Designing the replacement for the A-10

[Scott Kenny]

Okay, to get this discussion out of the A-7 versus A-10 thread.

I think we all agree that Ukraine shows the A10 (and Su25) are nowhere near as survivable in the 2020s as they were in the 1980s and 90s.

Also, the USAF corporate offices hate the A-10, it's super slow both tactically and strategically, and it has several type-specific schools and pieces of equipment that come purely out of the AF budget instead of being split across the entire DOD budget. Oh, and it's supposed to directly support the Army, of all things. Eeeewwwwww.

But the mission still needs filled. And no, the F-35 can't do the dance at the FEBA. The F-35's job is to interdict the units while they're still in march order and not shook out into battle formations, the job the A-7 did in the 80s and 90s.

The major complaint A-10 pilots will give you is that it is underpowered. The total bombload an A-10 can carry weighs more than the two engines produce in thrust, nevermind the weight of the plane! This leads to A-10 pilots not on a leash like in Desert Storm going in and dumping most of their bombs in a marginally-effective way at altitude, so that they can get down low and maneuver right.

The minor complaint is the straight wing makes a painfully slow airplane when ferrying, as it runs into "coffin corner" at 20,000ft

=====
Based on all of this, the design requirements I have come up with are as follows:

• Needs much more powerful engines, and those engines need to be ones in common use in the DOD already.
• Needs to be able to fly higher and faster.
• Uses the 25mm GAU-12 or GAU-22, which are used across the DOD and NATO and can therefore be reloaded at any base that operates F-35s.
• Other avionics also need to be used on other aircraft.
• Needs to be somewhat LO at a minimum, does not need to be absurdly LO like the B-21.
• Needs to be as resistant to battle damage as the A-10, if not more.
• Needs to be as quickly repairable as the A-10.
• Needs to have the loiter time of the A-10.
• (bonus points for figuring a way to get the Army to pay for the plane, unless we throw the Key West Agreement out entirely and let the Army fly their overhead CAS while USAF does interdiction)

(will add more requirements as suggested in the thread)

=====
Now, the plane I am picturing has the following features:

• Uses CFM-56s, which are in the DOD inventory as F108 engines. They're shared across a pretty large number of airframes, and are stupid reliable. Bonus is that the core is F101, so even more of the engine is shared across the DOD inventory. Specifically the 60" diameter fans, as used on P-8 Poseidons and C-40 Clippers. The other engine option is the RR F130 being used for the B-52 re-engining, but it's much less common than the CFM-56.
• Uses a supercritical airfoil wing, like that of the Boeing 787. This gives good lift at low speed, without stupid amounts of drag at high speed. Wing will probably be swept at about 35deg, so other edges will line up with that angle. The thick leading edge of a supercritical airfoil probably compromises radar LO a good bit, but is necessary for flight performance.
• Uses GAU-12 25mm, but with a fixed 3300rpm firing rate. The extra barrel helps to keep the gun from overheating during multiple strafing runs. Has roughly 1000rounds in the feed system. Gun is not on the centerline like the A-10, instead it's off to one side like the F-35A, F15, F16, etc. This allows the installation of an actual radar in the nose.
• Uses the full F-35 DAS EOTS system, but still has a tall bubble canopy more like the A-10 in case of DAS trouble. This encourages pilots to fly heads-up. Yes, stealthing this will be a challenge.
• Carries 10klbs or so internally, can add stuff under the wings for a total of about 25klbs (taking advantage of bigger engines and wing)
• OML is all edge-aligned and panels have LO shaping. I do NOT expect to use a lot of RAM on the airframe, that's expensive and time-consuming to repair. Another LO feature is the relocation of the IFR receptacle to the spine instead of the nose.
• Canopy is armored, cockpit has an A-10 like Titanium Bathtub but the Bathtub is sized for a two-seater by default. Fuel tanks are nitrogen purged, fuel lines have check valves to minimize leaks. Hydraulics are multiply redundant and the lines have check valves to minimize leaks.
• As many pieces as possible are symmetrical, so that they can be used on either side of the aircraft. The entire tailplane, for example. Rudders and Ailerons are symmetrical, Horizontal and Vertical Stabilizers are as well. Even the attachment points are symmetrical, and they're bolted to the end of the V-stab before being bolted to the H-stab.
• Because the engines are 3x the power of the A10, it carries more fuel. But because it mostly flies on internal weapons, it doesn't need triple the fuel capacity to equal the loiter time. I guesstimate 20klbs of fuel internally.
• I would actually toss the Key West Agreement entirely, allowing the Army to fly armed fixed wing aircraft for their CAS.

