F-35B Races Super car

Discuss the F-35 Lightning II
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steve2267

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Unread post08 Feb 2020, 02:46

Oh, for crying out loud... it was a TIE!

But before they could run the tiebraker, the Killer Bee hovered over the runway -- it was supposed to be behind the McLaren, but with telephoto effect would appear above the McLaren. The McLaren folks failed to heed the warning of LM and the Royal Navy and declined to spray the speshul heat-resistant metallic paint from HMS QE flight deck on their car... and someone bolloxed something up,and when the Bee hovered OVER the McLaren, the car was almost melted from the ultra high heat from the F135... well, they think the car body survived, but all the lithium ion batteries melted, then one caught on fire and the car... it was was a runaway electric fire... quite a mess.

:drool:
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 post08 Feb 2020, 03:01

steve2267 wrote:Oh, for crying out loud... it was a TIE!'... :drool:

Yep the TIE FIGHTER wins every time. https://starwars.fandom.com/wiki/TIE/LN_starfighter
A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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marsavian

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Unread post08 Feb 2020, 06:37

No, the F-35B won including with neat Dojo bat-turns thrown in (7g and 35 AoA). Course was triangular and involved three turns. The pilot described each turn thus :

"250 ft, 400 mph at first turn, put the bank on and it will be a 7g limiter pull to get to 35 alpha to minimise the radius of the turn and again repeat at the next turn. Won't be able to make the last left turn at 500mph at 250 ft so do a right turn at 7g to bleed down to 35 alpha and skid around the corner to out drag the car at 550mph at 100ft"

Does beg the question, why 35 alpha and not 50 ?

From 9min+ (try using a UK VPN outside the UK)

https://www.bbc.co.uk/iplayer/episode/m ... -episode-2
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basher54321

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Unread post08 Feb 2020, 14:41

marsavian wrote:
Does beg the question, why 35 alpha and not 50 ?


Assuming the pilot "AK" was accurate then would have to guess 35 degrees AoA is what the limiter is scaled for to produce the best turn performance for that speed / altitude / config - as in the best turn performance is not always going to be simply the biggest number.
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basher54321

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Unread post08 Feb 2020, 14:44

steve2267 wrote:Oh, for crying out loud... it was a TIE!

But before they could run the tiebraker, the Killer Bee hovered over the runway -- it was supposed to be behind the McLaren, but with telephoto effect would appear above the McLaren. The McLaren folks failed to heed the warning of LM and the Royal Navy and declined to spray the speshul heat-resistant metallic paint from HMS QE flight deck on their car... and someone bolloxed something up,and when the Bee hovered OVER the McLaren, the car was almost melted from the ultra high heat from the F135... well, they think the car body survived, but all the lithium ion batteries melted, then one caught on fire and the car... it was was a runaway electric fire... quite a mess.



Ha they still have time maybe to make this the US version when it is finally shown :D
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Unread post08 Feb 2020, 15:36

basher54321 wrote:
marsavian wrote:
Does beg the question, why 35 alpha and not 50 ?


Assuming the pilot "AK" was accurate then would have to guess 35 degrees AoA is what the limiter is scaled for to produce the best turn performance for that speed / altitude / config - as in the best turn performance is not always going to be simply the biggest number.


x2
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steve2267

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Unread post08 Feb 2020, 17:37

Pilots have previously stated that the F-35 will happily give them more and more alpha if they ask for it... but the really high angles of attack will result in a LOT of drag, and will rapidly slow the aircraft, so the pilot needs to take care how much alpha (s)he asks for.

But as Basher and QS point out, if the 7g limiter kicks in at 35 deg alpha, you won't get anymore since the g-limiter has engaged.

Here's a question: does the F-35 CLAW implement hard g-limits? I seem to recall a pilot stating that it was possible to over-gee the aircraft? Or am I confusing or remembering soft g-limits that were in place BEFORE the full 3F software load? That is, before 3F, were g-limits on the "honor system" by pilots?
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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steve2267

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Unread post08 Feb 2020, 18:55

basher54321 wrote:
marsavian wrote:
Does beg the question, why 35 alpha and not 50 ?


Assuming the pilot "AK" was accurate then would have to guess 35 degrees AoA is what the limiter is scaled for to produce the best turn performance for that speed / altitude / config - as in the best turn performance is not always going to be simply the biggest number.


