Supercruise for F-35 ?

[Abraham Gubler]

But, most importantly, the Navy is nowhere near as capable as it would have been with the A/FX instead of the Super Hornet.

Yeah but they (USG) saved some money. Don't know what they spent it on but. Housing development? That worked out well...

There is a reason the Super Hornet has never won an export competition.

Ahem: RAAF gap fill fighter. Sure it wasn't a bells and whistles competition where everyone gets to have a party and make a big name of themselves but the RAAF had a blank cheque and could have brought anything it wanted. They chose the Block II Super Hornet.

 

[F-14D]

But, most importantly, the Navy is nowhere near as capable as it would have been with the A/FX instead of the Super Hornet.

Yeah but they (USG) saved some money. Don't know what they spent it on but. Housing development? That worked out well...

There is a reason the Super Hornet has never won an export competition.

Ahem: RAAF gap fill fighter. Sure it wasn't a bells and whistles competition where everyone gets to have a party and make a big name of themselves but the RAAF had a blank cheque and could have brought anything it wanted. They chose the Block II Super Hornet.

Whether they saved money is open to interpretation. After all, a number of extra Hornet C/Ds had to be ordered in order to keep the line "warm" for the E/F, but were not charged to the cost of bringing the Super Bug on line. Even so, the AF could have saved money by sticking with the F-15, France with the Mirage, UK with the... never mind. Yes, the A/FX would have cost more to develop than the E/F and would have cost more, but you would have got so much more if what the Navy needed, which is the point those would lament its loss make.


Australia... Ahem: Australia didn't look at anything else. There was no comparing of alternatives, no competition; they were totally open and above board about this They wanted a gap filler with the F-111s wearing out, and figured that since they already had Hornets, they might as well stick with the plane until their real next generation a/c was available. I was simply observing that as of today, the SH has never won an export contest where anything else was on the table.


My original post was essentially saying it's not so much the SH was a step back, as much as it wasn't enough of a step forward. We probably shouldn't reopen the "should we have" or "shouldn't we have" debate under this topic, it's all academic anyway.

 

[Abraham Gubler]

Australia... Ahem: Australia didn't look at anything else. There was no comparing of alternatives, no competition; they were totally open and above board about this They wanted a gap filler with the F-111s wearing out, and figured that since they already had Hornets, they might as well stick with the plane until their real next generation a/c was available. I was simply observing that as of today, the SH has never won an export contest where anything else was on the table.

That's not quite true. I don’t know who told you there was no comparison. I spoke to the people who ran the project in the RAAF HQ at that time and there was. It was based on the data provided for the AIR 6000 RFI (with updates via a DSTO watching brief) and entirely an in-house exercise. Once the Block II Super Hornet was selected in this process then the USN and Boeing were approached for delivery data – much to their surprise and delight. It was selected for its capability particularly its mission systems. No doubt USAF and the RAF would have offered equally attractive introduction into service packages as the USN for their strike fighters.

The advantage of the Super Hornet was not that it was a well understood platform (82 Wing never operated Hornets) but that it was backwards compatible with the classic Hornet with only a few hours of conversion training needed. The issue of airframe life was not just about the F-111 it was also very much about the F/A-18A/B. If at that time (2006) it was just the F-111 with life expiration then the Govt. probably wouldn't have brought a gap fill and just gone without a fourth squadron until the F-35 was ready. But what got the $3 billion cheque book out for 24 new aircraft was the serious fear that a large number of F/A-18A/Bs were going to require centre barrel replacement (CBR) in the 2012-16 timeframe which would so reduce the RAAF’s airworthy fleet that there would not be enough annual flying hours to sustain combat pilot numbers. That is the RAAF would have a huge loss of manpower.

You can always buy another plane and in emergency quite quickly but you can’t pull fighter pilots out of a hat. With a force of brand new Super Hornets on hand if a third of the classic Hornets were grounded for a few years then the pilot force could still be raised, trained and sustained. The F-15 or Typhoon couldn’t do this because of the time needed to convert a pilot to the new aircraft.

