Could a Bf-109 with a 20 mm integrated gun, have its engine replaced by an engine equipped with an integrated 30 mm gun?

[Daniel BASTIEN]

Hello, I am part of a group investigating WW2 Bf-109 crash sites in North-eastern France related to the May 27 1944 air battle, in which the following JGs, equipped with Bf-109s, had been involved: JG3, JG5, JG27, JG53. On a crash site where we should normally find 20 mm bullets of Bf-109 normally equipped with 20mm guns, we have found 30 mm bullets. That could mean that this specific aircraft had his engine (equipped with a 20 mm gun- Motorkanone) replaced by another engine equipped with a 30 mm gun. Was such an engine change possible? Did that ever happen in those JGs? Thank you for your help. Best regards. Daniel

 

[fubar57]

 

[GrauGeist]

Also:
The G-10/U4 was equipped with a MK108 30mm motorkanone.
The G-14/U4 was equipped with a MK108 motorkanone.
The Bf109G series also had the option of being equipped with Rüstatz kits (R4) that were two MK108 canons in an underwing pod (one pod for each wing).

 

[fubar57]

According to the book "Day Fighters in Defence of the Reich-A War Diary 1942-45", on May 27, 1944 the Luftwaffe lost 23 aircraft from the following JG's...

• III/JG 3 - 6
• I/JG 5 - 7
• II/JG 27 - 6
• II/JG 53 - 4

All were Bf 109G's

 

[mad_max]

Don't need a new motor. Just swap out the cannon as it's not a part of the motor.

 

[MiTasol]

I suspect there are more than a few structural differences to fit the MK108 gun and ammunition

 

[GrauGeist]

Some Bf109F variants had a motorkanone, but it was a MG151 and had different mounts for the weapon beneath the engine.
Trying to change the cannon (in either the Bf109F or Bf109G) would not have been practical.

 

[Snautzer01]

Don't need a new motor. Just swap out the cannon as it's not a part of the motor.

No, wiring will be different. It is not only the gun but everything that makes it go boom. From fuses to cable lenght to etc.

 

[Shortround6]

Bf 109 with the engine removed.

The engine had very little to do with the cannon, I believe the tube through the engine would take any barrel under 70mm in diameter.
Once you have planes in production with the 30mm MK 108 the parts needed to convert an older fighter become more available. Either from the factories or scrounged from wrecks (landing accidents would be the most convenient.) Parts would be the gun mounts, charging system, firing system, ammo boxes/chutes. How much of this type "stuff" could be fabricated by good armourers/mechanics I don't know. Might depend on the base they were at and access to equipment.

 

[tomo pauk]

'Engine cannons' were fixed to mounts (lavettes), not on the engines themselves (possible/likely exception being H-S engines and their spin-offs). Lavettes also included the blast tube.

 

[MiTasol]

Bf 109 with the engine removed.

The engine had very little to do with the cannon, I believe the tube through the engine would take any barrel under 70mm in diameter.
Once you have planes in production with the 30mm MK 108 the parts needed to convert an older fighter become more available. Either from the factories or scrounged from wrecks (landing accidents would be the most convenient.) Parts would be the gun mounts, charging system, firing system, ammo boxes/chutes. How much of this type "stuff" could be fabricated by good armourers/mechanics I don't know. Might depend on the base they were at and access to equipment.

Excellent photo showing that the cannon is inside the fuselage with only the barrel extending forward through the engine V.
If the rounds are longer than the 20mm rounds that means the structure retaining the ammo box must be changed to accept the new box and I doubt that would be an easy change given there is little waste space in the 109.
You must remember that the MK108 is mounted between the rudder pedals and the whole area is very tight as shown below.

German readers will be able to clarify this as they will be able to read this manual

from www.109lair.com

 

[Juha3]

109F-2, F-4, G-1... Motorkanone MG 151 cartridge 15x96 mm, MG 151/20 20x82 mm, MK 108 30x90 mm, so 30 mm cartridge was shorter than the original 15 mm.

 

[Shortround6]

The cartridge case was shorter, the overall length of the round was not.
However we may be arguing over a couple of inches (5cm). I believe the ammo belt container was in the wing root?

Pictures of Bf 109F cockpits show a large housing for the breech of a cannon between the rudder pedals.

MK108 2nd from bottom
MG 151/20 5th from bottom.

G is the 30mm MK 108 round.
F is the 20mm MG 151/20 round
D is the 15mm MG 151/15 round.

 

[Juha3]

Yes, you are right, just checked that from Williams & Gustin, Flying Guns World War II.

 

[MiTasol]

Item 13 in the first picture in post 11 is the Gurtkasten MK108 which google translates as beltbox. This therefore should be the MK108 ammobox though it may be just a feed chute as Shortround is usually accurate in his posts. Looking at walkaround photos on 109lair I can see no fuselage access panels in the right area so that also suggests Shortround is correct. Someone with the ability to read German will probably be able to resolve this from the manual linked in the same post.

This is the MG151 installation in the 109F-2 - again no indication of where the ammo is stored but it does show what I am guessing is the spent casing chute on the side of the gun just above the number 18.

 

[Juha3]

The ammobox for the MG 151 & 151/20 was inside the left wing

 

[fubar57]

This is a cutaway of the G model, can't vouch for the accuracy....https://scale-model-aircraft.com/wp-content/uploads/Messerschmitt-Bf-109G-Cutaway-Drawing.jpg

 

[mad_max]

Making mountains out of molehills. Did you need to change a some parts to accommodate the MK108? Of course, but not as much of a problem as some believe.

 

[MiTasol]

Going by that diagram the 20mm ammo drum is above the gun and behind the firewall which makes sense given putting it in the wing would put it very close to the main landing gear where you cannot afford to weaken structure but now two people say it is in the wing.
I went back to the manual and that shows this picture with the caption

To me that suggests the ammo box sits on top of the gun and is pulled aft using ropes attached to those handles to remove it. Sounds very clumsy but????


Further in the book it shows

which leaves me totally confused

Hopefully someone like GrauGeist can translate this properly so it makes sense to those of us who cannot understand a Google translation

 

[Juha3]

Going by that diagram the 20mm ammo drum is above the gun and behind the firewall which makes sense given putting it in the wing would put it very close to the main landing gear where you cannot afford to weaken structure but now two people say it is in the wing...

How? The landing gear was attached to the fuselage, this made it possible to remove the wings so that the machine was still on its landing gear, e.g. it could be towed behind a truck so that the wings were on the platform and the rest of the machine was towed tail-up tail first.