Forum: F-35 versus XYZ

Remember that the F-35 is a software defined aircraft, so as long as you are producing quality software the physical aircraft is getting ever more effective over the years.

http://www.northropgrumman.com/analysis ... tealth.pdf

On the other hand, these are the most complex software systems that anybody has ever made and tiny mistakes will kill the pilot:

http://www.latimes.com/business/la-fi-f ... 6553.story

So I ask again, where is the evidence of anybody, anywhere in the world doing a tenth the software effort for a 5th gen fighter that LockMart is doing?

The Raptor is indisputably the best fighter aircraft in the world at this time, and look at its software line count vs. the F-35. Hint: It's less. I don't care HOW fancy the software is if it can't perform. No weapons tests, HMD issues, structural restrictions, etc. doesn't paint a picture of an already sound aircraft made more effective by a kickass software package. I have a stake in the game here (I'll quite possibly be flying F-35s in 8-10 years), and I also have other career options. If I don't feel reassured that I'll be flying a safe and reliable aircraft, I can go private-sector in other fields, and the USAF will be down one pilot candidate. I'm not sure if I'm alone in thinking this, but LM and USAF need to maintain a generally positive impression (and back it up with DOING STUFF WELL!!) if they want to ensure legislative support and a ready, willing pool of future personnel. If people lose faith in the F-35, the program will begin to starve both from reduced funding and the simple refusal to join a service centered around a potentially unsound aircraft.

The lift fan on the B doesn't generate that kind of thrust. It's the motor, they're speaking of, generating 28% more thrust than spec. That would apply to the A/B/C variants.

I'm referring to simple combat performance. Given the choice between a four-ship of JSFs with AWACS and tanker support and a four-ship of Raptors with the same support, for an OCA/DCA/SEAD mission, I would unhesitatingly choice the Raptors. With such a high-performance aircraft, quirks are to be expected, but you're right in that the fighter has some issues which need to be fixed as soon as humanly possible.

My main point was in regards to public relations/recruitment. An aircraft that is seen as performance-limited, glitchy without gaining anything for it (and potentially a flying coffin unless the structural issues are resolved) will not generate the large crop of prospective pilots necessary to keep the fleet in the air. I've already heard things about a major pilot shortfall coming up, and plan to try to help fill this if I know I have a good shot at a reliable aircraft I'm comfortable with.

I'm not TEG but TEG is 'history' (in a good way OK) here with an excellent explantion:

F135 Question Scroll down for dat TEG explanation:

http://www.f-16.net/f-16_forum_viewtopic-t-14353.html
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The man with the fan [STOVL Engine Designer] By Karen Auguston Field

http://www.designnews.com/document.asp?doc_id=214108

"....The additional power to drive the fan comes from the exhaust jet of the turbofan engine. Like a turbocharger on a high-performance car, which uses the energy in the exhaust gases to spin a turbine that pushes more air through the engine, Bevilaqua's system is able to extract more thrust from the engine by transferring the energy in the exhaust jet to a larger mass of air. This is done by adding another turbine stage to the engine...."

This website may or may not have graphics. Google the title to find another example with the graphics....
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All the details required would be in this dense PDF, except only below....

Genesis of the F-35 Joint Strike Fighter Paul M. Bevilaqua [STOVL Engine Desigher] (7.7Mb PDF)
JOURNAL OF AIRCRAFT - 2009 WRIGHT BROTHERS LECTURE - Vol. 46, No. 6, November–December 2009

http://pdf.aiaa.org/getfile.cfm?urlX=-% ... 0%20%20%0A

"....It became apparent that the best way to extract power from hot high-pressure
exhaust gas is with a turbine, the best way to get the power forward in an aircraft is with a driveshaft (it is light and does not increase the cross-sectional area of the fuselage), and the best way to produce vertical thrust is with a fan (increasing mass flow is the best way to increase thrust per horsepower).

Therefore, the best solution to the problem of producing thrust ahead of the center of gravity would be to add another turbine stage to extract power from the exhaust gases. It would have to be variable-pitch, so that it could be feathered during cruise. Another driveshaft could be run from the added turbine stage through the engine to a lift fan: Rolls-Royce was already building three spool engines. The lift fan provides one lift post. Vectoring the cruise nozzle down would create another lift post. Shifting power between the lift fan and cruise nozzle would provide control in pitch. Similarly, engine bypass air could be ducted off to nozzles in the wings and thrust could be shifted from one wing to the other to provide roll control.

But ducting off the bypass air would effectively increase the nozzle exit area for the core flow and lower the back pressure on the turbine section. That would increase the power produced by the turbine [4], so that it would be necessary to close the cruise nozzle down to keep the engine from over speeding. On the other hand, if the lift fan was connected to the turbine at the same time that the bypass air was diverted to the wings, the lift fan would absorb the extra turbine power and keep the engine from speeding up. Then varying the nozzle area would shift power back and forth for pitch control.

When the lift fan was disengaged for cruise, the bypass flow would be returned to the cruise nozzle. This would match the nozzle area to the cruise power requirement again. In fact, it would not be necessary to add another turbine stage. The existing turbine would move off its design operating point to provide shaft power for hover and back to its design operating point for cruise. The existing driveshaft for the engine fan could just be lengthened to power the lift fan.

