Forum: F-35 Armament, Stores and Tactics

As a lurker on the board for some time I have followed the choice of cannon on the A-model migrate from the BK27 to the GAU-22, I wondered how difficult would it have been for Mauser to change the BK-27 to the 25mm NATO Standard round? Obviously there was a political dimension to the weapon choice in the end, however I can't help but wonder whether the BK-27 was a victim of it being an additional burden on the supply chain unlike the GAU-22? Which creates the greater problem decreasing the calibre or decreasing the rounds length?

My experience as a ground pounder with weapons such as the FN SCAR (5.56 and 7.62mm interchangeable through the swap of some parts) would lead me to hypothesise that as you're moving to a smaller round in the BK-27, this should be possible, however, as there are many greater minds than mine at work on this board, I thought I'd ask the question?

Thanks in advance

Badmash

F-16.net Sponsor

I don't know the answer to the original question, but I am concerned with the utility of the GAU-22. Lockheed claims: "It is designed for increased effectiveness against ground targets compared to the 20 mm M61 Vulcan cannon carried by other USAF fighters." While no doubt the round is more deadly, with only 180 carried by the F-35A, how many bursts can the pilot even get at 3300 rounds per second? If the round capacity were so limited, it seems saving the money and simply going with the proven 20mm Vulcan would have been prudent. Particularly since everything short of the heaviest main battle tanks turn to swiss cheese when hit from a Vulcan from above.

redbird87 wrote:

I don't know the answer to the original question, but I am concerned with the utility of the GAU-22. Lockheed claims: "It is designed for increased effectiveness against ground targets compared to the 20 mm M61 Vulcan cannon carried by other USAF fighters." While no doubt the round is more deadly, with only 180 carried by the F-35A, how many bursts can the pilot even get at 3300 rounds per second? If the round capacity were so limited, it seems saving the money and simply going with the proven 20mm Vulcan would have been prudent. Particularly since everything short of the heaviest main battle tanks turn to swiss cheese when hit from a Vulcan from above.

3300 rounds per second? What?

redbird87 wrote:

only 180 carried by the F-35A

- Typhoon: 150 (27 mm Mauser BK-27. Rounds 1700 p/min > 28.3 rounds per sec)
- Rafale: 130 (30 mm Defa 791B. Rounds: 2500 p/min > 41.6 rounds p/sec)
- Gripen: 150? (27 mm Mauser BK-27. Rounds 1700 p/min > 28.3 rounds per sec)

Source Typhoon:
Quote: One of most striking features of the Eurofighter Typhoon (EF-2000) is its internal cannon. It is equipped with a single Mauser GmbH developed BK-27 cannon mounted internally in the fuselage forward of the starboard wing. It utilizes 27mm high explosive shells with a maximum firing rate of some 1700 rounds a minute; each aircraft will likely carry approximately 150 rounds.
http://www.defencetalk.com/eurofighter- ... n-2-16807/

Source Rafale:
Quote:30mm DEFA 791B cannon, which can fire 2,500 rounds a minute
http://www.airforce-technology.com/projects/rafale/

[/quote] 3300 rounds per second? What?[/quote]

Sorry, I meant 3300 rounds per minute. That's what General Dynamics advertises the gun at. The point was, 180 rounds internal, with a rate of fire of 3300 rounds per minute, is a pretty limited amount of firepower. Perhaps the gun has a 30 round burst mode, so you'd get 6 such bursts. I guess that's decent for one or two air to air engagements. Not much utility for ground work though, and the main marketing advantage you read about for the GAU-22 is it's increased effectiveness on ground targets. I'm curious how many 20mm rounds would have fit into the F-35 size cannon drum? 500+ perhaps as is the case with the F-16, F-18 and F-15E?

I'm not saying it's a bad system. I have a lot of practical experience with the Vulcan and none with the GAU-22. I'm just saying 180 rounds at that rate of fire doesn't seem like much.

I think the gun is meant for targets of opportunity when other ordinance are used up, rather than deliberately setting out to engage ground targets with it.

count_to_10 wrote:

I think the gun is meant for targets of opportunity when other ordinance are used up, rather than deliberately setting out to engage ground targets with it.

I agree.

Do any of these weapons offer a slower fire rate?
I would imagine that 8-10 rps would be fine for ground attack.

I wouldn't be surprised if the weapon could fire at a slower rate a la the M134's dual-rate 2000rpm/4000rpm. Also, if the laser-guided rounds we'll supposedly be seeing are loaded, the number of rounds in a burst could be lowered dramatically, thus allowing a larger number of bursts in a loitering CAS scenario. Imagine an F-35 operating in a low-intensity conflict with a few SDB (for larger targets), its cannon, and 2 AMRAAM (just in case) with a full load of external fuel. It would theoretically offer excellent endurance, as well as numerous possible engagements. Even better would be if EODAS could be linked into an external designator pod (if this is not already extant in an internal system).

