Question Re: F-35 main gun/25mm aiming system

[kcran567]

Would like to ask anyone who knows if the F-35 has laser guided rounds as part of its gun aiming system. Did it get this system? I read one of the posts on the A-16 topic and it was mentioned that the f-35 might get such a system that could possibly allow accurate firing of 25mm cannon rounds up to 4km.

what are those curious bumps on top of the F-35s nose? Is it such a system?

 

[GTX]

As far as I know, at this stage, there are no plans for the GAU-22/A to be equipped with laser guided cannon rounds. The bumps you refer to, if I am looking at the same ones you are referring to, are part of the EO DAS system.

 

[RadicalDisconnect]

Does the gun have a slight positive angle like most fighter jets or negative like in the A-10?

 

[Dragon029]

While I do not know, I would imagine that for the F-35A's GAU-22/A, it would have an upwards angle (considering that it's theoretical primary use is self-defence against aerial targets; due to USAF doctrine). For the F-35B and C's gun pod, I'm extra-uncertain, but I wouldn't be surprised if it was tilted downward or simply inline with the aircraft's bore; as for the Marines, their primary use would be for CAS and for the USN, they would probably not fly CAP / interception / etc missions with the gun pod (limiting its use for A2G or unexpected A2A scenarios).

Relevant cutaways:

 

[starviking]

How would laser guidance be achieved? If we're talking about air-to-air, then it has to be from the shooter - and that would either be a system with a very narrow FoV, or a much more complex system with a very wide FoV. The former would constrain the shooter's maneuvering, the latter not so much - but having a complexity that would have impacts on cost and availability.

Additionally, the rounds are going to have to be very complex, and will be used at a range of altitudes and attitudes, which must have a complex interaction with on-board maneuvering in the round. Seems much more complex than their naval cousins.

 

[Tony Williams]

There are no plans which have been made public for developing 25mm guided rounds of any type. The 76mm HEFSDS DART rounds from OTO Melara are currently the smallest such rounds available, although there has been a proposal for a guided Russian 57mm AA round, and I wouldn't be surprised if Bofors was working on one for their 57mm naval gun.

There have also been some experimental .50 cal projectiles devised and tested, but I suspect they're a very long way from entering service.

 

[Avimimus]

On the other hand - there was talk years ago about a 100Kw laser being integrated as a main weapon... I could never figure out how it would've been fitted into the airframe.


Btw. Thanks to the experts for chiming in. I remember dismissively shaking my head at claims of a hydraulically mobile GSh-301 and finding out years later that such a system had been proposed at one ppint.

 

[TomS]

On the other hand - there was talk years ago about a 100Kw laser being integrated as a main weapon... I could never figure out how it would've been fitted into the airframe.

The proposal I remember was putting the laser in the bay designed for the lift-fan, and running a generator off the drive shaft used for the fan.

 

[Jemiba]

http://www.secretprojects.co.uk/forum/index.php/topic,1843.msg34252.html#msg34252

 

[Abraham Gubler]

While I do not know, I would imagine that for the F-35A's GAU-22/A, it would have an upwards angle (considering that it's theoretical primary use is self-defence against aerial targets; due to USAF doctrine). For the F-35B and C's gun pod, I'm extra-uncertain, but I wouldn't be surprised if it was tilted downward or simply inline with the aircraft's bore; as for the Marines, their primary use would be for CAS and for the USN, they would probably not fly CAP / interception / etc missions with the gun pod (limiting its use for A2G or unexpected A2A scenarios).

The 25mm gun is on the F-35A for primarily air to ground. If USAF wanted an air to air gun they would have gone with the 20mm Vulcan which is lighter and better.

 

[Jeb]

On the other hand - there was talk years ago about a 100Kw laser being integrated as a main weapon... I could never figure out how it would've been fitted into the airframe.

The proposal I remember was putting the laser in the bay designed for the lift-fan, and running a generator off the drive shaft used for the fan.

That's the one. I heard about it back before 2006.

 

[John21]

There are no plans which have been made public for developing 25mm guided rounds of any type. The 76mm HEFSDS DART rounds from OTO Melara are currently the smallest such rounds available, although there has been a proposal for a guided Russian 57mm AA round, and I wouldn't be surprised if Bofors was working on one for their 57mm naval gun.

