F-35A versus Saab Grippen NG

The F-35 compared with other modern jets.
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viper12

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Unread post11 May 2018, 19:42

sprstdlyscottsmn wrote:You are correct in your understanding.


Just to be sure, how does one prove that ?

I made a couple derivations, and all I got are :

Ps = (1/mg)*dE/dt = (1/mg)*(d/dt)(0.5m*v^2 + mgh) = (v/g)(dv/dt) + 0 for a constant altitude turn
a_c = omega*v, a_c being the centripetal acceleration and omega the turn rate

So I'm not sure what are the next steps that show Ps = constant implies omega = constant. I suppose from f-16adf's post that a_c is constant too, but not completely positive about it.

Or it's simply that the Ps isopleth is flat in the doghouse plot, so if you can adjust your pull on the stick to maintain constant Ps, you're simply at the same omega ?
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fbw

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Unread post11 May 2018, 22:00

steve2267 wrote: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.



You can convert the information from the NATOPS turn rate charts on the F-18 into a a “doghouse plot”. I used to have some F-18C E-M diagrams saved. I will see if I can dig them up again. Working from an iPhone, the one most easily accessible is a simple comparison of the F-18E/F compared to the “C”. Not going to give any data on the Ps though.
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steve2267

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Unread post11 May 2018, 22:21

fbw wrote:
steve2267 wrote: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.



You can convert the information from the NATOPS turn rate charts on the F-18 into a a “doghouse plot”. I used to have some F-18C E-M diagrams saved. I will see if I can dig them up again. Working from an iPhone, the one most easily accessible is a simple comparison of the F-18E/F compared to the “C”. Not going to give any data on the Ps though.


Do those NATOPS turn rate charts include the information necessary to create the Ps isolines? I guess that was the biggest thing that left me scratching my head -- I couldn't find any Ps information. If it is not in the turn rate charts, do the NATOPS performance addendums (or the FM itself) have Ps data somewhere? (I'm drawing a blank.)
Take an F-16, add a dollop of A-7, a big gob of F-22, sprinkle on some AV-8B, stir well, then bake. What do you get? An F-35.
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viper12

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Unread post12 May 2018, 00:04

The Ps curves are visible in the Greek F-16's FM, page 427 and further : https://info.publicintelligence.net/HAF ... lement.pdf

And I remember seeing those Ps curves, approximation or real data, back in the Falcon 4.0 manual nearly 20 years ago.

Note that the Ps curves aren't always available ; from what I remember of the F-15A and F/A-18E's NATOPS, you just get doghouse plots without any Ps curves, though obviously, you can draw the Ps=0 contour if you've got the curve for sustained turn rate vs speed.

BTW, has there ever been Ps curves at a constant g value in function of speed, like say when you're pulling 9G's in a horizontal turn from 0.9M to 0.7M ?
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gta4

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Unread post12 May 2018, 03:56

During Indian MMRCA test, F/A-18E's STR was 93% as good as that of typhoon. That is a pretty impressive result for a jet with relative low T/W ratio. It proves F/A-18E's aerodynamic efficiency.
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gta4

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Unread post12 May 2018, 04:00

This figure is more convincing.
With same load out, F/A-18E has better performance and range.
P.S.: This is a 402 powered F/A-18C
18E18C.jpg
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loke

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Unread post17 May 2018, 12:58

Amazing, Saab seems to keep Gripen E in the competition in Canada.
Saab Group is confident that its single-engine Gripen E remains a viable contender for Canada’s next generation fighter aircraft fleet, even though there are currently no immediate plans for Royal Canadian Air Force (RCAF) pilots to actually fly the aircraft.


https://www.skiesmag.com/news/saab-posi ... n-fighter/

Canada is not just a NATO country it is also F-35 partner!

The probability of Canada buying non-US fighter is 0.0. The probability of Canada not buying F-35 is also 0.0.

Oh well I guess there might be some PR effect of staying in the race?? Or are they gambling that the Canadian politicians are so upset with Boeing, Trump, LM and whatnot and therefore go for a non-US platform in spite of being an F-35 partner?
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hythelday

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Unread post17 May 2018, 13:19

Is there a race at all? I'm not following this too close (soap operas aren't my taste) but AFAIK there isn't an official competition, now is there?
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gta4

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Unread post17 May 2018, 14:12

Why does SAAB advertise JAS39 as "SMART" plane?
Does it mean its avionic codes were written by python and tuned with TensorFlow :mrgreen: :mrgreen:
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magitsu

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Unread post17 May 2018, 14:34

It's probably meant to indicate that its buyers would be SMART.
Nobody want's to make a dumb purchase, so it's there for reassurance. :wink:
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ricnunes

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Unread post17 May 2018, 19:32

Because anyone purchasing the Gripen E will be dumber than SAAB and the Gripen itself which means that in turn that SAAB and the Gripen E will look "SMART" (at least compared to their customers)... :wink:
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