F-35 faults may delay USMC IOC

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smsgtmac

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Unread post30 Jan 2014, 14:34

spazsinbad wrote:A FlightGlobal look at the DOTE report.

F-35 faces familiar dogfight with competing facts 30 Jan 2014 Stephen Trimble
"...Although the teams are making progress, the F-35’s engineers are still struggling with overcoming the aircraft’s tendency for transonic roll-off and buffet, according to the report. The condition affects all supersonic fighters to some degree, but has appeared particularly acute on the carrier variant F-35C. Programme engineers have exhausted options for altering the flight control laws to compensate. Testing is still under way to decide if using leading edge spoilers on the F-35C will be necessary, the report says."

http://www.flightglobal.com/news/articl ... ts-395397/

Tons of stuff about the usual at the URL above.


I was perusing the report last night, and aside from statistical crimes against humanity the offending paragraph (pp.38-39) Trimble refers to stood out on its own: as the single best example of obscuration of a positive fact. Translated it says: "we haven't even tried to use the leading edge spoilers yet, which we can, but we don't want to because of software commonality".

The whole 'buffet and rolloff' so-called "issue" is, as "they" say -- 'cr*p'. I posted sometime ago that it probably comes down to past experience. I anticipate F-16 drivers transitioning in may experience "wow" moments, while F-15 drivers coming in may be thinking "wow, this is nothing".
--The ultimate weapon is the mind of man.
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Unread post30 Jan 2014, 17:59

Last night that last paragraph was highlighted / extracted because I was going to ask 'what does this mean'? But being very late I decided to just let it be as it was. I think Trimble has in mind the spoilers on the wings left unused - potentially - until now. Early Cs have them while AFAIK the further manufacture/installation of them for use was undecided. I think this is what Trimble is getting at in that paragraph; but that is not clear. Trimble is the reporter - I'm the reader - it should be clear to the reader what he is saying. Right? :D From the report:
".......F-35C discoveries included:
- Buffet and TRO continue to be a concern to achieving operational combat capability for all variants. Control laws have been changed to reduce buffet and TRO in the F-35A and F-35B with some success; however, both problems persist in regions of the flight envelope, and are most severe in the F-35C.

- Characterization testing of buffet and TRO in the F-35C with the current control laws and without the use of leading edge spoilers is ongoing. Unlike the other two variants, the program has the option to conduct flight testing with leading edge spoilers to reduce buffet and the onset of TRO with two of the F-35C flight test aircraft if trade-offs made in control laws are not sufficient to manage the negative impact of these effects...."


Here I presume the 'leading edge spoilers' are these?
http://sitelife.aviationweek.com/ver1.0 ... .Large.jpg

Also similar photo Zoomed when used in article below....
http://sitelife.aviationweek.com/ver1.0 ... .Large.jpg

Last I recall reading somewhere the thinking was these spoilers were going to remain unused. I'll look for that quote, meanwhile here is some old info:

F-35C Spoiler Tackles Wing Drop 05 Aug 2009 Graham Warwick
"A postscript to last week's roll-out of the F-35C carrier variant: I noted a spoiler on the upper surface of the folded wingtip that I did not recall being mentioned before, and wrongly concluded it had been added to reduce carrier approach speed.

The spoilers have been installed as insurance against wing drop, the aerodynamic phenomenon that proved so time-consuming to overcome on Boeing's F/A-18E/F Super Hornet.

F-35 deputy program manager J.D. McFarlan revealed the reason for the spoilers at the AIAA Joint Propulsion Conference in Denver yesterday (August 4). Wing drop can occur at transonic speed as a fighter approaches high turn rates, he says. One wing sets up a shock at a slightly different location to the other wing. This produces a lift gradient, one wing drops and the aircraft rolls in the turn.

After the F/A-18E/F experience, Lockheed Martin conducted windtunnel tests specifically to look for wing drop. On the CTOL F-35A and STOVL F-35B, J.D. says, careful scheduling of the leading- and trailing-edge flaps looked to control the phenomenon, but on the CV F-35C the combination did not seem enough. So the decision was taken to add the spoilers, which pop up to disturb the flow over both wings and keep the aerodynamics consistent on left and right.

J.D. says the leading- and trailing-edge flap scheduling has been flight-tested on the first F-35A, aircraft AA-1, and shown to work. The spoilers on the F-35C are described as a flight-test mitigation. If they prove not to be needed, they will be removed on production birds and the wing cavities "scabbed" over. J.D. says the hydraulically actuated spoilers are about 18in long by 5in wide and add only 10lb...."

http://www.aviationweek.com/blogs.aspx? ... 7414e42786
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Last edited by spazsinbad on 30 Jan 2014, 20:11, edited 1 time in total.
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Unread post30 Jan 2014, 18:14

Here ya go... the quote a bit old perhaps - again.

