With F-35 do we need F-22 anymore?

[steve2267]

That's a cool story and all. Thanks for sharing it....

...and... so... ?

[sprstdlyscottsmn]

Okay, I am going to imagine a twin-engine (ADVENT), lengthened F-35. Lengthened by how much? Enough to carry two internal GBU-28s, so 6+ft. The only puts the new plane around 56ft so lets add another 6ft for a fuel plug. Now we are the length of an F-22. Now let's put the wings of an F-22 on it.

Let's say it weighs 50,000lb empty (to the F-22s 44,000) as the "holes add weight" thing applies. With the bigger wing and longer body... an F-22 has 6.5lb of fuel per square foot (length x wingspan) while an F-35A has 10.5. As I am "scaling up" an F-35 to Raptor levels of size in effect, this would give an internal fuel load of 28,700lb. Consider that a 6ftx5ftx6ft box (the 6ft fuel plug with room for intakes/engines to go by) is about 1,350 gallons by itself, or 9,180lb of that 10,200lb fuel increase.

So, now we have an aircraft that could have a gross (stealth) weight of a bit under 90,000lb. ADVENT should be, 15% more thurst, dry and wet we will assume (32.2k and 49.5k respectively, with a TSFC 20% lower? (0.71). At take off, T/W is in the range of .715 dry and 1.1 wet (0.53 and 0.81 for the F-35). This is with two 5,000 bombs. Fuel fraction is on the order of 0.32 (0.35 for the F-35 with two GBU-31s) and a wing loading of 107 (115 for the F-35). The "wing of the F-22" is good for 585,000lb lift, so this plane at take off is 6.5G.

The greater T/W and lower wing loading mean this aircraft can fly higher than an F-35 for cruise (which is already 10,000-15,000 higher than a combat configured F-16) and the improved fineness ratio (near F-22 level) means it should have no problem with high speed cruise (say in the 0.95M range). So we have this plane cruising along at 50,000ft and 0.95M with an L/D of...12 (CFT only strike eagle is around 10). This gives a cruise fuel flow between 5,000pph and 3,850pph for 18,700lb cruise fuel, or 4.2hrs. At 544.5KTAS thats 2,280nm of cruise (assuming 5k used in climb and 5k saved for decent and reserves). That is a radius of 1,140nm with two big a$$ bombs.

Now, my cruise TSFC and L/D are WAGs, but as a rough draft I created an aircraft that could be capable of 1,000nm range, 7G maneuver in combat, and some super cruise ( say 60% more weight is 60% more drag but with 130% more thrust).

Is in that simple? heck no! can it be done? Yes. Expect FRP price to be $140M current year dollars based on the F-35s cost per pound.

[marsavian]

This gives an indication of what the difference would be between an SR-71 and F-111 combat wing loading (50 vs 100 lb/sq ft) in practice and how it would affect available G at altitudes.


Quest for Performance: The Evolution of Modern Aircraft

Part II: THE JET AGE

Chapter 11: Early Jet Fighters

Contemporary Fighters

https://history.nasa.gov/SP-468/ch11-6.htm

Figure 11.33 - Effect of wing loading and altitude on turning performance of a fighter aircraft. M = 0.85, CL = 0.7, constant altitude

[steve2267]

...

So, now we have an aircraft that could have a gross (stealth) weight of a bit under 90,000lb. ADVENT should be, 15% more thurst, dry and wet we will assume (32.2k and 49.5k respectively, with a TSFC 20% lower? (0.71). At take off, T/W is in the range of .715 dry and 1.1 wet (0.53 and 0.81 for the F-35). This is with two 5,000 bombs. Fuel fraction is on the order of 0.32 (0.35 for the F-35 with two GBU-31s) and a wing loading of 107 (115 for the F-35). The "wing of the F-22" is good for 585,000lb lift, so this plane at take off is 6.5G.

