F-35C design changes from -A

Design and construction
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quicksilver

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Unread post21 May 2019, 11:40

https://images.search.yahoo.com/images/ ... r2=piv-web

Note differences betwixt a B strut and that of C in this pic (and others on Interweb). I believe the mechanism aft of the strut is called a ‘drag brace.’ Where would that go on a B given the lift fan? Additionally, imagine a redesign of the whole forward fuselage to accommodate the size and weight of that strut in a B vs the existing gear. Now, add an entire (soup to nuts) test program to qualify said aircraft.

Use the existing strut? Using what device to attach said strut to the cat shuttle?

As you finally concluded, ‘crank up the WOD and/or add a ramp to the ship’ is the right answer.
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Unread post21 May 2019, 12:04

sprstdlyscottsmn wrote:By nearly any metric it is the "least capable" but it is by far the one that impresses me the most.


Just off the top of my head, the (six) exceptions to your ‘any metric’ are subsonic accel, transonic accel, max Mach, unassisted STO, VTO and VLBB.

And, STO, VL (and VTO) are not ‘compromises’; they are monumental achievements that expand the amount of tacair (5th Gen, no less...) that allied nations can put to sea in defense of their national interests.
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Unread post21 May 2019, 15:18

quicksilver wrote:
sprstdlyscottsmn wrote:By nearly any metric it is the "least capable" but it is by far the one that impresses me the most.


Just off the top of my head, the (six) exceptions to your ‘any metric’ are subsonic accel, transonic accel, max Mach, unassisted STO, VTO and VLBB.

STO, VTO, and VLBB are not metrics used by anything other than the AV-8B and the F-35B. You are correct that it can out accelerate the C and that it has the same max speed across the board. But is slower in acceleration than the A. It has less payload than the A/C, it has less range than the A/C, it has a lower G limit than the A/C.

You seemed to miss what I said next though. It is, BY FAR, the one that impresses me the most. I never said a single word about STOVL being a compromise.
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Unread post21 May 2019, 15:54

You made the statement about metrics; someone else mentioned ‘compromise.’ Both are worthy of alternative views.

The ‘A’ is the “least capable” at landing on a ship. The ‘C’ was ‘compromised’ by scar weight/features necessary to land on the CVN.

So what metrics are most important? What you see depends on where you stand. :wink
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sprstdlyscottsmn

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Unread post21 May 2019, 16:14

quicksilver wrote:The ‘A’ is the “least capable” at landing on a ship.

Nah, it can do it just fine.... Once. :whistle:
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Unread post21 May 2019, 16:40

It is almost ‘ritual’ (to be flattering) to talk about the ‘B’ using those two descriptives — ‘least capable’ or ‘compromised.’ I clearly don’t subscribe to those conventions, nor to the idea that the ‘B’ is some kind of ‘improvement on Harrier’ (see the thread about first ‘B’ combat sorties elsewhere). IMNSHO, some (many who frequent this site excepted) still haven’t gotten their head around the package of capabilities that is “F-35” — which includes how/where they takeoff and land.
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Unread post21 May 2019, 16:49

sprstdlyscottsmn wrote:
quicksilver wrote:The ‘A’ is the “least capable” at landing on a ship.

Nah, it can do it just fine.... Once. :whistle:


Note that I said ‘least capable’ as opposed to ‘not capable.’ :wink:
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Unread post21 May 2019, 18:20

I used the word "compromise." Perhaps I should have written trade-off instead. I believe either is an accurate term to use from where I stand as an engineer. I (pithely speaking on behalf of LM aircraft design engineers) could give you the same range as the F-35A by stuffing more gas in there... BUT... you either have to give up internal stores capacity, OR the airframe has to grow larger (cannot store gas where the fan goes, after all), which means more structural weight, very probably a decrease in kinetic / maneuver performance, AND you probably lose your VL or severely restrict your VBB weight. I could give you a 9g airframe... but the increased weight is going to kill your VL / VBB performance. So compromises had to be made. If you don't like the "c" word, call it a trade or trade-off.

