FW-190A - Mk-108 30mm cannon - Wing root station

[Mosshorn]

Pertaining to the FW-190A series, was the Mk-108 30mm cannon ever operationally mounted in the wing root stations? I know they were mounted outboard quite often, but I can't find any reference to mounting them inboard until the Ta-152 is talked about. The Mk-108 was an electrically fired round?

The question is of course: Wouldn't mounting the Mk-108 30mm cannons inboard and the MG-151/20 20mm cannons outboard have worked better? (Presuming it was possible.)

Moss

 

[Shortround6]

There may have been a problem sychronizing the MK 108 to fire through the propeller.

 

[Denniss]

Neither Fw 190 nor Ta 152 had the MK 108 as wing root gun, the Ta 152 had it as Motorkanone. Impossible to use the MK 108 as synchronized gun.

 

[riacrato]

There were plans to build a 'destroyer' variant of the Ta 152 (A?) with 3x MK-103 and there are pics of a prototype with the gun installed in the wing roots, no MK108 though since it couldn't be synchronized.

 

[davebender]

Why would you want to mix weapons with such different shell trajectories? Furthermore mounting high velocity MG151/20 cannons outboard negates their range advantage. Convergence plus wing flexing makes the outboard weapon positions useless for anything except close range.

 

[Mosshorn]

Why would you want to mix weapons with such different shell trajectories? Furthermore mounting high velocity MG151/20 cannons outboard negates their range advantage. Convergence plus wing flexing makes the outboard weapon positions useless for anything except close range.

Hard to disagree with any of the above. (Not to mention that many experienced pilots deleted the outboard Mk-108's and even the MG151/20's on their
190's.)

I'm still trying to figure out the best way to arm the Fw-190A series for both the fighter and bomber-killer mission. How about this: 2 x MG151 over the engine, 2 x MG151/20 in the wing roots, 2 x MG151 in the outboard stations. This arrangement would reduced the weight and wing flexing while adding the equivalent firepower of two .50 cal Brownings. As an added plus, a bullet impact would not detonate the ammunition drum of a MG-151 and blow the wing off the airplane the way 20mm drums did.

Moss

 

[tomo pauk]

What advantage brings 15mm cannon over 20mm, in order to overshadow 20mm as a weapon? Why would 15mm ammo be less susceptible to catastrophic detonation, than 20mm ammo (both were in box for MG 151s, not in drum BTW).

 

[Ratsel]

overkill IMO. 2x Mk 103's and the MG's were enough.

 

[davebender]

For German fighter aircraft powered by water cooled engines I would employ three MG151/20s. Delete the cowl mounted machineguns in favor of additional ammunition for the hub mounted cannon.

However you don't get that option for the Fw-190A. The historical Fw-190A weapons mix is probably as good as you can get without a hub mounted cannon.

 

[Shortround6]

I'm still trying to figure out the best way to arm the Fw-190A series for both the fighter and bomber-killer mission. How about this: 2 x MG151 over the engine, 2 x MG151/20 in the wing roots, 2 x MG151 in the outboard stations. This arrangement would reduced the weight and wing flexing while adding the equivalent firepower of two .50 cal Brownings. As an added plus, a bullet impact would not detonate the ammunition drum of a MG-151 and blow the wing off the airplane the way 20mm drums did.

Moss

the MG 151s won't fit. the MG 151/15mm and the MG 151/20mm used the same receiver. I am not sure you could convert one to the other in the field by changing barrels but there was darn little difference between the two guns except the 15mm version used a longer barrel.

 

[davebender]

The MG151/20 was a relatively small weapon and it was produced in large numbers. Luftwaffe units based in Europe would simply order a new weapon and turn in the old one.

 

[Mosshorn]

the MG 151s won't fit. the MG 151/15mm and the MG 151/20mm used the same receiver.

