The GAU-22/A thread

[steve2267]

The burst length is selectable. The pilot isn't "free gunning."

Oh, I understand this fact. But this is the first "hard" evidence I have seen of this capability -- a capability I do not believe any other tactical aircraft shares, short of possibly an AC-130 gunship.

But I am curious if the pilot can type in or specify the number of rounds in a burst, or if he has to select a preset burst length.

[wrightwing]

[



Oh, I understand this fact. But this is the first "hard" evidence I have seen of this capability -- a capability I do not believe any other tactical aircraft shares, short of possibly an AC-130 gunship.

But I am curious if the pilot can type in or specify the number of rounds in a burst, or if he has to select a preset burst length.

The end result would be similar, however the system works. I know from previous tests, there were specific round counts, so my guess is that it's round selectable. I'm not sure what the low end round count is, but if it's 10 to 12rds, that's 15 to 18 short bursts.

[spazsinbad]

'wrightwing' do you have an URL source for this info please? "The burst length is selectable. The pilot isn't "free gunning."" THANKS.

[steve2267]

A recent news quote about the Auto-GCAS capability refers to a "combat autopilot." If this leads to the capability of the pilot designating a target with a deathdot in his HMDS, and then letting George fly the aircraft within some pilot designated time-frame to automagically put a 15 round burst on that target... that would be some capability.

[mixelflick]

First all new gun since the Vulcan used in everything from the Phantom to Raptor, correct?

The bigger round is a step up and should do the job strafing most targets. It'll never be the GAU-8 but hey, what is? Hopefully it can punch a hole in a tank, or at least keep their heads down for a bit.

Of more interest to me is its air to air "punch". For decades we seem to have favored the lighter M61 20mm cannon for use in our fighters. The Russians and Europeans, heavier 23 and 30mm rounds (though carrying fewer of them than the M61). So what's the thinking here? Need more "umph" to cause more damage to bigger and more powerful (Flanker) airframes? Or is the move to 25mm solely to find a sweet spot for air to ground/air to air engagements?

[zerion]

Video of Dutch 323TES Squadron loading gun and gun run.

https://twitter.com/Kon_Luchtmacht/stat ... 5706190849

he seemed to like it.

(P.S. anyone know how to pull just a video off Twitter?)

[steve2267]

Edited to add:
I cannot cite references or sources stating the reason why a caliber larger than the 102x20mm was chosen. However, one of the first 3 PDF's I attached to the original post of this thread stated that the gun system was primarily intended for air-to-ground use. Either in that same document, or something I read in the past day or so, stated that the gun was estimated to be used about 70-80% of the time in an A2G role, and only 20-30% in an air-to-air role.

First all new gun since the Vulcan used in everything from the Phantom to Raptor, correct?

The AV-8B is (optionally) equipped with a 5-barrel GAU-12/A Avenger gun system, from which General Dynamics derived the GAU-22/A used on the F-35. Various AC-130 gunships have also used the GAU-12/A.

The bigger round is a step up and should do the job strafing most targets. It'll never be the GAU-8 but hey, what is? Hopefully it can punch a hole in a tank, or at least keep their heads down for a bit.

The GAU-8/A on the A-10 kills tanks by defeating the tank's armor where it is thinner (think top, sides, and rear). I do not have memorized the armor penetration values for the 30x173mm round the A-10 carries. The Nammo APEX PGU-47/A round will penetrate 50mm rolled homogenous armor (RHA) at 0° incidence. Taking into account a realistic incidence angle (30-45° ?) suggests there are places on modern MBTs that may be vulnerable to an F-35 strafing it: typically the top / back part of the turret, and/or the top / back part of the rear deck where the engine is typically located. That being said, I don't think anyone considers the GAU-22/A to be a primary tank-killing weapon of the F-35. That would be a SDB-II, SPEAR, or possibly a GBU-49.

The US appears to be standardizing on either a FAP or PELE round by ATK. IMO, the APEX is superior as it is usable across the full spectrum of targets from soft to hard, whereas FAP/PELE seems more appropriate to harder targets as they do not utilize any explosives.

