PDA

View Full Version : Bf 109 G Modification: fuselage MG151 gondola



Ratsack
12-18-2007, 07:53 PM
In one of the little Schiffer books on the Bf 109 G I saw some pics and part of a report on a modification to a G-4. It was done by Luftflotte 3, and it involved attaching a Mauser MG151/20E in a gondola under the fuselage. The weapon was bolted on behind the oil cooler, and was synchronized to fire through the propeller disc.

They tested this installation by flying tests with the fuselage gondola only, and then flying tests with fuselage gondola and the wing gondolas, too. They found that the fuselage-gondola-only arrangement was faster by 25 km/h (no altitude specified), with significantly better times to altitude. It also handled better at high altitude.

They didn't put this mod into production. I would be interested to know why, if anybody knows.

I can see only two downsides. The first and most important is that the plane couldn't carry the drop tank or any other fuselage stores in this configuration. I can see this would be a problem for the high-altitude bomber interceptor role, with its requirement to assemble large formations and place them appropriately to intercept. However, the Germans had already fitted drop tanks to the wings of the Gustav, so I don't see this as a show stopper.

The second down side is that the gondola arrangement only doubles the fire power of the Gustav, whereas the wing gondolas effectively triple it. However, the extra fuselage gun was centrally located, with all of the advantage that brings. That means easier gunnery, better concentration of firepower on the target when the gunnery is good, and the ability to carry more ammo.

The tests were done in early 1943, so there was time to play with this mod if they'd wanted to.

I wonder why they didn't pursue this?


cheers,
Ratsack

leitmotiv
12-18-2007, 07:58 PM
Answered the question yourself: no fuselage drop tank. Unless the LW had been willing to go with wing drop tanks for the 109, it had to have that belly drop tank because the 109 had such short legs. Without the drop tank, it would have been a point defense interceptor.

Ratsack
12-18-2007, 08:01 PM
...Unless the LW had been willing to go with wing drop tanks for the 109...

But as I said, they'd already gone with wing tanks for Gustav bombers.

cheers,
Ratsack

Viper2005_
12-18-2007, 08:08 PM
Probably because of the huge potential for accident associated with such an installation if carried out as a field mod on tired airframes by tired mechanics...

Also the ability to correct for the drop of the rounds would be inherently limited, and the landing gear would probably get in the way of the armourers attempting to reload which would hurt turn around time and further add to the risks associated with the installation.

leitmotiv
12-18-2007, 08:09 PM
Riiiiiiiight, but, clearly, they decided they were not going to do it with the fighter, and, anyway, the wing tanks were never anything but experimental with the Jabos.

Ratsack
12-18-2007, 08:14 PM
Hadn't thought of the rearming angle, Viper. Belly landing would be a bugger, too...

Regarding the wing tanks, I've seen pics of operational G-1s carrying an SC500 with the extra tail wheel (droppable, to provide clearance for de big bomb!) and wing tanks. I grant this is not the same thing as claiming it was common, but it wasn't just an experiment either.

cheers,
Ratsack

Viper2005_
12-18-2007, 08:22 PM
It is perhaps also worth considering the effects of firing the gun:

1) Nose down pitching moment - did this adversely affect ability to deliver accurate bursts of fire?

2) Vibration - if the extra gun is hanging under the oil cooler, it's probably transmitting firing loads through the engine mounting. Were the additional loads imposed unacceptable? Here I am thinking of low cycle fatigue in particular.

3) Gun gas - where did it go? Quite often gun gas can cause all sorts of trouble in and around engines. For example, did the oil cooler get covered in muck?

Ratsack
12-18-2007, 11:27 PM
I don't think any of those items would've been too much of a problem on this mounting. It was mounted under the fuselage behind the oil cooler. The muzzle came up somewhere below and behind the back of the oil cooler.

This leads me to think the gun gases wouldn't be a problem. The vibration would presumably be transmitted to the same structural members of the fuselage that took the bomb rack. I am obviously guessing here, but it seems logical.

Regarding off-centre recoil, I have no idea.

Luftflotte 3 were very enthusiastic about it, though.

cheers,
Ratsack

Xiolablu3
12-19-2007, 01:04 AM
I have read the apparant reason that they didnt pursue this method, but I cannot remember...


I will report back after a search through my books...

Kurfurst__
12-19-2007, 04:35 AM
The question arose as to provide an answer to high altitude combats; the FW 190A`s performance in the 8km region was lacking, the basic Bf 109G-4`s firepower was less, and the normal wing gondolas meant a heavy burden.

In this case, they were investigating the two solutions : a removable air intake? for the 190A (Ansaugschacht) and modded lighter gondola for the 109G-4. In the latter`s case, it was a single gondola with a syncronized and electrically fired MG 151/20E cannon, with only 80 rounds of ammunition; the MG 17 guns were removed to save weight, and their gun ports were sealed.

