9G sustained is not possible in the new F16 variants

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saberrider

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Unread post17 May 2019, 21:46

I believe that the 9G level turn is not possible in todays F-16 variants due to weight increases but not the wings area.
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southernphantom

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Unread post18 May 2019, 03:07

Do you have doghouse plots that indicate this, or are you just speculating?
I'm a mining engineer. How the hell did I wind up here?
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hkultala

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Unread post19 May 2019, 20:46

saberrider wrote:I believe that the 9G level turn is not possible in the today F16 variants due to weight increases but not the wings area.


Your beliefs have very little correletion with reality.

Modern F-16 models have MUCH higher thrust than early models; even though they need slightly higher AoA for same turn, they have the thrust to overcome the increased induced drag frm the higher AoA.
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vilters

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Unread post20 May 2019, 20:00

Also remember that the fuselage is providing most of the lift.
(The wings are more for low speed and to guide and steer.)

Also, the wings have too much lift at speed. That is why the Leading edges go UP at speed. To reduce the wing lift.

Well, actually, to get the lift vectors of the fuselage and wings in line. ( Wings are having too much lift once supersonic)

(At speed? You could simply cut the wings off and go even faster, but the canopy would melt.)
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Unread post20 May 2019, 23:39

Vilters, I don't think you could be any more wrong in your statements about too much wing lift, but you might surprise me if you try very hard.

The fuselage does indeed provide significant lift, but only at lower speeds where wing lift curve slope is reduced. But never does the fuselage provide most of the lift.

The wings do not produce too much lift at speed. They do produce too much nose down pitch moment. Yes, the leading edges go up 2 degrees when supersonic, as do the trailing edge flaps. But it certainly is not because the wing is making too much lift. The center of lift shifts aft of the CG past 0.95 mach, making a nose down pitch moment. To counteract that, the horizontal tails move slightly trailing edge up to create a down load on the tails and eliminate the pitch moment on the airplane. That means the wing/fuselage lift must increase to compensate for the tail down load. And of course drag is increased. Before F-16 first flight, our clever aerodynamics engineers found they could reduce the aft shift of lift by raising the LEF and lowering the TEF 2 degrees. That reduces wing and tail loads and total drag. Free lunch!
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saberrider

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Unread post21 May 2019, 04:34

johnwill wrote:Vilters, I don't think you could be any more wrong in your statements about too much wing lift . Before F-16 first flight, our clever aerodynamics engineers found they could reduce the aft shift of lift by raising the LEF and lowering the TEF 2 degrees.

I believe that what Vilters meant to say about fuselage lifting capabilities is the shaped structure of the LEX , (cobra hood types) because they go atf until speed breaks,provide lift(but this happens at high AOA).Also myself believe that at Mach 1 and above TEF's and LEF's go UP. The 9 G is in my opinion gained and Sustained at around 480 knots not 380- 450knots.Because engine power is there to gives/keeps the speeds, but with additional weight your jets tends to go more to outside in 9G hard turn (inertia).
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wrightwing

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Unread post21 May 2019, 05:06

The corner speed may have shifted, but the sustained G hasn't.
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johnwill

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Unread post21 May 2019, 05:47

saberrider wrote:Also myself believe that at Mach 1 and above TEF's and LEF's go UP.


Of course you are correct about TEF also going up. Thanks for catching the error.
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Unread post21 May 2019, 05:59

wrightwing wrote:The corner speed may have shifted, but the sustained G hasn't.


You are correct, but corner speed in a V-n (Velocity - g) diagram is a requirement only for instantaneous g, not sustained g. So sustained g capability does not affect corner speed, only instantaneous g capability does.
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saberrider

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Unread post21 May 2019, 12:42

Maybe it's language barriers here, here is my opinion about increased speed for 9 G.If an extra power give you more thrust than the older jets blocks but in the same time you added more loads then at a given altitude and the same 15 *AOA allowed by CAT 1not going to obtain the 9 G .This issue is my opinion. This is wrong?
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f-16adf

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Unread post21 May 2019, 15:04

Here is a comparison of the lighter block 15 and the heavier block 42.



F-16 Block 15 and Block 42  P&W F100-220.jpg



F-16CG Block 42 P&W F100-220.jpg







Looking at the diagram, the F-16A block 15 empty weight ~16,100lbs vs F-16CG block 42 empty weight ~18,200lbs. Both jets use the Pratt F100-220 and are fueled at 50% internal.

While still using the identical engine,and both with NSI, (although block 42 has the larger draggier vertical tail base); The effect of over 2,000lbs weight growth has diminished the 42's performance as compared to the earlier A model.


So even with the more modern Block 50/52 and their derivatives, keep adding more weight and that pushes everything to the right of the plot.



Here is the source of the diagrams (4-7-4-10), interesting read:
https://www.87th.org/sites/default/file ... 205%20.pdf
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sprstdlyscottsmn

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Unread post21 May 2019, 15:24

saberrider wrote:Maybe it's language barriers here, here is my opinion about increased speed for 9 G.If an extra power give you more thrust than the older jets blocks but in the same time you added more loads then at a given altitude and the same 15 *AOA allowed by CAT 1not going to obtain the 9 G .This issue is my opinion. This is wrong?

Not wrong, but incomplete. 15 AoA will always be the max AoA for 9G at any altitude, and here is the part you missed, given the appropriate speed. 9G can still be sustained at lower altitudes, but 9G was never sustained at 15 AoA. It was sustained at higher speeds/lower AoA.
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saberrider

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Unread post21 May 2019, 16:13

sprstdlyscottsmn wrote: given the appropriate speed. 9G can still be sustained at lower altitudes, but 9G was never sustained at 15 AoA. It was sustained at higher speeds/lower AoA.

Thanks,then turning radius it is bigger at sustained 9G(and the turn rate) than that 8.1G .
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sprstdlyscottsmn

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Unread post21 May 2019, 18:00

saberrider wrote:
sprstdlyscottsmn wrote: given the appropriate speed. 9G can still be sustained at lower altitudes, but 9G was never sustained at 15 AoA. It was sustained at higher speeds/lower AoA.

Thanks,then turning radius it is bigger at sustained 9G(and the turn rate) than that 8.1G .

Correct. At sustained 9 the radius is going to be bigger than at sustained 8.1 due to the greater speed. The rate may or may not be greater, some faster speeds result in lower rates.
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marsavian

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Unread post21 May 2019, 19:01

9g can be sustained at sea level at Mach 0.7 just under 22 deg/s at 22klb weight with a 29klbf engine. There will be few aircraft that you can't out-turn at that rate and the pilot will give out before the aircraft so the latest F-16s can still sustain 9g at some part of their envelope at combat weight.
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