Official statement: The F-35 CAN Supercruise.

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megasun

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Unread post04 Nov 2012, 07:14

cola wrote:
SpudmanWP wrote:This confirms two things.
2. It can

Spudman...150 miles at M1.2/tropopause is about 13 minutes, worth of flying.
Since when, 13 minutes out of 4 hours theoretical max. endurance, classifies as "cruising"?
F16 also does dash supersonic in dry...that's not supercruising.


13 minutes, or maybe less than that.
Why is there such a limitation of 150 miles? Obviously fuel doesn't burnt out in 13 minutes or 150 miles, then I take the aircraft is decelerating under military thrust, and after 150 miles, its speed is below Mach 1.2.

Now image what this claimed dash scenario can be. If I want to max the dash distance, I would afterburn to max speed then switch to max military thrust and hope it maintain longer above Mach 1.2. If the average speed during this 150 miles is higher than Mach 1.2, then the duration would be less than 13 minutes.

Anyway, I'm confident that F-35 can perform no less than Gen 4 fighters in term of speed, but it is not designed for supersonic like F-22 was. F-22 can do, for what I remember, 41 minutes of M1.5.
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johnwill

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Unread post04 Nov 2012, 07:29

sferrin wrote:
Image

AB to get over the hump.


sferrin's drag coefficient curve helps to explain why AB is needed to get past mach 1 and mil is enough to keep the F-35 at 1.2. However, the actual drag at those speeds increases much more than does the coefficient. To get drag, the coefficient must be multiplied by some constants and by velocity squared. So even if the coefficient were constant, drag goes up by velocity squared. That explains why more fuel is needed at 1.2 than at 0.95, using mil at both speeds.

Yes, other forms of drag (induced, trim) change as speeds goes up, but for this discussion, they are irrelevant.

Engine thrust does increase with speed up to a point, then drops as airplane speed starts to approach exhaust velocity.
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neurotech

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Unread post04 Nov 2012, 08:07

johnwill wrote:Engine thrust does increase with speed up to a point, then drops as airplane speed starts to approach exhaust velocity.

Certain aircraft, most notably the MiG-25, have an engine/intake combination that will produce thrust above M2.5 with the main limitation being engine core temperature. The engine will still produce thrust past the point overtemp, with more fuel being burnt as speed increases.
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Scorpion82

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Unread post04 Nov 2012, 11:48

neurotech wrote:That is a trade-off between engine performance and drag at varying altitudes. The curve would be different without canted wing pylons, as they contribute to the drag significantly.


And who says that these performance envelopes are based on a pylons fitted configuration? That the aircraft are regularly flown with empty wing pylons fitted doesn't mean that the performance envelopes in the FM are based on this configuration. AA standard load-out is 2 x AIM-9 and 2 x AIM-7/AIM-120 with the former being fitted to the wing tip rail launchers and the later being fitted to the fuselage stations. That's apparently the cleanest configuration used in the FM enevelope charts. And even if we'd assume that the wing pylons are being fitted it won't change the fact that the best performance is achieved at altitudes below 40k ft. The envelope curve would change in width and that's it.
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thegroundeffect

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Unread post04 Nov 2012, 12:20

falconedge wrote:
sketch22 wrote:As I've mentioned in another thread, I chatted with "Hog" from the 461st and he confirmed that yes the F-35 can indeed supercruise. It takes afterburner to get past the sound barrier but once hes supersonic he can pull the power back to mil and it'll stay there around Mach 1.2.

:? it quite hard to understand , i dont get it , if the pilot pull the power back then the force will be decrease how could the f-35 still able to remain it's speed ???
( i mean it physics :shock: )


From Mach .8 the drag on an aircraft wil start to incease significantly and will peak at Mach 1. After mach 1 the aerodynamic drag wil decrease, thus making it possible to fly faster with lower thrust. This is a characteristic that can only be found in aircraft. And this is the reason why legacy aircraft had to 'dive through' the sound barrier because they lacked the thrust to plow through it.
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cola

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Unread post04 Nov 2012, 12:34

megasun wrote:Why is there such a limitation of 150 miles? Obviously fuel doesn't burnt out in 13 minutes or 150 miles...

A good question...However, there are lot of parameters missing here.
If this is done in ideal conditions, then I'd say there's a structural limit present, probably overheating.
Maybe the engine is being pushed over 43klb of thrust, for this performance...there were hints the F135 is capable of 50klb thrust.
Cheers, Cola
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munny

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Unread post04 Nov 2012, 13:16

Interesting article and confirmation of a number of things. 6 missiles internal coming, maneuverability, ability to take over the shoulders shots, all aspect stealth, supercruise.... looks like it's slowly and surely beating the 4.5th (tiffy, rafale, su) gens into obsolescence.