Of more interest to me is its air to air "punch". For decades we seem to have favored the lighter M61 20mm cannon for use in our fighters. The Russians and Europeans, heavier 23 and 30mm rounds (though carrying fewer of them than the M61). So what's the thinking here? Need more "umph" to cause more damage to bigger and more powerful (Flanker) airframes? Or is the move to 25mm solely to find a sweet spot for air to ground/air to air engagements?

If you perused any of the PDF's I included in the first post of this thread, you will see that the gun system is (was) not intended to be a primary air-to-air weapon. It's intended, primary use is to service ground targets.

With that said, air-to-air gunnery is a tradeoff between accuracy, dispersion, shell velocity, shell lethality and firing rate. You want the gun to be accurate, yet you want a "dispersion" pattern at your optimum firing range to maximize the chances that a shell will detonate on the target (think shotgun pattern size at expected target distance). A former Phantom driver told me you ideally wanted 50 kts overtake or closure speed, and optimum firing distance was 1000-1500ft. He said you did not want to engage closer than 500ft (if saddled up) because the risk was high that you would fly through a debris field, to the detriment of your own jet's health. Also, 2000-2500 ft would be a really long shot. High velocity minimizes time of flight (TOF) of the projectiles, removing as much guesswork as possible from estimating where the target will be after 1 TOF (since both attacking aircraft and target are moving in 3D at (typically) high rates, afterall.) Firing rate relates to shot density (think number of pellets in a shotgun blast.) In fact, the shotgun analogy is apropos here. Do you choose a 12 gauge 00 shell with 9 pellets or a #7 shot shell for birds with lots and lots of tiny pellets? Percentage chance that you hit the target increases with the number of pellets, but the damage inflicted decreases with the smaller pellet size. What works for a duck probably won't work on a bear. For air-to-air gunnery, the US has historically favored higher firing rate and accepted smaller projectile size & mass with the 102x20mm round and the M61 Vulcan as the air-to-air cannon of choice since its choice on the F-104. Since WWII, the Europeans and Russians have favored 27mm or 30mm for their fighter aircraft cannon.

If you multiply firing rate by shell mass, you obtain throw weight which is a common metric used to compare aircraft gun systems. A succinct summary comparing the various aircraft cannons can be found in this post on ar15.com:

F-35A, 25mm GAU-22/A with 180 rounds.
3300 RPM / 55 RPS rate of fire, 223 gram projectile weight for 12.3 kg/s throw weight, 3.27 seconds firing time of ammunition and 40.1 kg of total projectile weight.

F/A-18E/F, 20mm M61A1 with 412 rounds.
6000 RPM / 100 RPS rate of fire, 102 gram projectile weight for 10.2 kg/s throw weight, 4.12 seconds firing time of ammunition and 42.0 kg total projectile weight.

Typhoon, 27mm BK 27 with 150 rounds.
1800 RPM / 30 RPS rate of fire, 260 gram projectile weight for 7.8 kg/s throw weight, 5.00 seconds firing time of ammunition and 39.0 kg total projectile weight.

Gripen, 27mm BK 27 with 120 rounds.
1800 RPM / 30 RPS rate of fire, 260 gram projectile weight for 7.8 kg/s throw weight, 4.00 seconds firing time of ammunition and 31.2 kg total projectile weight.

Rafale, 30mm GIAT 30 with 125 rounds.
2500 RPM / 42 RPS rate of fire, 275 gram projectile weight for 11.6 kg/s throw weight, 2.98 seconds firing time of ammunition and 34.4 kg total projectile weight.

Su-35, 30mm GSh-30-1 with 150 rounds.
1800 RPM / 30 RPS rate of fire, 390 gram projectile weight for 11.7 kg/s throw weight, 5.00 seconds firing time of ammunition and 58.5 kg total projectile weight.

The biggest difference with the F-35A and GAU-22/A is that it has more programmable bursts. For A2A, you could get 9 x 20rd bursts if you wanted, or 3 x 60rd bursts, etc.

