Navy: F-35C Will Be Eyes and Ears of the Fleet

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geforcerfx

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Unread post21 May 2018, 03:12

I agree with the sensor shooter concept( have for awhile) and agree with the dogfight being a death trap for all who enter.

I was asking based off his statement that the F-35C would have the best STR. I don't know a ton about aeronautics and still learning when I can. I thought T/W was a important factor in STR, I know lift to drag is as well, but it seemed people were saying power was more important in STR.
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Unread post21 May 2018, 16:49

blindpilot wrote:you can see how the question of maneuverability is rapidly becoming a "oh btw, even though it doesn't matter," type question.


I think of maneuverability much like speed. it was SA and Stealth before SA and Stealth became a thing. in the 60s, Supersonic dash speeds were the prime demand of most air forces. Thats why most planes designed during that era looked like missiles with cockpits.

but it slowly became the norm and we needed to move on to another capability to gain an advantage. But then again we never went back to designing subsonic fighters. Not to any extent at least.

And even though Supersonic isn't talked about anymore, the Supersonic capabilities of modern fighters are far and away so much better than how it was when it was still in premium demand. I'd bet the slightly slower F/A-18 would out run the Mirage 3 in combat.

So even though maneuverability isn't the top demand anymore, I think that as long as it's a requirement, even if its a secondary requirement would still be better on future platforms simply because of sheer technological advancements.
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Unread post21 May 2018, 19:27

geforcerfx wrote:Spaz asked for the F-35C questions to get moved off the UK carrier thread, so here I am.

.....

So better lift equals better turn, but don't you need power for sustained turn performance, the C's extra 7,000lbs puts it at power disadvantage compared to the A.
[/quote]
Sorry, I still ended up dropping an answer on the other thread.

"Better" lift equals "better" turns... way too oversimplified at yet very applicable to the current discussion.

I model the maneuver weight (max weight for max G) of the F-35A at ~52,000lb and for the F-35C ~59,000lb. The F-35C is indeed 7,000lb heavier under these conditions, 13% heavier than the A.

With max G loads of 9 and 7.5, respectively, the raw lift capability of the two variants is ~470,000lb and ~444,000lb (5.8% more lift for the A). The A at 9 G is making more lift with it's 460 ft "Wing Area" than the C with its 620 ft "Wing Area" (35% more lifting area). This means the maximum effort lift loadings are over 1,020 pounds of lift per square foot of "Wing Area" for the A and just over 715 pounds of lift per square foot of "Wing Area" for the C.

At any given speed and G, the C will need a lower CL to create the lift than the A. So if they are both making 5G at a given speed and altitude the C will have a significantly lower CL than the A even though it is making 13% more lift. As the A need ~20% more CL to generate any given G than the C, it has a corresponding 62% higher CDi (assuming they have matching Oswald's efficiency factors, which I expect the C has a better one of those too). A 62% higher CDi combined with the 35% smaller wing comes out to be that at any given speed, altitude, and G the F-35A will have 20% higher induced drag than the F-35C. In level and high speed flight this drag is less than form drag and wave drag so it is not much of a factor in acceleration. In high G flight this is the dominant form of drag.

So at a point where the thrust equals the total drag of a turning F-35C (speed and altitude remain constant), the lighter F-35A in a matching turn is going to have negative excess thrust and is going to lose speed and/or altitude.
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geforcerfx

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Unread post22 May 2018, 05:55

SO the smaller lighter A variant will lose speed at the C's max STR because it will create to much drag is what I got from that (again super basic aeronautics understanding). That just seems weird in my mind I guess, So if they were both at the same STR that they could both maintain would the C would be pulling less G as well?

Thanks for the answer
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Unread post23 May 2018, 01:21

A few self-interest aka hack job articles criticising the F-35C range will likely emerge. Source of this is a house committee comment. How one can identify an hack job is of course when they conveniently leave out the intent or selectively quote.

https://www.stripes.com/news/us/navy-s- ... e-1.528359

So instead of quoting the articles, I would instead quote the entire house committee's comment which is available in the link below. The item in bold of course can be read with all the existing and recent discussions about JASSM-ER, LRASM and AETP engines available in the various threads of f-16.net.

