Proof: F-35 can out-accelerate Su-27/35 in subsonic region

The F-35 compared with other modern jets.
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garrya

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Unread post24 Nov 2016, 17:21

gta4 wrote:This is because Su-27 will lose lift rapidly once it exceeds 24deg. Its lift drops much faster than eastern jets.

Any particular reason ? vortex separated from wing ?

gta4 wrote:By the way, according to F-16 test report by GD (the literature I recommended), F-16 could easily achieve a Cl of 1.7 at 24deg AOA, Mach 0.9. At lower subsonic speed I believe it could achieve it earlier.

I cant seem to be able to locate the literature
Can you post the link instead ?
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gta4

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Unread post24 Nov 2016, 17:28

garrya wrote:
gta4 wrote:This is because Su-27 will lose lift rapidly once it exceeds 24deg. Its lift drops much faster than eastern jets.

Any particular reason ? vortex separated from wing ?

gta4 wrote:By the way, according to F-16 test report by GD (the literature I recommended), F-16 could easily achieve a Cl of 1.7 at 24deg AOA, Mach 0.9. At lower subsonic speed I believe it could achieve it earlier.

I cant seem to be able to locate the literature
Can you post the link instead ?


I will upload one tonight.
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gta4

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Unread post24 Nov 2016, 17:42

So, are we agreed on these things?

1) Su-27's performance was calculated based off 18920-19000kg flying weight
2) Now Su-27 is much heavier. Fuel weight mush be sacrificed to meet the 18920kg flying weight standard
3) F-15 has a maximum Cl of 1.6 and has a better Cl/wing loading ratio
4) With the fuel for same AB duration, F-15 has better instantaneous turn, sustained turn, climbing rate and acceleration.
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gta4

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Unread post25 Nov 2016, 01:16

F-16 test data, look at the Cl at M0.9, AOA 19deg, is actually higher than 1.3.
F16 test 242.jpg

At medium lift coefficient, F-16 has steeper lift curve slope than Su-27. The initial slope is almost 0.09, significantly higher than Su-27
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gta4

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Unread post25 Nov 2016, 01:22

Look at your previous data, this is definitely not a F-16, because the initial lift curve slope is as small as 0.07. F-16 is close to 0.09.
And, the caption of the figure does not mention it is a F-16, right?
not_F16.jpg
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gta4

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Unread post27 Nov 2016, 19:46

OK back to the main thread, the acceleration. Obviously the F-35 is not good at transonic acceleration like a F-16, but the majority of dogfight takes place at subsonic, so the acceleration at lower speed is more relevant. It determines how you regain energy after each maneuver and how frequently you can execute each maneuver, like a "cool down" time.
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steve2267

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Unread post27 Nov 2016, 23:23

gta4 wrote:Obviously the F-35 is not good at transonic acceleration like a F-16, but the majority of dogfight takes place at subsonic, so the acceleration at lower speed is more relevant. It determines how you regain energy after each maneuver and how frequently you can execute each maneuver, like a "cool down" time.


Stooopid question: WHY is it obvious "not good acceleration like a F-16?"

Obvious because your numbers say so? Where again, do you get your numbers? Flight test data? Wind tunnel data? CFD results? Speculative numbers drawn from first-order, empirical studies with inputs gleaned from non-F-35 test reports / other aircraft?

I am not trying to slam you, just trying to understand "obvious" and "not good at transonic acceleration."

I am having difficulty reconciling your statement(s) with quotes from LM / BAE / Military pilots who swoon over the power of the motor, and compare F-35 acceleration to a clean F-16 (Beesley) and an otherwise clean F-16 with one centerline tank (which Gums says doesn't affect the F-16 much). I have also read statements / quotes here on F-16.net from program personnel stating the transonic acceleration is quite good and it goes through the Mach very easily. Granted, this last statement / assertion does not include a comparison to the Viper.
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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garrya

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Unread post28 Nov 2016, 00:17

F-16 acceleration chart directly from flight manual
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steve2267

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Unread post28 Nov 2016, 00:49

garrya wrote:F-16 acceleration chart directly from flight manual


OK. Do you have the same page from the F-35 flight manual?

If not, from where are you getting numbers for the F-35 acceleration? (I've been following this thread... but don't recall any times for accel V1 to V2 at 30,000 ft. OR are we using the same first order analysis that was used in comparing the F-35 to the SU-35?) If so, I apologize and will have to sacrifice some more brain cells and go back and re-read.)
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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vanshilar

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Unread post28 Nov 2016, 00:59

I think it has to do with the change to the F-35's KPP (Key Performance Parameter) on transonic acceleration. You can read more about it here:

http://elementsofpower.blogspot.com/201 ... sonic.html
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garrya

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Unread post28 Nov 2016, 01:10

steve2267 wrote:
OK. Do you have the same page from the F-35 flight manual?


I dont but i think OP and you would have heard about changed in F-35 KPP ( A version took 64 seconds to go from Mach 0.8 to 1.2 )
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garrya

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Unread post28 Nov 2016, 01:16

To make stuff more interesting , here is F-15A acceleration
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optimist

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Unread post28 Nov 2016, 07:41

I now know it was silly of me to open the thread again, come on guys, take it back to keypub. clean f-16s vs loaded f-35. :doh:

you have the flight manuals, put the pods EW ect on, along with tanks and similar weapon load. They show what you think transonic acceleration is.
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garrya

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Unread post28 Nov 2016, 08:10

optimist wrote:I now know it was silly of me to open the thread again, come on guys, take it back to keypub. clean f-16s vs loaded f-35. :doh:

you have the flight manuals, put the pods EW ect on, along with tanks and similar weapon load. They show what you think transonic acceleration is.

there are drag index value in the table optimist, or you can add individual values as you like
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Corsair1963

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Unread post28 Nov 2016, 08:23

steve2267 wrote:
gta4 wrote:Obviously the F-35 is not good at transonic acceleration like a F-16, but the majority of dogfight takes place at subsonic, so the acceleration at lower speed is more relevant. It determines how you regain energy after each maneuver and how frequently you can execute each maneuver, like a "cool down" time.


Stooopid question: WHY is it obvious "not good acceleration like a F-16?"

Obvious because your numbers say so? Where again, do you get your numbers? Flight test data? Wind tunnel data? CFD results? Speculative numbers drawn from first-order, empirical studies with inputs gleaned from non-F-35 test reports / other aircraft?

I am not trying to slam you, just trying to understand "obvious" and "not good at transonic acceleration."

I am having difficulty reconciling your statement(s) with quotes from LM / BAE / Military pilots who swoon over the power of the motor, and compare F-35 acceleration to a clean F-16 (Beesley) and an otherwise clean F-16 with one centerline tank (which Gums says doesn't affect the F-16 much). I have also read statements / quotes here on F-16.net from program personnel stating the transonic acceleration is quite good and it goes through the Mach very easily. Granted, this last statement / assertion does not include a comparison to the Viper.


QUOTE: the F-35 very nearly matches the performance of its' larger, more powerful cousin, the F-22 Raptor, Beesley explained. The "subsonic acceleration is about as good as a clean Block 50 F-16 or a Raptor- which is about as good as you can get." Beesley said.
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