Would the F-35 have been a twin if not for STOVL?

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SpudmanWP

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Unread post22 Jul 2013, 15:19

popcorn wrote:
Corsair1963 wrote:What about the J-31???

Ah! What the F-35 would have turned out to be if not constrained by the STOVL requirement, including two engines to ensure redundancy over water.


IMHO the USAF would have NEVER signed off on a twin engine JSF. Since they are the largest customer by far (along with all the partners) the JSF would still have been a single engined fighter.
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lamoey

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Unread post22 Jul 2013, 15:56

SpudmanWP wrote:
popcorn wrote:
Corsair1963 wrote:What about the J-31???

Ah! What the F-35 would have turned out to be if not constrained by the STOVL requirement, including two engines to ensure redundancy over water.


IMHO the USAF would have NEVER signed off on a twin engine JSF. Since they are the largest customer by far (along with all the partners) the JSF would still have been a single engined fighter.


I agree and it would have become more expensive and less international customers.
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Unread post22 Jul 2013, 17:32

Another thing to keep in mind is that the JORD requirement for internal carriage on the F-35A was for 1k. If the F-35C was of a different design (two engined) than the F-35A, then the present 2k capability would likely never have made it into the F-35A.

That means no 2k JDAM, no JSOW, no JSM, and likely no SDB or 6xAMRAAM at Blk5/6.
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sprstdlyscottsmn

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Unread post22 Jul 2013, 17:47

What do SDB and 6XAAM have to do with 2k carriage?
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Unread post22 Jul 2013, 17:56

SpudmanWP wrote:
popcorn wrote:
Corsair1963 wrote:What about the J-31???
Ah! What the F-35 would have turned out to be if not constrained by the STOVL requirement, including two engines to ensure redundancy over water.
IMHO the USAF would have NEVER signed off on a twin engine JSF. Since they are the largest customer by far (along with all the partners) the JSF would still have been a single engined fighter.
Didn't we have this out with maus a few months back? :roll: .......and where'd the J-31 comment from?
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Unread post22 Jul 2013, 17:59

sprstdlyscottsmn wrote:What do SDB and 6XAAM have to do with 2k carriage?


Space rather than total mass.
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Unread post22 Jul 2013, 18:04

lookieloo wrote: where'd the J-31 comment from?

It was in the F-22 Forum and I thought it better to talk about it here.

http://www.f-16.net/index.php?name=PNph ... 965#255965
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Unread post22 Jul 2013, 19:22

SpudmanWP wrote:
lookieloo wrote: where'd the J-31 comment from?
It was in the F-22 Forum and I thought it better to talk about it here.

http://www.f-16.net/index.php?name=PNph ... 965#255965
That gives me an idea...
http://www.f-16.net/index.php?name=PNph ... 983#255983
... for general J-31 stuff.
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Unread post22 Jul 2013, 20:06

SpudmanWP wrote:
popcorn wrote:
Corsair1963 wrote:What about the J-31???

Ah! What the F-35 would have turned out to be if not constrained by the STOVL requirement, including two engines to ensure redundancy over water.


IMHO the USAF would have NEVER signed off on a twin engine JSF. Since they are the largest customer by far (along with all the partners) the JSF would still have been a single engined fighter.

One of the big factors is that the USAF already have a twin-engine "heavy" fighter called a F-22, and the US Navy have the F/A-18F. Hypothetically, If the were to go with a twin-engine design, the USAF would most likely be pushed towards a 2x F414 variant. There would have to be a very compelling reason for the Navy (other than twin reliability) to go for a clean sheet design over the F/A-18F.

I'm not sure how much this is lobbying, and how much was serious R&D, but Boeing were considering an internal design for a 5th Gen+ fighter for the Air Force, using two smaller engines, along the lines of a F-22 scaled down to F/A-18 size, but without the aerodynamic and design constraints of the legacy F/A-18 or carrier capability. The USAF wouldn't go for it, because the JSF design was further along, and it didn't have enough benefit over a lower risk F/A-18F derivative for the short term.

