Author Topic: The F-35 No Holds Barred topic  (Read 485985 times)

Offline LowObservable

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Re: The F-35 No Holds Barred topic
« Reply #570 on: August 13, 2010, 10:25:33 am »
The greatest weights are probably the most reliable. I believe the current quotes are: F-35A 29300 lb, F-35B 32,100-32,300 lb, and F-35C (oink) 34,800 lb.

Offline Colonial-Marine

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Re: The F-35 No Holds Barred topic
« Reply #571 on: August 13, 2010, 02:20:00 pm »
The greatest weights are probably the most reliable. I believe the current quotes are: F-35A 29300 lb, F-35B 32,100-32,300 lb, and F-35C (oink) 34,800 lb.

Well, your not very optimistic about the whole program I see. I fear that may be the case (higher is more accurate) but what about that weight reduction program?
"Politics is the art of looking for trouble, finding it whether it exists or not, diagnosing it incorrectly, and applying the wrong remedy."

Offline LowObservable

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Re: The F-35 No Holds Barred topic
« Reply #572 on: August 15, 2010, 06:59:42 pm »
Those are post-SWAT weights. The primary SWAT issue was with the B model, which was ballooning towards 34-35,000 pounds. The C had not completed CDR at that point and has a bigger wing than expected at that time.

Offline Colonial-Marine

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Re: The F-35 No Holds Barred topic
« Reply #573 on: August 15, 2010, 09:36:44 pm »
No offense to anybody but at this point I can't bring myself to believe anything until the aircraft is entering service. It seems even Lockheed doesn't have their figures straight. I know one guy who is swearing by 27,000 for the F-35A and 30,000 for the F-35B and F-35C.
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Offline LowObservable

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Re: The F-35 No Holds Barred topic
« Reply #574 on: August 16, 2010, 06:47:33 am »
CM - I looked for the numbers that I cited, and Lockheed Martin has vaporized them.

But never fear, the Intertubes are not lightly mocked...

http://web.archive.org/web/20080612204013/http://www.lockheedmartin.com/products/f35/f-35specifications/index.html

Offline bobbymike

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Re: The F-35 No Holds Barred topic
« Reply #575 on: August 16, 2010, 05:33:26 pm »
Competition can be a good thing, maybe  ;) From Aviation Week

Alternate JSF Engine Thrust Beats Target
Aug 16, 2010
By Guy Norris
Los Angeles

The intense battle over powering the F-35 Joint Strike Fighter could be heading to new levels following test results that show the General Electric/Rolls-Royce F136 alternate engine has more than 15% thrust margin against specification, significantly exceeding the power of the baseline Pratt & Whitney F135.

The tests at the U.S. Air Force’s Arnold Engineering Development Center (AEDC) in Tullahoma, Tenn., are the first to officially calibrate the combat-rated thrust of a production-representative F136 at sea level conditions. Although the test program is only a matter of days old, it already appears to be showing greater performance margin in afterburner than expected, says the General Electric Rolls-Royce Fighter Engine Team.

News of the tests reaches Congress as it heads toward a showdown with Defense Secretary Robert Gates, who has made killing the second engine a centerpiece of his crusade to cut unnecessary defense spending. With the Obama administration promising to veto any defense bill that prolongs the F136, the House has defied Gates and passed provisions that fund the engine. The Senate has not weighed in, but key committee chairmen have voiced support for competitive engines. Details of the F136’s test performance could strengthen support and more broadly undermine Gates’s efforts to reform the Pentagon (see p. 20).

“Initial results show we have more than 15% margin at sea level combat-rated thrust than the specification. That’s significantly beyond the thrust requirement right out of the chute,” says GE-Rolls. In March this year, following the first maximum afterburner test of a system development and demonstration engine, the team quietly expressed confidence the F136 would exceed the thrust of the baseline F135 by 5%. Actual thrust achieved in the test remains undisclosed, but it is in excess of 40,000 lb.

Pratt & Whitney, which derived its F135 from the F-22 Raptor’s F119 engine, remains confident its own growth plans will stave off the challenge from the F136 without getting ahead of the need or increasing development costs. The company, which begins final qualification tests of the short-takeoff-and-vertical-landing (Stovl) engine in Florida this month, plans to start tests of a higher-thrust F135 in January 2011 and begin rig tests of a growth fan later next year.

Although the F135’s thrust meets specification for the Lockheed Martin F-35 as currently configured, future growth potential is becoming an important part of the ongoing alternate engine debate. Thrust growth, and the engine life and maintenance cost benefits if traded for lower operating temperatures, are recognized as key factors by both sides. Thrust growth is considered particularly important for the performance of the F-35B Stovl variant, while the ability to use additional temperature margin to cut long-term support costs is applicable to all models, including the conventional-takeoff variants.