Because the lift fan is not connected to the engine during cruise flight, the engine operates like a conventional mixed-flow turbofan engine during cruise. For STOVL operations, the lift fan is connected to the cruise engine by engaging a clutch on the driveshaft. The cruise engine nozzle is simultaneously opened, increasing the pressure drop across the engine’s turbine section. This causes it to extract additional
shaft power, which is used to drive the lift fan. The engine then operates in hover like a separate-flow turbofan with a higher bypass ratio. This dual-cycle operation is the novel feature of the engine in the F-35 [5].

To summarize, the solution was to extract some of the energy from the engine exhaust jet by changing the operating point of the turbine, move it forward with a shaft, and turn it into additional thrust by adding it to a larger mass flowof air with a fan. The lift fan is attached to a driveshaft extending from the front of the cruise engine, as shown in Fig. 3, and bypass air for the roll jets is tapped off from behind the cruise engine fan. Thinking about howto extract power from the back of the airplane and transfer it to the front resulted in a flash of insight that produced the dual-cycle-engine concept as the solution for the STOVL Strike Fighter.

Principle of Operation
To appreciate how this dual-cycle engine turns jet thrust into additional shaft power, it is necessary to consider the changes in the static pressure of the air as it flows through the engine. The variation of total energy (top) and static pressure (middle) through an engine are shown in Fig. 4. The pressure rises through the compressor (2–3), remains constant through the combustor (3–4), and then drops through the turbine section (4–5) and nozzle (5–6), in two steps. As the pressure drops through the turbine section, the flow accelerates. The resulting thrust of the jets from the turbine nozzles spins the turbine disk that powers the driveshaft...."

Did not intend to mislead - just making a joke - AFAIK TEG is fine and well and I am just responding because I remember the TEG thread. 'history' was used in an ironic multifaceted meaning jokey way. OK? I reckon educating yourself via Google is the only way to become an autodidact. Given the amount of collective knowledge (and misinformation) on the internet I'm not going to make it. But at least if I make an attempt to answer the question I'm learning stuff. Yeah?

Did you follow the link to TEG explanation?: (scroll down)

http://www.f-16.net/f-16_forum_viewtopic-t-14353.html

How is an oxygen problem related to programming? As the Concurrency report states, while software is a few months behind schedule, there are no apparent problems with the code. Most of the issues are with the onerous release demands imposed on the programmers (SDD and LRIP).

There is little to worry about programming and the core flight systems. Aircraft must meet have flight standards and regulations in order to be considered airworthy... these are among the most heavily tested systems and there are multiple redundancies. I think you can infer from the concurrency report that there aren't any major issues in this area (or they would have called it a high risk).

By comparison, F-22 entered service with alot of software glitches, but they didnt affect the flight systems. They might be issues in other areas, but they can be rectified over time without endangering the crew or airframe.




I don't have the precise numbers, but by 2016 the F/A-18E will probably have the same level of functionality and software challenges. However its incremental approach meant that it was completed over 20+ years, unlike the 8 for the F-35.

Nobody else is doing it, partly because nobody else can.



You're sounding overly dramatic and pretty misleading. You state that the F-22 is "indisputably the best fighter in the world." Sure if you only look at it in the narrow terms of raw performance figures. However then you start talking about its software system, which means you must start considering software reliability and broader statistics on maintenance and sortie availability. Within those criteria the F-22 drops pretty quickly as the "best fighter." Its unbelievably costly, requires inordinate amounts of maintenance to keep flying, and is still riddled with dangerous design flaws. Its software remains quite buggy, and its flight systems pose a significant threat to pilots life. Sure the F-22 is the best performance fighter, its about the absolute worst however for actual sustainment (maybe besides the B-2.)

It reminds me of the F-111 during the Cold War. Sure it was an amazing platform, able to deliver pinpoint atomic weapons quickly across Europe. But it required alot of maintenance to keep flying, thus decreasing its availability to undertake these operations.

As I noted in another thread the F-35 is different from the F-22 because it included the Navy's participation. This meant that the project had to meet stringent sortie availability and reliability metrics set out by that service, unlike the F-22. If I was a flight student in the USAF today and wanted to chose between the two.. I'd probably go with the F-35 (you might have no choice the way the F-22 has been going lately.

Thanks Spaz. We live in an ambiguous world, due to the free but mis-informative internet world as you mention. I was just pointing out that you cannot take a simpleton mathematical equation of 43K + 28%=55K. This is how misinformation is a virus.



BTW...GO Australia, Great Britain, and all the Commonwealth nations. And as we say in Tennessee, Get-R-Done LM.

I posted the link that said they tested to F-135 on the test stand to 28% over the 43K spec. The "B" has nothing to do with it. The STOVL test was at a differant time. Read it again. Also the "B" has showed about 8% less thrust "installed" at speed do to intake constraints placed on it by the lift fan.

TSFG

OK. I'm game. I looked at the past several pages and the only link you have provided that I have seen is for the F135 PROPULSION SYSTEM varaint. Now show mw a link for an F135 motor that does not include the lift fan. The only links I have seen state the STOVL variant. Not trying to be a butthead.

Later the f-35 will be able to hold 6 AAM internally.