F-35A Stealth Test OK

Lockheed Martin’s F-35 Fighter Jet Passes Initial Stealth Hurdle By Tony Capaccio - May 5, 2011

http://www.bloomberg.com/news/2011-05-0 ... urdle.html

"Lockheed Martin Corp. (LMT)’s F-35 fighter jet has passed its initial radar-evasion testing and there are no “major potential changes contemplated for any of the stealth design,” according to the U.S. program office.

The program office has collected radar cross-section information on the Air Force version of the aircraft and “we are very pleased, very pleased,” U.S. Navy Vice Admiral David Venlet, the program manager, said in an interview.

Still, “this is not a one-test ‘Eureka’ and it’s done,” he said. The Air Force version will comprise the greatest number of the 2,457 planned F-35s.

Venlet said he expected similar results from the Navy and Marine Corps short-takeoff-and-vertical-landing versions when they are tested. Lockheed Martin in November measured two early- production Air Force models, which also passed with no “major variances,” Venlet’s office said.

“So we do not have major concerns,” Venlet said. “We are always going to pay attention to it, because if you don’t, it will always be a source of rework and cost growth. But as early as we are, we are very pleased.”

The F-35 is being developed as the Pentagon’s premier fifth-generation stealth fighter, capable of penetrating the heaviest enemy air defense. When fielded, it would join the B-2 bomber and the F-22 fighter in the U.S. stealth jet inventory.

DCMA Concerns
The Pentagon’s Defense Contract Management Agency told congressional investigators that it had “noted difficulties” with Lockheed Martin manufacturing of the aircraft’s outer surface, or “mold line.” The process involves detailed attention to the skin’s finish, fasteners and drain holes that affect an aircraft’s radar-evading profile.

The U.S. Government Accountability Office, in an F-35 report last month based on DCMA input, said the “inability to meet the outer mold line requirements could have major impacts on cost as well as stealth requirements and capabilities.”

“This problem is not expected to be resolved until the June 2015 time frame, after which a large number of aircraft will have been built and would need to be retrofitted for any design changes,” the GAO wrote.

Venlet said the DCMA raised valid concerns and reflected “signs of the early attention being paid” to outer mold line manufacturing tolerances “because it can’t get out of control.”

The DCMA’s reports “are extremely accurate, and we act on them,” he said. “It triggered attention, drove action.” Action has been taken to “optimize production for stealth requirements,” his office said.

Lockheed Martin spokesman Michael Rein said in an e-mail that “while there are challenges in holding tight tolerance specifications, all F-35s are meeting the requirements and are compliant in form, fit, function and stealth.”

“Manufacturing improvement processes and changes are in place to address tolerance challenges,” Rein said, and more changes are being made “to continually improve the product.”...

I'm a bit vague on what the problem with the mold line is all about. If its an issue of improving the production process then why retrofit earlier production JSFs w/c apparently have aced their stealth tests? Are they implying the JSF's stealthiness will be degraded with time thus requiring a retrofit?

Because the GAO is flat wrong, and finally JPO got around to stating it. The GAO is playing the telephone game, and got the wrong message at the end of the line.

good news.

I think “we are very pleased, very pleased,” sounds like the results were exceptionally good. Better than some had expected or predicted.

I'm guessing the mold line problem refers to where individual composite panels meet and any discrepancy in height between two (or more) panels at the mating joint.

That WOULD be a manufacturing nightmare if tolerances among many individual parts and assemblies of parts were not being held very, very tightly. Holding those tolerances in a production environment where they're building an aircraft per day is going to be really challenging.

stereospace wrote:Holding those tolerances in a production environment where they're building an aircraft per day is going to be really challenging.

Not particularly if you have good tooling and talented people.

stereospace wrote:Holding those tolerances in a production environment where they're building an aircraft per day is going to be really challenging.

And thats what Venlet is referring to. There's no question that its hard, especially with a VLO jet that also has to be supportable. The easiest way to hold OML tolerances on anything (jets, cars) is to spend more money on fabricating parts so that your parts are delivered exactly as you designed them. These "Cadillac" parts are always perfect, but they cost a fortune. So you run into another "conflicting" requirement: cost. So, at the beginning of the program you have to predict the right balance between all of these conflictng requirements. When you actually start building aircraft, you may have to "re-tune" this balance based upon reality. I think this is a perfect example of that. Usually there are many different options/ways to "re-tune", and sometimes it takes some ingenuity and creativity.