Brief comparisons at JG 26 showed, under operational circumstances (ie. not strict climb test, but two aircraft racing, and not at optimal climb speeds but rather the ones used operationally) that the 109G with the fuselage gondola is better in it`s time-to-altitude figures than the normal FW 190, but it`s no better than the proposed FW 190A with the Ansaugschacht modification.

My guess is that the above results, combined with the fact that the fuselage gondola had limited ammo capacity, the need for further development (ie. working out any/all bugs of the fuselage gondola) made the idea seem less attractive then boosting the FW 190s altitude performance; in the long term, the fitting of the MK 108 in the nose with little fuss, and the development of potent high altitude DB engines probably sealed the mods fate.

Bf 109G-4/R3s (also G-6/R3) with the two underwing 300 liter droptanks were used operationally with long-range recon wings of the Luftwaffe, I know of their use in the Med and over England. These were armed long-range fighter-recces. Pierre Clostermann (or rather, one of his buddies who`s story he tells) met one of these over Scapa Flow.

http://i38.photobucket.com/albums/e133/Kurfurst/109G4R3recce.jpg

One13
12-19-2007, 05:17 AM
I thought the reason was that the nose gun in the Bf109 (MG151) used percussion primed ammunition and syncronised guns (firing through the propeller) used electrically primed ammunition.

In the Fw190 both the syncronised guns and the wing guns (when MG151 were fitted) used electrically primed ammunition.

The Luftwaffe never liked to mix the two types of ammunition in one plane. It meant there was no chance to mix them up. Pesumably they thought changing the nose gun to electrically primed (in the Bf109) was too much trouble.

Ratsack
12-19-2007, 06:26 AM
Originally posted by One13:
I thought the reason was that the nose gun in the Bf109 (MG151) used percussion primed ammunition and synconised guns (firing through the propeller) used electrically primed ammunition.

In the Fw190 both the synconised guns and the wing guns (when MG151 were fitted) used electrically primed ammunition.

The Luftwaffe never liked to mix the two types of ammunition in one plane. It meant there was no chance to mix them up. Pesumably they thought changing the nose gun to electrically primed (in the Bf109) was too much trouble.

They mentioned this issue in the report. They recommended that the engine gun be modified to take electrically primed ammo so there'd be no difference between the two.

At Kurfurst, what was the normal ammo load for the R6 gondolas?

[edit]: Don't worry, I just found it. The other little Schiffer title on Rustsatze gives it as 125 RPG in a drum, using disintegrating links.[end edit]

In relation to high alt performance, the report mentions that the fuselage gondola was a significant improvement over the wing gondolas at very high alt. The text surrounding the report fragment implies that this was one of the motivations for the tests.

cheers,
Ratsack

JG53Frankyboy
12-19-2007, 06:33 AM
Originally posted by Ratsack:
....................
At Kurfurst, what was the normal ammo load for the R6 gondolas?

...........

135 rounds as max

Xiolablu3
12-19-2007, 07:21 AM
Originally posted by One13:
I thought the reason was that the nose gun in the Bf109 (MG151) used percussion primed ammunition and synconised guns (firing through the propeller) used electrically primed ammunition.

In the Fw190 both the synconised guns and the wing guns (when MG151 were fitted) used electrically primed ammunition.

The Luftwaffe never liked to mix the two types of ammunition in one plane. It meant there was no chance to mix them up. Pesumably they thought changing the nose gun to electrically primed (in the Bf109) was too much trouble.

Thats the very reason I read and had forgotten.

The mod was good, but the risk of mixing up the ammunition was seen as very undesirable and a constant risk.

Kurfurst__
12-19-2007, 07:41 AM
Originally posted by Ratsack:
They mentioned this issue in the report. They recommended that the engine gun be modified to take electrically primed ammo so there'd be no difference between the two.

Indeed that`s what the report says.. it sounds like a good idea to simplify things, but when you imagine a unit with some 109s with percussion fired guns, others with all electric...


At Kurfurst, what was the normal ammo load for the R6 gondolas?

[edit]: Don't worry, I just found it. The other little Schiffer title on Rustsatze gives it as 125 RPG in a drum, using disintegrating links.[end edit]

125-135-145 are given. I belive it was 135 officially, but it was common to use less in any gun to reduce chance of jams.


In relation to high alt performance, the report mentions that the fuselage gondola was a significant improvement over the wing gondolas at very high alt. The text surrounding the report fragment implies that this was one of the motivations for the tests.

cheers,
Ratsack

Indeed. Overall, I believe fitting the MK 108 was a far better overall solution.