F-35A maximum G rating lower than 5?!

Discuss the F-35 Lightning II
  • Author
  • Message
Offline
User avatar

steve2267

Elite 2K

Elite 2K

  • Posts: 2548
  • Joined: 12 Jun 2016, 17:36

Unread post12 Feb 2020, 22:59

quicksilver wrote:
I never thought it would be anything but a beast. I knew/know some folks who flew the X-jet and others who are familiar w its development, DT and fleet intro.


Cool beans.
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.
Offline

quicksilver

Elite 3K

Elite 3K

  • Posts: 3133
  • Joined: 16 Feb 2011, 01:30

Unread post12 Feb 2020, 23:12

steve2267 wrote:
quicksilver wrote:
I never thought it would be anything but a beast. I knew/know some folks who flew the X-jet and others who are familiar w its development, DT and fleet intro.


Cool beans.


As one of the first MDAPs of the ‘age of information’ and social media, I did have some doubts about whether it would survive the acquisition system.
Offline
User avatar

steve2267

Elite 2K

Elite 2K

  • Posts: 2548
  • Joined: 12 Jun 2016, 17:36

Unread post12 Feb 2020, 23:20

quicksilver wrote:As one of the first MDAPs of the ‘age of information’ and social media, I did have some doubts about whether it would survive the acquisition system.


That was probably the biggest achievement of LM and the JPO.

I recall all the stink 8-12 years ago, though I didn't follow it as closely then, and more or less just dismissed all the naysayers out of hand. After all, how could the manufacturer of the F-16 Viper not know how to create a jet that performs? I think I was also suitably impressed by several of Dr. Bevilaqua's papers on the development of the lift fan and how that also folded into the overall design of the X-35.

Hopefully the defense industry has paid attention and learned some things about how to best develop products in this age of social media.
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.
Offline

quicksilver

Elite 3K

Elite 3K

  • Posts: 3133
  • Joined: 16 Feb 2011, 01:30

Unread post13 Feb 2020, 01:44

This is the podcast I referred to...(from the Favorite Quote thread...:doh:)

http://tun.in/tjA2rX
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 886
  • Joined: 25 Dec 2015, 12:43

Unread post14 Feb 2020, 05:40

f-16adf wrote:Steve, here are a few:

F-16A Block 15 turn charts.jpg


F-16 Block 15 and Block 42 P&W F100-220.jpg


Wow where did you get these charts from?
Offline
User avatar

steve2267

Elite 2K

Elite 2K

  • Posts: 2548
  • Joined: 12 Jun 2016, 17:36

Unread post14 Feb 2020, 07:13

FWIW, I was just looking again on the Blk 15 @ SeaLevel E-M chart that F-16adf posted a few days ago. The red dot below is an F-35B performing at show center -- 350 KIAS (0.53 Mach). Not an Aye, but a 7g limited Bee.

F-35B 5.5g @ SL (on F-16A Blk15 E-M Turn Performance @ SL).png


Here is what a Bee driver told me:

For example, in this video from the 2016 Miramar Air Show: https://www.youtube.com/watch?v=OoQbAj_ICYA at the 1:25 mark the pilot is hitting show center at 350 kts and executes a 5 - 5.5G turn in full a/b for 180 degrees of turn, pulls the throttle out of a/b to mil power for the next 90 degrees of turn to bleed off some energy (the jet will accel at 5.5G's in a/b at sea level), and then plugs blower back in for the last 90 degrees of turn for the "acoustic" effect... 30deg/sec is probably a bit high.




Now, this is not quite apples to apples... We don't know the fuel load in the Bee. It probably is not armed with AIM-120's for its routine. But still... this is a 7g limited F-35B rating around like a slick Blk 15 Viper with a full fuel load. Pretty damned impressive IMO... and speaks to the absolute beast to which QS refers earlier.

