JFS Operation
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I’m grasping at understanding at this but I think the JFS is an intermediary between the stored pneumatic bottle(s) and the full engine. There is some mention of using the JFS as a way to supplement the EPU in the case of engine failure. The JFS actually burns JP-8 in a piggyback arrangement on the engine. The pneumatic accumulator bottles blow the JFS to turn and the JFS turning makes the engine turn. The JFS is making the engine turn by a torque on an engine gearbox output-input shaft and is declutched from the engine operation when the torque inverts.
The JFS is sort of a pneumatically-started APU geared and clutched into the main engine. The pneu bottle air doesn’t blow directly on the compressor/turbine stages of the main engine. It’s shafts and gearboxen.
Pneumatic bottle -> hydraulic fluid -> JFS -> ADG -> (internal clutch) -> PTO shaft -> engine.
What I’m not sure of if the JFS actually consumes JP-8 or not when self-sustaining. From the sound of it by the JFS exhaust duct and doors it must burn fuel to turn the main turbine over.
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“The JFS is a gas turbine that operates on aircraft fuel”
Im gonna go ahead and say yeah it does.
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The JFS is sort of a pneumatically-started APU geared and clutched into the main engine. The pneu bottle air doesn’t blow directly on the compressor/turbine stages of the main engine. It’s shafts and gearboxen.
What I’m not sure of if the JFS actually consumes JP-8 or not when self-sustaining. From the sound of it by the JFS exhaust duct and doors it must burn fuel to turn the main turbine over.
Ok a few things. I am not an engine/JFS guy but the accumulators should work the same as others. That would mean the air pressure is only to push against the hydraulics in the accumulators and the hydraulics are what does the actual spinning of the JFS. No air at the JFS to start it.
Yes the JFS uses the same fuel as the main engine and will consume some to stay running. Both of the flight manuals I referenced agree that the master fuel shutoff has no bearing on JFS operation.
Pneumatic bottle -> hydraulic fluid -> JFS -> ADG -> (internal clutch) -> PTO shaft -> engine.
JFS/Brake hydraulic accumulators > hyd lines to JFS > JFS start then the rest.
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Maybe we should request a Viper Haynes manual…
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Maybe we should request a Viper Haynes manual…
The Chilton’s are usually helpful too, just less pictures :rofl:
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Maybe we should request a Viper Haynes manual…
You mean like this?
It’s been done. It’s a good series, not actually a Technical Manual, but rather a general interest book. There’s a fair bit of technical stuff though, along with a good training sortie description by a Viper driver.
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You mean like this?
It’s been done. It’s a good series, not actually a Technical Manual, but rather a general interest book. There’s a fair bit of technical stuff though, along with a good training sortie description by a Viper driver.
… and if Haynes had any input, it’ll be full of inaccuracies!
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… and if Haynes had any input, it’ll be full of inaccuracies!
Yeah I’ve heard that more and more over the years. They don’t even do one for the petrol mark 2 Octavia, and look how popular that car is!
Still, could be tempted to get that F-16 haynes for the novelty feature.
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Still, could be tempted to get that F-16 haynes for the novelty feature.
You know you want to click that button… http://www.ebay.co.uk/itm/361841938227
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You know you want to click that button… http://www.ebay.co.uk/itm/361841938227
Damn, the last one just sold.
Oh wait, to me! Good times!
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Damn, the last one just sold.
Oh wait, to me! Good times!
Enjoy it. It’s a good read. Can I recommend the titles on the SR-71, B-52, Harrier and Phantom in the same series. They’re the good ones of a somewhat variable bunch.
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Enjoy it. It’s a good read. Can I recommend the titles on the SR-71, B-52, Harrier and Phantom in the same series. They’re the good ones of a somewhat variable bunch.
I only have eyes for the Viper, but thanks. Looking forward to geeking out by reading it
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After reading this, I’d say - judging from sound, heat blur and the black jet of smoke - that in the video linked below the JFS is spooled completely at 1:59, then it sounds like it’s straining a bit while spooling the turbine, then fuel is introduced to the engine at 2:14, followed by JFS shutdown at 50% engine RPM at 2:34. I’d love to hear other suggestions / corrections if any:
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After reading this, I’d say - judging from sound, heat blur and the black jet of smoke - that in the video linked below the JSF is spooled completely at 1:59, then it sounds like it’s straining a bit while spooling the turbine, then fuel is introduced to the engine at 2:14, followed by JSF shutdown at 50% engine RPM at 2:34. I’d love to hear other suggestions / corrections if any:
Thanks for the vid. Just one suggestion: It’s JFS, not “JSF”
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Fixed