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2017-11-20

 

Me109 - Additional Notes

 

 

 

 

Me 109

 

(retrieved from a Forum - lost link)

Hi Tomo,

Gents, I presume that this question was brought on the board, but anyway: why haven't the Germans produced Me-109Fs with more cannons (eg. 2 wing mounted)? Or add a couple of those for the -109Gs for that matter?

The MG FF/M, which was used in a wing position in the Me 109E (even in a specially modified Me 109F flown by Adolf Galland), had been replaced by the more powerful MG 151/20 which could not be installed within the wings of the Me 109. MG FF/M production had actually been terminated, so there were no new guns even if one would have wanted to go this path.

(After WW2, the Spanish actually installed big Hispano cannon in the wings of their license-produced Me 109 models, so maybe it was not impossible to use larger wing-mounted cannon, but except for a test installation of the MK 108 in a wooden wing intended for the Me 109K which was only ground-tested, it doesn't seem like it was attempted in Germany.)

Of course, I'm not talking about Rustatze kits here

The MG 151/20 gondola weapons according to a Messerschmitt type overview added 215 kg of mass and subtracted 8 km/h of speed.

Kurfrst - Leistungzusammenstellung Me 109 G.

For comparison, 2 Hispano II cannon with 135 rounds per gun like the MG 151/20 gondolas carried weighed 166 kg only considering guns, ammunition and belting, and the speed difference between two fairly comparable Spitfire V aircraft - one with 8 machine guns, the other with 4 machine guns and 2 cannon - came down to 4 mph (6.4 km/h).

These figures are not directly comparable, but they illustrate that if you add anything to a fighter, it will inevitably deteriorate performance a bit ... and the engine question was more important for performance than the question of internal or external mounting of the wing cannon, in my opinion.

Regards,

Henning (HoHun) Hi,

there was a Friedrich with 2 add. wing cannons (MG FF), but it was Galland's personal toy. I assume it has to do with the switch to the MG151, I'm not sure one of those would fit into a Bf 109 wing.

I'm only guessing though, maybe Kurfuerst knows more. The gondola armament was in fact quite practical. From what I have seen, it did not cause either more drag or more weight than if the same installation would be added inside the wings.

As far as weight goes, two MG 151/20s installed inside the wings weighted 130 kg w/o ammunition, as oppose to the pair of MG 151/20gondolas 135 kg in the 109:
 


Dazu ein interresanter Vergleigh ,,SchrotschuB versus BüchsenschuB":
RAF-Bewaffnung mit 12 MGs von 7.7mm Kaliber (wie in Hurricane Mk IIB)
LW-Bewaffnung mit 1 MGs 151/20 (wie in FW 19014/U8)
                            2 MG 151/20        12 Brownng MG 7.7mm
Montagegewicht                 130.0 kg                   134.0 kg
Zielgerät                        2.5 kg                     6.5 kg
Munition Spr. Gr.
                   (SchuB 600) 135.0 kg      (SchuB 3990) 137.0 kg
VerschieBt GeschoBgewicht   4.92 kg/Sek                2.77 kg/Sek
VerschieBt Sprengstoff      0.89 kg/Sec                     -

Schon bei der ungünstigen Spr.Gr. des MG 151/20 zeight sich der Vorteil


  
Installing them in gondolas OTOH meant that they were easily added when needed, and, no redesign of the wing structure was necessary.

Via Fritz Hahn, he also has the breakdown of the installation somewhere. Apart from the weight of guns, there are also ammunition boxes, rails to install the guns on etc., and these add considerable weight. The gondolas were sort of a kit, and included all these items already. Ammunition, of course, would weight the same.

Installing the guns in gondolas OTOH meant that they were easily added when needed, and, no redesign of the wing structure was necessary.

I have not found figures for the drag in the FW 190 MG 151 installation, however I have seen some for the Spitfire Hispanos, understood for 360 mph at altitude. The overall amount of drag for these installations looks very comparable to the 109 gondola installation, again.