The greater T/W and lower wing loading mean this aircraft can fly higher than an F-35 for cruise (which is already 10,000-15,000 higher than a combat configured F-16) and the improved fineness ratio (near F-22 level) means it should have no problem with high speed cruise (say in the 0.95M range). So we have this plane cruising along at 50,000ft and 0.95M with an L/D of...12 (CFT only strike eagle is around 10). This gives a cruise fuel flow between 5,000pph and 3,850pph for 18,700lb cruise fuel, or 4.2hrs. At 544.5KTAS thats 2,280nm of cruise (assuming 5k used in climb and 5k saved for decent and reserves). That is a radius of 1,140nm with two big a$$ bombs.

Now, my cruise TSFC and L/D are WAGs, but as a rough draft I created an aircraft that could be capable of 1,000nm range, 7G maneuver in combat, and some super cruise ( say 60% more weight is 60% more drag but with 130% more thrust).

Is in that simple? heck no! can it be done? Yes. Expect FRP price to be $140M current year dollars based on the F-35s cost per pound.

Spurts,

point of clarification (and learning) on my end... I thought you had the F135 drinking between 4000 and 4500lb/hr in cruise for the F-35. Ignoring the increase in thrust, and just doubling the fuel consumption owing to two motors and then taking 80% of that fuel flow rate, gives me between 6400 and 7200lb/hr for cruise. Assuming cruise of 544KTAS, and 18700lb to burn, and the lower burn estimate of 6400, that seems to yield 2.9hrs of cruise, or 1590nm (795nm out and back). What am I missing? Or did you pull a Gums and shut one blower down during cruise?

Or am I doing my math all wrong, and you are assuming some thrust level for cruise, and then applying the SFC to that thrust number?

[steve2267]

OK, I think I see where you went...

90,000lb GTOW - 5000lb (T/O + climb + accel to cruise) = 85000lb weight --> 85000lb lift. L/D of 12 yields 7083lb thrust required * SFC ==> fuel flow per hour required.

Question about SFC... from TEG... I thought the best SWAG we had on F135 SFC was 0.71(ish). So wouldn't 20% decrease mean an SFC of 0.57? Which would give a fuel flow of about 4040lb/hr? (Less than your swag of 4450pph?) Which would yield a strike radius of 1260nm... inching closer to Marsavian's specs.

[spazsinbad]

On previous page 'marsavian' claimed via wickedpedia: https://en.m.wikipedia.org/wiki/Air_eng ... e_Gulf_War

"...Denton [EF-111] decided to head for the deck to try to evade his pursuer. As he went down he pulled up to avoid the ground, the Mirage followed him through, but did not pull up in time and crashed. An unarmed EF-111 had thus scored an air-air victory against a Dassault Mirage F1, although Graeter was credited with a kill. The EF-111A crew were awarded the Distinguished Flying Cross...."

Good on the triple-one, good strategy however the MIRACLE did not pull out of dive in time - pilot error of course and nothing to do with ACM in any sense except in the imagination of the writer. One may wonder why the NON triple-one pilot was credited with the kill? Perhaps there is more to this story than told here. Yes the triple-one guys were brave.

[marsavian]

Go Raven !

https://youtu.be/YhzJPKVSyEk



https://youtu.be/KciJUVoHHjo

First dogfight about 52secs in.

[sprstdlyscottsmn]

Question about SFC... from TEG... I thought the best SWAG we had on F135 SFC was 0.71(ish).

I like to go conservative so I used the public 0.886 figure I've seen.