Overall, picture an A10 with bigger engines, longer intakes that are blended into the airframe instead of being in separate pods, and thick leading edge swept wings. It will be a physically larger aircraft, between the 10klbs internal bays and the ~20klbs of internal fuel.

What else can you add to the list?

 

[isayyo2]

I think we all agree that Ukraine shows the A10 (and Su25) are nowhere near as survivable in the 2020s as they were in the 1980s and 90s.

This might derail the thread... But shouldn't we argue the opposite? Despite facing, in theory, a totally integrated air defense threat from Iglas to S-400s and MiG-31s Ukraine can still operate ground attack aircraft like the Su-25 in an effective manner with dumb munitions.

Yes the A-10 is physically aged, though with modern avionics and munitions, a subsonic attack focused aircraft clearly has value despite modern threats.

 

[aim9xray]

Good Lord! Are you aware of the size of the CFM-56 or the ungodly long spool-up time it takes to get that fan moving? Even the the TF-34 FeatherFan (TM) was barely acceptable!

 

[Scott Kenny]

There are also two other weapons programs that would be very helpful to the A-10 replacement:

1. Making another run of AGM-122 Sidearms. This would give all planes that can carry a quick reaction weapon to smite a Shilka or Tunguska that suddenly turned on its radar.
2. Either adopting the CRV7 rocket motor or developing an equivalent for the Hydra 70mm rocket. This would give much better standoff range compared to the APKWS Hydra 70mm rockets due to their higher speed. (weird, why does wiki give a 4km effective range for the CRV7 and an 8km effective range for the Hydra 70s? Does someone have a better effective range for CRV7s?)

 

[Scott Kenny]

Good Lord! Are you aware of the size of the CFM-56 or the ungodly long spool-up time it takes to get that fan moving? Even the the TF-34 FeatherFan (TM) was barely acceptable!

Yes, it's a 5000lb engine. I mean, it's an F101/F110 with a 60" fan on the front instead of a 45" fan. But that huge fan also means low IR signature, since about 10klbs of thrust comes from the fan alone.

Do you have a better suggestion for a good engine to use? I suppose a non-afterburning F135 would work, but that has a much higher IR signature.

 

[Scott Kenny]

This might derail the thread... But shouldn't we argue the opposite? Despite facing, in theory, a totally integrated air defense threat from Iglas to S-400s and MiG-31s Ukraine can still operate ground attack aircraft like the Su-25 in an effective manner with dumb munitions.

Yes the A-10 is physically aged, though with modern avionics and munitions, a subsonic attack focused aircraft clearly has value despite modern threats.

I'd honestly argue that the Russian forces in Ukraine are not exactly showing their competence.

 

[aim9xray]

What the Lieutenant meant to say: "But that huge fan also means a gadawful bump to the RCS signature"

 

[aim9xray]

Well, if you are trolling for airliner engines, take a look at the CF34 series. Evolved from the TF-34 so far that the only thing that hasn't changed is the GE logo on the dataplate.

However, I suspect that you'll encounter some ugly surprises if you try to throttle jockey er, match the performance spectrum endured by a military qualified engine.


Ugly surprise == Genuine GE Turbine Gravel (TM) in the tailpipe after the IFE (Inflight Emergency).

 

[Scott Kenny]

What the Lieutenant meant to say: "But that huge fan also means a gadawful bump to the RCS signature"

That's what the long intake is for, to do some B-1B style serpentine and vane work to block the view of the fans from the front.

Well, if you are trolling for airliner engines, take a look at the CF34 series. Evolved from the TF-34 so far that the only thing that hasn't changed is the GE logo on the dataplate.