There have also been some experimental .50 cal projectiles devised and tested, but I suspect they're a very long way from entering service.

I've been reading through my copy of "Janes AFV retrofit systems 1990-91" and on pages 146-147 there are details on guided/steerable rounds and fire control systems for 40MM gun systems. Raytheon, Ford Aerospace and LTV did research, prototypes and real world testing.

They seemed to use spin stabilized projectiles, explosive impulse charges for course correction and radio frequency guidance.

 

[Tony Williams]

I've been reading through my copy of "Janes AFV retrofit systems 1990-91" and on pages 146-147 there are details on guided/steerable rounds and fire control systems for 40MM gun systems. Raytheon, Ford Aerospace and LTV did research, prototypes and real world testing.

Yes they did, but this seems to have abandoned. I haven't noticed any presentations on this subject at the last few annual NDIA conferences where such advanced technology ammunition projects are normally discussed.

As I said, there was some publicity about .50 cal guided projectiles a year or two back, but that seems to have gone quiet too.

 

[sferrin]

There are no plans which have been made public for developing 25mm guided rounds of any type. The 76mm HEFSDS DART rounds from OTO Melara are currently the smallest such rounds available, although there has been a proposal for a guided Russian 57mm AA round, and I wouldn't be surprised if Bofors was working on one for their 57mm naval gun.

There have also been some experimental .50 cal projectiles devised and tested, but I suspect they're a very long way from entering service.

I've been reading through my copy of "Janes AFV retrofit systems 1990-91" and on pages 146-147 there are details on guided/steerable rounds and fire control systems for 40MM gun systems. Raytheon, Ford Aerospace and LTV did research, prototypes and real world testing.

They seemed to use spin stabilized projectiles, explosive impulse charges for course correction and radio frequency guidance.

Yep. Like a mini ASAT kill vehicle. I remember an article in Military Technology back in those days covering those same projectiles. They said it could scall from 20mm up to 16in shells.

 

[pathology_doc]

Only 182 rounds? Seriously. NOT. ENOUGH.

 

[sferrin]

Only 182 rounds? Seriously. NOT. ENOUGH.

Flanker only has 140. Gripen only has 120. Typhoon 150. Rafale 125.

 

[Abraham Gubler]

Only 182 rounds? Seriously. NOT. ENOUGH.

Why not? It’s not an issue of each round across every aircraft being of equal value (and if it was many high successful gunships like the Mirage III only carried around 240 rounds). The 25mm gun is for air to ground. Compared to a M61 20mm it is far more accurate and has much better range and lethality. A 60 round burst (one second of firing) is typical for air to ground providing three such strafing runs for the F-35.

 

[Abraham Gubler]

It’s worthwhile comparing the metrics of the M61 20mm and GAU-22 25mm in terms of putting lead into the target. To suppress some of this “not enough” shells in the F-35 complaints.

The GAU-22 is a 5 mil dispersion weapon (80% of rounds will land within a 5 milliradian circle) the M61 is 8 mil. Which is good for air to air as you want a bit more dispersion to create a higher cone of lethality. But for air to ground when you want your shells to actually hit a point target the M61 has to fire twice as many shells to get the same number hitting the target as the GAU-22. Then the 25x137mm shell is 180 grams while the 20x102mm shell is only 100 grams. So if you want to achieve the same lethality (assessed by weight of shells hitting the target) you need to fire 3.6 times as many shells. There are other negative factors against the M61 in such a comparison but let’s keep it simple.

So those 182 rounds on the F-35 are equal to 655 rounds if it had a M61 Vulcan. So it can shoot more weight into a ground target than the F-16, FA-18 and the F-15E. Not so bad when you actually think about it.

 

[jsport]

Wow, Abraham, thank you for splainen.. Do you know why the Mauser BK-27 27mm was dropped ?

 

[Tony Williams]

Wow, Abraham, thank you for splainen.. Do you know why the Mauser BK-27 27mm was dropped ?

Both of the JSF competitors selected the BK 27 as being the optimum choice for their aircraft, and a fair amount of development work was done on "Americanising" the gun, with plans made to make it in the USA.

