Forum: F-35 Lightning II

Just read it. Nothing noteworthy except it was done four times in an afternoon. I think when it comes to testing no news is good news.

http://www.star-telegram.com/business/s ... 38570.html
http://www.f-16.net/news_article3120.html

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I think that the rate of testing with the F-35, and the X-35 before it, is excelent. Granted the seemingly rushed and reckless days of '50s style testing is done, so is the test pilots 4 day life expectancy. Two flights in one day, 4 super sonic ventures, 8-12 minutes of SS time under its belt. I personally never understood the concept of testing super sonic conditions at Mach 1.05 myself, except that I guess the component of drag due to wave drag would be at its highest there. Based on the climb performance it previously demonstrated against the F-16 I imagine that the lowest possible AB setting was used. I cant wait to see the planes engine fully unleashed.

ZOOM, ZOOM, ZOOM!!! Crazy Pilot

Quote:

I cant wait to see the planes engine fully unleashed.

Dtto, That thing is gonna prove to be a Beast.

wow, I go to other posts for 20 minutes and suddenly there are already two more posts here! I guess anything reguarding the Lightings performance grabs attention.

sprstdlyscottsmn, the reason for testing at 1.05 is simple. As the airplane speed moves from .9 mach to 1.1 mach, many changes of pressure distribution on the airplane abruptly occur. Flutter, structural load, and stability are significantly affected. In order to evaluate these effects, it is necessary to test at frequent intervals - .9, .95, 1.05, and 1.1 mach. At higher or lower speeds, test inervals are larger (.6, .7, .8. ... 1.2, 1.4, 1.6 for example. At those higher or lower speeds, pressure distribution changes are smoother and not so abrupt.

The beast definitely screams, it's loud and proud, I was at the entrance of our hanger at JRB yesterday morning when it took off for it's morning sortie, it makes the F18's the Marines fly and our F16's engine here sound like they wear mufflers on the engines.

Not sure if burners are lit to get to 1.05 though. Maybe maybe not. If the aircraft is capable of breeching the barrier in dry, they may actually want to do that to linger in the transonic zone longer to gather more data.

sprstdlyscottsmn wrote:

I think that the rate of testing with the F-35, and the X-35 before it, is excelent.

4001 demonstrated supersonic flight in half as many flight tests, and more near Mach 2 I believe. Shocked

johnwill wrote:

sprstdlyscottsmn, the reason for testing at 1.05 is simple. As the airplane speed moves from .9 mach to 1.1 mach, many changes of pressure distribution on the airplane abruptly occur. Flutter, structural load, and stability are significantly affected. In order to evaluate these effects, it is necessary to test at frequent intervals - .9, .95, 1.05, and 1.1 mach. At higher or lower speeds, test inervals are larger (.6, .7, .8. ... 1.2, 1.4, 1.6 for example. At those higher or lower speeds, pressure distribution changes are smoother and not so abrupt.

That makes perfect sense. The transonic regime is the trickiest part as the plane is still just forming shockwaves at some places and not others and such. Thanks for the reply.

In the fpast, test pilots are asked to push the aircraft to its limits (or near it) at the early stages of flight testing because that is needed to figure out what those limits are. The design is then changed to adjust those limits if needed.

Today, modeling is so good that we basically known what those limits are. Flight testing is basically a verification task and the focus shifts to the details like fine tuning the control software or checking for possible buffet resonance an the like.

dwightlooi,

People (analysts, not flight testers) have been saying that for as long as I can remember (since 1963), and it is still a pipe dream. I can absolutely guarantee you flight test will uncover unexpected results for the F-35. There is no question that analysis methods have improved over the years, but they still aren't perfect. One of the biggest sources of uncertainty is the flexibility of the structure. Whether from wind tunnel or CFD, flexibility corrections have to be made to the pressure distributions from analysis. That uncertainty affects structural load, flutter, stability and control, and performance. Rolling Eyes

dwightlooi wrote:

Not sure if burners are lit to get to 1.05 though. Maybe maybe not. If the aircraft is capable of breeching the barrier in dry, they may actually want to do that to linger in the transonic zone longer to gather more data.

Very interesting! I never stated if it required afterburner or not to make Mach 1.05??? Wink

And we may never know!!! Shocked

nah, it was at flight idle.....

sprstdlyscottsmn wrote:

And we may never know!!! Shocked

nah, it was at flight idle.....

Oh, let's be realistic............it was half power! Cool

Forum: F-35 Lightning II

F-35 Breaks Mach 1 Today