Given the added margin, GE-Rolls says its baseline F136 will be able to achieve a 5% thrust growth through a simple digital engine control “throttle push,” without eating into what it says could be a 25% maintenance-cost advantage over the F135. Russ Sparks, GE Aviation vice president for military strategy, says the reduced costs are directly related to the lower turbine operating temperatures in the engine, which was resized with a larger core and higher-flow fan in 2005, when Lockheed Martin increased the airflow capacity of the F-35 inlets to 400 lb./sec. The F136 fan was enlarged to pump up to 380 lb./sec., and the AEDC tests are being conducted within the airflow limits of the JSF inlets.

Pratt & Whitney Military Engines President Warren Boley says growth testing is part of a medium- to long-term strategy to increase F135 thrust by as much as 20%. “There is no doubt Pratt & Whitney has the suite of technology, and we are dedicated to do that,” he says. Although initial growth is aimed at satisfying F-35 thrust requirements, Boley says more power will also accommodate future applications on other platforms—including unmanned aircraft.

The first growth step, starting with tests in January, is based on digital engine control and turbine airfoil changes. These will provide 5-10% thrust growth and could be applicable for F-35s in production Lots 6, 7 and 8, “if needed,” Boley says. The changes could also form the basis of an engine upgrade that would be retrofitable at a depot level, he adds.

Beyond this, Pratt & Whitney’s advanced program team is studying more fundamental changes to the basic cycle of the F135 that could enhance performance and provide more growth potential. The initiative would introduce adaptive technology for the core and fan similar to that being developed by Rolls and GE under the U.S. Air Force-led Adaptive Versatile Engine Technology (Advent) research program. Although Pratt & Whitney was not selected to work major elements of Advent, it has continued to refine the technology it originally proposed for the competition.

“We are looking at a third fan stream that would take advantage of a gear,” says Boley, adding that this would “bring geared turbofan technology to the front end of the F135.” Studies for the growth engine, dubbed F135 plus, include looking at a “classic bigger fan.” The current focus is on whether it would be better to combine a larger fan with an adaptive core, or make both the core and fan adaptive.

GE’s Sparks contends that “maintaining the engine flow path is the key to affordable growth. We don’t need to make it bigger, or make the fan flow more air, to give our engine more thrust. A 5% growth will be achieved with the current F136 hardware, and we’re far enough into performance testing to verify that component efficiency is equal to or better than predicted. That’s the basis for retaining the margin in terms of fan speed and temperature.”

To boost thrust by 10%, the team plans to import technology being developed under the Air Force’s Versatile Affordable Advanced Turbine Engine program. “We’re talking things like better cooling and more [ceramic matrix composites], and we’ll do it all without making any airflow changes through the engine,” he says. Ceramic matrix composites are used in the first stage of the F136 low-pressure turbine and would be used for other stages in the higher-thrust version, says the engine team.
Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats. 
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Offline Matej

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Re: The F-35 No Holds Barred topic
« Reply #576 on: August 17, 2010, 12:00:48 pm »
I made some discussion with the GE-Rolls Royce representatives and they see the main advantage of their product in the fact, that it is specially developed for the JSF (compared to F135, which is only a derivate of the other engine). Meaning size, overall shape and the configuration with a significantly bigger development potential than the F135.

What I wanted to know the most is if the F136 is at least in some way dual-core design. It is not.

Bizarre aviation expert.

Offline bobbymike

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Re: The F-35 No Holds Barred topic
« Reply #577 on: August 17, 2010, 03:46:16 pm »
So if I read the story correctly the F136 peak thrust will approach 50,000 lbs? I read somewhere the the Air Force had a idea for a nominal Long Range Strike Aircraft that was to be powered by two "50,000 lbs" thrust class engines and be capable of Mach 2.5+ dash speeds.
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Offline sferrin

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Re: The F-35 No Holds Barred topic
« Reply #578 on: August 17, 2010, 03:54:35 pm »
So if I read the story correctly the F136 peak thrust will approach 50,000 lbs? I read somewhere the the Air Force had a idea for a nominal Long Range Strike Aircraft that was to be powered by two "50,000 lbs" thrust class engines and be capable of Mach 2.5+ dash speeds.

That second part might be Vulcan.  They mentioned 50,000lb thrust engines powering a future "SR-71-ish or F-22-ish" aircraft.  As for the F136 approaching 50,000lbs that doesn't seem impossible.  The version of the F135 in the X-32 produced 34,000lbs dry and 51,000lbs in max afterburner.
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Offline Abraham Gubler

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Re: The F-35 No Holds Barred topic
« Reply #579 on: August 17, 2010, 07:43:27 pm »
That second part might be Vulcan.  They mentioned 50,000lb thrust engines powering a future "SR-71-ish or F-22-ish" aircraft.  As for the F136 approaching 50,000lbs that doesn't seem impossible.  The version of the F135 in the X-32 produced 34,000lbs dry and 51,000lbs in max afterburner.

