F-35 Lightning II status and future prospects

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energo

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Unread post18 Sep 2009, 20:09

Don't forget our F-35 update:

http://www.f-16.net/news_article3837.html


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SpudmanWP

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Unread post18 Sep 2009, 20:29

I was surprised to see a Blk 3 IRST. I was under the impression from the Norway docs that it was a Blk 5 item.

Good catch.

If Blk 5 is not the first use of IRST, I wonder if it an upgrade to QUIP, multi-band, etc.
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VarkVet

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Unread post18 Sep 2009, 20:41

Actually a very informative article … glad to see the program “stepping up”

This bit confuses me?

“Another example of preemptive measures is found on the folding wing section on the F-35C carrier model. Jets flying in the transonic regime are prone to a phenomenon called "accelerated stall". One way this can occur is in a steep, high G turn where asymmetric shock formation can cause one wing to loose lift -- or stalling -- forcing the plane into a roll, and possibly a spin. Wing drop problems has plagued some earlier fighter programs and due to the inherently unpredictable nature of transonic airflows modern computer tools and wind tunnel procedures are still not refined enough to accurately predict airflows in these cases. As a practical solution Lockheed Martin designers have mounted an aerodynamic spoiler towards the leading edge of the folding wing. In case of a wing drop the spoiler pops up interfering with the airflow and restoring control. This is simply a precautionary step; if the problem does not show up during flight testing, the spoilers will be removed on the production planes. A simple procedure when compared to the extensive task of having to redesign the wing. This kind of "lessons learned" from earlier programs is an essential condition for the F-35 program.”

I’m assuming the spoiler deploys on the opposing wing? Then why remove it if not needed? (just pull and collar the circuit breaker?)
Murphy ’s Law … if you think the wing may stall … someone is going to do it eventually with all configuration changes that will take place in future!

Must be a Stealth thing to take it off the production models?
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FlightDreamz

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Unread post20 Sep 2009, 02:21

VarkVet
As a practical solution Lockheed Martin designers have mounted an aerodynamic spoiler towards the leading edge of the folding wing. In case of a wing drop the spoiler pops up interfering with the airflow and restoring control.

I'm pretty sure this is just a knee jerk reaction to the problems the redesigned F/A-18E&F's had when they scaled up the aircraft from the older F-18A-D's see http://www.cobaltcfd.com/index.php/site/applications/abrupt_wing_stall/ just my :2c:
With any luck those spoilers won't be needed on the production models of the F-35C and will be designed out!
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Thumper3181

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Unread post20 Sep 2009, 02:43

energo wrote:Don't forget our F-35 update:

http://www.f-16.net/news_article3837.html


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Excellent article! Well written and informative. Please keep up the good work.
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johnwill

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Unread post20 Sep 2009, 04:03

Excellent work, Bjornar!

Quote

"Compared to some legacy programs the F-35 is in a favorable position. "We have completed the structural static tests in a mere 350 days". "And without a major problem", Burbage adds. In comparison, the F-22 took about 1000 days, or almost three years, which is more typical for legacy programs. Because of this the F-35 can open up the flight envelope sooner than the jets before it. "We don't have to wait for the structural testing and then slowly expand the envelope", says Burbage. In addition, all the flyable production representative aircraft - the so called SDD vehicles - can fully explore the flight envelope, giving the flight test program more flexibility in the flying schedule."


What Burbage says is misleading, probably because someone in his position simply doesn't understand the details of structural certification. The tests he mentions are ground tests, and provide proof of the strength of the airframe for many different conditions. Those loads are 150% of the largest loads expected in flight. Expected is the key word, as no one knows what the actual loads are until they are verified by flight test measurements. The structure is designed to those expected loads, but until the loads are verified in flight test, the SDD airplanes will not be allowed to fly the full maneuver envelope. Usually the airplanes are limited to 80% maneuvers until the flight and ground tests are complete.

If flight load test shows some loads larger than expected (a common occurence) the over-loaded structure will have to be ground tested to the higher loads or in worst case it may have to be redesigned and retested (a common occurence).



Another correction is needed in the description of the effects of vortex flow over the vertical tails. The vertical tails do not in any way "flutter", nor did the tails on the F/A-18. Flutter is a completely different structural response. The tail are subject to intense vibration from the vortex flow, but do not flutter. Here again, whoever provided this information was probably not familiar with the details of structural engineering.

This sort of thing happens all the time, engineers providing technical details to upper management types, they don't fully understand them, then the information gets passed along, sometimes incorrectly.
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Unread post20 Sep 2009, 07:08

John, very interesting inputs - thanks for your insights always.

Energo, did you actually speak with Tom Burbage and Steve O'Bryan in person, when taking these quotes? Very impressive interview to say the least.

One point of discrepancy I'm still stuck on, and one which SpudMan already eluded to, relates to the actual 'IRST' mode of the 'EOTS'. E.g., It is in fact advertised to RN MoD, that the IRST mode should be expected by the BlockV?

Now I don't have any reason to doubt Mr. O'Bryan's 'confirmation' of a block III 'air-air' IRST standard issue, if that's precisely what he was confirming, but if true, I'll write that up as a definite plus and will indeed make one fewer critical remarks in future critiques.

The problem I have though with all due respect, is in the exact wording of Mr. Obryan's quotes related to the apparent 'IRST confirmation'. And yeah, I'm sorry to be so hard a$$ on this issue, but I guess I'd be more confident if the quote actually said something like "Yes, IRST will be fully functional as part of entire sensor suite and weapon system integration in block III". Not saying that because he is a 'Business development' VP, he might not quite understand all the technical and engineering specifics...

