So if energy efficiency is now a good thing, possibly KC-Y ends up switching to the 764F frame, a bit more payload, the GEnX engines, and Boeing gets someone to pay for the 767 NEO certification! LM seen howling in the background.

Avatar2go wrote:

VMCA787 wrote:

Apparently, the USAF has decided on the use of a BWB for the next Cargo/Tanker aircraft.

https://www.airandspaceforces.com/air-f ... t-by-2027/

Important to note this is a research effort that is charged with reducing the USAF climate footprint. One way to do that is with BWB designs. This project is developing an experimental prototype, to gain experience and test results for the type.

It is very far removed from the notion of a USAF operational tanker or cargo aircraft. It's possible that if the prototype is successful, development could continue toward a production aircraft. But we are at least a decade out from anything like that.

Not really sure why this gets hyped so much in the press. The USAF looks at many prototype designs, the majority don't become operational aircraft. It will be awhile before we know about this one.

Yes and AFRL already had a project for this in this timeline which we’ve discussed a bit in some other tanker thread I think, but it’s been a little vague (some thought it meant stealthy). Whatever is produced though will be the Genesis I bet for some follow on procurement programs, even if it takes as long as going from the XV-15 to the V-22.

par13del wrote:

So in this case rather than follow the civilian market they are going to lead?
Cool

Happened before.

The KC-135 preceded the 707 and the 747 fell out of the cargo competition with the C-5.

bt

VMCA787 wrote:

Apparently, the USAF has decided on the use of a BWB for the next Cargo/Tanker aircraft.

https://www.airandspaceforces.com/air-f ... t-by-2027/

What could possibly go wrong? I mean, the KC-46 was going to be a doddle what with Boeing having all that tanker experience.

bikerthai wrote:

They have to start somewhere.

If we believe future airlines will also go to BWB then this is a good a start as any for full scale R&D work.

What if we don't believe it?

scbriml wrote:

What if we don't believe it?

Feel free to put R&D in where you believe

bt

Will the future Loyal Wingman drones use boom or probe refueling?

I think probe and drogue has advantages for smaller aircraft. Obviously in terms of a small emergency tanker it is easier to fit a drogue refueling system than a boom. An automated boom appears to be a big and expensive challenge.

I wonder if the USAF has recently considered fitting refuel probes? The F-35 has the ability of both systems. The NGAD could easily have both.

Instead of the USAF developing and buying dedicated unmanned tankers with a boom it wmcould be easier buy a large fleet of MQ-25 tankers and fit probes to the F-35A fleet.

Most if Europe uses probe and drogue. The KC-46 can refuel two fighters at once using the drogue so it slightly offsets the lower refueling rate. Loyal Wingman drones might be what pushes the USAF fighters to use prove and drogue.

bikerthai wrote:

par13del wrote:

So in this case rather than follow the civilian market they are going to lead?
Cool

Happened before.

The KC-135 preceded the 707 and the 747 fell out of the cargo competition with the C-5.

bt

Not to turn this into a civ-av discussion, but I would argue these were the two most successful jet aircraft Boeing has manufactured.

RJMAZ wrote:

Will the future Loyal Wingman drones use boom or probe refueling?

I think probe and drogue has advantages for smaller aircraft. Obviously in terms of a small emergency tanker it is easier to fit a drogue refueling system than a boom. An automated boom appears to be a big and expensive challenge.

I wonder if the USAF has recently considered fitting refuel probes? The F-35 has the ability of both systems. The NGAD could easily have both.

Instead of the USAF developing and buying dedicated unmanned tankers with a boom it wmcould be easier buy a large fleet of MQ-25 tankers and fit probes to the F-35A fleet.

Most if Europe uses probe and drogue. The KC-46 can refuel two fighters at once using the drogue so it slightly offsets the lower refueling rate. Loyal Wingman drones might be what pushes the USAF fighters to use prove and drogue.

A KC-46 could be the mother ship for say 2 to 4 MQ-25 alongside, after the -25's consume or deliver their fuel they refuel via the boom before flying 400 miles ahead of the distance the KC-46 is safe at. Control of the drones could be passed from the initial tanker to the reliever, the drones are likely able to have a 16-24 hour endurance so can stay out twice as long, two could fly out with the -46 and two drones join the -46 out at station distance.

