Powering the Fifth Generation: Inside the F-35’s Engines

All about the Pratt & Whitney F135 and the (cancelled) General Electric/Rolls-Royce F136
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spazsinbad

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Unread post26 Apr 2012, 13:36

Powering the Fifth Generation: Inside the F-35’s Engines 26 April 2012

http://www.airforce-technology.com/feat ... -analysis/

"Engines aboard Lockheed Martin’s next generation F-35 fighters are almost 30 years in the making. Liam Stoker takes a look at the development of Pratt & Whitney’s F135 engine, from concept to refinement, and details its performance against foreign counterparts....

...Three engine variants have been designed; the F135-PW-100 and F135-PW-400 for use aboard the conventional and carrier variants of the aircraft respectively, and the F135-PW-600 for the STOVL variant. Both the conventional and carrier engines are largely similar and produce almost identical results, with a maximum wet thrust of 43,000lbf and a dry thrust of 28,000lbf. The major difference is the use of salt-corrosion resistant materials in the carrier variant...."

At the URL - Knock yourself out! This question about the STOVL engine being 'salt-corrosion resistant' also has been asked earlier but I don't recall if any answer given?
Last edited by spazsinbad on 26 Apr 2012, 19:25, edited 1 time in total.
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Unread post26 Apr 2012, 16:30

Interesting. Thanks!
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river_otter

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Unread post26 Apr 2012, 16:59

The corrosion-resistant materials have been previously cited as why the A is the only model with any thrust growth potential. The C's engine materials are less heat-resistant. It literally can't produce more thrust without failing durability specs. The B has no thrust growth potential even though the turbine engine is identical to the engine in the A. Re-design of the 3BSM and lift-fan drive to handle it would be prohibitive. The A's engine has been tested to over 50,000 lbf while still meeting durability specs. While the current exhaust tunnel wouldn't handle much over 43,000 lbf, re-designing a fairly straight tube for a future block upgrade or F-35D wouldn't be that difficult.
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SpudmanWP

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Unread post26 Apr 2012, 17:13

Thrust increases are in the cards for Blk6.
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Unread post26 Apr 2012, 19:10

Did the lift-fan concept prove to be the decisive factor in winning the JSF competition for LM?
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Unread post26 Apr 2012, 19:23

popcorn wrote:Did the lift-fan concept prove to be the decisive factor in winning the JSF competition for LM?


I heard it said thus, "If Lockheed can make the lift fan work, it's all over". Direct lift (Boeing's and the Harriers mode) is about the worst there is from an efficiency/versatility standpoint. It had ZERO growth margine and IMO would have been cancelled by now.
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Unread post26 Apr 2012, 19:52

Lift fan was deemed riskier as the harrier used the direct lift method and as such was more "proven." Still, the lift fan can be better optimized for operating at lower altitudes and zero aircraft airspeed unlike the harrier's and X-32's method. As such you can use better optimized main engines for the actual cruising at altitude and ultimately have better performance with said flight optimized main engine.
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Unread post26 Apr 2012, 20:16

The fact that "Mission-X" (STO-supersonic dash-VL in one flight) was performed by the X-35 was a big deal too, but the lift fan was a large portion of why it was able to do it.

I heard that during the fly-off test pilots were calling the X-32 "Monica." It's never a good sign when test pilots start calling a plane names like that.

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Unread post26 Apr 2012, 20:39

I think grown potential had a lot to do with it.

The X-32 had problems with it's VL performance before the inevitable weight growth that occurs in dev is factored in. The X-35 has lots of spare thrust that lessened the risk of development weight growth.
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Unread post26 Apr 2012, 21:29

Ya, the lift fan essentially means the engine gets to work as a high-bypass engine during launches & landings, as if it had a bigger fan than its main fan alone is, but still work as a low-bypass engine in forward flight. Normally, fighters have small fans and low-bypass engines, but high bypass is better for the STOVL task in particular; Harriers need to have a bigger fan than normal for fighters in order do that trick, and that's part of why they're slow for a fighter.

Using the intake fan system also allowed X-35 to avoid building in extra ductwork along the sides or locating the engine so far forward in the plane's body, which would give the fighter a thicker overall shape and give X-32 its classic "hey, that F-16 swallowed a bus!" look. Even if you figure the judges in the competition made their choice objectively based on performance instead of just disliking X-32 from the start for looking like an obese pelican with a goiter, that difference in shapes was still relevant anyway: there are purely pragmatic, performance-based reasons why fighters usually aren't made like that. Also, when you have stealth requirements to meet, you have to hide your engine's fan from view, and an engine mounted in the back like with X-35 and most other fighters lets you do that by just S-curving the intake duct(s), just like in F-22. That avoids what X-32 was stuck with, which is cramming extra airflow obstructions in the way because the engine fan was practically right behind the intake.
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Unread post27 Apr 2012, 04:57

spazsinbad wrote:Powering the Fifth Generation: Inside the F-35’s Engines 26 April 2012

http://www.airforce-technology.com/feat ... -analysis/

"Engines aboard Lockheed Martin’s next generation F-35 fighters are almost 30 years in the making. Liam Stoker takes a look at the development of Pratt & Whitney’s F135 engine, from concept to refinement, and details its performance against foreign counterparts....

...Three engine variants have been designed; the F135-PW-100 and F135-PW-400 for use aboard the conventional and carrier variants of the aircraft respectively, and the F135-PW-600 for the STOVL variant. Both the conventional and carrier engines are largely similar and produce almost identical results, with a maximum wet thrust of 43,000lbf and a dry thrust of 28,000lbf. The major difference is the use of salt-corrosion resistant materials in the carrier variant...."

At the URL - Knock yourself out! This question about the STOVL engine being 'salt-corrosion resistant' also has been asked earlier but I don't recall if any answer given?


NAVIAR requires all Navy, Marine Corps, and Coast Guard designs intended for shipboard use to designed for a salt water.
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spazsinbad

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Unread post27 Apr 2012, 04:59

'bjr1028' have any references for your claim please? Thanks. It would seem common sense as you say but I require some documentation for my purposes, specifically for the STOVL engine components. Thanks again in advance.
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Unread post27 Apr 2012, 22:31

river_otter wrote:The corrosion-resistant materials have been previously cited as why the A is the only model with any thrust growth potential. The C's engine materials are less heat-resistant. It literally can't produce more thrust without failing durability specs. The B has no thrust growth potential even though the turbine engine is identical to the engine in the A. Re-design of the 3BSM and lift-fan drive to handle it would be prohibitive. The A's engine has been tested to over 50,000 lbf while still meeting durability specs. While the current exhaust tunnel wouldn't handle much over 43,000 lbf, re-designing a fairly straight tube for a future block upgrade or F-35D wouldn't be that difficult.


I've read about the 50,000 lbf test, is that also said to meet durability specs? I thought that was some overload test?
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Unread post27 Apr 2012, 23:09

So if a customer was going to operate said -C model strictly over land then they should be able to use the -A engines after being uprated?
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Unread post27 Apr 2012, 23:30

megasun wrote:
river_otter wrote:I've read about the 50,000 lbf test, is that also said to meet durability specs? I thought that was some overload test?


Sweetman insinuated it was a one-off but he didn't cite any evidence. Pratt & Whitney and the USAF certainly never said it was an "overload" test.
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