Also, I timed that turn at 32.4sec. Assuming it was a 360° turn, that works out to 11°/sec. Not quite 5.5g, eh? So, don't know what to say. If the pilot had to pull back out of AB to keep from accelerating, then maybe he backed off to 3g as well.

But my point remains: an F-35B will accel @ 5.5g at sea level, not something even the vaunted F-16A Blk15 could do @ 350kts. (NOTE: The F-16 really likes it faster. Get that rocketship up to 450kts, and it's sustaining around 18.5°/sec, and really rates around at 18°/sec from 7g @ 0.65 Mach (430KIAS) to 9g @ 0.83 Mach (545KIAS).

I guess this is yet another data point bearing out the comment by a test pilot or higher ranking officer that F-35 pilots should be really pleased with the performance of their jet, even the F-35B, which will not be noticeably different.
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.
Offline
User avatar

marsavian

Elite 1K

Elite 1K

  • Posts: 1723
  • Joined: 02 Feb 2018, 21:55

Unread post14 Feb 2020, 07:32

Steve, you can accelerate and hold a tighter turn at Ps=0 too, in the F-16A example above it can go up to Mach 0.7 at 8g without losing height while turning tighter. It can then continue to ride the Ps=0 curve up to Mach 0.9 at 9g losing turn rate before falling back again and losing speed regaining turn rate as it it holds the 9g turn. Also wasn't the F-35B limited to 5.5g in 2016 as well, Block 2B ? It was the F-35A that was limited to 7g at Block 3i in the same time period.
Offline
User avatar

steve2267

Elite 2K

Elite 2K

  • Posts: 2548
  • Joined: 12 Jun 2016, 17:36

Unread post14 Feb 2020, 08:08

marsavian wrote:Steve, you can accelerate and hold a tighter turn at Ps=0 too, in the F-16A example above it can go up to Mach 0.7 at 8g without losing height while turning tighter. It can then ride the Ps=0 curve up to Mach 0.9 at 9g losing turn rate before falling back again and losing speed regaining turn rate as it it holds the 9g turn.


Yes, I see that the F-16A can rate a bit higher @ 0.7 Mach. Didn't I acknowledge / state that in my post? Now, I'm not sure that you will turn tighter. The turn radius lines aren't drawn on this chart, and I have not sacrificed the brain cells to those calcs. Going faster suggests the radius might open up a bit. ("Turning tighter" means a smaller radius to me.)

Having said that... if the Viper is @ 0.53 Mach as well, on his Ps=0 curve, so right about 5.3g (?), since he's on Ps=0, he has no excess energy to accelerate, correct? Or am I understanding Ps incorrectly? Since he's already at SeaLevel, he can't descend... so he needs to relax some g's to go Ps>0, at which point he can accelerate up to 0.7 Mach, then pull to 7g (at which point he'll be Ps=0, and will not be accelerating anymore.)

This example demonstrates that the Viper's "sweet spot", if you will, is up around 0.7 Mach to 0.9 Mach. While this is only one point for the F-35, it suggests the Lightning is happier at a bit slower speed than the Viper: with a rate band maybe from 0.6(ish) to 0.8(ish).

IMO, the other thing to note here is that @ 5.5g, the Bee is rating around 17°/sec, (and for all we know it can also get the full 7g too, here). The Viper can rate 18°/sec (maybe 18.5°/sec) up between 0.7 Mach (7g) to 0.83 Mach (9g). BUT, one thing I've learned around here is that 1°/sec difference is not a deal breaker, it is not clearly superior. In fact, from what I've heard, a 1°/sec difference is equal, for most intents and purposes. So, even at 5.5g the Bee can hang with with the Viper. The Viper has an energy advantage... could he go vert? I suppose, but two things. As QS said... the Viper has to respect the nose of the Lightning. Also, the Lightning is also over 300KIAS. The rule of thumb I have heard from two different pilots is... if over 300kts, you can take it up. So if the Viper goes vert, the Lightning would seem to be able to go up as well. Viper & Lightning in a vert rolling scissors... there's a question for "Dolbe" or Dojo or somebody...
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.
Offline
User avatar