Is that cheaper per gallon delivered, ie is the cost per gallon delivered by the -25 compare to the -46 alone. It gains that 400 mile more penetration and is already not bad in terms of stealth.

I see the average fuel load carried shrinking in the future, less big planes, similar middle sized planes, lots more small planes. Many mouths to feed, A KC-46 and 2 -25 would be 4 drogues at the same time. Probably enough for 12 drones before the -25s would need to refuel. 30 minutes later ready for another dozen.

If a drone fueling relay is employed, then the argument for a boom system would be that you want to transfer fuel as fast as posible in order for the drone to be on its way.

And at the forward position, you want the refueling to be as fast as posible to reduce the time span of vulnerability.

bt

JayinKitsap wrote:

A KC-46 could be the mother ship for say 2 to 4 MQ-25 alongside, after the -25's consume or deliver their fuel they refuel via the boom before flying 400 miles ahead of the distance the KC-46 is safe at.

That is exactly my thought. The F-35A should get the F-35C refueling probe so it can take advantage of the MQ-25 tankers stationed closer to the front line.

The USAF MQ-25 could stay in the air for 48 hours getting regular top ups from the KC-46. The current MQ-25 mission profile for the Navy might involve 2 hour transit, 2 hour on station and 2 transit back. The Navy MQ-25 tanker is then on station for only 33% of its 6 hour mission.

With the USAF 48 hour mission profile for the MQ-25 getting regular top ups by the KC-46 it might look more like this:
3 hour transit to area of operation.
Top up from the KC-46
30 minute transit to the front line
5 hours time on station
1 hour transit to the KC-46 and back
5 hours on station and repeat back to the tanker every 6 hours.
After 48 hours transit 3 hours back to a land runway.

The USAF MQ-25 is then on station for 80% of the 48 hours period. This massively reduces the number of tankers required. The KC-46 tankers would arrive in the area of operstion and off load their fuel straight away to say 6 MQ-25 and then return to base. The KC-46 would then spend most of their mission in transit so you would probably need one KC-46 for every MQ-25.

bikerthai wrote:

And at the forward position, you want the refueling to be as fast as posible to reduce the time span of vulnerability.

The loyal Wingman drones might only carry 1,000kg of fuel in total. Probe and drogue can deliver 500kg of fuel very quickly. The biggest issue with the boom is the tanker has to be very large. With a swarm of unmanned drones it would be better of the tankers were MQ-25 sized.

RJMAZ wrote:

The biggest issue with the boom is the tanker has to be very large.

The large boom was probably originally designed for large bombers.

For tactical (fighters and wingmen) wonder if they can redesign for a shorter boom?

It would require massive R&D spending though.

bt

bikerthai wrote:

RJMAZ wrote:

The biggest issue with the boom is the tanker has to be very large.

The large boom was probably originally designed for large bombers.

For tactical (fighters and wingmen) wonder if they can redesign for a shorter boom?

It would require massive R&D spending though.

bt

Amazing that digital technology can be used for new a/c to speed design / production / delivery but for something like a new and smaller boom just for fighters the OEM would probably charge billions for R&D.
The things that make you say hhhmmmm....

par13del wrote:

bikerthai wrote:

RJMAZ wrote:

The biggest issue with the boom is the tanker has to be very large.

The large boom was probably originally designed for large bombers.

For tactical (fighters and wingmen) wonder if they can redesign for a shorter boom?

It would require massive R&D spending though.

bt

Amazing that digital technology can be used for new a/c to speed design / production / delivery but for something like a new and smaller boom just for fighters the OEM would probably charge billions for R&D.
The things that make you say hhhmmmm....

The thing is the USAF has an unbroken track record of tanker procurement failures going back over 50 years now.

texl1649 wrote:

The thing is the USAF has an unbroken track record of tanker procurement failures going back over 50 years now.

Wouldn't say the hardware have been failures. KC-10 was a success, and KC-46, although troubled, will be a success.