Problem is that they're not used anywhere in the DOD, so the USAF (or Army, if we let them fly armed fixed wings) would have to pay for the maintainer school on their own.

First bullet point in the requirements section.

 

[aim9xray]

Well then, something in the BR-700 series. Otherwise you're SOL.

 

[quellish]

Why would you make it RF low observable? It would be ineffective in the environment this operates in.

 

[aim9xray]

In fact...

Hold my beer.

Howabout shortening up a Gulfstream G350 fuselage, using the big, beefy supercritical wing from the G550, shorten up the pax area, replacing most of it with internal weapons bays and guns in the nose. Retain the stand-up lav, wet bar, fridge, microwave oven and field deployable satcom-networked crud pit for those really long missions (autopilots are reallly reliable these days). There's even room for the pilot's golf clubs. (This is the Air Force, you know.) Reconfigure the nose for a single-pilot under the bubble canopy.

Add some chines, because, well, RF stealth is kewl. And with the other requirements imposed, you have no hope of reduced visuals (being larger and louder than the F-15 Flying Tennis Court). And add some provision for wing pylons (seriously, there are a few Gulfstreams flying with pylons...)

And when the pilot retires, he's already qualified for the cushy corporate job (minus recurring qual for strafing).

/sarcasm.

 

[red admiral]

Why would you do this when we already have organic CAS down towards the company level through the likes of FPV drones, at many orders of magnitude lower cost?

 

[Scott Kenny]

Why would you do this when we already have organic CAS down towards the company level through the likes of FPV drones, at many orders of magnitude lower cost?

Because a Reaper cannot replace an A-10.

 

[Firefinder]

It will need F35 electro optical thermal sensors.

Specifically the nose/chin mounted ones.

The biggest issue with the A10 outside of engine power is that it basically have WW1 era sensor.

AKA just the pilot Mark 1 eyeball.

The replacement sorely needs a Ground Search Radar and the optical sensor so the pilot can find and see the targets.

That the biggest non-negotiable deal.



Other then that?

Make it a two seater, decreases the work load and allows for one to run all the sensors.

Make low level ops far safer as well as enable the thing to act as a drone control ship.

Weapons, basically the same as the A10 but with all hardpoints fully wired for PGMS and like. Would like for each hard point be capable of 2 SDB quad packs, those will eat tanks for a snack, and should be the main anti tank weapon imo.

And have enough reserve power for the laser weapons the military been screwing around with. Likely only be useful in blinding sensors and burning pick ups trucks, but if you need to hit pick ups then you in Coin so no point in wasting anymore money. Thru it could be useful in anti drone work.

I going to commit heresy and say put the Armys M230 30mm cannon or Aden/Defa cannon modified to take Army shells, preferably in a flex mount. Those 30mm mine shells will tear thru everything short of a MBT and even those will get properly mauled. And as shown by the Apache, they do nasty things to personal. Plus the Army just made a Proxy fuse one, that be terrifying in a Strafing run.

A full suit of countermeasure for survivability, jammers, chaff, flares, tow array, DIRCM, the works. That should keep missile hits to a minimum.

Throw in some LIGHT stealthing, enough so that while its down in the weeds it be a pain to detect from range. Think how the San Antonio class is reduced visibility compare to the older class of the LPDs. Or B1 verse the B52 or B2, the Bone is stealthier compare to the B52 but is nothing compare to the B2. But the exhaust thermal signature should have all attempts made to be minimize to make heat seeking weapons jobs the hardest. The biggest threat to this is the Manpeds and Shorads systems, not the big SAMs.


As for the Airframe to put all that in?

Am of two minds.

Either a B57 Canberra size airframe, big holds lots of ammo, reinforced enough to make a battleship jealous.

Honestly that Gulfstream idea is not a half bad one once you stop to think bout it. Those are pretty agile and with some reinforcements it will make for a decent bomb/missile truck that modern CAS be. While being just agile enough to do the odd strafing or strike mission.

Or basically have it be a tilt rotor gunship based on the V280 valor so the Army can have full control of it. Of course modified for more speed.

Of course top speed needs to be within the 400 mph (700kmph) area, with similar to the A10 cruise performance.