The article mentioned stealth being second to the F-22's. On the whole I agree due to the F-22 side surface cant angles yielding RCS an order of maginitude better (but the F-22 needs that because of the altitude it operates at). I still maintain that if materials are the same on aircraft leading edges, the F-35 should still have a better frontal, specular RCS. The F-35 is smaller and doesn't have any resonance causing cavities like the F-22's intakes.
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munny

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Unread post04 Nov 2012, 13:47

sferrin wrote:I wonder if Bill Sweetman will tell us about this at Ares. ;-)


If LowObservable on key publishing forums is in fact BS, then this is all he's got.

"As far as the AFA story goes, it should be read in a conjunction with the briefer's record of statements and predictions since he first became a public spokesman for the program."
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count_to_10

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Unread post04 Nov 2012, 15:19

johnwill wrote:
sferrin's drag coefficient curve helps to explain why AB is needed to get past mach 1 and mil is enough to keep the F-35 at 1.2. However, the actual drag at those speeds increases much more than does the coefficient. To get drag, the coefficient must be multiplied by some constants and by velocity squared. So even if the coefficient were constant, drag goes up by velocity squared. That explains why more fuel is needed at 1.2 than at 0.95, using mil at both speeds.

Yes, other forms of drag (induced, trim) change as speeds goes up, but for this discussion, they are irrelevant.

Engine thrust does increase with speed up to a point, then drops as airplane speed starts to approach exhaust velocity.

I thought military power was a fuel pump rate. Are you saying that, at subsonic speeds, military power is less than full pump speed? I guess I could see that, if there is some other limitation on thrust.
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1st503rdsgt

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Unread post04 Nov 2012, 15:29

munny wrote:
sferrin wrote:I wonder if Bill Sweetman will tell us about this at Ares. ;-)


If LowObservable on key publishing forums is in fact BS, then this is all he's got.

"As far as the AFA story goes, it should be read in a conjunction with the briefer's record of statements and predictions since he first became a public spokesman for the program."

Top link in a Google search: "Key Publishing Ltd: Europe's Leading Aviation Publisher"

nuff said
The sky is blue because God loves the Infantry.
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Scorpion82

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Unread post04 Nov 2012, 16:01

count_to_10 wrote:I thought military power was a fuel pump rate. Are you saying that, at subsonic speeds, military power is less than full pump speed? I guess I could see that, if there is some other limitation on thrust.


It's always about the right mix of fuel AND air. The fuel feed must be adjusted to the amount of air that's being available to the engine and that is dependent on speed and altitude due to compressability of the air which is linked to airspeed and the density of air linked to altitude. The fuel/air mix must be kept within a certain ratio, otherwise the engine will flame out. Whether too much air or fuel both isn't good.
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sferrin

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Unread post04 Nov 2012, 17:50

johnwill wrote:
sferrin wrote:
Image

AB to get over the hump.


sferrin's drag coefficient curve helps to explain why AB is needed to get past mach 1 and mil is enough to keep the F-35 at 1.2.


That's all I was trying to show.
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sferrin

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Unread post04 Nov 2012, 17:54

munny wrote:
sferrin wrote:I wonder if Bill Sweetman will tell us about this at Ares. ;-)


If LowObservable on key publishing forums is in fact BS, then this is all he's got.

"As far as the AFA story goes, it should be read in a conjunction with the briefer's record of statements and predictions since he first became a public spokesman for the program."


LOL Not surprised. :lmao:
"There I was. . ."
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falconedge

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Unread post04 Nov 2012, 20:00

how far can the F-35 fly at top speed mach 1.6 ? , if it can only fly for 150 miles at mach 1.2 then the distance it can fly at mach 1.6 will even shorter right ?
btw even the F-22 which is designed to supercruise can only maintain mach 1.82 for 100 nm (185 km ) :shock: not very impress if go know that F-22's ferry range is over 3000 km :?
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bigjku

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Unread post04 Nov 2012, 20:11

falconedge wrote:how far can the F-35 fly at top speed mach 1.6 ? , if it can only fly for 150 miles at mach 1.2 then the distance it can fly at mach 1.6 will even shorter right ?
btw even the F-22 which is designed to supercruise can only maintain mach 1.82 for 100 nm (185 km ) :shock: not very impress if go know that F-22's ferry range is over 3000 km :?


Compared to what exactly? The main point to be noted with the F-22 is that it can fly faster for longer than any fighter that can hope to kill it can. With the F-35 I think the main takeaway here is that the thing is plenty fast enough to deal with legacy fighters quite well.
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