One of the assumptions most outside observers have made is that the F-35 will rely on missiles for its first kills in A2A, when the gun is more of an option in the F-35 than any 4th Gen jet as a first kill system when approaching VLO. Threat air is flying along, all of a sudden they get shredded by 25mm dual-purpose projectiles and don't know why.

https://www.ar15.com/forums/general/F-3 ... #i74212670

IMO, the GAU-22/A represents a masterful compromise, especially if the Nammo PGU-47/U APEX round is used, of

• high rate of fire (though not as high as the Vulcan, but probably more than "dense enough for air-to-air work)
• very good throw weight (in fact, highest of all cannon listed above)
• decent total throw weight
• high velocity (~1000m/sec)
• very good shell lethality against both soft and hard targets (PGU-47/U APEX)
• very good gun accuracy / low dispersion (nascent F-35 aiming issues aside)
• high round / burst efficiency with the ability to select very short bursts (e.g. 12-15 rounds each)

That is, the GAU-22/A appears to be a really good gun system, quite possibly the best in any modern fighter, 4th or 5th generation. It will certainly shred trucks and kill APC's and light armor. It appears it may be effective against armor if attacked from the correct direction.

If combined with a combat autopilot function (think AutoGCAS for a gun solution), it may be a truly killer air-to-air solution especially combined with efficient, short round count bursts.

I hope I have addressed your questions.

[spazsinbad]

Video of Dutch 323TES Squadron loading gun and gun run.
https://twitter.com/Kon_Luchtmacht/stat ... 5706190849
he seemed to like it. (P.S. anyone know how to pull just a video off Twitter?)

Yep. Doing it now (see GIF) WinX YouTube Downloader is FREE. It will truncate the video file name but works well.

https://www.winxdvd.com/download.htm SCROLL DOWN THE PAGE:
https://www.winxdvd.com/download/winx-y ... loader.exe FREE DOWNLOAD 27.6Mb

Luchtmacht - Wederom een mijlpaal voor het 323TES .mp4 (10.5Mb) attached for you.

[zerion]

Thanks

[marauder2048]

. Taking into account a realistic incidence angle (30-45° ?) suggests there are places on modern MBTs that may be vulnerable to an F-35 strafing it

For a typical F-35 high-angle strafe (45 degrees, 9,000 ft) Nammo claims that APEX penetrates all of 8mm RHA NATO.
Not sure that's a meaningful increase over the PGU-32. And the PGU-48 will be superior to both.

Against enemy personnel operating on anything other than a hard surface, there's a need for a
programmable airburst or proximity round given that even very expensive, low impact velocity,
low-drag contact fuzes like the one used in the PGU-46 are going to dud.

[steve2267]

For a typical F-35 high-angle strafe (45 degrees, 9,000 ft) Nammo claims that APEX penetrates all of 8mm RHA NATO.
Not sure that's a meaningful increase over the PGU-32. And the PGU-48 will be superior to both.

maud, can you provide a source or link for your statement? I am not seeing the "8mm RHA NATO" penetration by the APEX (PGU-47/U). In several Nammo PDF docs, I am seeing results stated to be for 20mm RHA 45° NATO and 50mm RHA 0° NATO (first APEX PDF I attached in my first post of this thread). 20mm is 0.8". Unfortunately, I am not seeing any range distances provided for these APEX penetration numbers. A General Dynamics or Northrop Grumman (who bought ATK) PDF states 19mm RHA penetration at 0° NATO at 960m for SAPHEI (PGU-32/U). I'm not sure I've found penetration performance numbers for FAP (PGU-48/U).

Against enemy personnel operating on anything other than a hard surface, there's a need for a
programmable airburst or proximity round given that even very expensive, low impact velocity,
low-drag contact fuzes like the one used in the PGU-46 are going to dud.

What is PGU-46?

Re-thinking my earlier statements... I think any 25mm round is going to be hard pressed to disable, let alone destroy, a modern MBT. Maybe, if no other options are available, a mobility kill might be possible by a strafe attack from the rear or sides. Probably much better options of guiding or targeting weapons from other platforms utilizing the F-35's sensors / networked comms if SPEAR / SDB II are unavailable.

I view the 25mm GAU-22/A gun system as an improvement over the Vulcan for A2G operations, perhaps not as capable as the 27mm or 30mm rounds, but better than those in an A2A role.

