F-35A versus Saab Gripen NG

viper12 · by **viper12** » 11 May 2018, 01:21

But...

Spurts didn't properly integrate, as Ps = some constant*2v*dv/dt (if flying at a constant altitude), v being the velocity.

OK, I'm nitpicking because it's way faster and surely accurate enough with quick averages. :mrgreen:

steve2267 · by **steve2267** » 11 May 2018, 01:38

viper12 wrote:But...

Spurts didn't properly integrate, as Ps = some constant*2v*dv/dt (if flying at a constant altitude), v being the velocity.

OK, I'm nitpicking because it's way faster and surely accurate enough with quick averages.

Maybe not, but he explained and gave examples about how to convert a Ps value into a meaningful acceleration / deceleration rate. :drool:

Something that has baffled me for eons. :bang:

Accurate enough? Shirley... since people are arguing over YouTube videos... :roll:

sprstdlyscottsmn · by **sprstdlyscottsmn** » 11 May 2018, 01:54

PS is expressed in ft/s. It's nominally a climb or descent rate required to maintain speed. But as PS=(T-D)V/W, if you divide PS by V (both in ft/s) you end up with (T-D)/W. This is acceleration or deceleration expressed in G. Multiply this by 32.2 to get Acc/Deceleration in ft/s/s. Divide that by the speed of sound and you get Acc/Deceleration in Mach units per second. Over short, fairly linear, sections of the turn chart you can average the Acc/Deceleration to determine the time to decelerate. That's all I did. The math is easy, it's more about being comfortable with what PS is.

steve2267 · by **steve2267** » 11 May 2018, 02:47

That makes perfect sense. I got wrapped around the axle thinking Ps was an expression for energy. The fact that units were [ D/T ], e.g. ft/sec, just served to further confuse me. Thanks for the further explanation. Does the "P" and the "s" in Ps stand for anything, or is it a mnemonic?

sprstdlyscottsmn · by **sprstdlyscottsmn** » 11 May 2018, 02:58

Pee-sub-ess. The P stands for Power and sub-ess is Specific, which means divided by weight or normalized. It is also referred to as Specific Excess Power, SEP, as it is measuring the excess power remaining after the power lost to drag is taken into account.

F-16ADF · by **F-16ADF** » 11 May 2018, 04:29

Spurts,

I have a question.

Basically you are using airspeed and not altitude gain/loss? I think this is similar or spot on to what one of the F-16 pilots on here has previously said : "If you overlay this EM diagram with other jets like the Hornet you will see their impressive nose rates as G/aero spikes to high turn rates but even higher negative Ps. So they have one good turn and then they are slow ducks. The smart pilot flying these jets knows the same strategy I described above and only uses that for specific advantage gain and then goes to energy conservative modes. But the F-16 has what we call a Plateau not a spike. See how the Ps lines level off in the 300-500 CAS range? No other jet has such a large region of high performing yet preservative capability."

So basically with these linear or level horizontal Ps lines (in the 300-500KCAS region ((depending on altitude)), the Viper pilot can hold turn rate, while giving up speed to a point. This is technically the heart of the "plateau" right? Where as you really cannot do this with a jet that has a spike (ex. can't do this as easily with a 5K Tomcat chart since it has no linear Ps horizontal plateau (but a sharp spike, the negative Ps lines are all over the place))?

So I guess with the F-16, the AOA limiter is actually helping conserve energy to a point. Instead of blowing everything on a max lift pull and subsequent aero spikes??

Am I right or wrong here-

sprstdlyscottsmn · by **sprstdlyscottsmn** » 11 May 2018, 04:44

You are correct in your understanding.

steve2267 · by **steve2267** » 11 May 2018, 06:03

f-16adf wrote:
So basically with these linear or level horizontal Ps lines (in the 300-500KCAS region ((depending on altitude)), the Viper pilot can hold turn rate, while giving up speed to a point. This is technically the heart of the "plateau" right? Where as you really cannot do this with a jet that has a spike (ex. can't do this as easily with a 5K Tomcat chart since it has no linear Ps horizontal plateau (but a sharp spike, the negative Ps lines are all over the place))?

So I guess with the F-16, the AOA limiter is actually helping conserve energy to a point. Instead of blowing everything on a max lift pull and subsequent aero spikes??

While the Viper AoA limiter helps conserve energy, it also prevents the Viper pilot from being able to cash in all his chips at once even if he really wanted to. The really good Hornet pilots are dangerous because they know when to hold 'em, and know when to fold 'em -- they can conserve energy (to a point), and then when the situation is right, they can cash in that energy for nose pointing. (QS or anyone else, feel free to slam me if I'm wrong here.)