 

[aussienscale]

And in a smart move 12 of the 24 RAAF S/hornets have been pre-wired by Boeing on the line for possible future conversion to Growler

 

[Abraham Gubler]

And in a smart move 12 of the 24 RAAF S/hornets have been pre-wired by Boeing on the line for possible future conversion to Growler

Well actually this was a desperate attempt by the then Defence Minister to divert negative public attention away from his dealings as a poll-for-hire. The RAAF had a requirement for 4-6 Growlers in the >2020 timeframe to counter evolving threats. The acquisition concept was planned as part of the F/A-18F disposal plan when they are to be replaced by the last batch of F-35s (~2020). As the F/A-18F is wound down and the aircraft sold to the USN 4-6 new EA-18Gs would be purchased or part bartered. Pre-wiring of an entire contract batch (12) was something Boeing insisted on to accept the CCP and for a nice earner from an easy mark. Now 12 Super Hornets will fly around with some extra weight of cabling they won’t need and if any are converted to Growlers the RAAF will have the handicap of their Growler having half of its airframe life consumed when they would have wanted a new >20 year life aircraft. Not to mention it was a pretty expensive way to divert the media’s attention for a week or so from the inevitable demise of the minister.

 

[AeroFranz]

Maybe you can use some of the cabling to provide the guy in the back with some bada$$ IFE ;D

 

[chuck4]

Is the F-35's inability to super cruise cased by worse thrust-drag characteristics then F-22, or by design of the engine?

 

[Abraham Gubler]

Is the F-35's inability to super cruise cased by worse thrust-drag characteristics then F-22, or by design of the engine?

What else could it be?

 

[chuck4]

So which is? High transonic drag or engine tuned for subsonic speed?

 

[Abraham Gubler]

So which is? High transonic drag or engine tuned for subsonic speed?

Well it isn't transonic drag because you're talking about supersonic cruising. But of course its neither one OR the other but both: drag and thrust. Or to be more precise specific excess power in the supersonic regime.

 

[chuck4]

The reason why I separate the two is to determine whether F-35 can be made to super cruise simply by reconfiguring the engine or intake while retaining similar maximum dry thrust, or if either major increase in dry thrust or major drag reduction is essential.

 

[Abraham Gubler]

The reason why I separate the two is to determine whether F-35 can be made to super cruise simply by reconfiguring the engine or intake while retaining similar maximum dry thrust, or if either major increase in dry thrust or major drag reduction is essential.

Well specific excess power is thrust power (TV ) minus the drag power (DV ) divided by the weight of an aircraft. This is basic aircraft engineering 101.

You can’t just change an aircraft's drag without introducing exotic technology like laminar flow control or designing an entirely new aircraft. Since the F-35 never had a supercruise requirement it is aerodynamically shaped accordingly with little concern for drag at supersonic flight.

For an F-35 to supercruise it would need an engine and inlet that could sustain the production of very high levels of dry thurst (~45,000 lbs) at supersonic speeds (~Mach 1.5). Such an engine – keeping within the 1.7 tonne weight of the F135 – is obviously way beyond current technology. It is in effect producing around twice as much thrust as the F119. We will probably see such an engine in our lifetimes but not any time soon.

 

[F-14D]

Australia... Ahem: Australia didn't look at anything else. There was no comparing of alternatives, no competition; they were totally open and above board about this They wanted a gap filler with the F-111s wearing out, and figured that since they already had Hornets, they might as well stick with the plane until their real next generation a/c was available. I was simply observing that as of today, the SH has never won an export contest where anything else was on the table.

That's not quite true. I don’t know who told you there was no comparison. I spoke to the people who ran the project in the RAAF HQ at that time and there was. It was based on the data provided for the AIR 6000 RFI (with updates via a DSTO watching brief) and entirely an in-house exercise. Once the Block II Super Hornet was selected in this process then the USN and Boeing were approached for delivery data – much to their surprise and delight. It was selected for its capability particularly its mission systems. No doubt USAF and the RAF would have offered equally attractive introduction into service packages as the USN for their strike fighters.

