200 might be the best bet.

[vilters]

A Tigershark , all that thing needed was some extra wing and 2.000 lbs more gas.

Some will never stop wondering why that project was canceled and never revamped.
THAT was a proven airframe with TONS of potential. (Unlike the complete disaster called Griphen).

HAD the Swedes bought the rights of the Tigershark, they could have competed for some SERIOUS contracts.

[vilters]

A Tigershark , all that thing needed was some extra wing and 2.000 lbs more gas.

Some will never stop wondering why that project was canceled and never revamped.
THAT was a proven airframe with TONS of potential. (Unlike the complete disaster called Griphen).

HAD the Swedes bought the rights of the Tigershark, they could have competed for some SERIOUS contracts.

[knowan]

A-7 Corsair with an F-404

There was the YA-7F, which stuck a F100-PW-220 into the A-7.

https://en.wikipedia.org/wiki/Vought_YA-7F
https://foxtrotalpha.jalopnik.com/can-w ... 1591155307

[hornetfinn]

The F-404 is an incredible engine, and lends itself well to these possibilities...

A-4 Skyhawk with an F-404, would have loved to see it!

There was ST Aerospace A-4SU Super Skyhawk:
https://en.wikipedia.org/wiki/ST_Aerosp ... er_Skyhawk

The modernised A-4SU and TA-4SU versions with its new F404 turbofan engine had 29% more thrust, which resulted in a 30% reduction in takeoff time as well as an increase in usable payload, range and maximum speed. The maximum speed now at sea level is 610 knots (1,130 km/h; 700 mph), and maximum cruise speed at 30,000 feet (9,100 m) is 446 knots (826 km/h; 513 mph)

Pretty impressive performance increase.

[sferrin]

The F-404 is an incredible engine, and lends itself well to these possibilities...

A-4 Skyhawk with an F-404, would have loved to see it! - Done.

A-7 Corsair with an F-404 - They did it with an F100 engine.

F-8 Crusader with an F-404, or even 2! - See XF8U-3 with J75. (F404 would have been a step back in power.)

An F-4 Phantom with twin F-404's would be interesting. But you'd lose the brute force, smoke and noise the Phantom is coveted for. Plus, those F-404's would sure look wimpy on its airframe! - Try PW 1120s.

"Two PW1120 powerplants were installed in the same F-4E and it was flown for the first time on 24 April 1987. This proved very successful, allowing the Kurnass 2000 to exceed Mach 1 without the afterburners, and endowing a combat thrust-to-weight ratio of 1.04 (17 per cent better than the F-4E). This improved the sustained turn rate by 15 per cent, the climb rate by 36 per cent, medium-level acceleration by 27 per cent and low-level speed with 18 bombs from 1,046 km/h to 1,120 km/h (654 - 700 mph or 565 kn to 605 kn). It was demonstrated at the Paris Air Show in 1987. "

Capture.PNG (610.71 KiB) Viewed 19908 times

A-6 Intruder with twin F-404's. HUGE increase in capability, on an already hugely capable airframe. - Done A-6F

[sprstdlyscottsmn]

While we are dreaming, Phantom inlets could probably handle F414 EPEs. Still doubt it would out do a J79-19 above Mach 2, but in Sub and Trans-sonic it would be a beast.

The noise of those J79s though...

[mixelflick]

Wow!

Thanks for posting these guys. I'm surprised the up rated Super Phantom never garnered many buyers, considering how prevalent they were around the world. Yes, read where that up-engined F-8 was an absolute beast and would have trounced any Phantom of the day. As far as the F-20 goes, that's a real head scratcher. Perhaps had it come along during the 1970's energy crisis it would have fared better.

Incredibly capable, zippy little jet. For the time period, it struck me as the ideal aircraft for many air arms - including Taiwan You had Chuck Yaeger's blessing, and those promotional videos put out by Northrop were slick IMO. But as long as the F-16 had the USAF's stamp, it was going to be an uphill battle.

As for the F-104, the J79 was the perfect fit. On the one hand, it was supremely capable in the speed/altitude dept. But that razor thin wing that made it possible was also its downfall in a turning fight. I still consider it one of Kelly Johnson's greatest creations though. We have a Starfighter here at the New England Air Museum that zoomed to 90 something thousand feet and something like mach 2.4. I know some rumors had it hitting mach 3 and getting to over 100,000 ft!

For any time, that was damn impressive..