 

[red admiral]

Because a Reaper cannot replace an A-10.

I'm not talking about Reaper though; rather small armed drones in Army units so you have organic fire support at much reduced cost.

 

[TomcatViP]

I think A-10 can stay as they are. Make it a MuM-T dedicated asset and arm them with long range gliding weapons (as already experimented).

The only really thing needed is a satcom and new engines.

 

[GTX]

Because a Reaper cannot replace an A-10.

Why not?

 

[Scott Kenny]

Why not?

Insufficient capacity and situational awareness, inadequate self protection measures (including LO treatments) for near-peer combat. They're perfectly adequate for Counter-Insurgency CAS.

 

[Scott Kenny]

I think A-10 can stay as they are. Make it a MuM-T dedicated asset and arm them with long range gliding weapons (as already experimented).

The only really thing needed is a satcom and new engines.

With only one pilot? You like working really hard while dodging cumulogranite, don't you?

The Apache Es have demonstrated that you need a back seater to control current drones.

And if you're going to give them long range glide or rockets, you're wasting the 3000+lbs of gun+ammo the plane carries (or rather, the 10+ strafing runs the plane has).

 

[TomcatViP]

Probably that a serious sonic weapon would make a good replacement (dazzle, fry or interdict launched guided artillery shells and enemy UAS).

Regarding the risk of Cumuloconcrete (didn't know that one!)!, the idea is to orbit dozen of miles away from FLOT, at low alt. GA pilots routinely navigate freely at level 1000. 500 if you are lucky.

 

[Scott Kenny]

Regarding the risk of Cumuloconcrete (didn't know that one!)!, the idea is to orbit dozen of miles away from FLOT, at low alt. GA pilots routinely navigate freely at level 1000. 500 if you are lucky. And they have a full gamut of Red Baron and romantic dreams to tackle to stay concentrated!

Low altitude orbit means short range for glide bombs unless you're doing toss bombing, which also requires significant engine power to do the loop. Guided high velocity rockets would be a much better option for that CONOPS, IMO.

And I got "cumulogranite" from Dale Brown's Day of the Cheetah, when the Dreamstar pilot got distracted and missed a mountain by about 200ft via VIFFing. The two pilots in the super F-15 were snarking about it.

 

[red admiral]

Insufficient capacity and situational awareness, inadequate self protection measures (including LO treatments) for near-peer combat. They're perfectly adequate for Counter-Insurgency CAS.

Sounds like you need a B-21 for CAS then

 

[Scott Kenny]

Sounds like you need a B-21 for CAS then

Not quite that LO, and flying wings are no bueno to fly close to the ground. If they're not all tied up in strategic ops, B21s should be doing the interdiction raids behind the FEBA (or whatever the current term is for the front lines).

Maybe an F35D, that loses either the LiftFan or mid-body fuel tank for another bomb bay so it can carry 10klbs internally.

 

[DrRansom]

The A-10's major advantage over the F-35 is it's pricet-tag, cheap to buy, cheap to operate. Yes, it won't survive over high-capability air defenses, but the US spends most of its time fighting over countries with low-capability air defenses.

For some reason, the USAF thinks it has the budget for 2000 F-35's and 200 B-21s and NGAD and state-of-the-art-space and ... - the budget won't be getting meaningfully bigger, cheaper aircraft are needed.

In that case, keep the replacement simple and aim for a CPFH that's at most half of the F-35.

 

[paralay]

 

[Desertfox]

Y'all need to think simple and cheap, two different version of the Scaled Composites ARES, an unmanned UCAV, and a two-seater FAC version with the sensors from the AT-6 and no gun. Cheap, disposable, small, and you might sneak it under the Key West Agreement, also already designed specifically for this mission.

 

[VTOLicious]

A14 Wild Wolf by @Rodrigo Avella

View: https://youtu.be/BNq3kmkT2_Y?feature=shared

 

[jcf]

The A-10's major advantage over the F-35 is it's pricet-tag, cheap to buy, cheap to operate. Yes, it won't survive over high-capability air defenses, but the US spends most of its time fighting over countries with low-capability air defenses.

