F-35C design changes from -A

Design and construction
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steve2267

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Unread post28 Jan 2017, 19:45

The design changes from the F-35A to the F-35C to support carrier ops are substantial. Larger wing to enable lower approach speeds, larger control surface to increase control at those lower approach speeds, beefier landing gear, beefier structure in general to handle shock / impact / vibration loads of arrested landing etc.

My specific question: Can someone estimate the weight of the changes required to support EMALS catapult assisted takeoff, but nothing else. I'll break the question in two:
  1. How much weight would you have to add to an F-35A to support an EMALS CATO in conventional configuration? (I realize this may not be possible with the -A's smaller wing.)
  2. How much weight would you have to add to an F-35B to support an [b]EMALS/b] CASTO where you are launching the -B in a STO mode using the liftfan / vectored main engine and you only need to get it to ~80 knots?

Are we talking 500lbs of extra structural weight? 1000lbs?

EMALS is a smoother acceleration compared to a steam cat, at least from what I've read. Combined with only having to accelerate a -B to 80kts, I would think the additional structural weight would be minimized.

Obviously extra weight in a -B reduces its bring-back capacity, but I am curious nonetheless.
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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spazsinbad

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Unread post20 May 2019, 06:36

Regarding Q.2: An F-35B is able to STO from 300 feet [length of CVN EMALS] AFAIK with a useful fuel load - there are always whatevers regarding WOD Wind Over the Deck and air temperature. May one be curious to know: WHY 80 cannots?
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sprstdlyscottsmn

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Unread post20 May 2019, 15:32

That was my first thought as well Spaz. The Killer Bee already STOs in the distance of a cat shot, so if you are trying to CATASTO then go for 120kt at max weight.

Your real question is "how much structure is needed to fling a 30 ton aircraft at 4 G by the nose wheel and do it thousands of times without fail?"
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steve2267

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Unread post20 May 2019, 16:45

Wow, this is a thread from the past.

I do not recall entirely where the 80 kannohts came from. I am thinking I may have read somewhere that the rotation / takeoff speed for a Killer Bee was 80kts.

At that time period... I may have been playing around in my head with how small could one make a ship to fling Killer Bees off the front end and vertically recover them on the back. At one point, I had hair brained ideas of destroyer-sized ships where the Killer Bee cat shot may have started from within the superstructure, launching ala Battlestar Galactica. Then vertically recovering on a largeish landing area at the rear of the ship. But then I got edjeemukated on the dynamic movement of a small boat and that if helos have a challenge recovering to frigates and destroyers, Killer Bees recovering in sea states of varying nastiness is not smart. Plus there's the whole WOD thing, especially as it relates to superstructure wake turbulence etc. My original idea was spun off a what-if question having to do with dispersing Killer Bees across a wide area... so the enema would have a harder targeting problem, and would not know from where the next attack was coming.

I think the original question was an attempt to swag the weight required for a CASTO and whether it would kill your vertical recovery weight.

I came to the conclusion the smallest ship that would be potentially useful as a small aircraft carrier would be between 10,000 and 20,000 tons (ish), and potentially be able to embark between 10 and maybe up to 20 Killer Bees. Of course, we have other threads to discuss light carriers, and various nations are potentially interested in LHA / lightning carriers.

Best I can recall my thinking behind this old thread from the past.
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 post20 May 2019, 21:36

:crazypilot: :devil: It was a good zombie thread (unanswered) to resurrect but.... F-35B is amazing - as it is. :mrgreen: 8)
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Unread post20 May 2019, 23:23

:cheers:
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 post20 May 2019, 23:25

By nearly any metric it is the "least capable" but it is by far the one that impresses me the most.
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Unread post20 May 2019, 23:36

I guess it depends on your metric.

The ability to STO with a decent payload, accelerate supersonic, conduction mission, RTB and VL is quite a capability. In fact, no other aircraft in the world can accomplish it. As I recall, that capability won the JSF team the Collier Trophy a while back.

What I find even more impressive, is even with design compromises forced by the STO and VL requirements... the Killer Bee can still (apparently) handily dispatch F-16's, F-18's, F-15's etc.
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 post20 May 2019, 23:49

Thinking about this a little more...

There have been endless debates here (and elsewhere) over E-M diagrams. I'll toss this idea out for debate: one of the (primary?) reasons the F-35 is so dangerous, is that it can slide left <--> right (e.g. velocity) faster than any other aircraft to date, save the F-22. That is, in totality, it can brake faster, accelerate faster, and perform maneuvers at high alpha better / faster than any other aircraft.

One might argue that the F/A-18 / Super Duper can fly at high alphas like the F-35, and it can slow down fast too... BUT... the F-35 can re-gain its energy faster than the F/A-18 / Super Duper. The Bug/Rhino can piss away its energy to perform magical butterfly tricks, but regaining that E is going to suck. On the other hand, the F-16 performs really well towards the right end of the E-M domain at high energy states. And from reading what Gum's has written, the F-16 can dump it's energy if the pilot wants via a bat turn. The F-16 can regain it's E (almost) like nobodies business... BUT the F-16 is alpha limited.

The F-35 is the first aircraft to be able to (out?) decelerate other aircraft, utilize the high-alpha flight regime to its advantage, but regain it's E quickly when it is needed.