But in the binary metric of STO / VL / VTO (re-positioning) / VBB / ability to operate out of a 1000ft (or shorter?) strip when all AF base runways have been cratered, or CVNs sunk or driven out of the AO... it gives you a bright shiny "1", where everyone else, save the Harrier, gets a dull, dark "0."
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, 19:25

Heh, my favorite "that would be neat, but stupid" thought experiment is a Typhoon sized and shaped SSCVN. Instead of ballistic missile tubes, a small Hangar deck. An elevator right in front of the conning tower to get the F-35B to the launch deck. Have the top hatch that opens be the JBD and have the elevator treated for heat resistance. STO right off the elevator and VL right back on it.

Yes I already know it's stupid and would never work in reality, but its still fun from a Sci-Fi kinda perspective.
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Unread post21 May 2019, 21:14

Steve, some understand that ALL aircraft designs are an amalgam of trade-offs between a multiplicity of competing requirements. Most do not.

‘Compromise’ in reference to F-35 (...in general, and F-35B most often) is used in its pejorative, i.e. to “accept standards that are lower than is desirable.” Hence, in my view, its use tends to perpetuate the negative rather than accentuate the positive. Some would say that’s splitting hairs; so be it. Engineers will understand that precision. :salute:
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Unread post21 May 2019, 22:09

quicksilver wrote:Note differences betwixt a B strut and that of C in this pic (and others on Interweb). I believe the mechanism aft of the strut is called a ‘drag brace.’ Where would that go on a B given the lift fan? Additionally, imagine a redesign of the whole forward fuselage to accommodate the size and weight of that strut in a B vs the existing gear. Now, add an entire (soup to nuts) test program to qualify said aircraft.

Use the existing strut? Using what device to attach said strut to the cat shuttle?

As you finally concluded, ‘crank up the WOD and/or add a ramp to the ship’ is the right answer.


The drag brace on the C is aft of the gear and on the A and B it is forward of the gear. No interference with the lift fan.

Adding a launch bar was mentioned as a necessity for cat shots. Could it be done? Maybe. Should it be done? No.

I don't claim to be an expert on this topic, but I was the General Dynamics structural engineer on F-111B carrier suitability tests at Pax River in 1968 and for F-16 arrestment tests in 1979 at EAFB.
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Unread post21 May 2019, 22:23

“The drag brace on the C is aft of the gear and on the A and B it is forward of the gear. No interference with the lift fan.”

The point I was trying to make from the pic of the ‘C’ was that to put a ‘C’ strut on a ‘B’ would require accommodation of the drag brace in space/structure that is occupied by lift fan. Is that incorrect?
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Unread post21 May 2019, 22:42

quicksilver wrote:Steve, some understand that ALL aircraft designs are an amalgam of trade-offs between a multiplicity of competing requirements. Most do not.

Compromise’ in reference to F-35 (...in general, and F-35B most often) is used in its pejorative, i.e. to “accept standards that are lower than is desirable.” Hence, in my view, its use tends to perpetuate the negative rather than accentuate the positive. Some would say that’s splitting hairs; so be it. Engineers will understand that precision. :salute:


Your beating is finally getting through. Keeping in mind a wider potential audience than just other technically astute individuals is smart, and something to bear in mind. Thank you.
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, 23:45

sprstdlyscottsmn wrote:Heh, my favorite "that would be neat, but stupid" thought experiment is a Typhoon sized and shaped SSCVN. Instead of ballistic missile tubes, a small Hangar deck. An elevator right in front of the conning tower to get the F-35B to the launch deck. Have the top hatch that opens be the JBD and have the elevator treated for heat resistance. STO right off the elevator and VL right back on it.

Yes I already know it's stupid and would never work in reality, but its still fun from a Sci-Fi kinda perspective.


Neat but (goofy)? Try this on for size —
https://www.secretprojects.co.uk/thread ... rier.2372/

Or how about a people pod?
https://theaviationist.com/2013/12/06/e ... ng-pods-2/
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Unread post21 May 2019, 23:53

Oh yeah! I remember reading about that system. Supposed to be gyro stabilized so that the Harrier only needed to hover and the arm would grab it. Good times.
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