https://www.congress.gov/115/crpt/hrpt6 ... rpt676.pdf

Briefing for the Senate Committee on Armed Services and the House Committee on Armed Services on US Navy’s efforts to expand carrier air wing long-range strike capability

The committee notes that the aircraft carrier air wing has been optimized for striking power and sortie generation and believes that it may not be configured to support the long-range strike required by current and future threat systems. While the introduction of the F–35C will significantly expand stealth capabilities, the F–35C could require increased range to address necessary targets. The committee believes that several options could be used to address this issue to include developing a stealth tanker capability, improved engine technology or to develop and procure a strike capability that is purposely built to strike at increased range. The committee further notes that the Navy previously desired to significantly increase the carrier air wing range with the development of the A–12 aircraft. The committee understands that the A–12 would have included a 5,000-pound internal carriage payload, stealth, and a range of 800 nautical miles. While the committee believes that requirements to support this capability remain relevant and the technology available, the development of the A–12 aircraft was mired in acquisition challenges that eventually resulted in the cancellation
of the program. While the committee further believes that the Department of Defense has successfully developed a suite of long-range intelligence, surveillance and reconnaissance capabilities, the committee also believes that it is vital that the Navy develop a carrier-based long-range strike capability.

Therefore, the committee directs the Secretary of the Navy to provide a briefing to the Senate Committee on Armed Services and the House Committee on Armed Services by January 25, 2019, on options to expand the strike range of a carrier air wing in a contested environment, including manned and unmanned capabilities, and, Department of the Navy capabilities it plans to pursue in the Next Generation Air Dominance capability.
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steve2267

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Unread post23 May 2018, 02:45

Geforce, perhaps think of the -A vs -C turning question thusly:

All aircraft flying at X knots, pulling Y G's, will have a turn rate of Z °/sec. The difference between aircraft being how much drag they generate to pull those Y G's, and whether they have a big enough motor to sustain that rate (STR).

What I hear spuds saying, is that since the -A has a smaller wing (460 ft^2), it has to fly at a higher angle of attack to generate the lift necessary to pull the same G's as a -C. As angle of attack increases, induced drag also increases. So the -A, with the smaller wing, is less efficient at pulling those G's and must fly at a higher AoA than the -C to develop the lift required for Y G's, and the higher AoA results in additional (i.e. higher) induced drag which ends up exceeding the power developed by the F135, so the -A ends up losing speed compared to the -C. If it loses speed, then the -A cannot sustain the
STR of the -C, and it will slow down to some smaller STR where it's total drag equals the thrust of the motor.

Isn't this what wing loading tells us about STR performance? Aircraft with lower wing loading have better STR -- they can generate the required lift for those Y G's at a lower angle of attack than the aircraft with a higher wing loading -- as long as they have the engine power to equal the generated drag. The -C and the -A have the same motor, so engine power is equal (for all intents and purposes.) So the aircraft with the lesser wing loading will be able to fly Y G's at a lower AoA, thereby generating less drag. The -C at 59K lbs and 668 ft^2 has a wing loading of around 88 lb/ft^2, whereas an -A at 52K lbs and 460 ft^2 has a wing loading of 113 lb/ft^2. The -C has about a 23% lower wing loading than the -A, so it should not be surprising that it "turns better" than the A.

Have a look at the Ps=0 curve below. Joe Studly could turn at 14°/sec at 0.9 Mach pulling about 7.4G for a turn radius of 4000'. Sam Slacker could get those same 14°/sec at 0.76 Mach but pulling a less demanding 6.2G and with a smaller turn radius of 3300' +/-. So just because one aircraft can out-G another, does not mean that the higher G aircraft is necessarily going to outmaneuver or outturn the lesser G aircraft. If you're driving with your hair on fire at 0.9 Mach and pulling 9G for your life, and I can slow down and pull the same or better turn rate at 0.5 or 0.6 or 0.7 Mach, I will be at lesser G (easier on my body, easier to maintain my SA), and I will have a smaller turn radius. It is for this reason, I think (someone please correct me if I'm wrong), that the ability to slow down quickly (e.g. Morten 'Dolby' Hanche's comments) and accelerate quickly ("it's like a Hornet with a TURBO!") are just as important, perhaps more so, than being able to drive around with one's hair on fire and pull uber-G.

