Forum: F-35 Lightning II

I am actually working on a spreadsheet to cover this based on what I have been able to dig up from old manuals and flight test results. Weapon drag is a killer! An F/A-18E with a few tanks and big bombs has over twice the drag of a clean one.

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sprstdlyscottsmn wrote:

I am actually working on a spreadsheet to cover this based on what I have been able to dig up from old manuals and flight test results. Weapon drag is a killer! An F/A-18E with a few tanks and big bombs has over twice the drag of a clean one.

And this is news worthy? I remember a book by Lou Drendel I read (actually I bought for the pictures) about 25 years ago on the F-15 and there was a chart of the F-15 clean, versus 2 drop tanks, versus 2 FAST packs... Drag induced by hanging sh*t on the wings is nasty stuff.

What is shocking to me is that even with the -35's large volume of fuel that it's range in AB is so very short. Something like 200nm... I was hoping that not being able to supercruise would be offset by the planes internal fuel load and being able to buzz about the sky with the burners lit and still have some relatively long legs.

Depending on the spool up of the engine, and the planes wing loading, and minues some pounds of fuel, the TTW ratio and wing loading mean that the -35 should be capabe of "dogfighting" with th best of them. But it's a dying requirement given weapons technology....

Not only that, but knowing the state of the art in computer technology, if the passive sensors are "good enough" on the -35, it may very well be the first hands-off ACM fighter, ever. And I'd pit silicone versus grey matter any day of the week. Regardless of the airframes in question (to an extent). And remember that the the -35 has 360 field of vision. So if not in the early configurations, it certainly could be added in later models.

Furthermore, the USAF is/was actively looking at the B model and instead of stuffing a lift fan in in the "hole", they were looking at adding a solid state laser. That again, if it comes to fruition, will negate the need for ACM even more so.

Wasn't saying it was news worthy, its just something people often forget.

sprstdlyscottsmn wrote:

Well lets see, Blk60 weighs in at 11 tons empty due to increased structure for heavier loads and the addition of CFTs. It carries some 6.5 tons of fuel. as such it weighs in (without weaponry) at 17.5 tons. As such any thrust to weight rating is decreased by 6% per ton of weaponry carried (1 heavy bomb, 4 light bombs, 2 AGMs, 6 MRM, or 10 SRM). It motor produces 9.5 tons thrust mil and 16 tons AB. It gives a T/W ratio of 54% mil and 91% AB. it also yeilds a Fuel Fraction of 37%

F-35A weighs in at 14.5 tons empty and carries 9 tons of fuel for a weapon free weight of 23.5 tons. this yields a weapon sensitivity of 4%, and thrust to weight ratios of 60%/91% in mil/AB (rated thrust of 14tons/21.5tons) and a fuel fraction of 38%

Do your figures take into account P&W's announcement that their "43k in afterburner" engine is actually more like a "50k+ in afterburner" engine? Cool

sprstdlyscottsmn wrote:

Wasn't saying it was news worthy, its just something people often forget.

Well... at least 'some' people might forget. The folks at GD at least were thinking F-16XL. That would have changed quite a few of the rules and diverted much of any 'drag' based disucussions, vs range and performance. Wink

And alloy...

Unfortunately... regardless of how advanced next gen BVR missiles get, so too will the counter measures and tactics. As such, 'BVR' pK will not likely improve much vs 70s or ODS era pK stats, within the next 10 yrs at least.

Perhaps one must always have a potent WVR secondary deterrence... or at least have the capacity to run once the BVR contest is depleted? imho.

A lot of great ideas were first documented on the backof an envelop but in this matter I think i'll go with the guys in white coats with room full of supercomputers. Very Happy

A lot of great ideas were first documented on the backof an envelop but in this matter I think i'll go with the guys in white coats with supercomputers snd windtunnels. Very Happy

@Popcorn..... A room full of supercomputers is great; but an airplane is only good as its physical real world testing. Many an engineer has made a pretty picture or done a pretty calculation on super computers only for it to crash and burn in the real world. (ie. X-30,X-33,XB-70) This is why the Wright Brothers method of design, build, test, modify, then test some more will also be the way of aviation.

