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Why were ME-109G wing cannon underslung?


Ryan B.

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...when they apparently fit quite nicely into the wings of the BF-109E? Aside from rounding the wingtips, were the wings that extensively redesigned? IF too bulky, could they have compromised with the 15mm cannon?

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The wings were thinner and the internal construction was changed. From the F version the powers-that-were decided two cowling heavy mgs and a spinner cannon would be sufficient fire power. By the mid-life of the G it was found more fire power was needed, especially to shoot down the US bombers, but it was too late to redesign the thin wing to take the cannon internally, but they were strengthened

The first F series used a modified E wing thus it was that Galland was able to put cannon inside the wings of his F version.

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there were plans for internal wing cannon fittings in some of the planned K versions, K-6, K-8 and K-14 according to the old Monogram close up

scanned here https://boxartden.com/reference/gallery/index.php/Modeling-References/Monogram-Close-up/16-Bf109K-Messerschmitt

eg

0Q6NL4e.gif

 

 

though while googling I found this which I'd not see before

 

Quote

 

though there has never been any evidence that any K other than the K-4 being built in any quantity or seeing service.

 

 

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The cannon in the wings of the Bf109E were the short and low velocity MG FF design.  The MG151 was a longer weapon, heavier and higher velocity.  That's part of the reason why they wouldn't fit in the wing of the Bf109.  I don't think that the 15mm version was appreciably smaller overall.

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Extra wing ordnance made Bf 109 sluggish as she had been originally designed for fuselage armament only. Especially her roll suffered so both cannons and rockets were much disliked by Bf 109G's pilots. The wing with integral 30-mm cannons Troy Smith mentioned was one-off (I think Henschel built it) and, being made of wood, would be even heavier. It that wing would be produced, armament would soon revert back to 20-mm cannons, as I believe MK 108 manufacturing plant in Eastern Prussia had been overrun by Red Army at the end of 1944/beginning of 1945 anyway. Cheers

Jure

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The effect of wing armament on agility was appreciated by Yakovlev, who refused to put guns in the wings of his WW2 fighters.  It is also why the use of four cannon is rare on Spitfires and two were often removed from the wings of Hurricanes.  However, the Russians had a very good line of light cannon, eventually being bale to put three and even four in the nose of Lavochkins, whereas the RAF had chosen a particularly long and heavy cannon in the Hispano.

 

Moving from fact to a bit of extrapolation: at this time the effect on manoeuvre of having heavy weights distant from the roll.pitch/yaw axes of the aircraft were not understood.  Aircraft appeared sluggish (understandable enough with increased roll inertia) but forcing the matter could result in severe uncommanded manoeuvres leading to the break-up of the aircraft.  It took the failures of the He162 and F-100A to provide incentive for a full mathematical understanding of this effect.  I have not seen the unhappiness of WW2 fighters with heavy wing mounted armaments described in these terms, but it seems the most probable cause.

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5 hours ago, Jure Miljevic said:

The wing with integral 30-mm cannons Troy Smith mentioned was one-off (I think Henschel built it) and, being made of wood, would be even heavier.

The  mock up cannon was made of  wood,  as  can be seen in the photo,   I have never heard of a wooden wing being planned,  but would  be interested to  know more.

FWIW, I  remember when the Monogram book I linked was about the best information on the K series available...I found the K series of particular interest as the final  German Bf109,  and so I have greatly enjoyed all the new photos that become available in the last 35 since then! (the linked book has most of the known pics known then BTW)

 

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The 15mm MG151 was the same size as the 20mm version: essentially, the Germans took the 15mm cartridge and necked out the case to take a 20mm shell. The barrel and chamber dimensions were different, but in terms of the size/weight for an installation, you could barely get a sheet of paper between them.