For some reason, the USAF thinks it has the budget for 2000 F-35's and 200 B-21s and NGAD and state-of-the-art-space and ... - the budget won't be getting meaningfully bigger, cheaper aircraft are needed.

In that case, keep the replacement simple and aim for a CPFH that's at most half of the F-35.

"... cheap to buy ..."??

The A-10 hasn't been built in almost 40 years, from whom are they going to be purchased?

 

[Scott Kenny]

A14 Wild Wolf by @Rodrigo Avella

View: https://youtu.be/BNq3kmkT2_Y?feature=shared

That's actually pretty close to the appearance I had in mind, though I don't believe that airframe is properly shaped for basic LO. Gun needs to be covered, and the intakes are too small for the size engines the plane needs. Minimum of a 48" fan.

Not so weird. As you had already kind of noted, the point of the CRV7's C15 motor is providing higher velocity not longer range.

I expected the higher velocity to result in better range after motor burnout. I guess the CRV7 rocket motor burns significantly faster than the Hydra, so it spends far less time/range under thrust?

The A-10's major advantage over the F-35 is it's pricet-tag, cheap to buy, cheap to operate. Yes, it won't survive over high-capability air defenses, but the US spends most of its time fighting over countries with low-capability air defenses.

The A-10 replacement is really supposed to be used for the high capability battlefield. Reapers or Mojaves are perfectly acceptable for low capability Air defenses.

Remember, you can't operate a plane forever. There is a fatigue limit to parts. Even the unstoppable B-52 will run out of fatigue life after about 37,000 flight hours, when the upper wing skins need to be replaced. The A-10 will need to be replaced pretty soon, the A-10Cs already needed their wings replaced once.

For some reason, the USAF thinks it has the budget for 2000 F-35's and 200 B-21s and NGAD and state-of-the-art-space and ... - the budget won't be getting meaningfully bigger, cheaper aircraft are needed.

In that case, keep the replacement simple and aim for a CPFH that's at most half of the F-35.

All the systems and sensors necessary for an adequately capable aircraft these days mean a plane that is expensive to buy. I'm fully expecting this plane to be in the $70-90mil price range, not counting development costs. But in terms of cost per flight hour, I think we can keep that to 1/3 that of an F-35, if not less (engines are less at the edge, so don't need as much maintenance per flight, etc).

As a serious point, the USAF is stuck with an entire fleet of aircraft that are aging out at about the same time. The USN was in the same boat in the 1960s, as all the WW2 production was aging out and the whole fleet needed to be replaced.

It's much easier on the budget to set things so that you can replace fleets on a rotating basis.

 

[GTX]

(engines are less at the edge, so don't need as much maintenance per flight, etc).

You might be surprised to learn that it often works the other way.

 

[Scott Kenny]

You might be surprised to learn that it often works the other way.

When you start pushing the engines past their design levels, lifespan gets greatly shortened. For example, the J58s in NASA's Blackbirds went from 400 hours between overhauls to about 50 hours TBO when NASA needed a bit more power for the big Linear Aerospike experiments. And that was for only a few more % power!

Turbines are also very narrowly optimized for one level of airflow. Whether that's at 80% rpm or 100% rpm doesn't really matter. Running them at their most efficient setting is where you have the least maintenance, the more you cycle from idle to full power and back the more maintenance they need.

 

[DrRansom]

"... cheap to buy ..."??

The A-10 hasn't been built in almost 40 years, from whom are they going to be purchased?

It isn't LO, it doesn't have state-of-the-art radar and EW systems. An A-10 replacement would inherit those design traits and be substantially cheaper than a F-35.

 

[Scott Kenny]

It isn't LO, it doesn't have state-of-the-art radar and EW systems. An A-10 replacement would inherit those design traits and be substantially cheaper than a F-35.

Honestly, I think an A-10 replacement will end up with pretty high-end radar and EW, and at least LO shaping, if not lots of RAM surfaces.

Otherwise it just won't survive!

 

[red admiral]

Sounds more and more like an F-35 (but maybe subsonic?) Or a B-21

 

[GTX]

When you start pushing the engines past their design levels

No operator/designer in their right mind will do that though.

