Forum: F-35 Lightning II

Newbie Joined: Aug 29, 2006 Posts: 11 Status: Offline

I can picture a massive f-135 with a USB cable dangling down!! lol

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Elite Joined: Jul 22, 2005 Posts: 955 Status: Offline

VarkVet wrote:

Quote:

I agree that financially it would not make sense for the US to have two different engines, but as has been argued in this forum before, when one engine is grounded for a suspected problem, the other is most likely flying. Do you want to ground all "3000" F-35's or only those with the "other" engine?

I concur … single engine; single engineer blunder during the design process can leave a lot of “holes” (aircraft without engines) on the flightline if a major engine problem is encountered. (Seen it before)

When will the fault show up? (If any) IFT 100, 200, 1000 hours? I have confidence that if such an anomaly exists, it will be caught at Edwards during flight test and fixed before we need to rely on the F-35 for combat.

In my opinion, the root of the problem is single engined fighter

Interface … plug and play between PW, GE and RR “THAT’S BRILLIANT”

Thing is nothing with a J-75, J-79, J-57, or TF-30 ever had a second engine readily available and they seem to have done alright. And technically they don't right now anyway. Yes F-16s and F-15s have flown with both the F100 and F110 but can you roll either into a hanger, pull out the F100, stick in the F110 and go fly? The fact that the F-16 (and to a lesser degree the F-15) ended up that way is an anomoly that would have never existed had the F101 not been easily modified into a fighter-sized engine.

Elite Joined: Dec 19, 2005 Posts: 651 Status: Offline

VarkVet wrote:

Quote:

I agree that financially it would not make sense for the US to have two different engines, but as has been argued in this forum before, when one engine is grounded for a suspected problem, the other is most likely flying. Do you want to ground all "3000" F-35's or only those with the "other" engine?

I concur … single engine; single engineer blunder during the design process can leave a lot of “holes” (aircraft without engines) on the flightline if a major engine problem is encountered. (Seen it before)

When will the fault show up? (If any) IFT 100, 200, 1000 hours? I have confidence that if such an anomaly exists, it will be caught at Edwards during flight test and fixed before we need to rely on the F-35 for combat.

In my opinion, the root of the problem is single engined fighter

Interface … plug and play between PW, GE and RR “THAT’S BRILLIANT”

Further, you have to look down the road also! You can't keep your technological base without competition. That's like everyone using the same car at the race track...................

Some good points. Lets take it further. As some may know there was a PW engine in waiting for the Super Hornet which currently uses GE. If alternate engines are so useful, one would think the PW should have a chance at Super Hornet customers for best value Laughing

http://www.flightglobal.com/articles/20 ... -18ef.html

Quote:

The PW7000 would use the combustor, high-pressure turbine and compressor from the commercial PW6000 along with a scaled low-pressure turbine and fan from the JSF119 engine. The engine is sized as a F414 drop-in replacement, with a 5:1 bypass ratio and up to 25% more thrust. P&W claims it would extend F/A-18E/F range by 31%, increase acceleration by 27% and boost meantime between overhaul to 1,000h.

Elite Joined: Jul 22, 2005 Posts: 955 Status: Offline

P&W should be using this kind of pork-barreling to get the F119 on the B-1 Wink

What if the F136 turns out to put out higher performance in the end? Isn't it worth it then? It sounds to me like the F-16 engine situation worked out well. The two companies designed engines with different by-pass ratios for the F-16, and now customers get a choice of engine based upon the needs in their country. As far as the plug-n-play goes with the F135 and F136, the JSF team is driving requirements that mandate this. Yes, we poored a bunch of money into what seems like a "copy", but I think the rewards will be huge in the long run.

Elite Joined: Dec 19, 2005 Posts: 651 Status: Offline

LMAggie wrote:

What if the F136 turns out to put out higher performance in the end? Isn't it worth it then? It sounds to me like the F-16 engine situation worked out well. The two companies designed engines with different by-pass ratios for the F-16, and now customers get a choice of engine based upon the needs in their country. As far as the plug-n-play goes with the F135 and F136, the JSF team is driving requirements that mandate this. Yes, we poored a bunch of money into what seems like a "copy", but I think the rewards will be huge in the long run.