Some of the procurement efforts have certainly failed, before reaching the hardware stage.

texl1649 wrote:

The thing is the USAF has an unbroken track record of tanker procurement failures going back over 50 years now.

Can you elaborate on why you think this? If you'd said 20 I'd understand, but >50? I'd say the KC-10 was a pretty damn successful acquisition - 16 originally planned, 60 actually purchased. Reengining the KC-135 (twice!) was also successful use of the jet's very low hours.

LyleLanley wrote:

Can you elaborate on why you think this? If you'd said 20 I'd understand, but >50? I'd say the KC-10 was a pretty damn successful acquisition - 16 originally planned, 60 actually purchased. Reengining the KC-135 (twice!) was also successful use of the jet's very low hours.

Tangent, but I didn't realize the KC-135's hours were considered low. I don't really have a basis for comparison, but it seems a little surprising, given that it seems like nearly everything else needs tanker gas and they've all been at work since the 1960s. Was it just a lot of airframes built to spread out the flying hours over? Not an expert at all of course, it just made me curious.

Newark727 wrote:

Tangent, but I didn't realize the KC-135's hours were considered low. I don't really have a basis for comparison, but it seems a little surprising, given that it seems like nearly everything else needs tanker gas and they've all been at work since the 1960s. Was it just a lot of airframes built to spread out the flying hours over? Not an expert at all of course, it just made me curious.

Two reasons: first since they are commercial jets, they are designed for nearly 10 times the hours of most military aircraft, while flying about as often.

Second is that they receive regular inspection and remediation to extend their lives, during heavy maintenance checks & overhauls. That involves the latest non-destructive testing technologies, that weren't envisioned when they were built.

Also the USAF has a teardown program to evaluate every part of the KC-135, and establish a statistical life for that part in the fleet. Then the parts are replaced before they fail. Some are also upgraded with better components and technology.

End result is that they aren't allowed to get into a state that would force retirement. They receive whatever repairs they need.

https://www.airandspaceforces.com/article/0410tankers/

https://www.aviationpros.com/engines-co ... e-aircraft

Newark727 wrote:

Tangent, but I didn't realize the KC-135's hours were considered low. I don't really have a basis for comparison, but it seems a little surprising, given that it seems like nearly everything else needs tanker gas and they've all been at work since the 1960s. Was it just a lot of airframes built to spread out the flying hours over? Not an expert at all of course, it just made me curious.

Good question. Along with the reasons Avatar mentioned, the KC-135s sat for decades with a good portion of the fleet on SIOP alert against the Soviets and didn’t fly for a week at a time. Combine that with the usual fly-once-a-day workload when off alert and you have a fleet with relatively low hours.

Since the 90s the KC-135 has been utilized much more, but the reserve/guard low flight hours helps to keep the fleet average low. By comparison, the KC-10’s flight hours surpassed the KC-135s a few years ago, and the jet is decades younger. The KC-10 never sat SIOP alert.

Thanks! The standing alert as a factor never occurred to me.

Avatar2go wrote:

Newark727 wrote:

Tangent, but I didn't realize the KC-135's hours were considered low. I don't really have a basis for comparison, but it seems a little surprising, given that it seems like nearly everything else needs tanker gas and they've all been at work since the 1960s. Was it just a lot of airframes built to spread out the flying hours over? Not an expert at all of course, it just made me curious.

Two reasons: first since they are commercial jets, they are designed for nearly 10 times the hours of most military aircraft, while flying about as often.

Second is that they receive regular inspection and remediation to extend their lives, during heavy maintenance checks & overhauls. That involves the latest non-destructive testing technologies, that weren't envisioned when they were built.

Also the USAF has a teardown program to evaluate every part of the KC-135, and establish a statistical life for that part in the fleet. Then the parts are replaced before they fail. Some are also upgraded with better components and technology.

End result is that they aren't allowed to get into a state that would force retirement. They receive whatever repairs they need.

https://www.airandspaceforces.com/article/0410tankers/

https://www.aviationpros.com/engines-co ... e-aircraft

The KC-135 is not and never was a commercial jet.