 

[T. A. Gardner]

Personally, I think for a CAS aircraft, they should go retro and update this:

You don't particularly need it to be stealthy, but rather resistant to detection by IR MANPADS. Speed isn't an issue either, loiter time is far more important and a turboprop gives you lots of that. Make it a true bomb truck capable of carrying something like 12 or more stations of ordinance along with a large cannon, maybe not the 30mm but a 25mm or something else. Ammo capacity is more important than tank killing alone--you have PGMs for that and if you made it compatible with Hellfire or another ATGM, you could tote like 24 or more if necessary with all those ordinance stations.
Make sure the pilot(s) have great visibility forward and down so targets can be picked out.

Armor today is advanced enough you can easily protect all the vital systems and you build an airframe that will absorb huge amounts of damage and still fly. Pick engines that give it so much power to weight at normal loads it can climb vertically using something like a six-bladed modern propeller. Make it nimble where it can turn on a dime, and do acrobatics while loaded down. That makes it far easier for the pilot(s) to evade ground fire when necessary.

For defense against radar guided AA and smaller missiles (think the Rapier system)

You substitute ECM drones, small ones, that the plane can launch and are disposable. These can be burst noise jammers, or designed to be massive radar targets that distract the system, that sort of thing.

You aren't going to be doing diving attacks or flying at higher altitudes in this thing. It's low and slow most of the time. With a crew of 2, you have redundant controls and one crewman can be the weapons operator while the other concentrates on flying 5 meters off the ground at 250 kts IAS. You come over a tree line or hill in this, the pilot using the cannon and flying engages stuff while the WO is letting stuff off the flight path have it with PGM's.

Of course, the USAF would absolutely hate it...

 

[H_K]

@Scott Kenny First you need to answer the question “What effect(s) are you trying to achieve?”

The A-10 was designed to autonomously find & destroy armored vehicles, close to front lines where it could be shot at by Manpads and 23mm canon. It was not designed for strike or reconnaissance behind enemy lines.

It could also be used for Close Air Support but as @red admiral says today troops on the ground (whether 1st or 2nd echelon) have many options for guided fires that can destroy a target much faster than waiting for a pair of A-10s to be vectored in.

Likewise, drones of all kinds are very able to find & destroy armored vehicles these days. And being attritable they can even do some deep reconnaissance (though jamming of comms link can be a problem).

Finally if the goal is to penetrate some distance at low altitude behind enemy lines to do armed reconnaissance, perhaps helicopters operating at night with ALE-style munitions are going to be even more successful given their ability to stop/hide.

So what mission are we really talking about that can’t be done by other existing assets?

 

[Desertfox]

I'll just repeat it again, we have an aircraft designed specifically for this mission that can be modified or "fudged" to fit under Key West in the Scaled Composites ARES.

 

[Scott Kenny]

No operator/designer in their right mind will do that though.

Turbine engines have a very narrow "power band" where they are most efficient. Different versions of the engine can have that particular band in different locations in terms of RPM.

Let's use the CFM-56 for an example. While it's said to have an F101 core, that's really just referring to the HP spool. The LP spool is completely different, and later engines even the HP spool is different.

IIRC, the CFM-56 LP spool is optimized to run at flight idle/cruise power. The F101's HP spool isn't totally happy with that, but it's not too far off the design optimization. This gives best fuel economy at flight idle and increased fuel burn per lb thrust at takeoff, as well as a reliability rate that is mindblowing for a jet engine at over 300,000 hours TBF. That's one failure after 100 overhauls. The engines basically don't come off the wing once installed at the factory unless they eat a bird (or a ground crew).

In comparison, the F101 and F110 are optimized to spend more time at 100% power or even overspeeding the HP spool at Military power (compressors do NOT like spinning over Mach 1 at the blade tips!). This actually puts their time between overhauls as something measured in cycles instead of flight hours. One cycle is flight idle to full power (or MIL/AB) and back. This also means that the F101/F110 get best fuel economy in terms of lb fuel per lb thrust at 100% instead of the flight idle HP rpm of the CFM-56. How often does an F101 or F110 come out of the aircraft?