Its very likely the GE F-136 will produce more thrust than the current P&W F-135. As a matter of fact I believe its a much more advance design? The P& W while less powerful was consider safer. (i.e. less risky)

I thought that was the case for the GE F120 vs. the PW F119. I don't believe GE even had a flyable engine for the flyoff competition between X-32 and X-35.

Hi Corsair,

I am going to see if I can find the source as I am going by memory, your statement brings up some good points.

Were there not some testing concerns some time back of putting the PW in for STOVL service? In that in order to... ( and this may have tied in with the SWAT STOVL weight reduction event a few years ago )... make the PW do what they wanted with the STOVL they had to juice up the thrust in excess of the original requirement for the engine and this was bringing in other concerns such as heat and the kinds of quality of engine output that the engineers preferred.... so my question would be: Will the PW make a suitable STOVL engine particular to the weight of the STOVL aircraft in combat trim while doing vertical activity?

Some additional reading here:
http://www.sbac.co.uk/community/cms/con ... =10527&t=0

Interesting as they state the PW met the spec requirement yet they were doing this.

Note: The obvious, I am not an engine troop or engineer.

Elite Joined: Aug 02, 2006 Posts: 932 Status: Offline

elp wrote:

Hi Corsair,

I am going to see if I can find the source as I am going by memory, your statement brings up some good points.

Were there not some testing concerns some time back of putting the PW in for STOVL service? In that in order to... ( and this may have tied in with the SWAT STOVL weight reduction event a few years ago )... make the PW do what they wanted with the STOVL they had to juice up the thrust in excess of the original requirement for the engine and this was bringing in other concerns such as heat and the kinds of quality of engine output that the engineers preferred.... so my question would be: Will the PW make a suitable STOVL engine particular to the weight of the STOVL aircraft in combat trim while doing vertical activity?

Some additional reading here:
http://www.sbac.co.uk/community/cms/con ... =10527&t=0

Interesting as they state the PW met the spec requirement yet they were doing this.

Note: The obvious, I am not an engine troop or engineer.

Well, think about it for a second. The F135 is rated for 28,000 lbs dry in regular mode. For STOVL mode the P&W engineers have to get it to 39,400 lbs dry. In fact, they got it to 40,550 lbs. That is a 45% increase in dry thrust with essentially zero airspeed. The only thing that physically helped increase the output of the engine is the lift-fan which allows for higher mass airflow. The core is undoubtedly being asked to work overtime. It's a tall order.

Part of what resulted was an operating temperature that is higher than they will like. 190 degrees F (~104 deg C) higher to be exact. But they have addressed the problem in part by tweaking the top intakes and in part by adjusting the bypass ratio slightly. Part of the problem with the temperature is that the F-35 is targeting higher mean time between overhaul numbers than previous aircrafts (6000 hours).

The F-136 has a larger core -- it is based on the F-120 engine which has a larger core than the F-119. So, perhaps this is a non-issue for it.

dwightlooi wrote:

The only thing that physically helped increase the output of the engine is the lift-fan which allows for higher mass airflow. The core is undoubtedly being asked to work overtime.

Just a point of clarification: the JSF lift-fan is coupled to the low-pressure spool (same as the fan), not the high-pressure spool (or engine core).

Another think-tank weighs-in on the costs and merits of funding an alternative engine for the F136:
http://lexingtoninstitute.org/1156.shtml

The more I read, the more convinced I become that there is no cost benefit from funding a second engine manufacturer. If this idea was such a cost saver, then the Navy would already have funded two engine designs for the F-18, and the Air Force should have two different engines under the F-22. The development, tooling, and logistics cost for two separate designs are just prohibitive.