Spurts, is this a new datapoint for you, or is it merely more confirmation of your model?

It's not clear to me if the "Aye" model gets to 9g at 350kts too, by just relaxing CLAW a bit and allowing max alpha to increase, but if CL vs alpha is linear, that would suggest 45 deg for 9g... which seems too high, in that, yeah, you could go to 45 deg to get 9g, but the drag will be so high you won't stay there. But.. that could be your Dojo drift point, I suppose.

On the other hand, if CLmax occurs @ 35 deg alpha (where have I seen that before -- was that a plot from Spurts?), then the 9g corner for the "Aye" would be at slightly higher airspeed.

Do we know if the F-35A can pull and maintain 9g continuously at some point in its envelope? I recall Gums saying he could take the Viper to 9g and stay there all day until he ran out of gas below a certain altitude (5000' MSL?). But the drag at 9g at 35alpha must be very, very high. It would not surprise me if the "Aye" might not maintain 9g at its corner speed, but slow to 350kts where it could maintain 7g, same as the Bee. That would seem to explain a lot regarding past statement(s) by pilots (Flynn?) that performance differences between the Bee and the Aye would be negligible or not noticeable.

Corner speed refresher question: I know that corner speed is where structural load limit meets aerodynamic limit (i.e. at CLmax, correcdt?) ... but does it imply Ps=0 (i.e. that that speed can be maintained) ? My memory whispers that Ps is not necessarily 0 at corner speed.

But corner airspeed is in reference to max rate of turn, correct? And AK refers to minimizing radius... so, perhaps the better question is: was the Bee at its corner airspeed for this race? On the one hand, 35 deg alpha sounds suspiciously like CLmax angle-of-attack, and we know 7g is the load limit of the Bee... so that strongly suggests the Bee's corner is 350kts at 7g.

Arrrggh... where's the damn dash One?
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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marsavian

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Unread post08 Feb 2020, 19:43

Corner speed is max ITR and on the F-16 at low altitude Ps < -400. Notice the best turn is actually at 8+g although there is very little in it.

Cfwk2Ou_d.jpg


At 20kft F-16C vs F-35A

Image

F-35maneuverPerformanceGraph.gif
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basher54321

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Unread post08 Feb 2020, 20:11

steve2267 wrote:But corner airspeed is in reference to max rate of turn, correct? And AK refers to minimizing radius... so, perhaps the better question is: was the Bee at its corner airspeed for this race? On the one hand, 35 deg alpha sounds suspiciously like CLmax angle-of-attack, and we know 7g is the load limit of the Bee... so that strongly suggests the Bee's corner is 350kts at 7g.

Arrrggh... where's the damn dash One?



The F-16 has a corner range or plateau as oposed to just a single speed point:

viewtopic.php?t=10416
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steve2267

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Unread post08 Feb 2020, 20:20

CHAPTER NINE
BASIC FIGHTER MANEUVERING (BFM) THEORY


Turn rates are further divided into:
  1. Instantaneous turn rate: the max turn rate at any given airspeed (energy depleting).
  2. Sustained turn rate: the max turn rate available while sustaining energy.
    The fixed and variable factors begin to interrelate. G is the ratio of lift to weight. As you know,
    in turns or directional changes, lift must exceed weight, and you must apply G loads greater than
    one. At a constant TAS, to increase "G", you must increase AOA. Radial "G" will dictate the
    turn radius and rate. Maximum instantaneous g is the maximum lift a wing may generate at a
    given airspeed. Maximum instantaneous g is dependant upon the aircraft airframe capabilities.

Corner Speed

Corner speed is an important factor of maximum turn performance. Corner speed is defined as
the minimum airspeed at which the maximum allowable g can be generated
. At corner speed,
the aircraft can attain its maximum turn rate.
For our purposes, 280 KIAS is the T-2C corner
speed. Below this speed, if you attempt to pull more "G", the aircraft will enter buffet and stall
at its aerodynamic limit
. This results in an increase in the turn radius and a decrease in the turn
rate. On the other hand, if the aircraft is maneuvered above the corner speed, the max allowable
"G" becomes the limiting factor
. The excess airspeed (above corner speed) will result in a turn
radius increase and a turn rate decrease.
Knowing and flying the corner speed and the appropriate AOAs will give the fighter the most
bang for the buck: the best turn performance for the minimum amount of energy loss. These
numbers will be further detailed in the "Energy and maneuverability" section of this chapter.