Spacepope wrote:

The KC-135 is not and never was a commercial jet.

True the KC-135 has a slightly smaller fuselage. But basically the design and construction is pretty much the same.

bt

bikerthai wrote:

Spacepope wrote:

The KC-135 is not and never was a commercial jet.

True the KC-135 has a slightly smaller fuselage. But basically the design and construction is pretty much the same.

bt

Have you never seen one up close? Plywood floors and doublers around the aft fuselage - not exactly commercial grade.

Plus vert and horizontal stabs came from scrapped 707s long after the 135s were built.

Please keep in mind the 135 was an interim tanker for SAC, never intended to be kept in service as long as it has been.

zanl188 wrote:

Have you never seen one up close?

As a matter of fact yes. And I saw cracks with crack stopper drilled holes in the wheel well bay. Did not look inside the fuselage though.

zanl188 wrote:

doublers around the aft fuselage

Commercial airlines do the same. They may just be better at touch up and make it looks good.

bt

Spacepope wrote:

The KC-135 is not and never was a commercial jet.

Yes, KC-135 is a derivative of the Dash-80, and a different branch of that tree than the 707 commercial airliner. It was designed for heavier loads and lesser fatigue life than the 707, but still far longer than most military aircraft. The current fleet is only about halfway through it's life in terms if flying hours, and that is a tribute to it's heritage.

bikerthai wrote:

Commercial airlines do the same. They may just be better at touch up and make it looks good.

bt

No, they don’t. Boeing patched up the design with the doublers - this wasn’t a damage repair.

I can see adding a doubler as an expedient way of reinforcing sections of the skin. The decision on whether to use a doubler vs. chem-milling pockets depends on the function of the design and manufacturing capability. For pure strength and efficiency, chem-mil or machined pocket is better. For crack propagation prevention, a doubler may be better.

I've seen photos of major repair damage on a commercial 737.
An example here.
https://www.reddit.com/r/mildlyinterest ... t_my_work/

And yes Boeing typically do not do repair on delivered aircraft unless its an AOG. Their labor rate is too high.

Airline can and do repair damages themselves, including replacing or adding large doublers to whole skin sections.

bt

RJMAZ wrote:

DigitalSea wrote:

Why on Earth would the USAF need a B-21 tanker?

Because the KC-46 will get shot down and you've lost 3 crew.

B-21 or not, explain how you're going to pull off air-to-air refueling in a contested environment without being detected, lol come on...

DigitalSea wrote:

RJMAZ wrote:

DigitalSea wrote:

Why on Earth would the USAF need a B-21 tanker?

Because the KC-46 will get shot down and you've lost 3 crew.

B-21 or not, explain how you're going to pull off air-to-air refueling in a contested environment without being detected, lol come on...

Please explain how stealth aircraft survive once their weapon bays doors open...

So you would rather the KC-46 shot down and 3 lives lost?

RJMAZ wrote:

DigitalSea wrote:

RJMAZ wrote:

Because the KC-46 will get shot down and you've lost 3 crew.

B-21 or not, explain how you're going to pull off air-to-air refueling in a contested environment without being detected, lol come on...

Please explain how stealth aircraft survive once their weapon bays doors open...

So you would rather the KC-46 shot down and 3 lives lost?

I wouldn't have a KC-46 fly anywhere it's vulnerable, nor risk 2 B-21s getting shot up due to an aerial refueling exercise that glows hot to enemy air defenses.

What a stealth tanker give you is the ability to tank nearer to the front line ro reduce risk of detection of strike packages (opsec). It would be foolish to be tanking over contested air space, even if both planes are stealth

bt

With the B2 still being a larger aircraft than the B21, maybe they can make it be a stealth tanker after retired from bomber service? They still have plenty of time to develop such a program and have feedstock available. Plus a larger (I assume) bomb bay for a longer, telescopic boom. They can also make the bomb bay stealthy as part of the retrofit.

Crazier things have happened. Like modern engines and glass cockpits for the B52, KC135, and C5 which even had it's wing structure replaced.

