Forum: F-35 Engine

spazsinbad wrote:

According to the current KPP (elaborated on threads many times now) the F-35B can operate as required regarding STO and VL. What we do not know are the conditions of WX for these conditions - hence discussion.

The 'unfavourable condition' needs to be quantified but is meaningless when we also don't know the 'power available margin' but it is known to be within KPP for the KPP condition - so it goes. Maybe some online hackers know? Rolling Eyes

Clear enough, thanks.

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spazsinbad wrote:

Tame? What a funny choice of words. How about 'tropical day 90 degrees F' and 'hot day 103 degrees F'? And we are still guessing what it is 'East of Suez'. Also we have only a 'Scoreboard' assessment of what the KPP conditions are. We have no inkling what 'the powers that be' consider the conditions for KPP to be. The 'Scoreboard' is the only reference I have seen (apart from East of Suez malarkey). If you consider a 13 degree F difference a show stopper then be my guest.

It is possible to use aircraft takeoff distance charts to figure out what that F difference might make on it; but let us not forget our runway can make more speed into wind, which is likely to cater for such matters.

90F is pretty tame as far as gas turbine design points go. 103F is pushing it a bit. And conditions exceed 103F in certain areas. 13F difference at the inlet makes a huge difference to the turbine performance, and don't forget that for any non nuclear carriers, the runway will also see the same performance deterioration (and if the rest of the fleet is going the other way, you don't really want to be steaming upwind any longer / faster than necessary....)

Much Ado About Nothing - just guesswork - without facts.

spazsinbad wrote:

Much Ado About Nothing - just guesswork - without facts.

Isn't that always the problem with APA type arguments?

That_Engine_Guy wrote:

[.I'm looking for documentation about the state of any sea going corrosion proofing for the F-35B STOVL engine.... According to MIL-HDBK-516B both engines have the same materials requirements....TEG

My issues;

1- my reference? "The major difference between the -100 and -400 models is the use of salt-corrosion resistant materials". no document is referenced. Is any document available?

2- my results of examining the PW contracts announcements from the Navy;

137 propulsion systems on order thru LRIP 6
11 spare engines
??? modules & spare parts (what are engine modules (FADECs?))

price averages

-100 $2.872 million
-400 $2.967 million
-600 $4.722 million

-100/ -400 delta $95 thousand
-400/ -600 delta $1.755 million (fan assembly, roll posts, exhaust nozzle)

9 contracts and modifications from 2001-2012 at $8,778,948,634.00 for; studies, special tooling, spare parts, spare modules, spare engines and the 223 propulsion systems, etc. Question

neptune wrote:

My issues;

1- my reference? "The major difference between the -100 and -400 models is the use of salt-corrosion resistant materials". no document is referenced. Is any document available?

Wikipedia references an article that says as much. I've seen it before, and the P&W individual quoted in the article said so. I've referenced it before; nobody ever said it didn't say what I said it said, in nearly a year of it being online in these forums. Unfortunately, that article is no longer available, so the reference is indirect now. Wikipedia also references, specifically for that point about corrosion resistant materials, an article from Jane's. Unfortunately I don't have a subscription to Jane's.

Quote:

2- my results of examining the PW contracts announcements from the Navy;

137 propulsion systems on order thru LRIP 6
11 spare engines
??? modules & spare parts (what are engine modules (FADECs?))

price averages

-100 $2.872 million
-400 $2.967 million
-600 $4.722 million

-100/ -400 delta $95 thousand
-400/ -600 delta $1.755 million (fan assembly, roll posts, exhaust nozzle)

Remember though the -600 is being built in smaller numbers, and has a lot more parts. The -400 is just a -100, possibly with different materials used in some places. Both all the extra parts, and the paltry build numbers of the extra parts for the -600, raise the price. Nearly $100K for a few parts of the -400 (shaped exactly the same as the parts of the -100) to be made of a different alloy?

So I'd reverse this. Does anyone have a reference specifically saying the materials are identical between the -100 and -400? If they're the same engine, why any price difference at all?

I've been giving that some more thought, and as TEG pointed out, the corrosion resistance is likely to be more important in the hot sections. Heat accelerates chemical reactions. The cold sections may exceed any needed corrosion resistance needs in all three variants. That may explain why the -600 is not mentioned as having specifically corrosion-resistant materials. Mentioning it may be redundant. In other words, the -600's unique exhaust including 3BSM may already be made of the same materials as the exhaust module of the -400. Furthermore, the -600 can't take off on afterburner at sea, so the afterburner module may not need the extra corrosion protection since it won't be as hot when it's exposed to salt. The -100's afterburner may already meet corrosion specs for the F-35B's operation.

Modules as I understand it is that the F135 is designed to be quickly broken down into a few pre-made assemblies. You don't necessarily have to disassemble much to replace a fairly inaccessible bad part. You can quickly swap out the entire compressor module, burner module, augmentor module, etc. of the engine, and the engine is back airworthy very quickly. Then you can disassemble the removed module and fix that part more at your leisure. They probably bought a few spares of modules that might need more frequent replacement than the others. You probably also don't need the same stock of replacement engines if you can just stock e.g. a few more hot turbine modules.

Forum: F-35 Engine

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