Forum: F-35 Lightning II

they already have them on the SR-71X, they just want you to THINK is decomissioned.... j/k

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That_Engine_Guy wrote:

Most sources state the F135-PW-600 for the B (AKA - STOVL) makes 39,800lbs of thrust in "hover," making this the MAXIMUM weight the F-35B will be able to operate in any type of pure vertical flight.

17,600lbs from the engine exhaust
18,500lbs from the LiftFan
3,700lbs from the roll posts
-----------
39,800lbs of vertical thrust

Actually, the latest P&W literature now lists Maximum Hover Thrust as 40,550lbs...

That yaw angle of +/-13 degrees for the nozzle...can it be used in conventional flight for improved agility? Sorry if it's a bit off topic.

Kryptid wrote:

That yaw angle of +/-13 degrees for the nozzle...can it be used in conventional flight for improved agility? Sorry if it's a bit off topic.

No; if you look at how the 3BSN works, it will only yaw when vectored down at least to clear the structure around it's upper half. Also when the nozzle is in the horizontal the lower panels around it close, so when it is level there is no room for it to move. Remember, it's not the nozzle "vectoring" thrust, but the entire augmentor duct and nozzle rotates down.

Looks like it may need to be 60* or more down before it would clear the structure around it?

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TEG

EDIT: Added photos to illustrate

@ Kryptid

I don't think so. IMO, that will be done by rotating the first bezel around the engine axis. Then it will be effective only when the nozzle is bend. Otherwise rotating the first bezel will not change the thrust vector. That design will be the most reliable, IMO.

About SFC (once again and finally);

PPHMIL-HOVER must be 1.42(*) times PPHMIL (that is the engine will burn 1.42 times more fuel during hover at max available throttle setting then max available thrust in-flight) in order to get exactly the same SFC for both modes of flight.

Take the basic turbofan equations. Simply double the by-pass ratio. See how SFC changes.

Of course you are not doubling (perhaps tripling) the by-pass ratio for free. Losses due to the roll-posts and the transmission(**) will occur.

But the extra-high-by-pass ratio will balance them out.

Harrier system is a different case. The Pegasus lifts with nozzle(s) and two large roll-posts (forward ducts) and smaller roll-posts here and there. It does NOT make use of a higher by-pass ratio turbofan. Principle is completely different.

The Harrier example was given so here is an exaggerated example;
Think of an helicopter. Remove its rotor, locate the engine(s) vertically. Try to take-off.

(*) 1.42 is 39800/28000
(**) the term 'transmission' includes turbine connections and extra power extracted from the turbine as well as gearbox, shaft, etc.

dwightlooi wrote:

Actually, the latest P&W literature now lists Maximum Hover Thrust as 40,550lbs...

That's right! Guess the F135 is getting more powerful all the time!

So much for the F135's "naysayers"... Poke

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TEG

r2d2 wrote:

About SFC (once again and finally);

PPHMIL-HOVER must be 1.42(*) times PPHMIL (that is the engine will burn 1.42 times more fuel during hover at max available throttle setting then max available thrust in-flight) in order to get exactly the same SFC for both modes of flight.

Take the basic turbofan equations. Simply double the by-pass ratio. See how SFC changes.

Of course you are not doubling (perhaps tripling) the by-pass ratio for free. Losses due to the roll-posts and the transmission(**) will occur.

But the extra-high-by-pass ratio will balance them out.

I'm not discounting the extra thrust or almost double the air-flow; but to gain 1.42X thrust you'll NEED to burn more fuel. If it is anything HIGHER than 1.42X during the MFC's fuel bias the SFC will be higher.

With the losses in compressor efficiency I've pointed out, and mechanical (friction) losses in the drivetrain, I suspect the SFC will be higher during hover to supply the extra power needed. I highly doubt it will be a equal (or less) trade of fuel for thrust as you're suggesting.