The advantage of the Super Hornet was not that it was a well understood platform (82 Wing never operated Hornets) but that it was backwards compatible with the classic Hornet with only a few hours of conversion training needed. The issue of airframe life was not just about the F-111 it was also very much about the F/A-18A/B. If at that time (2006) it was just the F-111 with life expiration then the Govt. probably wouldn't have brought a gap fill and just gone without a fourth squadron until the F-35 was ready. But what got the $3 billion cheque book out for 24 new aircraft was the serious fear that a large number of F/A-18A/Bs were going to require centre barrel replacement (CBR) in the 2012-16 timeframe which would so reduce the RAAF’s airworthy fleet that there would not be enough annual flying hours to sustain combat pilot numbers. That is the RAAF would have a huge loss of manpower.

You can always buy another plane and in emergency quite quickly but you can’t pull fighter pilots out of a hat. With a force of brand new Super Hornets on hand if a third of the classic Hornets were grounded for a few years then the pilot force could still be raised, trained and sustained. The F-15 or Typhoon couldn’t do this because of the time needed to convert a pilot to the new aircraft.

My apologies for the delay in getting back to you Abraham, I had to disappear, as I occassionally am wont to do.

I suspect that once again our differences are semantical. By comparison I'm referring to a competition as is done around the world where various aircraft are proposed in response to a tender, and are evaluated against each other regarding performance cost, capabilities, technology and technology transfer, offsets, etc. As you noted, Australia was an in-house exercise rather than formally going out and seeing what would be offered. . Because of the reduced training required, it seemed a good fit for a gap filler until the F-35 arrived and, like you said, Australia then went to the USN and Boeing saying, "Look! We've got money! Wanna sell us some Super Bugs"? If Australia had been looking for a long term, permanent solution, I wonder if they would have done it that way.

For all the actual competitions for those nations looking for an end-solution, the Super Hornet has never been selected, and I believe in most cases so far hasn't made the finals.

 

[Abraham Gubler]

For all the actual competitions for those nations looking for an end-solution, the Super Hornet has never been selected, and I believe in most cases so far hasn't made the finals.

But not all Super Hornets are equal. Boeing provided the RAAF an unsolicited offer on the Block II Super Hornet in late 2005. With the JAST derived avionics the Block II is way ahead of the Block I in combat power. About twice as capable in a RAND analysis using actual air combat SMEs as opposed to the school yard stuff that abounds in this area.

 

[seruriermarshal]

Official statement: The F-35 CAN Supercruise

The F-35, while not technically a "supercruising" aircraft, can maintain Mach 1.2 for a dash of 150 miles without using fuel-gulping afterburners.

"Mach 1.2 is a good speed for you, according to the pilots," O’Bryan said.

http://www.airforce-magazine.com/MagazineArchive/Pages/2012/November%202012/1112fighter.aspx

 

[chuck4]

Can it do it while carrying some reasonable weapon load and an amount of fuel typical of midpoint of a mission?

 

[SpudmanWP]

Since a dash is usually used at the midpoint in a combat mission, I would say 60-70% fuel and 4 AMRAAMs.

 

[chuck4]

The question is, is the dash in question representative of combat dash, or is it a dash staged just to say it supercruised?

 

[SpudmanWP]

Since LM/JPO/DoD has tried to always speak of the F-35 in its combat config, I would say this is the same.


I suppose we'll have to wait for either clarification or confirmation in flight testing results.

 

[GTX]

Well it is not like adding a combat load adds any drag to the F-35...

 

[Racer]

Official statement: The F-35 CAN Supercruise

The F-35, while not technically a "supercruising" aircraft, can maintain Mach 1.2 for a dash of 150 miles without using fuel-gulping afterburners.

"Mach 1.2 is a good speed for you, according to the pilots," O’Bryan said.

http://www.airforce-magazine.com/MagazineArchive/Pages/2012/November%202012/1112fighter.aspx

Not supercruising.
If Mach 1.2 with a "slight" use of afterburner is now supercruising, then nearliy every >Mach 1,6 topspeed figther is a supercruiser.

