What were the weight savings from removing FW 190 outer wing cannons?

[Jens]

Indeed weight does very slightly (up to 1% for 200kg) influence maximum speed.

For D9 german Documents show an decrease of perfomance by 10km/h, 0,45m/s climb and 150m height, if you use mk108 rüstsatz.

[philippe willaume]

hello
The outer wing guns Affair

You have all seen pictures of FW 190 of all series with and without outer wing guns. The amount of ammunition for the MG FF varies from one publication to another and the type of guns changed from version to versions.

The guns used in the outer wing inboard position were the MG FFM, MG151/20E and MK108.

In this paragraph we will just concerned ourselves with what determined the presence of the gun in the outer position. You will find the ballistic and the effect of the weapons on the plane in the Weapon chapter.



According the version of the A there was two types of gun used the MG FFM and the MG 151/20E.

As far as the MG FFM is concerned, the part number in the production sheet never changed, save for the A1 and the Aa-3.

The MG FFM had slightly better performance than the MG FF and had the ability to fire Mine (highly capacity explosive) ammunition. See the gun section for more details.

As far as the A2, A3, A4, A5 are concerned, this was a rustsatz (optional) and it is described as

such in production sheets (except for the A1 and the Aa-3 sold to the Turks where it is part of the plane).

The manual for the A1, A2, A3, A4 gives the weight for a version with and without the outer guns. The magazine usually used is the T 60-FF with 60 rounds.

The manual for the A5 gives one the version with the outer guns and the drum with 90 rounds but precise that removing those guns will save around 1345 kg (98 for the weapons and 37 for the ammo), so it seems clear that this was still an option.

The manual for the A1-to A4 and the manual for A5 /A6 clearly states that the T 60-FF (60 rounds) could be replaced with T 90-FF (90 rounds) without any modification.

Note: the A6 used MG 151/20E in the outer position but the A5 still used the MG FFM.

Of course there is plenty of evidence where the guns were installed.



The MG 151/20E in the outer wing position is mandatory equipment, according the plane’s production sheet anyway and the manuals do not mention any removal or rustsatz.

That being said there is plenty of photo evidence where even the outer MG151/20 was removed.

In September 44, the Uk captured, a deserting ferry pilot crash-landed in England, an A8 with the TU engine. The plane was without the outer MG 151/20E. (PR0 AIR 40/151).

The weight for the outer guns 177 kg (112.6 and 64 kg for the ammo)



So far I have not being able to determine a set of rule that led to the deletion of the outer guns. These comments only concern fighter planes, Jabo (ground attack) ans Jaborei (long-range ground attack) did not have the external guns installed at all. So here the list of the case where it did happened, just bear in mind that this is just a very generic rule of thumbs.

Pilot wish, Installation of the FuG 16 ZY or more precisely the Y or E add-on to the FuG 16 Z, main mission to fight against fighter or to assume a pure fighter role, possibly some gun shortage or re-use of ground attack plane wings in fighter production line.

[Franek Grabowski]

xxxxxx

Originally Posted by Jens

Indeed weight does very slightly (up to 1% for 200kg) influence maximum speed.

Pardon?

[Dick Powers]

Maybe the real reason wasn't the weight, but the effects on the moment of inertia about the roll axis. Two 100 pound weights at mid span could have significant effects on the roll inertia, amking the FW 190s superior roll rate much less.

Also, might the recoil effect of the two wing guns firing at slightly different times effect the directional control and creat a wandering effect of the aiming point?

[Mifletz]

A "Heath Robinson" in the UK is known as a "Rube Goldberg" in the USA! = an extemporised lash-up job.

Originally Posted by Tony Williams

Yes, they made a rather Heath Robinson attempt at a belt feed

[robert_schulte]

Originally Posted by Franek Grabowski

xxxxxx


Pardon?

It may not be obvious, but the reason why weight does influence speed is quite simple.
Adding weight to a specific plane means, that this plane has to achieve more lift to stay in in level flight. More lift with the same wing needs a higher angle of attack of the air flowing around the wing. And a higher angle of attack does produce more drag.
The speed advantage by using less weight is dependent on the aerodynamic efficiency of the plane. The speed advantage with a 2 percent lighter "Me 323 Gigant" will probably be much smaller than with a "Mustang" for example.
Regards
Robert

[George Hopp]

"I have read that sometimes, some FW190 pilots had the outer wing cannons of their planes removed to save weight---especially with earlier marks of FW(A2 thru A5), where the outer cannon was the older MG/FF with a very different ballistic performance that the MG150/20 of later FW marks; So...how much weight did this actually save & how much of an improvement did it make in the performance of the FW?"

Sorry I didn't get onto this sooner. The weight of the outboard MG FF/Ms was 135kg (Waffen 98kg plus Ammunition 37kg) (from Rodeike's "FW Jagdflugzeug", page 147). Sorry, no info yet on speed loss, or maneuverability gain.

[Tony Williams]

Originally Posted by George Hopp

Sorry I didn't get onto this sooner. The weight of the outboard MG FF/Ms was 135kg (Waffen 98kg plus Ammunition 37kg) (from Rodeike's "FW Jagdflugzeug", page 147). Sorry, no info yet on speed loss, or maneuverability gain.

The guns by themselves didn't weigh anything like that much - the 'Waffen' weight must include associated equipment, presumably to do with mounting the guns.

Tony Williams: Military gun and ammunition website and discussion forum

[Graham Boak]

For a WW2 fighter at maximum speed, the lift-induced drag will only be some 10-15% of the total drag. If the 200kg weight increase was 5% of the weight of the fighter (What is the weight of an Fw.190?) , then you are looking at 5% of 15%, or less than 1% increase in total drag. As drag is proportional to speed squared, so you will get no more than 1% change in top speed. This comment appears to be supported by the FW estimate quoted above.

A difference of 1% is less than that expected between adjacent aircraft off the production line, or from consecutive flight trials, and is about the measurement accuracy of the time. This is the background to arguing that weight does not affect top speed. Strictly speaking, yes it does. Practically speaking, it does not.

[philippe willaume]

Originally Posted by Tony Williams

The guns by themselves didn't weigh anything like that much - the 'Waffen' weight must include associated equipment, presumably to do with mounting the guns.

Tony Williams: Military gun and ammunition website and discussion forum

yes tonny you are spot on.
however i think that only includes what you could actually remove.
This is for both guns and both drums wich were 90 round drums.
those figure are comming from the A5 maintenace manual.teil 0 page 11 on the december 43 revision of the manual replacing the august 43 version.

if you are interested I think I have a break down of the different element (in weight document on the F and G from FW, it is in the simthoniams)


if you read the A1-A4 manuals or the report on the captured derated A3 handed over by Faber the weight of the ammo for the 60 round drums is 29 kg.(this is with 55 rounds)

philippe