http://navyflightmanuals.tpub.com/P-821/Corner-Speed-200.htm


(I figured QS would drag out the definition 'cording to the Navy, so I figured I'd spare him the trouble.)
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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steve2267

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Unread post08 Feb 2020, 20:30

In the definition I posted above, there is no mention of whether the corner speed is energy depleting or energy sustaining, just that it is where the aerodynamic limit meets the structural limit. Below the corner speed, if you try to pull more gee (by honking back on the stick more), you will stall (in most aircraft -- I don't think this manual takes the F-35 / F-22 / F/A-18 into account). You stall when you exceed the stall angle of attack. If memory serves, CLmax occurs right at the maximum angle of attack, so corner speed is where CLmax meets structural load limit.

Oh, I see other posts... I'm a gonna post this, then do some more reading...
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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steve2267

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Unread post08 Feb 2020, 21:02

Basher, thanks for that link, I went and (re)read it.

Question about "corner plateau" for the Viper. I have been looking at these doghouse plots, I've been looking for a curve that is relatively flat (parallel to) the X-axis... that is, turn rate is constant vs speed. But it occurs to me, and please confirm if I finally understand this correctly, that the "plateau" is not turn rate vs speed, rather gee vs speed. If gee vs speed, I definitely see where for the Viper @ sea level plot above (is that a Block 50?), it can maintain (or accelerate) at 9g from about 0.66 Mach to 0.99 Mach. Is this the "plateau" of which you speak?

Regarding my comments above, I was going to the very top of the chart, and was seeing that, again for the Viper @ sea level, the max turn rate was 26.2 deg/sec @ about 0.52 Mach, but that Ps < -400, so that if the pilot goes there, and stays there pulling max stick... he's going to slow down AND his gee's will also bleed off. Is this also known, or an example of, being on the backside of the power curve? (A place one generally does not want to be?)

Back to the McClaren race... it sure sounds to me like CLmax is at 35deg alpha, and at 350kts (400mph), Ps=0... as it would seem in a race one would not want to lose speed. If it really was a min radius turn... then that 350kts would below minimum sustained turn speed... Oooh... I'm reasoning myself into confusion. Am a gonna shut up now and await further comments...
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 post08 Feb 2020, 22:38

35 degree corresponds with my models CLmax. This would be the same in the A/B. The A may be the only one that goes to 50, but CL would reduce beyond 35, meaning the nose points but the flight path doesn't change as quickly as in a 35 degree AoA turn. If you want min radius, you want AoA for max lift. If you want max rate, you want AoA for max lift. This would be 35 degrees based on my model and these statements.
"Spurts"

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-Aerospace Engineer
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basher54321

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Unread post08 Feb 2020, 23:49

steve2267 wrote:Back to the McClaren race... it sure sounds to me like CLmax is at 35deg alpha, and at 350kts (400mph), Ps=0... as it would seem in a race one would not want to lose speed. If it really was a min radius turn... then that 350kts would below minimum sustained turn speed... Oooh... I'm reasoning myself into confusion. Am a gonna shut up now and await further comments...




Oh sorry didnt think this was new info - have always known it as a corner plateau although been a while since I had to think about what that was.

The F-16 does not have a true corner speed/velocity according to various pilots (and the USAF BFM fundamentals guide) - and this is due to the way the FLCS is set up to produce a decent turn rate based on....checking.........available G.

As a rough example given on that above sea level chart the plateau would be between ~M0.5 to ~M0.67.


A difference here is unlike the F-16, it appears the F-35B despite the limiter is allowed to get to where it can generate max lift (35 degrees) during a max or near max G turn.


How much energy a pilot wants to give up or gain depends entirely on the situation (jbgator said it better):

It is a constant evaluation of how to use energy. ITR is only important when you need to cash in energy to either survive an attack or to gain a position of advantage or exploit a fleeting weapons employment opportunity. Using it at any other time is wasting energy for no gain and provides an opportunity for your adversary (that mistake). If you pay more or less for that turn you are at more or less disadvantage after.

There are times to gain energy and times to expend it. ITR expends it, STR is neutral, and less than STR is gaining it. So in a normal fight you actually spend less time at ITR and STR than you do at something less (if you know what you are doing and are not defensive from the outset). Even when defensive you use it as long as you need to survive and then get back into energy gaining performance as fast as you can.
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