Have you ever seen how much air comes out of a N2 compressor bleed at high N2 RPM? Or how it affects EPR/EGT? Shocked

r2d2 wrote:

Harrier system is a different case. The Pegasus lifts with nozzle(s) and two large roll-posts (forward ducts) and smaller roll-posts here and there. It does NOT make use of a higher by-pass ratio turbofan. Principle is completely different.

True; I agree. But have you ever noticed how much more smoke is generated by a F402 in hover versus conventional flight? Remember a STATIC SFC will be different than SFC in forward-flight... even without some sort of fuel bias or water-injection to compensate simply because of the inlet pressure being higher.

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TEG

Quote:

If it is anything HIGHER than 1.42X during the MFC's fuel bias the SFC will be higher.

I'm expecting a LOWER-than-1.42.

Quote:

Have you ever seen how much air comes out of a N2 compressor bleed at high N2 RPM? Or how it affects EPR/EGT?

Never saw it but assume it to be something like 1/2 of total thrust.
The roll-posts on 135-600's ratio is approx 1/10.
That is the reason for new & innovative design.

Quote:

But have you ever noticed how much more smoke is generated by a F402 in hover versus conventional flight?

The pegasus works fuel-rich during hover in order to prevent flame-out. Thus the smoke, as far as I know. We will not see smoke in a vertically-landing f-35.

r2d2 wrote:

The pegasus works fuel-rich during hover in order to prevent flame-out. Thus the smoke, as far as I know. We will not see smoke in a vertically-landing f-35.

This is exactly what "at an increased turbine temperature" means. The engine won't be getting any additional air, and will be loosing some of it to the roll-posts. The only other way to add power is additional fuel. The engine will run rich, but it is additional power needed to operate under the additional load.

Our friend J@ne'$ says OPR for the F135-PW-100/-400 is 35, in the 135-PW-600 during conventional flight 34, and powered lift 29. So as you can see the compressor's is loosing almost a 5/1 compression ratio. SFC is inversely affected by the engine's thermal efficiency, which depends on the OPR.

Watch this video... http://www.jsf.mil/video/x35/mission-x_high.wmv

Notice the smoke pour out of the engine when the nozzle rotates down (00:22) and as the aircraft leaves the ground. Also notice the visible column of smoke (01:11) as the X-35 hovers.

I'm not saying that the newer F135 (unlike the JSF 119-PW-611 in the tests) won't have less smoke, or perhaps none at all; but I still suspect a higher SFC during hover. (but again; not that it matters... much.)

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TEG

(34-29) / 34 x 100 That is 14.7

%15 pressure loss is excellent. It will not smoke, thanks to such low pressure loss and state of the art engine management hardware & software.
BTW It will be more fuel efficient (less SFC) although it consumes more fuel (higher PPH).

Forum Veteran Joined: Jul 01, 2007 - 07:22 PM Posts: 605

Just out of curiosity, how much does AF-1 weigh? Anyone know?

Is this a F136 for F-35 B (with the air exit for the RHS roll-post and the lift-fan shaft housing visible)?

Photo taken from here: http://www.tei.com.tr/1/en/image_previe ... 1_20_1.jpg
The link says it is a F136.

BTW, how is the F136 for F-35 B called? F136-600 like F135-600 or something else?

r2d2 wrote:

Is this a F136 for F-35B (with the air exit for the RHS roll-post and the lift-fan shaft housing visible)? The link says it is a F136.

BTW, how is the F136 for F-35B called? F136-600 like F135-600 or something else?

Looks like it.
Following the MIL standard... F136-GE-600

Are engines supposed to look that gorgeous?

singularity wrote:

Are engines supposed to look that gorgeous?

When they are "new" yes...

That one doesn't have any of the plumbing/wiring on it; seems to be just a mock-up.

Look at the F136 in the last 7 photos here: http://www.arnold.af.mil/photos/index.a ... amp;page=2

Gives you an idea what an "instrumented test engine" looks like.... if you can see it...

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TEG

Forum: F-35 Lightning II

F-135 or F-136 fuel burn rate