You can make a F119/F135 engine produce more thurst but you need to add more turbine segments, bigger fans, etc to do so. But this adds weight. The F120/F136 was always a more efficent engine because it used a more advanced design. Just that it would cost more is why USAF chose the F119 and the JSF bidders chose the F135. So whilst you may have a F119 derivative engine producing as much as a F136 it is going to be a bigger and heavier engine for it - but probably costing a lot less (certainly in gross cost from only having a single engine program).
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Offline Wolfhound

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Re: The F-35 No Holds Barred topic
« Reply #580 on: August 17, 2010, 08:52:23 pm »
I don't know whether either the F136 or F136 currently make use of this technology, but I believe PW & GE are aiming for combustors that do away with dilution & cooling holes.  So the future combustor would probably make use of ceramics (in greater quantity than is currently used) and probably support significantly higher temperatures.

Offline sferrin

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Re: The F-35 No Holds Barred topic
« Reply #581 on: August 17, 2010, 08:58:48 pm »
That second part might be Vulcan.  They mentioned 50,000lb thrust engines powering a future "SR-71-ish or F-22-ish" aircraft.  As for the F136 approaching 50,000lbs that doesn't seem impossible.  The version of the F135 in the X-32 produced 34,000lbs dry and 51,000lbs in max afterburner.

You can make a F119/F135 engine produce more thurst but you need to add more turbine segments, bigger fans, etc to do so. But this adds weight. The F120/F136 was always a more efficent engine because it used a more advanced design. Just that it would cost more is why USAF chose the F119 and the JSF bidders chose the F135. So whilst you may have a F119 derivative engine producing as much as a F136 it is going to be a bigger and heavier engine for it - but probably costing a lot less (certainly in gross cost from only having a single engine program).

The F136 is not based on the F120 IIRC.  Also, the version of the F135 in the X-32 was huge (more airflow which turned into big thrust in afterburner).
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Offline saintkatanalegacy

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Offline Abraham Gubler

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Re: The F-35 No Holds Barred topic
« Reply #583 on: August 17, 2010, 09:22:02 pm »
The F136 is not based on the F120 IIRC.

Ahh yes it was. But of course there is no such thing as the F120. There was a YF120 however... So its not the same thing as the YF119-F119-F135 relationship. But the same design and the same tech.


Also, the version of the F135 in the X-32 was huge (more airflow which turned into big thrust in afterburner).

Like I said you can add bigger fans but there is a weight penalty to reach that thrust compared to the F136 with its more advanced YF120 core design.
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Offline saintkatanalegacy

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Re: The F-35 No Holds Barred topic
« Reply #584 on: August 17, 2010, 11:51:32 pm »
^
Quote
With P&W supplying the engine for both the F-22 and all the JSF
prime contractor contenders, not to mention all F-15s and a good
number of F-16s, concerns grew about the need to provide greater
competition and continue support for GE, the country’s sole second
source for high-performance fighter engines. In the summer of 1995,
Congress directed the JSF Joint Program Office to pursue a second
engine source to maintain engine competition during production in
the JSF program, as had existed in the 1980s with the F-16 “Great
Engine War.” In late November 1995, initial development contracts
were awarded to P&W for an F119 derivative and to a GE/Allison
team for design studies for the YF120 and F110 variants for the JSF.

In early 1997, P&W received an EMD contract which, when added to
earlier JSF engine contract money, amounted to a nearly $1 billion
development effort. By that time, GE, Boeing, and Lockheed had settled
on the YF120 as the baseline for development of a second engine
for the JSF in what had now become the Alternate Engine Program
(AEP).14 Rolls-Royce also now teamed with GE, mainly because of
the British firm’s acquisition of Allison. Rolls-Royce’s share of the
YF120 Advanced Technology Engine core development effort stands
at 25 percent.15
The GE alternative engine is not expected to be available for competition
with the P&W engine until the production of JSF Lot 7 commences
in 2013. However, Congress has increased funding for the
AEP in several annual budgets, and it is possible the GE engine could
be available for procurement competition by 2010, or very early in
the planned JSF production effort.
The P&W and GE engine variants for JSF are expected to benefit from
the ongoing research efforts taking place in the IHPTET program.
Initiated in 1988, IHPTET is another ambitious government/industry
technology development and demonstration program, which includes
the continuation of some earlier efforts mentioned earlier in
this appendix. For example, in the interim between the YF120’s loss
in the ATF competition and its entrance into the AEP for the JSF, the
Air Force continued to work with GE through the IHPTET program to
mature the YF120’s advanced technologies. IHPTET’s flagship goal is
to double the thrust-to-weight ratio of military turbofans while reducing
production and maintenance costs by 35 percent by 2003.16
IHPTET, which is half funded by industry and half funded by government,
is expected to eventually make possible the development of
more-reliable next-generation engines with dramatically higher
thrust. This development continues the tradition of U.S. leadership
in development of gas turbine combat aircraft engines, established
definitively in the 1950s with the J57 and continuing on to this day.
http://www.rand.org/pubs/monograph_reports/MR1596/MR1596.appb.pdf

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