How can a 7g limited aircraft like the Killer Bee kill Bugs / Rhinos / Vipers / Eagles etc? I think it is because it can take advantage of the high alpha regime when the situation calls for it, yet slow down to it's optimum turning speed (e.g. smaller radius + v. good rate) but with the power to either re-accelerate to get-out-of-dodge speed or power into the vertical. It's the combination of all these traits that make it so deadly.

Having said all that, yes, the F-35C and F-35A are more "capable", but the Killer Bee is still better than everything else out there save the F-22 (i.e. in an air-to-air role).

Back in the '80s, if you had asked someone how'd they like an F/A-18 Hornet that accelerates like a Viper, is invisible on radar, oh, and it can do that Harrier thing, yet have a top speed of 1.6 Mach... they'd probably look at you like you had just come from a Cheech and Chong party hosted by Saab... :devil:
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 post21 May 2019, 00:48

So, tell us again what your question might be...

I think you’re making waaay too much out of the structural load limit.

Wrt your scar weight question, there would be the difference in weight between the cat-capable nose strut; a different keel structure; and, given significant differences in load paths there is structure (like the keel) that has to be accommodated in the overall design. It’s not like there is a kit that could be created to do some kind of ‘conversion’. Johnwill would have the most insight on this topic.

The bottom line is it would kill your VLBB.
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Unread post21 May 2019, 02:46

quicksilver wrote:So, tell us again what your question might be...


I have no question.

In trying to recall why I made my origial post almost 2-1/2 years ago -- in my earlier posts of this resurrected zombie thread (tanks a lot Spaz! :shock: ) -- as best I can recall, I was a wondering how much additional structural weight would be required to be able to make an F-35B catapult-able on an EMALS catapult. I vaguely recall thinking that EMALS should result in far less shock loading on a catapulted aircraft, and thus, could the structural weight required be minized such that VLBB is not squooshed?

quicksilver wrote:I think you’re making waaay too much out of the structural load limit.

Wrt your scar weight question, there would be the difference in weight between the cat-capable nose strut; a different keel structure; and, given significant differences in load paths there is structure (like the keel) that has to be accommodated in the overall design. It’s not like there is a kit that could be created to do some kind of ‘conversion’. Johnwill would have the most insight on this topic.

The bottom line is it would kill your VLBB.


I never envisioned "a kit." I didn't fall off the Sprey-inspired turnip truck. But I was looking for a swag on how much additional weight would be required.

As became clear from other threads, it was a stoopid idea.
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 post21 May 2019, 03:18

“I never envisioned "a kit." I didn't fall off the Sprey-inspired turnip truck. But I was looking for a swag on how much additional weight would be required.“

I wasn’t suggesting you did. But, your hypothetical comes near a too-common public perception that it’s relatively easy to make ‘other’ jets successfully cat/trap capable (eg APA and F-22). Thus, my query about what you were trying to resolve.

The other matter in ANY weight addition to the B is location of that weight relative to thrust split between the lift fan and the main engine.
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Unread post21 May 2019, 04:23

Given all we know with posts about how NAVAL AVIATION Aircraft are designed & TESTED (SHAKE & ROCK & ROLL!) is this:

Navalising the F-22 Raptor 23 Feb 2009 Chris Mills: http://www.ausairpower.net/APA-NOTAM-230209-1.html
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Unread post21 May 2019, 06:13

The memory jogs once more.

The other idea that had been bouncing around my head was to fling a modified F-35B (F-35BC ?) off the ship with an EMALS catapult, with the idea, that again, an EMALS system would have less of a weight impact to the "BC" structure. Then leverage the STOVL mode 4 of the Killer Bee to do SRVL recovery on the boat... negating the need for an arresting gear system. I seem to recall thinking that the EMALS could maximize the load carrying capacity & range of the Killer Bee (Cat) -- i.e. enable an aircraft to carry more on a catapulted Bee than the max you could get on a STO.

Having said all that... the KISS solution is a ramp at the front of the boat, then architect the boat to maximize aircraft flow: launch, recovery, re-arm, re-fuel etc. The new Queen Elizabeth class probably has that all figured out. None of the boats in development now, with possible exception of one of the Italian boats, in the 20-30,000 ton class seem to be optimized for F-35B operations. They seem to be more LHA adapted to be able to conduct F-35B ops. But that is probably all best for another thread.
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 post21 May 2019, 06:58

Using the EMALS system to launch an F-35B from a deck seems really impractical to me, considering all the weight and cost needed to strengthen the airplane. Not just the landing gear and fuselage backup structure, but every piece of internal equipment (systems, weapons, engine, lift fan, etc. would have to be re-qualified to the new conditions. But there is a possibility to develop an EMALS-assisted launch capability, using only a fraction of EMALS capability. The idea would be to conduct a thorough analysis and test program to determine how much added launch thrust from EMALS could be accommodated without any structural changes other than a launch bar on the nose gear.

Why do it? Increased gross weight takeoff, reduced WOD requirement, reduced lift thrust from engine and lift fan for increased life, less deck space required, etc. Would I try it? Absolutely not. And if anyone says I suggested it, I'll deny it.

Back to the bicycle shop!

Added:
Steve I see you added a post whilst I was pecking away at my keyboard. Seems we are thinking along the same lines. By the way, you will never get an arresting hook installed on a B.
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