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15 hours ago, Graham Boak said:

 

Moving from fact to a bit of extrapolation: at this time the effect on manoeuvre of having heavy weights distant from the roll.pitch/yaw axes of the aircraft were not understood.  Aircraft appeared sluggish (understandable enough with increased roll inertia) but forcing the matter could result in severe uncommanded manoeuvres leading to the break-up of the aircraft.  It took the failures of the He162 and F-100A to provide incentive for a full mathematical understanding of this effect.  I have not seen the unhappiness of WW2 fighters with heavy wing mounted armaments described in these terms, but it seems the most probable cause.

I think one of the earliest aircraft demonstrate inertia problems was the P-39. It had very high pitch and yaw moments of inertia which sometimes led to pitch and yaw rates that could not be countered with elevators or rudder. Often referred to as 'tumbling' in contemporary accounts. As well as the increase in rolling inertia that you mentioned, another factor affecting stability with increased, or heavy armament in the wing is the fact that generally the CofG of the weapon and its ammunition are aft of the A/C moment center, resulting in the CG of the A/C moving aft with deleterious effect on stability, unless weight is added forward, opening up a whole new can of worms. (e.g.. the Buffalo after they added wing armament).

 

Post war A/C with their roll/yaw inertia coupling are a whole new ball game. A number of years ago I did some work on a proposed intermediate trainer that had an aft fan engine in the extreme rear fuselage, the tandem cockpit at the front and the fuel over the wing. Apart from the U/C, there was nothing in the wing. Very high pitch and yaw MofI, and very low roll MofI. As you can imagine the free flight spinning model tests were quite exiting! And we were't even modelling the MofI of the rotating engine. Just as well they never built the thing.

 

Regards,

Peter

 

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19 hours ago, Graham Boak said:

The effect of wing armament on agility was appreciated by Yakovlev, who refused to put guns in the wings of his WW2 fighters.  It is also why the use of four cannon is rare on Spitfires and two were often removed from the wings of Hurricanes.  However, the Russians had a very good line of light cannon, eventually being bale to put three and even four in the nose of Lavochkins, whereas the RAF had chosen a particularly long and heavy cannon in the Hispano.

 

 

Slightly OT, but worth mentioning that most Soviet aircraft guns of WW2 could be considered among the best if not the best in their class. The quality of these weapons is unfortunately often forgotten in the West

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Peter, I remember sketches of proposed light ground attack aircraft appearing in magazines several decades ago. One was very similar to your description and another was a canard propfan. I am not quite certain but I do think there was only a single multi-blade propeller and not two contra-rotating. If that is the case it was probably the closest modern equivalent of the old Sopwith Camel as any elevator movement would also produce considerable yaw. Good thing nothing ever came out of it.

Troy Smith, Hirth (not Henschel, my mistake) company started to develop wooden wing for proposed Bf 109 K in summer 1943. Progress was far from smooth and especially wood-metal attachments were problematic. In November Messerschmitt requested incorporation of Mk 108 cannons, buried in wings. Hirth finished that task three days before the end of the year. However, by that time wooden wing had been canceled. This is an extract from Manfred Griehl's Messerschmitt Bf 109 G-K Flugzeug Profile 5, a special edition of Flugzeug magazine. More or less the same is also given in English summary of Bf 109 K book by Ales Janda and Tomas Poruba, published by JaPo. Cheers

Jure

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4 hours ago, Jure Miljevic said:

Peter, I remember sketches of proposed light ground attack aircraft appearing in magazines several decades ago. One was very similar to your description and another was a canard propfan. I am not quite certain but I do think there was only a single multi-blade propeller and not two contra-rotating. If that is the case it was probably the closest modern equivalent of the old Sopwith Camel as any elevator movement would also produce considerable yaw. Good thing nothing ever came out of it.

 

Hi Jure,

That was not the aircraft I was referring to. The engine in this aircraft was a fan-jet engine. It was of the type developed by GE with the fan aft of the turbine, rather than in front of the compressor as is now the norm. It was a trainer in the same class as the Macchi 326. The design was developed in Australia, but was never built, the RAAF electing to buy the Macchi 326 instead.

Cheers,

Peter

 

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A big issue not mentioned so far here is convergence and rate of fire. 