[spazsinbad]

Having watched the first RAVIN' video I'm not convinced there was ACM as the EF-111 flew low level (in TFR mode? whatever) to then abruptly pull up (no mention of a dive) at full power while the MIRACLE flew into the ground. This is not ACM - I'll watch 2nd video now which says "early morning hours" - was it night or daylight? Pilot says they are at 100 feet at night [at 6min] - tell me how aircraft (one without armament) DOGFIGHT at NIGHT. This is silly - because some people (not pilots I gather) say 'dogfight' then it must be true. Not tonight not this encounter but for sure good moves by the EF-111 to escape by going LOW at NIGHT while it had TFR Terrain Following Radar to do so whilst the MIRACLE had no such gizmo. No wonder the MIRACLE over reached to die. Later at about 7min 30sec we hear '400 feet for MIRACLE' being targeted by the F-15C with radar missile. Then MIRAGE/MIRACLE flies into the ground. So now we know why the KILL is credited to the F-15C. <sigh>

[marsavian]

It was defensive ACM, they evaded two missiles and a guns attack, they lived to go home whereas the F1 pilot died not having shot down a 5g Sparkvark. On the deck those TF30s really worked.

[spazsinbad]

When was the gun attack? Sure the EF-111 was able to defensive maneuver down low and for sure TFR worked - the RAAF also had some ground collisions with TFR at night, so it was not always easy, even when flying unopposed. Full Marks to the EF-111 team work AT NIGHT (over flat desert terrain or was it mountainous? dunno). But not ACM - no cigar.

[spazsinbad]

Zzzzzz...

No one is addressing the cultural aversion to risk that is endemic to how the government has recently done aircraft development/acquisition. Most of the timelines cited for previous aircraft development ignore what kind of activity occurred in which stages of the program. Even if one looks at a milestone overview of the acquisition process and notes tech maturation and risk reduction, what gets ignored (or not realistically characterized wrt ‘time’) is risk aversion or acceptance in flight test and verification. Because we can instrument, monitor, download, and analyze more facets of an aircraft design and/or performance than ever before (by orders of magnitude), we thereby know more and learn more about what might be ‘wrong’ and consequently face far, far more decisions about not only how to address those ‘wrongs’ but to what degree we want to spend time and effort doing so. Those kinds of decisions are made by humans and, over time — the humans that occupy progressively higher levels of oversight in the various acquisition bureaucracies.

Thus, in the engrained culture and politics of risk, the aversion to same is not diminished, it is increased and intensified by the simple math of knowing more about what’s happening in the design. The consequence is one of time, and as we all know, time is money. Who are these new acquisition warriors that are going to sign up to the scale of risk acceptance that is necessary to meet some of these highly ambitious development timelines for new aircraft?

Saw this today will He HYTEN the risk with SPEED?

Hyten Leading JROC Reform Process To Speed Decisions
17 Jan 2020 Theresa Hitchens

"...Hyten, [Vice Chief of Staff Gen. John Hyten] an Air Force general who previously led Strategic Command, says the the critical problem is DoD’s crippling need to avoid risk. This has led to bureaucratic approaches that value risk avoidance above all else — including moving most decision-making authorities into the Pentagon and away from the field....

...Hyten noted that DoD acquisition undersecretary Ellen Lord, research and engineering head Mike Griffin and other DoD leaders are starting to work on how to reform and speed up the processes. As Breaking D readers know, Lord has been overseeing a sweeping review of DoD’s infamously Byzantine series 5000 acquisition rules. That review, as Sydney reported, includes a new streamlined process for buying software...."

Source: https://breakingdefense.com/2020/01/hyt ... decisions/

[zero-one]

That would actually favor a derivative since you'd get to the fixed-price production sooner where profit margins
aren't capped the way they typically are in longer clean sheet development contracts.

Well who had more profit? Boeing's Superhornet or Lockheed's Raptor?

[quicksilver]

Well spaz, they gotta start somewhere and recognition/acknowledgement that there IS a problem is a start.

Wanna change behavior in government acquisition? Change ‘process’. In order to get the new-think ‘in’ ya gotta get some of the old-think ’out.’ Review the old rules, regs, and processes and kill some of them; ’bullet in the head’ kill — not ‘review and rename’ for the sake of rebranding a la another ‘Better Buying Power’ x.x. Gotta involve the Congressional pro-staffs as well.