Is FAP a Rheinmetal product? For some reason, I thought it was YAAP (Yet Another ATK Product).

Here is another APEX PDF I had found somewhere: APEX – Armor Piercing with Explosive The Dual Purpose Round for the F-35, Eva K. Friis, Nammo, Seattle 17.05.2012. Pages 14 and 15 have some charts giving APEX performance for a -45° dive angle from an altitude of 6500' at 550kts. Given those parameters, I am unclear on how slant range would vary (if the dive angle is specified)? Unfortunately, the axis of the figure are not given. It would appear that armor penetration is dropping with increased range.

APEX.pdf

APEX – Armor Piercing with Explosive The Dual Purpose Round for the F-35, Eva K. Friis, Nammo, Seattle 17.05.2012

(2.32 MiB) Downloaded 1106 times

[marauder2048]

https://www.nammo.com/globalassets/pdfs/ammobook/nammo_ammo_handbook_aw_screen.pdf

PGU-46 is the low-drag, low-impact velocity fuzed 30x173 used on the AC-130J; even it has difficulty
with fuze functionality against dismounts on soft surfaces (soil). Just extrapolating that to 25mm ammo.

I think the PGU-48 projectile is Rheinmetall but the cartridge and propellant are GD.
Ultimately, there's an enhanced PGU-20 that's likely going to be the preferred round.

[spazsinbad]

Bad news for the internal GUN I guess; good news for the external variety though; so there is hope a fix is found for the A.

Air Force Presses Lockheed On F-35 Readiness: Lt. Gen. Bunch
01 Feb 2019 Colin Clark

"The Pentagon's independent tester reports that F-35 readiness is stuck at 60 percent, while the A model's gun is unacceptably inaccurate.…

...F-35 Gun Misses Mark
The other notable fact in the DOTE report, beyond continuing problems with ALIS, the logistics and mission planning system for the F-35, is that the F-35A 25mm gun, needed for its Close Air Support role, is not very accurate. Here’s the damning language in the report:

“Based on F-35A gun testing through September 2018, DOT&E currently considers the accuracy of the gun, as installed in the F-35A, to be unacceptable. “F-35A gun accuracy during SDD failed to meet the contract specification. Although software corrections were made to the F-35 mission systems software to improve the stability of gun aiming cues, no software or hardware corrections have yet been implemented to correct the gun accuracy errors.

“Investigations into the gun mounts of the F-35A revealed misalignments that result in muzzle alignment errors. As a result, the true alignment of each F-35A gun is not known, so the program is considering options for re-boresighting and correcting gun alignments.

“During air-to-air gun testing, F-35A operational test pilots received intermittent ‘unsafe gun’ cockpit alerts while attempting gun attacks. These alerts occurred with two different aircraft; the root cause is under investigation.”

But there is good news! The F-35B and F-35C guns are accurate and “meet the contract specifications.” While the F-35A carries a permanently installed internal gun, firing through a shutter in the side of the fuselage, the B and C variants carry their gun in an optional external pod (see video below), which means it makes them less stealthy when installed, but apparently it shoots straighter."

Source: https://breakingdefense.com/2019/02/air ... gen-bunch/

[popcorn]

Strange, I would have expected the internal gun to be more accurate

[steve2267]

Strange, I would have expected the I vernal gun to be more accurate

Disappointing, but I'm ever hopeful the engineers will figger it out.

For me, the key part was:

“Investigations into the gun mounts of the F-35A revealed misalignments that result in muzzle alignment errors. As a result, the true alignment of each F-35A gun is not known, so the program is considering options for re-boresighting and correcting gun alignments."

Not quite sure how an aircraft that is so precisely designed ends up with misalignments. But it is what it is. Am guessing that if they can properly quantify where the gun is pointing on each airframe, they can Kentucky windage the sighting system for each aircraft. That is, numbers specifying a particular airframe's gun alignment, would be loaded into the flight / armament software as airframe-specific constants, which the gun sight software would use to put the '+' on the right spot.

IMO, the good news is that since the Killer Bee and SeaDragon guns are shooting within specs... there would not appear to be problems with the gun itself, which could have proved more problematic.