The other factor, which pushed the Navy towards going for the F-35C as a single-engine is that the F119 and F135 engines, are two of the most reliable fighter engines available. Neither engine has had a uncommanded In-Flight ShutDown incident. One F-22 auto-relighted after a very quick dual flameout. The pilot didn't notice, except for the flight test data. One F119 ingested a large bird and kept running, although the engine was damaged beyond repair. The cracked turbine in a (AF-2?) F135 engine was discovered during ground inspection, not a flight incident.

Compare that to at least one F/A-18F went down because of F414 engine related problems.
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Unread post22 Jul 2013, 22:39

SpudmanWP wrote:
sprstdlyscottsmn wrote:What do SDB and 6XAAM have to do with 2k carriage?


Space rather than total mass.



F-22 main bay is a 2 AMM + 4AAM/8SDB/2-1klb set of bays, the origional requirement would have been the same for the F-35A. 6AMRAAM and SDB would NOT have been effected.
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Unread post22 Jul 2013, 22:55

SpudmanWP wrote:Another thing to keep in mind is that the JORD requirement for internal carriage on the F-35A was for 1k. If the F-35C was of a different design (two engined) than the F-35A, then the present 2k capability would likely never have made it into the F-35A.

That means no 2k JDAM, no JSOW, no JSM, and likely no SDB or 6xAMRAAM at Blk5/6.


Originally, the requirement for the A was the same dual 1K weapons as the B. The A and B are very similar. It was only the Navy that specified the dual 2K capability. For that matter, the C was originally intended to have more sophisticated avionics than the other two. In the interests of commonality and to be all things to all people, the specifications were changed so that all three version would have the larger Navy bay, and would use the same level of avionics and sensors.

For weight reasons, the B later went back to the smaller bays. This didn't bother the Marines because that's all they asked for anyway.
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Unread post22 Jul 2013, 23:19

Just because a 1k JDAM can fit into the space of 2 AMRAAMs does not mean that 2 AMRAAMs can fit into the space of a 1k JDAM.

Keep in mind that the current bay of the F-35B is not the original 1k bay, but a 1.5k bay. Even then, it cannot mount 4 SDBs on a rack as it losses one on the inside corner. A more limited 1k bay would be even smaller.

Btw, I did say “likely” when talking about size limitations.
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Unread post22 Jul 2013, 23:20

The Navy went for the F-35C as a single engine aircraft was because they were told to. Since the USAF JSF was going to be the baseline (which the USMC was OK with, BTW), there was no way DoD was going to let USN's version be essentially a different airplane. Also, despite what is commonly believed, USN really doesn't have a prejudice against single engines. The number of engines on USN jets has been determined more by power needed to do what they wanted vs. available engines.
Last edited by aaam on 23 Jul 2013, 01:57, edited 1 time in total.
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Unread post22 Jul 2013, 23:32

'aaam' said above: (I'm joking right and agree with what 'aaam' says [but do not claim inside USN knowledge just public statements by many senior USN aviators about this issue].)
"...Also, despite what is commonly believed, USN really doesn't have a prejudice against single engines. The number of engines was been determined more by power needed to do what they wanted vs. available engines."

BUT WHAT ABOUT CANADA and there frozen wastelands? :D BTW Canada seems to have gone quiet on the F-35 and single engines. But I do not want to hijack the thread though. It seems the F-35 single engine is more than adequate for the USN.
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Unread post23 Jul 2013, 02:02

spazsinbad wrote:'aaam' said above: (I'm joking right and agree with what 'aaam' says [but do not claim inside USN knowledge just public statements by many senior USN aviators about this issue].)
"...Also, despite what is commonly believed, USN really doesn't have a prejudice against single engines. The number of engines was been determined more by power needed to do what they wanted vs. available engines."

BUT WHAT ABOUT CANADA and there frozen wastelands? :D BTW Canada seems to have gone quiet on the F-35 and single engines. But I do not want to hijack the thread though. It seems the F-35 single engine is more than adequate for the USN.


The North Atlantic and Pacific are no less inhospitable than Canad's frozen North, plus you can't pitch a tent on them or walk somewhere for shelter. At least since the mid '50s, twin engines have not shown they can justify the extra weight and cost they bring solely on reliability grounds.
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