F-104 J79 Dash 19: PPH & Excess Thrust

Cold war, Korea, Vietnam, and Desert Storm - up to and including for example the A-10, F-15, Mirage 200, MiG-29, and F-18.
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kdub104

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Unread post16 Feb 2019, 22:58

Pm'd Walt BJ and am hoping he will turn up at some point.

Taken from his article here:

http://www.fighterpilotuniversity.com/a ... at-fl-730/

"One thing I did notice exploring the Zipper's performance with its new mod engine. The normal fuel flow reading static on the runway before takeoff was about 8500 PPH. At 600 KIAS under 500 feet ASL right after T/O it read about 12500. Our GE Tech Rep affirmed that was factual and the standard engine/AB fuel proportion was still in effect. That meant that at that speed and altitude the Dash 19 was developing at least 25000 pounds of thrust. Zipper, indeed.."

A Fuel Flow of 8500 lbs PPH idling is 141.6 lbs per minute.
I gather 12500 PPH @ 600 KIAS after take off is in MILITARY and gives us 208.3 lbs per minute.

How is my math?

And spurts commented in a previous post the J79-19 made a lot more thrust at speed and altitude than just 17,900 lbs. Here we see it made AT LEAST 25,000 lbs at speed (Mach 2+) and altitude (35,000+ ft).

So here is my dismay or perhaps sheer astonishment, with the performance figures of the Dash 19 engine. Walt said at M2.0 at 73,000 ft with 3/4 AB the jet was burning 100 lbs of fuel per minute. Yet idling (M0.0) the engine was burning 141.6 pounds per minute.

Did I get this right?
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johnwill

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Unread post17 Feb 2019, 04:16

He didn't say 8500 PPH idling. He said 8500 PPH on the runway just before takeoff. I interpret that to mean ready for brake release,
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kdub104

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Unread post17 Feb 2019, 04:42

johnwill wrote:He didn't say 8500 PPH idling. He said 8500 PPH on the runway just before takeoff. I interpret that to mean ready for brake release,



Military power?
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sprstdlyscottsmn

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Unread post17 Feb 2019, 13:25

After burner
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Unread post17 Feb 2019, 15:09

Mach 2 and 70,000 ft plus sounds all well and good. But realistically, how long could it remain airborne using that much afterburner/fuel?

And could it do that with wingtip (or underwing) AIM-9's?

For all its performance, its record in combat wasn't exactly F-15/16 like. Awful in Southeast Asia, if I recall correctly. I often wonder if that irked Kelly Johnson and the boys at Lockheed...
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Unread post17 Feb 2019, 20:02

Salute!

Well, Mixel, et al, the Zipper never had any real engagements in SEA. The Thud had a fair amount, but not as many as the Doubble Ugly or even the F-8. One other buddy that got a Mig kill in the F-4E will attest to this. Yet another close buddy that bagged a Mig in the Thud has gone west, but the Mig flew out in front and he used the cannon.

Rumor on the street was the PNAF Fishbeds did not want to tangle, nor the Fresco.

However, my two close friends that flew the Zipper in 1966 - 67 in SEA say that the "fear factor" of the PNAF was an urban legend. One of them almost had an engagement but was called off due to another friendly that needed close support.
The Zipper was only a boom and zoom plane for any engagement versus a fighter, and PNAF already had the Mig-21, which could turn better than the Zipper and almost climb as fast.

About the only planned and intentional engagement with any planes in the whole war was Bolo, and sure enuf, another of my buddies was in back seat of Olds' jet that day. Oh yeah, you might wionder, our bunch had good timing, huh?

++++++++++++++++
The fuel consumption up high is lots lower than doen on the deck in burner or even mil. Gotta get "TEGS" on the thread to explain, but maybe we have another propulsion expert here.

In the VooDoo we could use min burner on one motor and mil on the other to maintain 1.15M or so up at 49,000feet. That was our basic target altitude for snap-up attacks by our practice guys. That burn rate was not much higher than using both motors at cruise power down low. So figure 6,000 pound per hour, or 100 pounds per minute. At 49,000 feet, that was about 12 n.mi/min for 100 pounds. Not too shabby.

The Viper was better, but not much, and I would demo to the nuggets a supersonic cruise at 1.1M or so and 40,000 feet using min burner, then use mil power for a bit, then back to burner when down to 1.05M. Neat, huh?

Gums recalls those days......
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kdub104

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Unread post17 Feb 2019, 21:09

mixelflick wrote:Mach 2 and 70,000 ft plus sounds all well and good. But realistically, how long could it remain airborne using that much afterburner/fuel?

And could it do that with wingtip (or underwing) AIM-9's?



I would imagine that once at 70K ft and Mach 2 the boys had at least 2,000 lbs of fuel to cruise with.

500 on take off
500 mil power climb to 35K ft
1000 to accelerate to from .9 to M2.0
700 to get from FL350 to FL700
Then 100 lbs a min in 3/4 AB

2700 lbs to get to FL700 @ M2.0

Started out with 5800 clean so Walt and company had 3100 to play with. Subtract 800 for landing (or was it more?) and there is 2300 lbs for slipping the surly bonds.