marsavian

Elite 1K

Elite 1K

  • Posts: 1723
  • Joined: 02 Feb 2018, 21:55

Unread post14 Feb 2020, 09:36

Yes, I meant rate higher rather then turn tighter. Strictly speaking you are correct about Ps = 0 but the reduction in G needed to ride the Ps = 0 curve is basically infinitesimal, Ps only has to turn slightly positive before gaining more speed to unlock more G. Boyd's original thesis on energy-maneuverability if you have not already read it ...

https://www.archives.gov/files/declassi ... 2-doc1.pdf
Offline

quicksilver

Elite 3K

Elite 3K

  • Posts: 3133
  • Joined: 16 Feb 2011, 01:30

Unread post14 Feb 2020, 10:24

So...

Your discussion has assumed in-plane (2-dimensional) maneuvering only, and situationally ignored geometric position and radius. What was the position of each fighter in 3-dimensional space relative to the other at the notional start of the engagement? Did one enjoy an offensive advantage or were they neutral, and how will their relative position(s) change as a consequence of maneuvering — to include not only nose position resulting from an achieved turn rate — but geometric position as a result of changing velocity (TAS) and turn radius?

After you grok that a bit — when and how does each fighter use 3-dimensional space to gain or neutralize an advantage versus the other fighter as the engagement progresses?
Offline
User avatar

steve2267

Elite 2K

Elite 2K

  • Posts: 2548
  • Joined: 12 Jun 2016, 17:36

Unread post14 Feb 2020, 14:30

marsavian wrote:Yes, I meant rate higher rather then turn tighter. Strictly speaking you are correct about Ps = 0 but the reduction in G needed to ride the Ps = 0 curve is basically infinitesimal, Ps only has to turn slightly positive before gaining more speed to unlock more G. Boyd's original thesis on energy-maneuverability if you have not already read it ...

https://www.archives.gov/files/declassi ... 2-doc1.pdf


OK, I see what you are saying there about riding the Ps=0 curve. Makes sense. I'm not sure it is easily determined how quickly one could change from 5.5g to 7g, i.e. is it near instantaneous, does it take a few seconds, or is it sluggish (tens of seconds), but I sense that would be a function of whether the Ps curves are closely spaced, or spread apart.
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.
Offline
User avatar

steve2267

Elite 2K

Elite 2K

  • Posts: 2548
  • Joined: 12 Jun 2016, 17:36

Unread post14 Feb 2020, 15:18

quicksilver wrote:So...

Your discussion has assumed in-plane (2-dimensional) maneuvering only, and situationally ignored geometric position and radius. What was the position of each fighter in 3-dimensional space relative to the other at the notional start of the engagement? Did one enjoy an offensive advantage or were they neutral, and how will their relative position(s) change as a consequence of maneuvering — to include not only nose position resulting from an achieved turn rate — but geometric position as a result of changing velocity (TAS) and turn radius?

After you grok that a bit — when and how does each fighter use 3-dimensional space to gain or neutralize an advantage versus the other fighter as the engagement progresses?


QS, while I have perused Shaw, and conceptually grok a hi yoyo, low yoyo, barrel roll etc, I do not have a good feel for what those 3D situations look. I was fascinated to read in Shaw how Johnson defeated a "more maneuverable Spitfire" with his Jug by taking advantage of its zoom climb and esp. roll performance, but I am hard pressed to visualize the engagement he described, let alone how that would play out on an E-M diagram. I am not sure these E-M diagrams describe, for example, roll performance, nor how quickly one can brake or accelerate. I suspect an experienced hand can look at one at a glance and say.... hmmm... turns pretty good here... slow energy addition there... don't fight over here... pretty good energy addition here, maybe consider going vert at this speed. But that's about all I got.