Yep, that's right. The MG-151 receiver was narrow, but kind of long. It would not fit above the engine in the cowling. Okay, how about this: 2 x MG-131 above the engine, 2 x MG-151/20 in the wing roots, 2 x MG-131 in the outboard stations?

To answer a previous question: The PETN/HA41 explosive in the 15/20/30mm cannon shell would detonate when struck by .50 cal rounds. The shell's explosive charge would explode--not the propellant in the case--and then the entire box (not drum) of ammo would sympathetically detonate and blow the whole damn wing off. There are several threads about this in the archives and even gun-camera footage of this happening. The MG-151 firing 15mm AP and MG-131 firing AP did not suffer from this.

Moss

 

[evangilder]

That seems a little odd. They both used the PETN/HA41, but the 20mm would cook off the rest of the ammo, but not the 15mm? I'm not questioning whether it did or didn't happen, I am just trying to figure out why that is. The only reason I can think of is maybe there is just enough of a difference between 15 and 20mm in the amount of explosive in the round itself to push it just over the limit to detonate the rest of the ammo.

 

[Shortround6]

Putting MG 131s in the wings might work, at least they won't run out of ammo in about 8 seconds like a MG/FF. For a fighter armament it might not be bad, for a bomber destroyer it is one the weak side. The German 13mm round has just over 1/2 the kinetic energy of a US .50 and while the HE ammunition makes up for this a bit it takes about 10 rounds (at best) to equal one MG/FFM mine round. granted the rate of fire is about double the MG/FFM but it is not a good trade against bombers.

 

[davebender]

PETN/HA41 explosive in the 15/20/30mm cannon shell would detonate when struck by .50 cal rounds. The shell's explosive charge would explode--not the propellant in the case--and then the entire box (not drum) of ammo would sympathetically detonate and blow the whole damn wing off

A single 3cm mine shell or a couple 2cm mine shells were normally enough to inflict crippling damage on the wing of an enemy fighter aircraft. Consequently you can kill enemy fighter aircraft on a single quick firing pass. Something that didn't often happen when firing machineguns. That's why mine shells are worth having even if they pose an explosive hazzard to your own aircraft.

 

[Ratsel]

"The PETN/HA41 explosive in the 15/20/30mm cannon shell would detonate when struck by .50 cal rounds. "

PETN is the explosive used in Minengeschoß. It is more difficult to detonate than primary explosives, so dropping or igniting it will typically not cause an explosion (at atmospheric pressure it is difficult to ignite and burns relatively slowly), but is more sensitive to shock and friction than other secondary explosives such as TNT or tetryl. Under certain conditions a deflagration to detonation transition can occur. The Mk 108 autokanon for example can use anywhere from 72g-85g of PETN with a .01% nitric acid content. So although difficult to prematurely ignite, its not impossible to do, but certainly not common.

 

[wuzak]

I noticed on a cutaway that the wing root station gun on an Fw190A has its barrel pass above the landing gear leg and wheel in its retracted position. Could such an arrangement have been used in a Spitfire with the Hispano?

Was the Hispano compatible with synchronisation?

 

[Shortround6]

The Hispano was not capable of being synchronized. As for having room it might depend on the actual thickness of the wing root.

 

[wuzak]

Thanks for that SR.

What about the Oerlikon?

The wing root has to be thicker than the position on the wing where the Hispano occupied. And the wing root fillet may help if the weapon is thicker than the wing.

And if they were able to use the Oerlikon in that position, could it use the same ammo as the Hispano?

 

[Shortround6]

Oerlikon would be worse to synchronize. Gun not only fired from an open bolt, it fired while the bolt was still moving forward. Exact timing from sear release is rather variable. The Hispano and Oerlikon could use the same projectiles but used different cartridge cases. The Spitfire had the entire depth of the wing out board of the landing gear to but the gun in instead of sharing depth with the landing gear leg. The elliptical wing of the Spitfire meant there was almost as much cord (and depth) to wing where the cannon were located as at the wing root if you don't count the fillet.