F-35B Races Super car

[Gums]

Salute!

Great EM diagram, and have been wondering about that for a long time but too lazy to run it down.

In short, too many here focused on 10 or 20 knots and 2 tenths of a gee.

The EM diagram for the Viper shows why it could wax most other planes with even an average pilot that used the excess energy to go vertical rather than pull a lotta gees at a high AoA. Look at the excess energy at 6 or 7 gees and 0.8 M or so.

Secondly, the limiter was not a rate doofer, but approx 9 gees until 15 deg AoA, then almost linear to 29 deg AoA and one gee. Later sfwe may have cranked in some roll rates and such, but not turn rate, Don't have time to link a good diagram, but it is a high school plot. Our rate was a function of the equations I show below.

Also do your own charts using a very simple approximation that gives rough numbers within a few percent of the real world ones using calculus and allowing for bank angle and the phase of the moon. So disregarding bank angle, use these simple equations to get radius and gee and rate,

r=vsquared/a
omega=v/r or simply, v=r*omega

Ypou will get very close to official flight test numbers and within the margin of error for an average pilot trying to achieve exactly 387 knots versus 400 when he yanks.

Gums sends...

[steve2267]

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, if I am reading you correctly, min radius or max turn rate are both at CLmax (i.e. angle of attack resulting in CLmax -- in a "classic aircraft" this would be right before the stall.) Max turn rate occurs at the intersection of the CLmax curve and the structural limit curve. Below that point you cannot generate enough lift to exceed structural limits, and above that point you cannot exceed some angle of attack (which is less than the CLmax alpha) lest you bend metal. I suppose you could rephrase that and state max turn rate is the turn rate that occurs for the min radius turn at your load limit speed? (A bit convoluted I admit.)

Since the F-35 does not have an alpha vs gee limit-curve like the Viper, if the pilot is at the intersection of CLmax and g-limit, i.e. @ the corner airspeed, the pilot can pull back on the stick a bit more, the increase in angle-of-attack increases drag, and he decelerates to a slower speed. If he reduces stick pressure and lowers alpha back to CLmax alpha, he will be flying a min radius turn at that speed (which is lower than the corner airspeed) -- correct?

"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" ... sure sounds like 7g @ 35deg alpha at 350kts is the Bees corner speed. With pretty much the same OML, and identical planform, that would translate to 396 or 400kts for 9g at 35deg alpha for the Aye. I think all the models will go to 50deg alpha (maybe more -- but I think Beesley said > 50 deg alpha doesn't get you much), but CLAW would limit alpha at times to prevent over-geeing the airframe.

[steve2267]

"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" ... sure sounds like 7g @ 35deg alpha at 350kts is the Bees corner speed. With pretty much the same OML, and identical planform, that would translate to 396 or 400kts for 9g at 35deg alpha for the Aye. I think all the models will go to 50deg alpha (maybe more -- but I think Beesley said > 50 deg alpha doesn't get you much), but CLAW would limit alpha at times to prevent over-geeing the airframe.

Re-reading this... I'm not so sure what I stated is necessarily accurate. It could be, but it is also possible that at 350kts (0.53 Mach) a 7g turn slows him down but increases alpha, so he keeps pulling on the 7g limiter until alpha reaches 35deg, then holds there until he completes the turn. Dunno. Nutz, there may not be enough info here.

[Gums]

Salute!

I think you are closer to the real performance than most here, Steve.

The only good thing about the high AoA capabilty is "nose pointing" when slow. That was one thing the Viper folks had to deal with. Saving grace was we could still roll really well without departing.

Gums sends...

[marsavian]

"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" ... sure sounds like 7g @ 35deg alpha at 350kts is the Bees corner speed. With pretty much the same OML, and identical planform, that would translate to 396 or 400kts for 9g at 35deg alpha for the Aye. I think all the models will go to 50deg alpha (maybe more -- but I think Beesley said > 50 deg alpha doesn't get you much), but CLAW would limit alpha at times to prevent over-geeing the airframe.

Re-reading this... I'm not so sure what I stated is necessarily accurate. It could be, but it is also possible that at 350kts (0.53 Mach) a 7g turn slows him down but increases alpha, so he keeps pulling on the 7g limiter until alpha reaches 35deg, then holds there until he completes the turn. Dunno. Nutz, there may not be enough info here.

In the last turn he did say it was a sustained 7g turn so I think you have the essence of what happened. It was impressive seeing a F-35B doing sharp turns followed by a zoom climb, all the F-35 birds can shake and move !

[steve2267]

I fired up my VPN and popped out in jolly old England. Even confirmed web sites thought my IP was in England, but no joy on watching the full clip.

In the last turn he did say it was a sustained 7g turn so I think you have the essence of what happened. It was impressive seeing a F-35B doing sharp turns followed by a zoom climb, all the F-35 birds can shake and move !

Not having been able to watch the quote, and just going by your phrasing: "was a sustained 7g turn" ... does sustained mean the 7g was sustained? Or does it mean the speed was sustained whilst pulling 7g? Was this at 400mph, 500mph, or 550mph?

I think I'm trying to squeeze too much from a grape, and will just enjoy the bit of video that I've been able to watch.