F-35C: Spoiler alert! 05 Aug 2009 Stephen Trimble
"...Lockheed currently believes the potential wing drop problem can be resolved with flight control software changes, but the spoiler will be added at least for the flight test phase....

...If you're wondering how the spoiler will affect the F-35C's radar cross section, Coppinger put that question to Lockheed executive JD McFarlan, who replied: "It has been designed to be LO [low observable, or stealth]-compliant"."

http://www.flightglobal.com/blogs/the-d ... ler-alert/
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Another reference same time: http://www.flightglobal.com/articles/20 ... light.html
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Unread post30 Jan 2014, 18:22

Here is the recent 2012 reference I had in mind earlier. However as often is the case I have misremembered the aircraft - it was the B and not the C.

Inside the Navy - 01/30/2012 - Software fixes should resolve issue, program said JSF JPEO: F-35B Probably Won't Need Spoiler For Airflow Problems Posted on InsideDefense.com: January 27, 2012
"...He noted that the program office was "hopeful it will not be needed, but they do not have the final answer yet."...

Inside-the-Navy/Inside-the-Navy-01/30/2012/jsf-jpeo-f-35b-probably-wont-need-spoiler-for-airflow-problems/menu-id-xxx.html
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Unread post30 Jan 2014, 19:24

Then there is this recent item which was vaguely to mind... unspecific and not that helpful - perhaps this is a storm in the cup-de-tea?

Don’t Ask ALIS, Yet; F-35 Wing Drop Issue Fixed 12 Aug 2013 Colin Clark
"
"On the other hand, wing drop is no longer a performance issue for the F-35, contrary to claims in some quarters, our authoritative source at the Pentagon tells us. The issue is, as almost always, much more complex than that simple statement indicates, but it’s been 18 months since the issue surfaced and software fixes leave the Joint Strike Fighter in fine shape, this source says."


What happened? Basically, new algorithmns were written, tested in the trans-sonic envelope where most of the problems occurred and the services found a solution that didn’t completely eliminate all drop at all times but left the plane performing to the highest standards achievable. In short, they found a problem and fixed it to a standard all three services could live with."

http://breakingdefense.com/2013/08/dont ... sue-fixed/
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Unread post30 Jan 2014, 19:39

Aaahhh the interwobble - full of stuff...

How the F-35 is designed to work 01 Apr 2012 Casey Coane
"Editor’s note: In late February, AUSN traveled to Naval Air Station (NAS) Patuxent River, Maryland, to interview Lt. Col. Matt Taylor, USMC, a test pilot in the F-35 program. A graduate of Georgia Tech, Taylor is an F/A-18 Hornet pilot with carrier deployments in his log book. He was the first pilot to take the Navy’s F- 35C up to Mach 1.4. He is also one of the first Marine non-Harrier pilots to perform a vertical landing in the STOVL F-35B. We walked the hangar and looked at a number of both C and B model aircraft and then went to a conference room for the interview....

...AUSN: I believe that Lockheed pre-designed some spoilers in the wing in case we got into that transonic region and found flutter that needed to be corrected. Are those spoilers now going to be needed?

Lt. Col. Taylor: What you are talking about is called “transonic roll-off.” When you are under “G” in a loaded turn near or slightly under Mach 1, the predictions show that we may see some uncommanded roll in the airplane. One way to counter that is with spoilers. They did put spoilers on in case we needed them. That testing is still ongoing. What we have seen so far is that it is not as severe as was predicted. In any case, whether we end up using the spoilers or not, the pilot will not know the difference. The airplane is going to fly like he wants it to in the transonic region...."

http://www.ausn.org/NewsPublications/Na ... -work.aspx
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Unread post03 Feb 2014, 23:53

The IEEE's take on software (and other) troubles:

"The F-35 Program Office complained that while Gilmore’s report “was factually accurate” it “did not reflect concerted efforts under way by this office and industry to address software, reliability and maintenance issues,” Reuters reported. “Of course, we recognize risks still exist in the program, but they are understood and manageable,” the Program Office insisted.

Gilmore may need to remind the F-35 Program Office (again) that the DOT&E office deals with facts, not promises."

http://spectrum.ieee.org/riskfactor/com ... nimpressed
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