Edit 1: Hm. I was under the impression that I read parts of this interview somewhere else, where it was mentionend that in case of F35 supercruise only a "little" afterburner was used, but in such low setting, that it enables the F-35 to cruise some range at this speed. But I'm not able to find this anymore.

Edit 2: And yes, additional load adds drag. Because more load needs more lift. To reach more lift, you add drag (use flaps or higher angle of attack).

 

[sferrin]

Official statement: The F-35 CAN Supercruise

The F-35, while not technically a "supercruising" aircraft, can maintain Mach 1.2 for a dash of 150 miles without using fuel-gulping afterburners.

"Mach 1.2 is a good speed for you, according to the pilots," O’Bryan said.

http://www.airforce-magazine.com/MagazineArchive/Pages/2012/November%202012/1112fighter.aspx

Not supercruising.
If Mach 1.2 with a "slight" use of afterburner is now supercruising, then nearliy every >Mach 1,6 topspeed figther is a supercruiser.

Edit 1: Hm. I was under the impression that I read parts of this interview somewhere else, where it was mentionend that in case of F35 supercruise only a "little" afterburner was used, but in such low setting, that it enables the F-35 to cruise some range at this speed. But I'm not able to find this anymore.

Edit 2: And yes, additional load adds drag. Because more load needs more lift. To reach more lift, you add drag (use flaps or higher angle of attack).

Go read it again.

 

[Kryptid]

I wish I knew why the minimum threshold for supercruise was defined to be Mach 1.5. It seems like such an arbitrary number since I know of nothing "special" that happens at that speed. I think they probably should have defined the lower limit as Mach 1.2, since that's usually the upper end of the transonic zone and therefore the speed when the aircraft and the airflow over it is "truly" going fully supersonic.

 

[Abraham Gubler]

Well considering you’d be hard pressed to get an F-15, F-16 or F-18 over Mach 1 with full afterburner while carrying the kind of weaponry that you’d need to attempt an F-35 mission this new announcement of the F-35 sustaining Mach 1.2 dry for 10 minutes is pretty good. Perfect for getting through an unexpected threat or a time sensitive gap in enemy defences.

Maybe we should come up with a new name for this? "Super-burst", "Trans-scram"...

 

[Colonial-Marine]

A useful capability to have. I wonder if the current specifications list more-conservative figures for other performance areas?

Is it known what limits the F-35 to a maximum speed of Mach 1.67? While clearly not a Mach 2+ design, I wonder what prevents it from reaching the Mach 1.8+ speeds of the F/A-18 family. IIRC they're only clearing weapons release to that Mach 1.67 figure, but maybe that isn't the limit?

 

[chuck4]

A useful capability to have. I wonder if the current specifications list more-conservative figures for other performance areas?

Is it known what limits the F-35 to a maximum speed of Mach 1.67? While clearly not a Mach 2+ design, I wonder what prevents it from reaching the Mach 1.8+ speeds of the F/A-18 family. IIRC they're only clearing weapons release to that Mach 1.67 figure, but maybe that isn't the limit?

Diverterless supersonic intake ?

 

[SpudmanWP]

Nope as DSI was tested to m2+ on the F-16.

The program has stated that the F-35 is capable of going above m1.67 but that since the requirement was for m1.6 and they want to save dev time & money, they will not be doing a lot of testing above m1.6. They have said that they will test a little above m1.6 for safety reasons but operationally it will top out at m1.6

 

[Colonial-Marine]

So would the flight control system prevent the pilot from exceeding that safety margin?

 

[Dragon029]

So would the flight control system prevent the pilot from exceeding that safety margin?

Without having experience, I would speculate that it likely would, but that there would be some sort of override that would allow a pilot to proceed past those limits manually (perhaps, in the event of a dangerous computer glitch).