The only rationale for funding a second source I can imagine (other than the pork barrel politics that is currently driving support for the F136), would be if it somehow salvaged the American defense industrial base. Even that argument rings hollow, however. GE will be providing spares for the F110, F404, and F414 for a long time to come - and they already dominate the civilian marketplace between the CFM-56 and GE90. Neither GE nor P&W are going out of business anytime soon.

Given the current budget status, I'd have to fall on the side of those opposing the whole "alternative" engine concept. Our warfighters need more F-35's in their future inventory, not more choices or two sets of spare parts to stock.

Elite Joined: Dec 19, 2005 Posts: 651 Status: Offline

Only only way to build a better mouse trap is to have competition! Which, gives the US the Superiority that won the cold war and many conflicts over the last half century. You never want to be just as good...................With all likely hood the GE Powerplant (i.e. F-136) will have higher performance and keep both designs on the cutting edge. "Competition is Always Good"

Elite Joined: Jul 22, 2005 Posts: 955 Status: Offline

dwightlooi wrote:

Well, think about it for a second. The F135 is rated for 28,000 lbs dry in regular mode. For STOVL mode the P&W engineers have to get it to 39,400 lbs dry. In fact, they got it to 40,550 lbs. That is a 45% increase in dry thrust with essentially zero airspeed. The only thing that physically helped increase the output of the engine is the lift-fan which allows for higher mass airflow. The core is undoubtedly being asked to work overtime. It's a tall order.

Part of what resulted was an operating temperature that is higher than they will like. 190 degrees F (~104 deg C) higher to be exact. But they have addressed the problem in part by tweaking the top intakes and in part by adjusting the bypass ratio slightly. Part of the problem with the temperature is that the F-35 is targeting higher mean time between overhaul numbers than previous aircrafts (6000 hours).

The F-136 has a larger core -- it is based on the F-120 engine which has a larger core than the F-119. So, perhaps this is a non-issue for it.

A couple of fixes. The F135 has never produced nor does it have to produce 39,000lbs dry. When the F-35 is in hover only about 13,000-18,000lbs is being produced by the exhaust of the engine with the rest being generated by the lift fan and roll posts. The X-32 was another matter but even then it was about 35,000 dry (which turned into 52k in full afterburner- and it was not today's F135).

What info do you have on the relative core sizes of the F119 and F120? Were you aware that the reason for the YF119 having lower thrust than the YF120 was due to P&W sizing the engine for the original 50,000lb airframe requirement while GE bumped their's up to deal with the revised 60,000lb airframe requirement? And that P&W rectified that in the production F119? What is your source of info that indicates today's F119 has a smaller core than the YF120?

Corsair1963 wrote:

Only only way to build a better mouse trap is to have competition! Which, gives the US the Superiority that won the cold war and many conflicts over the last half century. You never want to be just as good...................With all likely hood the GE Powerplant (i.e. F-136) will have higher performance and keep both designs on the cutting edge. "Competition is Always Good"

Wasn't this done during the "X phase" of this program? Isn't that how it's always been done? The engine that has the performance, weight, and price for the program wins? At which point the other engine is dropped. Buying 2 different engines AFTER you've already decided to buy a fighter is dumb in my book. (F-16 mixed fleet is a prime example of what NOT to do... Sad

)

If GE (or any other country) thinks the F136 is such a good option, why aren't they funding it? Idea

Call it investment? No, they want US tax-payer money to do the job, even though the US Government has decided against the F136 once, twice, do I hear three times? Shrug

It makes me mad being one of those tax payers, knowing they are still spending MILLIONS of dollars doing studies and research (of which none actually goes to making F-35s) just to determine IF they should reinstate F136 funding!? WTF

Say what they want about savings, but long term logistics supporting 2 different motors quickly kills any initial savings.

Upgrades are another matter; If you have a budget to enhance your engines with durability improvements over the next 30 years, (Like both USAF has done with the F100/F110) you need to split the money between both engines to support the F-35 program as a whole. (or double the budget to do so?)

How much are we saving here Question

Again it seems we're spending money in the name of saving it... Two Cents

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Forum: F-35 Lightning II

The engine no one wants - Except congress