TWA772LR wrote:

With the B2 still being a larger aircraft than the B21, maybe they can make it be a stealth tanker after retired from bomber service? They still have plenty of time to develop such a program and have feedstock available. Plus a larger (I assume) bomb bay for a longer, telescopic boom. They can also make the bomb bay stealthy as part of the retrofit.

Crazier things have happened. Like modern engines and glass cockpits for the B52, KC135, and C5 which even had it's wing structure replaced.

LOL, no, they have not. How many B-2’s would be converted? The B-2’s cost more than their weight in gold each, and over $130K per hour to operate (I would speculate closer to $200K today). We shouldn’t even be wasting money using them for fly overs any longer.

https://www.wearethemighty.com/articles ... ve-planes/

The costs to operate a large, stealthy manned aircraft/bomber are high, period. This is why a manned, stealthy tanker, let alone a conversion of some small set of 30 year old aircraft, makes no sense at all to me. Refueling in the air is expensive, slow, and one is vulnerable waiting/getting to/from the tankers. A stealthy orbiting gas tank…will need to be very special to make financial/procurement sense.

TWA772LR wrote:

With the B2 still being a larger aircraft than the B21, maybe they can make it be a stealth tanker after retired from bomber service?

Very doubtful but I will discuss.

The stealth coatings would make up a huge portion of the B-2 hourly operating cost. I assume they would stop doing coating maintenance on a B-2 tanker.

Comparing a B-21 versus a B-2 both without coating maintenance the B-21 will always be stealthier and have a lower operating cost. Newer stealth aircraft have better natural stealth due to better gaps. Older stealth aircraft need the larger gaps filled and maintained.

However the biggest advantage to the B-2 tanker is that it is owned outright. So it will take thousands of flight hours until the B-21 works out cheaper. Such a stealth tanker would fly very few flight hours per year. 20 stealth tankers is probably all that is needed. As 90+% of the fuel offloaded will be from the KC-46 fleet and the stealth tankers only do the final top up closest to contested airspace.

The biggest disadvantage to the B-2 is that it can't fly unmanned. The B-21 is planned to be optionally unmanned so this makes it the ideal tanker. That is a big added cost to make the B-2 unmanned.

Being unmanned is just as important as the lower radar cross section in terms of getting the tanker closer to contested airspace. The USAF would probably send an unmanned KC-46 closer to contested airspace than a manned B-2 tanker.

This raises a good point. Could the KC-46 be fully unmanned? That might satisfy the Pareto principle being 80% as good at only 20% of the price.

they fitted all kind of stuff into 130s including 105mm howitzers. Pretty sure they could fit a refueling boom onto it, if they really wanted.

RJMAZ wrote:

Please explain how stealth aircraft survive once their weapon bays doors open...

I don't know if I'm right on this but I can visualize an F-35 going inverted nose up 20°, opening the doors and releasing an AGM-88, while pulling the nose down to 20° below the horizon at about 2Gs.

If you quickly open the bay, release the weapon, and quickly close the bay, the chance of detection is reduced.

Note that returning signals are processed to filter out all sorts of anomalies. So if the blip from the bomb bay is small enough and disappear quick enough, computation to locate the blip may not be confirmed on the next pass.

Note that to obtain any actionable info from a radar return, you need several hits to get the aircraft vector. The trick is to reduce the numbers of hits while the door is open.

bt

Vintage wrote:

I don't know if I'm right on this but I can visualize an F-35 going inverted nose up 20°,

Going inverted though would expose the tail to more ground radar return. It would have to be a trade on which would have more impact.

You would also need some sort of ejector for the weapon, unless you can do an arch to lob or drop the plane away from the missile as opposed to the other way around.

bt

bikerthai wrote:

You would also need some sort of ejector for the weapon, unless you can do an arch to lob or drop the plane away from the missile as opposed to the other way around.

From above:

"while pulling the nose down to 20° below the horizon at about 2Gs

With the F-35s sensor fusion and central processor, this maneuver could be programed into the F-35, so that any time a radar source is detected and there is a ready to fire indication on a HARM missile, the plane could be commanded to take over and execute this maneuver.