@geogen..... As computers and missile seekers get better it gets harder and harder to fake them out. So I think the smart money is on the missiles rather then on the missile counter measure systems.

as Imaging Infrared Seekers defeat chaff we develop laser based Direct Infrared Counter Measures. As Radars develop the ability to detect smaller RCS targets and ignore chaff we develop the ability to use our radar to fry their radar. Countermeasures are hardly the "lets drop something and hope it works" that they used to be, now they actively destroy the sensors. In order to protect from that you would have to shield them in such a way as to render the sensor nearly useless. Think of this way, welding sparks can burn the eyes out (DIRCM analogy), so we make welders masks (possible counter of DIRCM). Can you imagine walking around in a welders mask all the time?

sprstdlyscottsmn wrote:

as Imaging Infrared Seekers defeat chaff we develop laser based Direct Infrared Counter Measures. As Radars develop the ability to detect smaller RCS targets and ignore chaff we develop the ability to use our radar to fry their radar. Countermeasures are hardly the "lets drop something and hope it works" that they used to be, now they actively destroy the sensors. In order to protect from that you would have to shield them in such a way as to render the sensor nearly useless. Think of this way, welding sparks can burn the eyes out (DIRCM analogy), so we make welders masks (possible counter of DIRCM). Can you imagine walking around in a welders mask all the time?

Agreed. The history of warfare is in part the history of measure vs. countermeasure. Offensive vs. Defensive.

SPY V. SPY: http://photobucket.com/images/spy%20vs% ... 1QQtppZZ16

alloycowboy wrote:

@Popcorn..... A room full of supercomputers is great; but an airplane is only good as its physical real world testing. Many an engineer has made a pretty picture or done a pretty calculation on super computers only for it to crash and burn in the real world. (ie. X-30,X-33,XB-70) This is why the Wright Brothers method of design, build, test, modify, then test some more will also be the way of aviation.

That's obvious, isn't it. Rolling Eyes

Popcorn..... You would think, but some people seem to think it should work perfectly as soon as it rolls out of the hanger for the first time.

alloycowboy wrote:

Popcorn..... You would think, but some people seem to think it should work perfectly as soon as it rolls out of the hanger for the first time.

You would think more people would look at historical aerospace development, but unfortunately they do not. Many (if not most) aircraft had problems/shortcomings in the beginning. But, they worked through the problems and became successes.

Couple things on this topic:

a) Only the UAE is flying F-16 block 60, so not really the best choice for comparisons. Given their geography, range and fuel isn't as much a requirement for them. Plus they have a LOT of EW gear that no other country can match (even us, since we aren't willing to pay for it).

b) T/W is NOT the key metric of a fighter in 2011, I'd dare say it's not really that important at all anymore. Kinda like the rest of our 80's tech. Don't care how maneuverable you think you are, a SAM or MANPAD (or A/A missile) that can pull 25 G's will beat you every time. Guns? Not much you can do with the 4-5 seconds worth of rounds you can carry.

c) The idea of EO/DAS is to make ACM obsolete. Leave the maneuvering to the much-more-maneuverable weapon systems, and just give them great targeting. Plus having low RCS and great passive sensors mean you are >> more likely to see him before he sees you, which really is the key metric in 2011 of who would win an A/A engagement.

d) You don't write a/c requirements by saying 'it has to be MORE than the last one'. That's a path to even more untenable acq programs than we already have. You base it on the mission and threat. You make design trade-offs to achieve overall performance goals. Don't put too much stock in any one metric (except cost and maintainability, because congress has been the biggest threat to US fighters Smile

Forum: F-35 Lightning II

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