F-35A AF-3 In Acceptance Test Facility

http://www.codeonemagazine.com/gallery_ ... lery_id=44

"F-35A AF-3 is the first flyable F-35 to go through the Acceptance Test Facility. The facility is used to measure radar cross section to ensure that the aircraft meets low observable requirements. The facility was used to test the full-scale pole model of the F-35 in 2009. AF-3 was tested in late October 2010. Photo by Randy Crites - Photo Posted: 14 December 2010

BigPic:
http://www.codeonemagazine.com/images/m ... 7_2552.jpg


____________________________________________

BigPic:
http://www.codeonemagazine.com/images/m ... 7_1506.jpg

Some articles about stuff:

Laser Measurement Guides Aerospace Assembly May 2007 Vol. 138 No. 5 Patrick Waurzyniak, Senior Editor

http://www.sme.org/cgi-bin/find-article ... 0509&&SME&

"With laser-based aircraft alignment system, wing and fuselage components for F-35 fighters find perfect fit."
_____________________

The Digital Thread - Key to F-35 Joint Strike Fighter Affordability 9/1/2010
"What do lasers, robots, fiber placement, electronic mate, and highly accurate gantry machining have in common?
These technologies are pieces of the Lockheed Martin F-35 Lightning II manufacturing system, woven together."

http://www.onlineamd.com/amd-080910-f-3 ... hread.aspx

"Specialized Equipment
Unique to the F-35 is the use of highly accurate NC technology to machine composite skins and substructures to eliminate shimming and facilitate excellent control over the outer mold line of the aircraft."

LMAggie wrote:

stereospace wrote:Holding those tolerances in a production environment where they're building an aircraft per day is going to be really challenging.

The easiest way to hold OML tolerances on anything (jets, cars) is to spend more money on fabricating parts so that your parts are delivered exactly as you designed them. These "Cadillac" parts are always perfect, but they cost a fortune. So you run into another "conflicting" requirement: cost.

Hopefully, as the suppliers climb the learning curve, the Cadillac parts get easier and cheaper to produce as tooling get adjusted and processes perfected, or replaced with better tooling and processes. I suspect that could take years. Meanwhile, you have buyers demanding their Cadillacs at (what was promised as) Camry prices.

If LM survives the transition from a 4th to 5th generation aircraft producer without bankrupting themselves, they'll be well positioned for the future. But change is hard, and massive change is massively harder. LM and its suppliers have a rough road ahead. Good luck to them. Sincerely. Let's all hope they succeed.

(Off topic but related, Boeing is going through their own transformation by producing their composite fuselage 787 Dreamliner. Good luck to them as well.)

stereospace wrote:

LMAggie wrote:

stereospace wrote:Holding those tolerances in a production environment where they're building an aircraft per day is going to be really challenging.

The easiest way to hold OML tolerances on anything (jets, cars) is to spend more money on fabricating parts so that your parts are delivered exactly as you designed them. These "Cadillac" parts are always perfect, but they cost a fortune. So you run into another "conflicting" requirement: cost.

Hopefully, as the suppliers climb the learning curve, the Cadillac parts get easier and cheaper to produce as tooling get adjusted and processes perfected, or replaced with better tooling and processes. I suspect that could take years. Meanwhile, you have buyers demanding their Cadillacs at (what was promised as) Camry prices.

If LM survives the transition from a 4th to 5th generation aircraft producer without bankrupting themselves, they'll be well positioned for the future. But change is hard, and massive change is massively harder. LM and its suppliers have a rough road ahead. Good luck to them. Sincerely. Let's all hope they succeed.

(Off topic but related, Boeing is going through their own transformation by producing their composite fuselage 787 Dreamliner. Good luck to them as well.)

One of the answers to using non-Cadillac parts is shimming. So Boeing and LM may be looking at automated shimming techniques to help with tight OML tolerances.

Good to see they're using a flyable F-35(A) for radar tests Spaz. I have to admit though I expected that to look more like this
http://www.codeonemagazine.com/images/m ... 7_5738.jpg

FlightDreamz wrote:Good to see they're using a flyable F-35(A) for radar tests Spaz.

Not just flyable, but production representative. Were it me, I'd get baseline numbers right off the line (like this), fly the jet for a year, retest it, fly it another year, test again. Rinse and repeat. That should establish how well the coatings and seals are holding up over time.

Fair enough about whatever the Acceptance Test Facility is called with several parts to it it looks like as per FlightDreamz:

F-35 Anechoic Chamber Testing By Eric Hehs Posted 25 October 2010

http://www.codeonemagazine.com/article.html?item_id=57

Posted here: http://www.f-16.net/f-16_forum_viewtopic-t-14673.html