When the contract for the F-35 was awarded to LockMart, they doled out sub-contracts for various aspects of the plane to other firms, and General Dynamics were awarded the job of managing the gun installation. After a short pause, GD produced their proposals in which the BK 27 had metamorphosed into the 25mm GAU-12/U which happened to be made by (pause for drum roll....) - GD! I think that the excuse was that the GAU-12/U and its ammo were already in US service, and all that fiddling about with the BK 27 was pushing the price up too high.

The problem then was that the five-barrel GAU-12/U was both heavier and considerably bulkier than the single-barrel BK 27, and when the F-35 ran into weight problems Something Had To Be Done. So GD helpfully set about designing a slightly smaller, four-barrel version of the GA-12/U yclept GAU-22/A - for which they were paid, of course.

The contract process for big military projects is a wonder to behold... :

 

[pathology_doc]

Thus once again the question of non-standard parts fitment raises its ugly head (see also "Spey Phantom"). However, I'm getting the vague feeling in my water that the F-35's "gun space" would fit the Bk-27 and its magazine and accessories (IIRC they shoe-horned one into a Lightning F-6's gun pack for initial tests at one point), and that Shenanigans with a capital S are involved.


On the separate matter of ammo capacity:
Your 182 round magazine might give you enough for three effective passes, but what happens when the troops on the ground need more than those three passes from whatever F-35 is in the neighbourhood supporting them? This is all well and good when you're fighting a brush-fire war, but what happens in a full-on slugfest when your enemy is a sophisticated opponent deploying well-masked SAM or AAA batteries or battlefield helicopters which might unexpectedly need to be engaged at short notice?


Then add the difficulties posed by allies of the US for whom the F-35 is their primary multi-role aircraft, without the Raptors that the US might be expected to deploy as top cover? Or if the top cover has been decoyed away by more important things (such as the possibility of an all-out, failure-not-an-option, gotta-kill-'em-all intercept on a possible nuke-carrying E/A & its escorts on their way to Tel Aviv, Taipei, or what-have-you).


Three gun engagements' worth on an aircraft whose tasking includes CAS? Not enough.

 

[LowObservable]

This is what actually happened.


The initial choice of the BK27-based gun was driven by weight, and not only the gun. A revolver cannon gets to full rate almost instantly; a Gatling does not and has a longer minimum burst, therefore more rounds are required per engagement.


The change to the 25-mm. Gatling was driven by two factors: the cost of introducing a new caliber of ammunition and the fact that, in 2003, the team thought that they had weight margin to play with. (Woopsers.)


However, now that it turns out that there is no 25-mm. round that is good for air-to-air and air-to-ground, and is insensitive and non-DU, the JSF needs a new round anyway.


https://www.fbo.gov/index?s=opportunity&mode=form&id=6765b49dc4c271fef60da7093fd22633&tab=core&_cview=0

 

[jsport]

This is what actually happened.


The initial choice of the BK27-based gun was driven by weight, and not only the gun. A revolver cannon gets to full rate almost instantly; a Gatling does not and has a longer minimum burst, therefore more rounds are required per engagement.


The change to the 25-mm. Gatling was driven by two factors: the cost of introducing a new caliber of ammunition and the fact that, in 2003, the team thought that they had weight margin to play with. (Woopsers.)


However, now that it turns out that there is no 25-mm. round that is good for air-to-air and air-to-ground, and is insensitive and non-DU, the JSF needs a new round anyway.


https://www.fbo.gov/index?s=opportunity&mode=form&id=6765b49dc4c271fef60da7093fd22633&tab=core&_cview=0

Thank you LO and finally someone points out the shortfalls of Gatling technology as it stands today ..more past opportunities not sufficiently explored.

 

[sferrin]

On the separate matter of ammo capacity:
Your 182 round magazine might give you enough for three effective passes, but what happens when the troops on the ground need more than those three passes from whatever F-35 is in the neighbourhood supporting them?
Three gun engagements' worth on an aircraft whose tasking includes CAS? Not enough.

What do these guys do?
Gripen only has 120. Typhoon 150. Rafale 125.

 

[LowObservable]

Gatlings use more rounds per burst, which is why typical M61 installations carry several hundred rounds.

 

[Abraham Gubler]

On the separate matter of ammo capacity:
Your 182 round magazine might give you enough for three effective passes, but what happens when the troops on the ground need more than those three passes from whatever F-35 is in the neighbourhood supporting them? This is all well and good when you're fighting a brush-fire war, but what happens in a full-on slugfest when your enemy is a sophisticated opponent deploying well-masked SAM or AAA batteries or battlefield helicopters which might unexpectedly need to be engaged at short notice?