2300 lbs gives them 23 minutes at a TAS of 1150 kts.
1150 kts TAS is 1323 mph
23 minutes at 1323 mph is 503 miles range

Its my understanding tip tanks were rated for Mach 2 and offered little drag. 170 gal per tip tank or 340 combined. 340 gal gives an additional 2,210 lbs of fuel. Could the boys take the tip tanks up to FL700 and Mach 2? If so, could they do it with 3/4 AB?

Wing tanks were 190 gal and could be jettisoned. That's 380 gal or nearly 2,500 lbs. Aren't they too rated for Mach 2 at altitude?

The Norwegians discovered AIM-9s on the catamarans under the fuselage had the least amount of drag at higher supersonic speeds compared to under wing location.

Walt! Walt! Where are you? TEG where are you?!

Shame we don't have Italian Zipper pilots on board. They could really fill in all these big holes. They also cruised at FL700 and up to M2.3.

Gums... you're a good man defending the honour of the Zipper!
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mixelflick

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Unread post18 Feb 2019, 15:15

Gums wrote:Salute!

Well, Mixel, et al, the Zipper never had any real engagements in SEA. The Thud had a fair amount, but not as many as the Doubble Ugly or even the F-8. One other buddy that got a Mig kill in the F-4E will attest to this. Yet another close buddy that bagged a Mig in the Thud has gone west, but the Mig flew out in front and he used the cannon.

Rumor on the street was the PNAF Fishbeds did not want to tangle, nor the Fresco.

However, my two close friends that flew the Zipper in 1966 - 67 in SEA say that the "fear factor" of the PNAF was an urban legend. One of them almost had an engagement but was called off due to another friendly that needed close support.
The Zipper was only a boom and zoom plane for any engagement versus a fighter, and PNAF already had the Mig-21, which could turn better than the Zipper and almost climb as fast.

About the only planned and intentional engagement with any planes in the whole war was Bolo, and sure enuf, another of my buddies was in back seat of Olds' jet that day. Oh yeah, you might wionder, our bunch had good timing, huh?

++++++++++++++++
The fuel consumption up high is lots lower than doen on the deck in burner or even mil. Gotta get "TEGS" on the thread to explain, but maybe we have another propulsion expert here.

In the VooDoo we could use min burner on one motor and mil on the other to maintain 1.15M or so up at 49,000feet. That was our basic target altitude for snap-up attacks by our practice guys. That burn rate was not much higher than using both motors at cruise power down low. So figure 6,000 pound per hour, or 100 pounds per minute. At 49,000 feet, that was about 12 n.mi/min for 100 pounds. Not too shabby.

The Viper was better, but not much, and I would demo to the nuggets a supersonic cruise at 1.1M or so and 40,000 feet using min burner, then use mil power for a bit, then back to burner when down to 1.05M. Neat, huh?

Gums recalls those days......


Those are some incredible figures! Especially the part about the Voodoo being able to supercruise with... one burner lit. Wow. I guess you don't really appreciate the F-104 until you hear these stories. Wing tanks rated out to mach 2? That's crazy. But it just goes to show you how impressive the airframe was.

What a career Gums. A-37's, F-101's, A-7's, F-16's. Sounds like you sure knew your stuff, and thankfully the USAF rewarded you with lots of stick time in different types. I'm not sure what you think about the F-35, but I just can't help being impressed the more I read about it. For your service, they should let you take one up for a spin... :)
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kdub104

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Unread post19 Feb 2019, 21:35

johnwill wrote:He didn't say 8500 PPH idling. He said 8500 PPH on the runway just before takeoff. I interpret that to mean ready for brake release,



8500 PPH ready for brake release in afterburner.
And 12,500 PPH after takeoff at 600 KIAS... also in afterburner or do you think military power?

I ask because from what I gather about the J79 in afterburner at low level, fuel flow is 1000 lbs a minute. Is it this much?
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sprstdlyscottsmn

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Unread post19 Feb 2019, 22:16

The more I think about these numbers the more I think they are Mil power. J79 was ballpark TSFC 1 in Mil and 2 in AB. This would be ~8,500lb-12,500lb of thrust in Mil with a "rated" ~12,000lb Mil. This makes sense. 1,000ppm would be 60,000pph or ~30,000lb thrust. I could see that for the Mach 1.2 or Mach 1.3 region at low level for a J79.
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Unread post19 Feb 2019, 23:30

Fuel flow in AB from the F-104G flight manual
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sprstdlyscottsmn

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Unread post19 Feb 2019, 23:54

Yeah, so 208ppm at 600KIAS is definately Mil Power.
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Unread post20 Feb 2019, 00:09

Salute!

Sounds about right, Spurts.

Once flew a Viper with 6 x MK-82 plus tanks at Red Flag. Zipped along at 540 KIAS and was using about 9000 - 10,000 pounds per hour. Not too shabby, but our motor was lots better than the J-79.

Gums sends...
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Unread post20 Feb 2019, 03:15

Thanks for this alfakilo!

Clean the 104G can get out to M.97 in mil, correct?

Chart is showing 490 lbs/min at M.97-ish.

On the deck MAX AB and hauling the mail looks like 850 lbs/min. Did you see higher fuel flow numbers than this?
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