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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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Unread post23 May 2018, 03:04

"Raging pulling G out over Atlantic Ocean in [F-35C] CF-5. Love this jet...flies like a kite and turns like a snowboard in deep powder snow." https://twitter.com/billieflynn/status/ ... 0411800576
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Unread post23 May 2018, 03:11

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"When a fifth-generation fighter meets a fourth-generation fighter—the [latter] dies,”
CSAF Gen. Mark Welsh
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Unread post23 May 2018, 13:05

Love that tweet by Flynn. Thanks for noting it spaz.

Question for the forum: it is hard to tell from a still photo, but is this another example of the F-35 stabs generating lift in a stable flight condition (i.e. left turn), or of using the stabs, along with the flaperons, to generate roll? I note the positive angle of attack of the right stab, and the slight deflection of the right flaperon. My interpretation was that the jet is using the stabs to generate lift, but the picture could have captured the left rolling transient.

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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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Unread post23 May 2018, 18:48

steve2267 wrote:Isn't this what wing loading tells us about STR performance?


Not really:

viewtopic.php?f=38&t=52948
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Unread post23 May 2018, 20:48

basher54321 wrote:
steve2267 wrote:Isn't this what wing loading tells us about STR performance?


Not really:

viewtopic.php?f=38&t=52948

From first post in the above link,

"Then you need to remember that the greater the difference between Wing Loading and Lift Loading the greater the induced drag will be meaning Sustained (Ps=0) turns are that much harder." In the case of the 5G F-35s, the F-35A has a greater difference between Wing Loading and Lift Loading compared to the F-35C. And this is a special case as except for weight and wing/stab size they are the same plane. Same body, same engine.
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Unread post28 May 2018, 17:47

sprstdlyscottsmn wrote:
zero-one wrote:
If I remember the operational performance comparison chart for the F-35A correctly, it'll pull an ITR of 9Gs at FL200 at both Mach 0.8 and Corner speed of Mach 0.74. Were there any revisions made to this

Using the weight conditions of 60% fuel, two AMRAAMS, and two GBU-31s the following is the performance my models show.

20,000ft

F-35A is 9G from ~0.82M with an ITR of just under 20.
F-35C is 7.5G from ~0.65M with an ITR of just around 20.

Assuming both start at the benchmark "0.8M at 20,000ft" mark and perform a max lift 180 degree turn, my current model shows the following.

The F-35A getting its nose around in 12.6 seconds (actual heading plus AoA) having decelerated to 0.34M with an average turn radius of 2,432ft.
The F-35C getting its nose around in 10.7 seconds (actual heading plus AoA) having decelerated to 0.31M with an average turn radius of 2,040ft.


A 10.7s 180deg at 20kft sounds very good for a loaded F-35C, what other aircraft in your models can broadly match that ? Maybe add the equivalent amount of fuel for
the two GBU-31s to get a clean airframe comparison.

p.s. the F-35C just looks perfectly proportioned from all angles, nice to know that has performance benefits too.
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Unread post28 May 2018, 21:37

steve2267 wrote:Love that tweet by Flynn. Thanks for noting it spaz.

Question for the forum: it is hard to tell from a still photo, but is this another example of the F-35 stabs generating lift in a stable flight condition (i.e. left turn), or of using the stabs, along with the flaperons, to generate roll? I note the positive angle of attack of the right stab, and the slight deflection of the right flaperon. My interpretation was that the jet is using the stabs to generate lift, but the picture could have captured the left rolling transient.

Image


Steve, in my opinion, the airplane is not rolling. The left flaperon appears to be deflected down about the same as the right (zoom in to see it), and the tail leading edge up is about normal for zero roll. There is no way to tell if the load on the tail is up or down due to the large effect of wing and flaperon downwash on the tail. If subsonic, the load should be up with no roll rate.

Surprisingly (maybe) in a subsonic roll using flaperons and tails to roll, in a left roll the load on the right tail will be down due to the very large downwash of the flaperon. But when supersonic, tail roll deflections are increased enough to overcome the downwash so right tail load is up in a left roll.
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Unread post28 May 2018, 22:37

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F-35CspeedbrakePDF.jpg
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Unread post20 Jun 2018, 03:57

spazsinbad wrote:http://www.codeonemagazine.com/images/media/2010_CF01_FW_Paint_04_1267828237_4142.JPG


Ooh, virtual speedbrake. Nice.
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