Operational Performace Comparison: Viper, Beagle, and Stubby

The F-35 compared with other modern jets.
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sprstdlyscottsmn

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Unread post09 May 2018, 22:53

viper12 wrote:
sprstdlyscottsmn wrote:There IS a 1,000kg ton (tonne, long ton, or metric ton) which is 2,200 lb.


Just to nitpick a bit, a long ton is actually different, being the heaviest of all tons around ; it's 2,240lb = 1,016kg : https://en.wikipedia.org/wiki/Long_ton

I did not know that. Thanks! I love learning new random bits.
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gta4

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Unread post10 May 2018, 02:29

The most evident proof of F-35's maneuverability limitation in 2015:
Pilots complained about F-35's pitch rate.
Now, who complains F-35's pitch rate? Those airshow moves clearly contradicts that.
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collimatrix

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Unread post11 May 2018, 10:23

Spurts, thank you very much!

Do you mind if I repost your explanation elsewhere?
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sprstdlyscottsmn

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Unread post11 May 2018, 14:20

By all means, do.
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collimatrix

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Unread post14 May 2018, 20:52

Further question; why would the F-35 be weaker in the 20-25 AOA range where the F-16 dominates? Is there anything to the idea that the F-35 was optimized for instantaneous turn rate while the F-16 was optimized for sustained turn rate?

Thank you for clarifying the issue of fineness ratio vs area ruling.

F-35C vs F-35A is interesting. The F-35C lacks the little wing root vortex generators that the A has. Presumably it has to generate a lot of lift at a fairly low AOA for carrier operations. Which makes me wonder; what would happen if you put an F-35C wing on an F-35B? STOVL operations require quite a bit of low-airspeed lift too.

One of the things I remember when I read earlier drafts of the operational performance comparison is that the F135 engine has surprisingly uninspiring specific fuel consumption. Given that it's a generation newer than the F100/F110, it should have a higher overall pressure ratio and a hotter turbine inlet temperature. It's also got a rather high bypass ratio. All else being equal, those things should make it an exceptionally efficient engine. But it isn't.

What is your guess as to why that is? I was thinking that the LO features of the nozzle trade away a bit of SFC. But that's just a guess. Could it be something else? Could the compressor have a rather low isentropic efficiency in exchange, say, for compactness, light weight or good throttle response?
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sprstdlyscottsmn

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Unread post14 May 2018, 21:55

collimatrix wrote:Further question; why would the F-35 be weaker in the 20-25 AOA range where the F-16 dominates? Is there anything to the idea that the F-35 was optimized for instantaneous turn rate while the F-16 was optimized for sustained turn rate?


We cannot draw the conclusion that the F-16 was also using 20-25 AoA. At no point does the test report indicate the regime the F-16 was using. If anything, we can conclude the F-16 was at less than 25 degrees as that only allows 1G in the CAT-I configuration while 20 degrees is around 7G IIRC.

The F-16 was optimized to reduce speed lost in a max pull. The F-35 is optimized to lose and gain speed as needed.

collimatrix wrote:F-35C vs F-35A is interesting. The F-35C lacks the little wing root vortex generators that the A has. Presumably it has to generate a lot of lift at a fairly low AOA for carrier operations. Which makes me wonder; what would happen if you put an F-35C wing on an F-35B? STOVL operations require quite a bit of low-airspeed lift too.


The F-35C also has full span flaps/flaperons and a large lifting tail. I expect its lift curve looks very different than the F-35A. As for a STOVL C (or big wing B) I doubt it would even be able to operate. Adding 160ft^2 of wing and likely another 60ft^2 of tail is going to add a lot of weight. The C is the heaviest variant and it isn't all in the landing gear and longerons. Think instead of it this way, the difference in weight from the A to the B is all STOVL requirement, now add that weight to the C. It would also then be too wide to operate from small deck carriers.


collimatrix wrote:One of the things I remember when I read earlier drafts of the operational performance comparison is that the F135 engine has surprisingly uninspiring specific fuel consumption. Given that it's a generation newer than the F100/F110, it should have a higher overall pressure ratio and a hotter turbine inlet temperature. It's also got a rather high bypass ratio. All else being equal, those things should make it an exceptionally efficient engine. But it isn't.


There are a LOT of systems on the F-35. That requires a LOT of power. That power comes from the gearbox on the F135. It takes fuel to keep that gearbox adequately powered. I agree that on the surface I would expect the F135/F119 to have a better TSFC than the F100/F110 line. I don;t have enough info here to give a better answer.
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Unread post15 May 2018, 05:18

zero-one wrote:
sprstdlyscottsmn wrote: Also, the F-35C still has enough "oomph" to break Mach 1 with six one-ton JDAMs and four A-A missiles. How many navy planes can even carry that load? (F-35C only) How many fighter aircraft in the world can even carry that load? (F-35A, F-35C, F-15E) And how many of those are single engine? (F-35A/C only)


Hi sprst, Im curious about this line? Its amazing, but were Flankers and other European fighters also taken into account?

Also when we say six 1 ton JDAMs are we talking tonnes 1,000 pound Jdams or tonnes 2,000 poud JDAMs. cause I tried to convert and it seems that there are a few different kinds of tonnes. 1 is equivalent to around 1k lbs and the other is around 2k lbs


6 2k lb JDAMS
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