The USMC like the 'networked aspect' of the F-35B/c for their use:

A Marine Corps Perspective on the F-35: Getting on With It June 2012

http://www.sldinfo.com/a-marine-corps-p ... n-with-it/

"...Situational awareness on the battlefield, especially the battlefield in the future is critical to us as a joint force with the other services to enable us to execute in that fight properly.

The technology of a fifth generation fighter, like the F35-B is not simply platform specific or internal to itself. It’s amongst the folks that are in that fight, whether they’re on the ground or in the air.

And the ability to transmit—to communicate seamlessly amongst platforms — is going to be the advantage that you will need in a fifth generation environment.

And that’s what makes the F35-B such a great advantage over the legacy platforms that we fly today....
&
Question: How good is this aircraft going to be at its close air support role?

Answer: All of the variants are going to share the same mission systems. The difference between the airplanes is purely how each service wants to operate them. Whether that’s off of a conventional land basing, sea basing with small decks for the Marine Corps and austere sites, which drives the B or carrier aviation for the Navy.

But the systems themselves are going to enhance the way that we do close air support because of the situational awareness that we’re getting from among other things the distributed aperture system on the airplane.

The ability to detect and identify is better. And identification is the key there. And the ability to seamlessly talk—not just with a single forward air controller that’s on the ground, but to share the information with the blue force network, if you will, that’s on the ground is huge. To say that the time to respond would be shortened, would be an understatement...."

redbird87 wrote:

with only 180 carried by the F-35A, how many bursts can the pilot even get

redbird87 wrote:

180 rounds internal, with a rate of fire of 3300 rounds per minute, is a pretty limited amount of firepower. Perhaps the gun has a 30 round burst mode, so you'd get 6 such bursts.

Pull the trigger six more times and clobber six more targets, without having to add anything extra on the hardpoints under the wings first... that's like having internal storage for six more bombs/missiles. That sounds pretty good to me.

redbird87 wrote:

I'm curious how many 20mm rounds would have fit into the F-35 size cannon drum

Well, with 80% of the diameter, each one would have 64% of the cross-section area, the inverse of which is 1.5625, so probably somewhere around 56.25% more bullets in the same space: 281. But Vulcans fire faster so they'd use that up faster than an Equalizer would use up the same number of bullets.

count_to_10 wrote:

I think the gun is meant for targets of opportunity when other ordinance are used up, rather than deliberately setting out to engage ground targets with it.

If you know it's there and what you can do with it, why not plan on using it and get a bit more out of each flight?

Last edited by redbird87 on Jun 21, 2012 - 05:11 AM; edited 1 time in total

Quote:

Well, with 80% of the diameter, each one would have 64% of the cross-section area, the inverse of which is 1.5625, so probably somewhere around 56.25% more bullets in the same space: 281. But Vulcans fire faster so they'd use that up faster than an Equalizer would use up the same number of bullets.

Thanks delvo. I knew the rate of fire was faster, but had no idea of the capacity difference. 281 to 180 does clearly swing the advantage to the 25mm. I had thought maybe it was more like 450 to 180.

Quote:

count_to_10 wrote:
I think the gun is meant for targets of opportunity when other ordinance are used up, rather than deliberately setting out to engage ground targets with it.
If you know it's there and what you can do with it, why not plan on using it and get a bit more out of each flight?

Risk-reward. What you gain by firing off a few gun rounds at a target of opportunity is not really offset by the, possibly remote but still real, change that you take a IR man-portable SAM up your tailpipe. If troops are in close contact you do what you have to do. Otherwise unless you have the next Bin Laden in your gun sight you just leave it for the next flight and bring your fighter home.

""As a lurker on the board for some time I have followed the choice of cannon on the A-model migrate from the BK27 to the GAU-22, I wondered how difficult would it have been for Mauser to change the BK-27 to the 25mm NATO Standard round?"

IMHO extremely difficult. If you read about the history of revolver cannons, they are extremly finicky peices of equipment. The tolerances needed for it to work are extremly tight, the heat transfer problems are a nightmare, and the parts are all pushed to limit of their performance. Even tiny problems will cause it to seize up. Usually those types of cannons seem to take around 10 years of develpment and testing to get right. Changing the round will essentially require a new design as everything is finely tuned to a particular round. A BK-27 25mm would not be a "clean sheet" design but probably most of the parts would have to change (I think).

ADEN actually started the design of a 25mm revolver cannon based on their 30mm design and just gave up because it wasn't working and was costing to much to develop.

One of the 'hidden' advantages of the GAU-22 is that rotary cannons are a lot easier to get working reliably.

archeman wrote:

Do any of these weapons offer a slower fire rate?
I would imagine that 8-10 rps would be fine for ground attack.

Revolver cannons (BK-27), no (the mechanism doesn't work that way).

GAU-22 could offer multiple rates, they've done that before, but then they took the option away. I guess they just fire shorter bursts.

Forum: F-35 Armament, Stores and Tactics

Mauser BK-27 conversion from 27x145 to 25x137mm NATO?