If you are in a high intensity battle the last thing you are going to be doing is more than three gun attacks per mission.

Then add the difficulties posed by allies of the US for whom the F-35 is their primary multi-role aircraft, without the Raptors that the US might be expected to deploy as top cover? Or if the top cover has been decoyed away by more important things (such as the possibility of an all-out, failure-not-an-option, gotta-kill-'em-all intercept on a possible nuke-carrying E/A & its escorts on their way to Tel Aviv, Taipei, or what-have-you).

Dua what?

Three gun engagements' worth on an aircraft whose tasking includes CAS? Not enough.

Says who? If you are going to be doing more than three gun passes fuel is going to be more of an issue than ammo.

 

[Abraham Gubler]

The initial choice of the BK27-based gun was driven by weight, and not only the gun. A revolver cannon gets to full rate almost instantly; a Gatling does not and has a longer minimum burst, therefore more rounds are required per engagement.

Maybe in the 1960s. But this is far from an issue today. For example the M61A2 (F-22) has a much lighter barrel assembly and almost twice the power in the rotational motor giving it a far faster spin up rate. And of course while the externally powered rotary guns may be slower of the blocks they can be up to four times faster once accelerated. Meaning they get the rounds out to cover the target within the burst. But this is an issue mostly for air to air engagements not air to ground.

 

[Tony Williams]

However, now that it turns out that there is no 25-mm. round that is good for air-to-air and air-to-ground, and is insensitive and non-DU, the JSF needs a new round anyway.

Apart from the fact that the AV-8B has been using various types of 25mm ammo for decades, so new ammo is a "want" rather than a "need", Nammo's APEX is not the only general-purpose option on the table. Rheinmetall are also developing a 25mm version of their established FAP (Frangible Armour Piercing) already in service in 20mm calibre.

This consists of a tungsten alloy penetrator in lightweight body and is designed to shatter into a cloud of high-velocity fragments on impact with an aircraft skin, with effects akin to an HE blast but without using any chemicals. It also penetrates light armour very well.

Last I heard, 25mm FAP was being considered by the USMC as a replacement for their DU-cored PGU-20/U.

I should add that none of the western fighter gun ammo (including FAP and APEX) is much good for the purpose it is normally used for - strafing personnel in the open. That is because they are designed to have a delayed effect so that they penetrate inside an aircraft or vehicle before exploding/fragmenting. So unless the ground is very hard they will penetrate into the earth before exploding/fragmenting, greatly reducing their effectiveness. This means that they pretty well have to score direct hits to be effective. Which gives the advantage back to the 20mm, as that can pepper the target with more projectiles and therefore stands more chance of scoring hits.

 

[quellish]

If you are in a high intensity battle the last thing you are going to be doing is more than three gun attacks per mission.

Can you elaborate? Why would doing more than 3 gun attacks be ill advised?

Says who? If you are going to be doing more than three gun passes fuel is going to be more of an issue than ammo.

Aircraft can be in-flight refueled, but re arming in flight is still elusive.
During Operation Anaconda the airspace above the ground fight was full of different aircraft performing CAS and interdiction. Aircraft would regularly hit nearby tankers and then return to the fight. Later in OEF it was not unheard of for tankers to be above aircraft performing CAS, the CAS aircraft popping up to "sip" fuel in between attacks instead of heading farther out of the fight to a refueling track.

 

[sferrin]

I should add that none of the western fighter gun ammo (including FAP and APEX) is much good for the purpose it is normally used for - strafing personnel in the open. That is because they are designed to have a delayed effect so that they penetrate inside an aircraft or vehicle before exploding/fragmenting. So unless the ground is very hard they will penetrate into the earth before exploding/fragmenting, greatly reducing their effectiveness. This means that they pretty well have to score direct hits to be effective. Which gives the advantage back to the 20mm, as that can pepper the target with more projectiles and therefore stands more chance of scoring hits.

https://www.youtube.com/watch?v=ZAkzrxN5Jn0

 

[quellish]

30mm HEI can ruin your day.

 

[Abraham Gubler]

Can you elaborate? Why would doing more than 3 gun attacks be ill advised?