Realistically, if an important mission was planned at least half-decently, such capability wouldn't ever be needed, but maybe it could be useful, from a military standpoint, for that 1/1,000,000,000 event when you're the closest (time-wise) asset, but even at M1.6, you're not going to be fast enough.

---

On topic though, wasn't there discussion that part of the F-35's velocity limitation was also to do with the F135's bypass ratio? Personally I wouldn't think so, with other Mach 2+ fighters using similar BPR's in their engines, but they don't have DSI's and imperfect shaping to accommodate stealth shaping.

Speaking of that, do serpentine intake ducts have much of an effect on airflow? Surely they might cut a few % off the airflow's efficiency?

Also, the F-35 apparently has a slightly long exhaust; could that have any effect?

I think overall, besides the designed limitation, there isn't any major, single reason it's not a M1.8 or 2+ fighter.

 

[sferrin]

Speaking of that, do serpentine intake ducts have much of an effect on airflow? Surely they might cut a few % off the airflow's efficiency?

Lot's of fast aircraft have had them. The F-104 and F-106 come to mind. Not to mention the F-22 and YF-23.

 

[chuck4]

On related issue, does f-35 exhibit so called supermaneuverability? I don't mean whether it can turn or climb with a f-16 at speed and altitude ranges where f-16 is at it best. I mean can it remain maneuverable at higher speed and higher altitude then f-16 or other G4 fighter, as the f-22 can, so f-35 can start with and retain an energy advantage in engagements against legacy fighters?


I think f-35's relative low (or even absent) absolute supercruise speed is less of an issue if can do Mach 0.9 without afterburners at 60,000 feet and remain maneuverable at that speed and altitude.

 

[AeroFranz]

Long ducts add friction losses, and inlets of fixed geometry are of necessity optimized for one flight condition only. It's a tradeoff. The F-16 has a fixed inlet and is penalized at higher Mach, but most of the time it gains from the weight savings of a simple inlet. If you have gobs of power you can afford the inefficiency at some off design point, provided you don't spend much time there.
The serpentine inlets are only a problem if the length to diameter ratio is under four, i.e., the turn is pretty sharp. Then you have problems keeping a uniform flow at the fan face.

 

[chuck4]

Long ducts add friction losses, and inlets of fixed geometry are of necessity optimized for one flight condition only. It's a tradeoff. The F-16 has a fixed inlet and is penalized at higher Mach, but most of the time it gains from the weight savings of a simple inlet. If you have gobs of power you can afford the inefficiency at some off design point, provided you don't spend much time there.
The serpentine inlets are only a problem if the length to diameter ratio is under four, i.e., the turn is pretty sharp. Then you have problems keeping a uniform flow at the fan face.

The font half of F-35B's intake consist of two rectangular section ducts with high length to width ratio. They turn in fairly abruptly towards centerline right behind the inlet at maybe 45 degrees, essentially wrapping around the lift fan. At centerline they merge and turn another 45 degrees to realign with center line. It then connects to engine via a straight, circular section duct about 2.5 fan diameters long, canted at an angle of about 5 degrees from the fan face.


In the B model, the airflow in the straight section of the duct is further disturbed by two things. 1. The drive shaft for the lift fan runs inside the straight section at an agle to the centerline of the duct because the duct itself is at an angle to the engine. 2. The top wall of the duct is interrupted by a large alcove formed by the auxiliary dorsal intake doors opened during STOVL operation.


I imagine the ducts on the A and C has similar configuration, but without the disturbanc of the shaft down the duct or the auxiliary dorsal intake doors.


Without quantifying it, it appears to me the front half of F-35 intake duct is much more "bendy" then f-22's serpentine ducts.

 

[TaiidanTomcat]

On related issue, does f-35 exhibit so called supermaneuverability? I don't mean whether it can turn or climb with a f-16 at speed and altitude ranges where f-16 is at it best. I mean can it remain maneuverable at higher speed and higher altitude then f-16 or other G4 fighter, as the f-22 can, so f-35 can start with and retain an energy advantage in engagements against legacy fighters?