I will note that the F-16 EM diagram posted earlier (F110 @ Sealevel) shows pretty much 7g @ Mach 0.53 at Ps=0 (maybe slightly negative Ps). This also happens to be the left hand edge of the "plateau" that Basher pointed out earlier, being the same turn rate as the 9g turn the Viper can hold (taking into account Gum's admonition to not get hung up over a few tenths of degrees) at Ps=0 at 0.66 Mach (500mph / 435kts). That would explain why a 7g F-35B can hang with a 9g F-35A, or the "you won't notice it" comments I have read in the past. A Bee against an Aye? In the hands of good pilots, yeah, the Bee may be at a slight disadvantage. A Bee against anything else? Yeah, I can see the "you won't notice it" comments, plus the Bee has that delightfully big blower in the back that all the pilots rave about, to regain any lost speed.

[marsavian]

You also have to state you have a UK TV license, it's being decriminalised to not have one so don't worry they won't pursue the matter across the pond . They block a lot of VPNs try using the Opera incognito mode one.

This is exactly what he said about all the turns starting at the first, 11:45 mins in ...

I'm going to be at 250ft, 400mph at this turn, put the bank on. It will be a limiter pull to get to 35 alpha to minimise the radius of the turn to then parallel with the runway. We then roll out level. I'll continue down, then there will be another left turn, again 7g 400mph, limiter pull around the corner to roll out. We continue up, I'm not going to make the left turn here, it's too tight, I'm going to continue off. Again 250ft, this time at 500mph to enter this turn. 7g sustained to then bleed down, 35 alpha, so you can see the jet skidding around the corner to then roll wings level. 100 ft, 550 mph finish, with the car down here ...

[steve2267]

OK, I think I'm tracking now. On the last turn, he's going too fast to make a left 120º turn, so instead he makes a right 240º turn? (Not knowing the race course, but since it has 3 turns, and Marham I think is a mil airfield with 3 (or originally 3) runways, am guessing roughly equilateral triangle...

From your Viper SeaLevel EM diagram posted earlier, and using Gums' 20kts / sec decel rate as a swag, I'm going to estimate that it takes 6 seconds for the Bee to decel from 550mph to 400mph whilst pulling 7g, so he'd start the turn at about 18º/sec and that would increase to 22º/sec as he slows, so I'll just average that to 6 sec @ 20º/sec... leaving (240º - 120º = 120º @ 22º/sec)... 5.5sec. So... since I cannot watch the video, here's my question:

Mars, does the Bee complete that last right hand turn in about 11-12 seconds? Assuming you get to watch the entire turn on the full video... am guessing you can do the old F-16.net Youtube counting trick...

[steve2267]

Marham's airfield is laid out as a 45-45-90 triangle:

From 0:47 and 1:10 of the video in post #1, they are starting on Rwy 24. First turn is a left, check, 2nd turn a left... check. And if the jet has to make 3 turns, the last one being a left... the jet (anyway) is finishing down Rwy 24 again. So instead of a left 135º turn, he's making a right 225º turn. Rejiggering my math above... 6sec right hand turn @ 7g whilst slowing from 550mph to 400mph (@ -20kts/sec swag per Gums' comment) averaging 20º/sec turn rate, leaving 105º @ 22º/sec (4.8sec)... Total time for turn 11sec (ish), allowing for time to roll in/out of bank... I'm still coming up with...

Mars, does the last right hand turn take 11-12 seconds?

[outlaw162]

After you nail down these calcs, QS made an interesting comment about the AV-8A in the VSTOL mode. Wonder how much better or worse off this guy would have been had the rules stipulated a VTO or VSTO and subsequent airborne acceleration instead of the conventional takeoff utilized.

I want to see the guy race a Formula 1 and make the turns at Watkin's Glen.

[steve2267]

After you nail down these calcs, QS made an interesting comment about the AV-8A in the VSTOL mode. Wonder how much better or worse off this guy would have been had the rules stipulated a VTO or VSTO and subsequent airborne acceleration instead of the conventional takeoff utilized.

I want to see the guy race a Formula 1 and make the turns at Watkin's Glen.

Are we racin' or rubbin'? Would the Bee be within racin' rights to, errmm... dissuade the McLaren from certain lines owing to the 20000+ lb blow torch comin' out the backend?

[outlaw162]

To make the chicanes on a Formula 1 course, I 'spect the B would have to go into the lift engine mode quite often so the blower would be in and out (so to speak)....but I'd definitely give him a little leeway on the lines....and wouldn't allow him in the pits.

[steve2267]

Mode 4 is good to what? 250kts? Just not sure how the Mode 4 CLAW works and if it allows one to bank @ 100kts or 200? We know down slow, the 'puter handles all the banking... the stick and throttle just command left/right, up/down, go faster forward/rearward... Would suck pretty bad to be motorin' down the straight, hit the chicane and not be able to bank...

The Lightning rider prolly just get pissed, tuck it all in, go vertical to a pedal turn, then drop one of 'em smart SDB-II's on the McLaren or F1... then head to the bar...

[outlaw162]

I was under the impression they would just 'translate' to the next straightaway with their magic inceptor....no bank required....like sliding over to the boat....kinda like teleportation or telekinesis.

[steve2267]

I recall when it was a big deal that a Corvette developed over 1g lateral on the skid pad. I just looked up F1 lateral gees... 4-6 lateral g's!!! If the stick is playing inceptor mode... not sure how da plane will handle a demand for 4-6g turns in Mode 4!