But in cautiously examining his precise wording: "It's a fully functional capability"... "It includes sensor fused input from both the Electro-Optical Distributed Aperture System and Electo-Optical Targeting System sensors..." One has to critically ask: what is 'It'? IRST? Really? Or maybe this sounds more broadly referring to fused sensor/weapon systems' integration?

Maybe I'm wrong, and I'll be first to concede, but just saying there might have been something specifically misunderstood by him in your question, or perhaps he was indeed trying to carefully and justifiably brush over a sensitive detail which was not yet prepared to be discussed publicly? (BTW, not sure if you could include F16.net's actual Question asked of him in this regard?)

And lastly, this line from the article caught my attention: "...MBDA Meteor and IRIS-T missiles... may be considered for integration in follow-on development." Perhaps Python could be added to this 'may be' list? Perhaps, depending on the final foreign customer list, such optional systems will indeed see early block III/IV 'follow-on' development.
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Unread post21 Sep 2009, 01:28

One of the key features of the F-35 is going to be UAI (Universal Armament Interface). The easiest way to put it is Plug and Play for weapons.

It will allow the interface of weapons to be SEPARATE from the block upgrade programs.

Quite literally, after the separation tests are complete and the launch criteria is created, the weapon can be used in any F-35 with the simple upload in the field of said criteria via a "USB thumbstick" like device. Customers will no longer have to wait for block upgrades to get new weapons certified.
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geogen

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Unread post21 Sep 2009, 03:57

As long as JPO/LM can, let's say... find the time and negotiate the special-funding contract to make said 'separation tests' and create the launch criteria? How much time and testing would this entail? The apparent 'JPO' public info regarding this issue just sounds a bit more iffy than a simple USB thumbstick upload?

They are finding themselves in a rather beneficial advantage, being a so-to-speak 'gatekeeper' of what gets plugged in?
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Unread post21 Sep 2009, 20:33

I did not say that the USB method will bypass the LM firewall, just the block upgrade method.

For example, it was recently released that many F-22s will not be able to carry the Aim-9x or AIM-12D because their computers cannot be upgraded to handle them without full replacement. Since the 9X and 120D uds the same launch rails and are otherwise compatible, all that is needed is the launch criteria.

In the F-35 (and other AC soon) the AC is updated via the MPI (Mission Planning Interface). No actual USB needed.

Here is a presentation from 2005 that lays out UAI pretty well.

http://www.jauswg.org/working_group/Jul ... 0Gibbs.pdf
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energo

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Unread post22 Sep 2009, 22:57

First of all, thank you all for your comments. I knew we could count on our expert panel for some good critique. :thumb:

VarkVet: Excellent question. As I understand the spoiler works similarly as some other legacy jets and kills the lift on one side. According to LM it would only be used in an extremely small portion of the flight envelope, at a particular mach number regime and angle of attack. It is, however, not expected to see any use. Removal will save weight, cost and complexity and is relatively easy to change on the production line.

SpudmanWP, geogen: Yes you are correct - as you mentioned on ELP's blog - that the Block 3 EOTS/DAS IRST is for air-to-air. Block 5 will extend the capability with air-to-surface modes. I most certainly will try to elaborate better in the future! My question was directly related to the Norwegian brochure and whether the EO sensor fusion would be integrated Block 5 or sooner.

JohnWill: Very good input there. Perhaps it's my poor choice of words, not beeing a professional. I suspect you are correct, I did not intend to say that the placard or limits (that is: full envelope) will be established first thing. However Burbage was talking about how the fleet of SDD or Flight Sciences aicraft will not be subjected to restrictions in the same way as some legacy programs, and thus that they will be able to explore the envelope quicker.

Indeed Burbage was talking about vibrations. Thank's for pointing out. I might have misheard the terms "buffet" and "flutter". Being a former Navy test pilot I'm guessing that Burbage is aware of the distinctions.


BTW, we uploaded a new higher res version of BF-3 with the gun pod close-up:


The F-35B with a full load of external weapons, including the 25mm gun pod as seen on August 10th, 2009. [Lockheed Martin photo]



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SpudmanWP

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Unread post23 Sep 2009, 00:00

Thanks for the clarification.
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StolichnayaStrafer

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Unread post23 Sep 2009, 23:56

That gun pod looks pretty radical- and stealthy too! :twisted:
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geogen

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Unread post24 Sep 2009, 06:42

energo -

I'm sorry for the relentless barrage of questioning but you noted:
My question was directly related to the Norwegian brochure and whether the EO sensor fusion would be integrated Block 5 or sooner.


Is that precisely how you asked the question, when it was posed to the F-35 project Business development VP?

It's just that.. could that question be perceived as slightly generic in scope? Being answered with a form-response: 'Yes, it will be functional by Block III'? 'It' being merely a vague EO sensor fusion? I mean, surely, there will be some fully functional EO sensor fusion integrated by mature block III delivery?

And also, excuse me for following up on a minor technicality.. but you mentioned: DAS IRST?? Is that different from an 'EOTS IRST' mode? I guess myself and others would expect the 'IRST' mode to be linked to the EOTS and NOT the DAS per se? Thanks for any follow up..

Respects-
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Unread post24 Sep 2009, 07:01

EODAS IRST is WVR range only and the EOTS IRST is the long-range unit under the nose.
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