I suspect what makes the F-35 so special in the WVR arena, is because the pilot can choose to fly it like a Viper -- conserving energy / maximizing rate... but the option is always there to go big (alpha) and honk the nose around like a Hornet/Rhino if the situation calls for it. This makes sense to me as the F-35 airframe is so slick to begin with (low drag), and its got that big honking motor (lots of excess power) in the back that everyone raves about, and the wing loading is similar to a Viper with 50% gas (give or take). This is also probably why Billie Flynn made the statement claiming that if you overlay the F-35 E-M diagram on any 4th gen aircraft, the F-35 beats them all.

With that slick airframe, big honkin motor, and a CLAW to match, the F-35 pretty much lets the pilot do whatever he needs / wants. I go back to what an F-35 driver told me: (paraphrasing) I can rate right along with a Viper -- a clean (airshow) F-16 Block 50 might outrate me by a bit -- but I have the AOA to out-radius him. A clean (airshow) F/A-18 might be able to outpoint me (barely), but I can out-rate him.

With regard to E-M diagrams, because the F-35 can fly to 50° alpha, I suspect its E-M diagram is "very spikey"... but the Ps curves I bet are right there with the Viper in the 300-500 CAS. So a Lightning driver that backs off the alphey thingey (and maybe plugs the blower back in, maybe not) will drop back down to a G / rate / Ps curve very close to an F-16 Blk 50. FWIW. This too makes sense to me because it agrees with what Dolbe Hanche said: he can slow down very quickly, be much more agressive (than he thought) in "diving in" (I took this to mean saddling up), but then the F-35 "sticks on like glue." So a Lightning driver might pull to 30-40° AoA (or whatever he needs -- more or less) to slow down, cut a tight radius, but then be able to let off the stick and he has the power to accelerate back up to his rate band (Berke seemed to indicate > 370kts). And he still has the J-turn / peddle turn in his bag of tricks. Or he can go vertical. It's all there. This is the picture forming in my mind and it very much agrees with "Cap" Gunn who said "without a doubt" when asked if the F-35 could win WVR.

steve2267 · by **steve2267** » 11 May 2018, 06:38

While we are yakking about E-M diagrams and Pee-sub-ess curves... does anyone have E-M doghouse plots for any Hornet or Rhino variants? The turn diagrams I found in some F/A-18C/D and E/F performance addendums seemed to have turn information, but I couldn't find any Ps data or curves. Something that could be overlaid on top of the Hellenic F-16C manual that's floating around out there would be interesting, as an intellectual exercise.

hornetfinn · by **hornetfinn** » 11 May 2018, 09:29

Here is a video of Super Hornet doing 270 degrees in about 2 seconds (from 2:10 onwards)...

Sorry, couldn't resist :wink:

spazsinbad · by **spazsinbad** » 11 May 2018, 09:34

I didn't know they could do that. :doh:

<sarc OFF the scale> Wot moving picture was that?

hornetfinn · by **hornetfinn** » 11 May 2018, 09:42

Movie is called "Behind Enemy Lines"

https://en.wikipedia.org/wiki/Behind_Enemy_Lines_(2001_film)

spazsinbad · by **spazsinbad** » 11 May 2018, 10:31

In Win10 IE11 that URL is broken: https://en.wikipedia.org/wiki/Behind_En ... (2001_film) THANKS :applause:

hornetfinn · by **hornetfinn** » 11 May 2018, 10:53

Argh... That was broken link as it seems the last parentheses gets lost in the link.... Should've tested it before sending... :bang:

gta4 · by **gta4** » 11 May 2018, 12:41

alphaxraylima wrote:
basher54321 wrote:
alphaxraylima wrote:really dont see

Please stop yes - take heed from what you have been told by others and learn instead of trying to argue yourself into a deeper hole.

There is no comparison between eyeballing a you tube video and a calculated level turn where altitude is a constant. Think about what is in the video - can you see weight, altitude, AoA, temperature, velocity, climb / loss of altitude? - No you cant - you cant even guess.

Find a HUD tape of an airshow - still mostly useless but can see the type of turns they do in real life at least.

I will stop as soon as someone actually provides a source of a F-16 turning like that with a similar load. That simple, I'm not going to stop just because someone starts throwing the word "gay" around, the complete opposite in fact. I have NEVER compared that Gripen video to a F-16 performing a level turn, going by the F-16C flight manual it would lose about 4000 ft trying to keep an average 21 degree turn rate for 13 seconds with a drag index of 100 and limited fuel (at sea level) and that is what I have been using as a comparison. If you think that is unfair that is fine, but as no one has been able to show any model F-16 turning like that, that is what we have to go on.

I think you misinterpreted the flight manual.
Just tell me how you get the "losing 4000 ft" figure. I am sure the manual does not mention that.