Because to shoot the gun at a target requires a very dangerous flight profile. Too high and too low.

Aircraft can be in-flight refueled, but re arming in flight is still elusive.

Well if you have access to a tanker and all that then you no doubt have more fighters on hand with more ammo.

 

[Abraham Gubler]

30mm HEI can ruin your day.

But this is not fighter ammo. So TW's point still stands.

 

[sferrin]

30mm HEI can ruin your day.

But this is not fighter ammo. So TW's point still stands.

Are they only planning on purchasing one type of ammunition for the F-35? Seems like if they were planning on it doing CAS (and looking at experience with F-15s/16s/18s strafing) they'd want to buy more than one kind of ammunition so they could use the appropriate type for the mission.

 

[Abraham Gubler]

Are they only planning on purchasing one type of ammunition for the F-35? Seems like if they were planning on it doing CAS (and looking at experience with F-15s/16s/18s strafing) they'd want to buy more than one kind of ammunition so they could use the appropriate type for the mission.

25mm APEX has an explosive point detonation effect.

 

[kcran567]

1) So if the F-35s main 25 mm gun is better suited for ground use, is it at a disadvantage vs another fighter with gun more suited for air to air? Is this just a few poster's opinion or is this actual disadvantage that the F-35 will have to settle with due to being a compromise for air to ground?

2) Along those lines is a Su/Mig gsh-30mm cannon a poor choice for air to air and better for air to ground?

3) (if anyone knows) Does the F-35 have any new/improved system for aiming its gun that is an improvement over previous generation that may improve aiming (air and ground) and require less ammunition?

 

[LowObservable]

It's not so much caliber itself as system weight.


The Su gun is very light and the idea is to fire in short bursts - the Russians apparently consider the integration of predictive sighting displays and flight control to be good enough to make long bursts unnecessary - so the total system is light.


As for the effectiveness of the F-35 gun in air-to-air combat... Surely not even the F-35's greatest fans would necessarily think that a guns fight is a good option for the aircraft.

 

[sferrin]

As for the effectiveness of the F-35 gun in air-to-air combat... Surely not even the F-35's greatest fans would necessarily think that a guns fight is a good option for the aircraft.

Shouldn't be any worse than an F-16 or Super Hornet. (Given that it's pilots say it's got the manueverability of an F-16 with the nose-pointing ability of a Super Hornet.)

 

[Tony Williams]

1) So if the F-35s main 25 mm gun is better suited for ground use, is it at a disadvantage vs another fighter with gun more suited for air to air? Is this just a few poster's opinion or is this actual disadvantage that the F-35 will have to settle with due to being a compromise for air to ground?

2) Along those lines is a Su/Mig gsh-30mm cannon a poor choice for air to air and better for air to ground?

All weapons are compromises between conflicting requirements, and for guns this is true not only for the guns but for the ammo chosen too. Also, all valid choices have strengths and weaknesses - just different ones.

In aerial combat, key plus points (ignoring for this analysis the vital issues of sensors and fire control systems and weight/bulk constraints) are:

- the ability to fire a lot of projectiles in a short burst to maximise the hit probability (firing opportunities may be measured in fractions of a second), which penalises externally-powered rotaries because of their spin-up time;

- a short time of flight for the projectiles to the target, also to maximise hit probability, which prioritises relatively light projectiles fired at a high velocity;

- and a projectile which is capable of inflicting serious damage with a single hit (the bigger the better).

In ground attack, you want:

- a long effective range, which requires a relatively heavy projectile (other things being equal) as this retains velocity better;

- if your primary target is vehicles and structures, you need very powerful ammunition.

- if your primary target is personnel in the open, you need a very high rate of fire (but spin-up time is unimportant), or alternatively, to fire a big shell with an instant acting or preferably airburst fuze.

As is obvious from the above, there is no such thing as an ideal gun/ammo combination for general-purpose use. However, given that a gun is very much a secondary weapon these days, it doesn't actually matter too much what the characteristics are as long as a fighter has one always ready to use (which favours integral rather than podded guns - they tend to be more accurate also).

 

[kcran567]

With the F-35 using helmet mounted sight and the large screens with no HUD, how is the pilot going to use the gun? Through the helmet mounted sight or looking down at the screens? Or either one?


And thank you for the previous explanations.