I suspect one of the reasons the F-35 is such a beast is that it can quickly decel and accel, move quickly move from a rate fight to a radius fight (Dolbe's comment about "sticking like glue" comes to mind) and back. To me that means moving quickly left and right on the E-M chart, but hard to visualize with the plethora of F-35 E-M plots available to us. I suspect it's rolling performance, especially at high alpha is a strength, but have no idea how that would "look" on an E-M diagram.
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.
Offline

quicksilver

Elite 3K

Elite 3K

  • Posts: 3133
  • Joined: 16 Feb 2011, 01:30

Unread post14 Feb 2020, 15:45

“I suspect one of the reasons the F-35 is such a beast is that it can quickly decel and accel”

Exactly. And, in the hands (feet, eyes, and brain) of an experienced pilot, provides the wherewithal to dictate most engagements on his or her terms.

For semantic reference, I always thought that ‘maintaining’ or ‘preserving’ ones energy were bad descriptives. ‘Managing‘ ones energy was a better descriptive imv because it involved both the gaining and ‘giving up’ of ones energy package, circumstantially, based on what was happening in the fight. Of course, for most jets, ‘giving up’ is always easier, but those which can do both with relative ease can be absolute monsters. The case, in point, (amongst a few others) is F-35.

Can’t visualize yo-yos etc? Try using your hands to visualize; pilots have been doing so for over a century — it works. Large watch not required. :wink:

I haven’t read Shaw since it first came out, so I don’t remember how he addressed each maneuver, but a good starting place for visualizing what each maneuver does is to understand its purpose. For example, a hi yo-yo does what? Helps you control your closure, maintain 3/9 control, decrease angles, and increase nose-to-tail. Common errors? Too much, too soon, too little, too late.
Offline
User avatar

steve2267

Elite 2K

Elite 2K

  • Posts: 2548
  • Joined: 12 Jun 2016, 17:36

Unread post14 Feb 2020, 16:06

quicksilver wrote:Can’t visualize yo-yos etc? Try using your hands to visualize; pilots have been doing so for over a century — it works. Large watch not required. :wink:


Nah, I got the hands part and what they look like with models etc. The inate understanding or relating that to actual distance and actual sight picture, the sensation of closure rate etc I do not grok. And probably never will, unless I fork out the $$ to get in a piston popper warbird "trainer" with some ex-fighter jocks that sell "dogfight training" to the public. (Maybe what I really need do is sacrifice my intellectual integrity and write crap for some aerospace blograg, get a name for myself, then ingratiate my way into a cockpit to get "edjeemekated" so I will no longer write crap about XYZ, but of course I will, cuzz I need another hop to better understand... and because I have neither the t*ts nor smile to bat-my-eyelashes way into the backseat...)

quicksilver wrote:I haven’t read Shaw since it first came out, so I don’t remember how he addressed each maneuver, but a good starting place for visualizing what each maneuver does is to understand its purpose. For example, a hi yo-yo does what? Helps you control your closure, maintain 3/9 control, decrease angles, and increase nose-to-tail. Common errors? Too much, too soon, too little, too late.


I understand all that "conceptually," perhaps I need to go re-read and try to put the manuevers in simple terms as you just described. But the "too much, too soon, too late, oh sh*t" parts prolly only come from having done it.
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.
Offline

quicksilver

Elite 3K

Elite 3K

  • Posts: 3133
  • Joined: 16 Feb 2011, 01:30

Unread post14 Feb 2020, 16:42

Long ago, doing penance in a staff job after lotsa time in the cockpit, I bought myself an air war game (don’t remember the name) and a fairly representative control stick for my desktop — just to maintain some semblance of ‘air sense.’ It was pretty good — and it was fun. Selectable cockpits, scenarios and adversaries. Didn’t have to spend much money either. Will help you exercise that part of the brain that doesn’t rely on numbers...
PreviousNext

Return to General F-35 Forum

Who is online

Users browsing this forum: No registered users and 15 guests