I think f-35's relative low (or even absent) absolute supercruise speed is less of an issue if can do Mach 0.9 without afterburners at 60,000 feet and remain maneuverable at that speed and altitude.

FTFA:

There is a major extension of the fighter’s range if speed is kept around Mach .9, O’Bryan went on, but he asserted that F-35 transonic performance is exceptional and goes "through the [Mach 1] number fairly easily." The transonic area is "where you really operate."

and:

As F-35s criss-cross enemy airspace, they also will automatically collect vast amounts of data about the disposition of enemy forces. They will, much like the JSTARS, collect ground moving target imagery and pass the data through electronic links to the entire force. This means the F-35 will be able to silently and stealthily transmit information and instructions to dispersed forces, in the air and on the ground.
Because it was designed to maneuver to the edge of its envelope with a full internal combat load, the F-35 will be able to run rings around most other fighters, but it probably won’t have to—and probably shouldn’t.

"If you value a loss/exchange ratio of better than one-to-one, you need to stay away from each other," said O’Bryan, meaning that the fighter pilot who hopes to survive needs to keep his distance from the enemy.

He noted that, in a close-turning dogfight with modern missiles, even a 1960s-era fighter such as the F-4 can get into a "mutual kill scenario" at close range with a fourth generation fighter. That’s why the F-35 was provided with the ability to fuse sensor information from many sources, triangulating with other F-35s to locate, identify, and fire on enemy aircraft before they are able to shoot back.

The F-35’s systems will even allow it to shoot at a target "almost when that airplane is behind you," thanks to its 360-degree sensors.

According to O’Bryan, the F-35 also can interrogate a target to its rear, an ability possessed by no other fighter.

If you survive a modern dogfight, O’Bryan claimed, "it’s based on the countermeasures you have, not on your ability to turn."

If the situation demands a turning dogfight, however, the F-35 evidently will be able to hold its own with any fighter. That is a reflection on the fighter’s agility. What’s more, a potential future upgrade foresees the F-35 increasing its air-to-air missile loadout from its current four AIM-120 AMRAAMs to six of those weapons.

 

[AeroFranz]

The font half of F-35B's intake consist of two rectangular section ducts with high length to width ratio. They turn in fairly abruptly towards centerline right behind the inlet at maybe 45 degrees, essentially wrapping around the lift fan. At centerline they merge and turn another 45 degrees to realign with center line. It then connects to engine via a straight, circular section duct about 2.5 fan diameters long, canted at an angle of about 5 degrees from the fan face.


In the B model, the airflow in the straight section of the duct is further disturbed by two things. 1. The drive shaft for the lift fan runs inside the straight section at an agle to the centerline of the duct because the duct itself is at an angle to the engine. 2. The top wall of the duct is interrupted by a large alcove formed by the auxiliary dorsal intake doors opened during STOVL operation.


I imagine the ducts on the A and C has similar configuration, but without the disturbanc of the shaft down the duct or the auxiliary dorsal intake doors.


Without quantifying it, it appears to me the front half of F-35 intake duct is much more "bendy" then f-22's serpentine ducts.

Interesting. I can't weigh on the overall merits of the solution, but we can also assume that the sharper turn makes it possible to hide the fan face in a shorter duct distance, and that was a consideration in the sub-optimal choice (at least in pure terms of powerplant integration).

 

[Abraham Gubler]

I think f-35's relative low (or even absent) absolute supercruise speed is less of an issue if can do Mach 0.9 without afterburners at 60,000 feet and remain maneuverable at that speed and altitude.

There aren't many aircraft that can fly at M0.9 and sustain a turn at 60,000 feet. And those that can do it without after burner is probably zero.

 

[Bon Plan]

From a MMRCA contestants analysis page 98 :

In fact, the Eurofighter remains the only aircraft among the MMRCA competitors to have demonstrated some sort of supercruise capability (though this capability falls far short of the sustained supercruise capability of the F-22A and the F-35).

http://carnegieendowment.org/files/dogfight.pdf

FALSE
EF was not the sole able to supercruise.