 Kurfurst, wasn't there a redesign to the internal structure of the F's wing from the previous one of the Emil.

It should also be noted that while long and heavy, the Hispano was very slim, similar to the Oerlikon guns (from which the MG FF was derived). The MG 151, while much shorter and lighter, was somewhat bulkier.

CANNON OR MACHINE GUN

On a slightly different note, was mounting MG 131's in the wings ever considered? I believe their internals remained pretty much the same in their structure. Galland even had his 109F field modified for two wing MG FFs!

Putting cannons inside the wings of the 109F-K was certainly a possibility, see this archieve drawing of the K-6s wing.

It mentions two possible wing armament configurations:

- one MK 108 in each wing, with 40 rounds, or
- one MG 151/20 in each wing, with 100 rounds.

It would also appear to me they would try to mount the guns as far ahead in the leading edge as possible, to avoid them interfering with the spar. A small bulge would resulted in the 109K-6/MK 108 configuration. For what its worth, the datasheets show 5-10 km/h speed loss compared to the wing armament-less K-4.

Thanks for the thorough answers

I have some further questions:

1) Were the gondolas some kind of general issue or not (so, a large scale use)?

2) Looking at the picture of different guns, seem to me that MG FF was a bulkier gun then MG-151. So (again), what was the reason for not mounting the -151 in the wings? 1, Yes, it would appear that many, though not all Gustavs were fitted with the gondolas at the factory and shipped to the front in this condition. But all Gustavs/Kurfürsts could accept and have installed (or removed) these gondola guns in the field, so it was an option like bombs or droptanks.

2, I do not have a definietieve answer as to the reasons. My best bet would be that with the installation of the engine cannon on the F the wing guns were superflous, as this kind of installation is detrimental on flight performance (added drag and turbulance, increased inertia in roll etc). Probably the gondola installation was seen more flexible, as it could be added in one package, without the need to create permanent holes and cover bulges on the wing. Finding a place for the ammunition would be also easier. Given the above drag and weight specs, it could be said that gondola installation was no more detrimental to performance as if the guns would be installed in the wings. Hi Marshallstack,

Statistics aside, didn't the Luftwaffe pilots dislike the gondola guns? I think this was due to a (real or imagined) performance degradation.

Of course, adding about 200 kg of mass to a light-weight fighter was going to have a negative impact on performance, regardless of whether this mass consisted of internally or externally mounted guns.

If you look at the time line, you'll see that the gondola weapons were introduced at about the time the Messerschmitts encountered the turbo-supercharged USAAF aircraft and the two-staged supercharged Spitfires, losing the advantage of high-altitude performance that they had previously held above the single-stage supercharged Allison and Merlin engined Allied fighters.

As additional weight plays a particularly important role at high altitude, the development of new Allied engines made the gondola weapons appear much less attractive than they had been at the moment of their conception (when the Me 109 held the altitude advantage).

That's why I consider this more of an engine question than an airframe question.

To put firepower into perspective, here is a comparison of total muzzle power (kinetic plus chemical power) of a couple of contemporary types:

Me 109G/3x MK108: 15.1 MW <- 30 mm MK 108 nose gun and gondola weapons, project only
Fw 190A-8: 5.5 MW
Me 109G-6/U4: 5.5 MW <- 30 mm MK 108 nose gun
Me 109G-6/R6: 4.2 MW <- 20 mm gondola weapons
Spitfire IXE: 2.7 MW
Spitfire VC: 2.5 MW
P-47D: 2.3 MW
P-38: 2.2 MW
Me 109G-6: 1.8 MW
Me 109E-4: 1.7 MW
P-51D: 1.7 MW
Me 109G-2: 1.6 MW
P-51C: 1.1 MW

Regards,

Henning (HoHun) I agree with KK
and it was easy to remove and put back wing cannons from and into the wings of for ex from Spit Vc, mayby even easier but in any case not much harder than install and remove gun gondolas. It was normal maintenance action IIRC.

Juha

 

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