 

When you sit on your guns like in a Me-109, Yak-9 or La-5 convergence isn't a issue. Just point your nose at the other plane and the bullets should land where your aiming. The trade off is a slower rate of fire because of the interrupter gear.  In other words more accurate, less lead going down range. 

     When you move the guns out into the wings, convergence (sometimes called harmonisation) becomes a huge issue. Here your guns are no longer aimed dead center and each gun must be kicked in so that your shots can connect easier. (this is an even bigger deal during deflection) So the guns are set a particular angle so that they all converge.  Here is an pic from an RAF training manual showing what I mean on a 8 gun Hurricane:

 

238px-Hurricane_gun_harmonisation_-_not_

    

Convergence could be changed for different pilots or staggered to create a "shotgun" effect. The total effect here is less accuracy, but with way more lead going down range. For example, an American 6 gun fighter has the  same rate of fire as a Vulcan gatling gun.

 This is why most twin engine fighters from that era (P-38, Me-110, Whirlwind, etc..) have their guns in the nose, it's the best of both words.  This can also be applied to jet fighters.

    There are also the problems of what kind of guns where available at the time of the aircraft's manufacture. 

   The Germans had a great LMG and a great HAC. The Orelikon was not a great gun nor was the available HMG. It made sense to move the guns into the nose to not only increase performance, but to increase lethality.  Later when the heavily built US aircraft where more common in theater, this layout became inadequate. Thus the reinstallation of the  wing guns into underslung gondolas because the wings  had been redesigned for maximum performance. 

   The US and the UK had access to very good LMGs. The US had an exceptional HMG. While the UK had (IMHO) the best LAC. This made placing the guns into the wings of their fighters, even though it had a effect on accuracy, the best choice to achieve maximum lethality.  It not only provides a greater rate of fire, it also meant you didn't have some crazy convergence issues like in the Fw-190 and the Ki-61. Placing low hitting guns in the nose was grossly ineffective; see most Italian fighters as an example. (I'm looking at you C.202)

   The Russians had an entirely different set of problems. They had an excellent LAC, so you would think they would get the same answers as the US and UK. But they didn't.  The excellent LAC the Russians were using was made out of softer materials than the British gun. That gave it a shorter service life. The best use of said gun was to put it in the nose. To slow down it's rate of fire and make it more accurate. This would help extend its short service life. (Before anybody points out that the Yak's cannon didn't fire through the propeller, all the Yaks had a crazy small magazine. Which not only addressed the cannon's issues but was more inline with the Red Air Force's tactical footing.)

  

 

 

 

Edited by Thud4444
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The other argument against wing guns is that in a turning fight the wings will be flexing, and so the guns will no longer be firing along the expected lines.  Arguably this may provide more deflection that expected, so improving the average pilot's chance of a hit. but that doesn't really work out well overall.

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Hello

Thanks, Peter. I do not know what plane you had been working on, but I think I recognize the engine. It is a power plant for Convair 880 and 990 airliners, right? IIRC on these engines turbine blades for very hot primary air and fan for not so hot secondary airflow was installed on the same combined turbine/compressor wheel. Time between overhauls must have been quite short.

Thud4444, there were problems even with harmonization of centrally installed weapons or with the same type of weapon installed in both nose and wings. Take a look at Bf 109 G-6/U4 weapons manual here and check ballistic curves on page 29. One can only imagine how difficult was to actually hit something if MK 108s in the wing had been replaced with MG 151 or 21-cm rockets. Not to mention defence fire from bombers ...

About Italian (or German and Japanese for that matter) 13-mm heavy machine guns in the nose: agreed, synchronization slowed rate of fire but all those HMG could fire explosive ammo, a kind of mini-grenades. Several early USAAC and USAAF types also had machine guns (P-36, P-39, P-40), firing through propeller arc and I doubt pilots complained much because of that. I think reasoning behind that was that two nose machine guns are worth three or four wing machine guns. Cheers

Jure

 

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The RAF in the Battle of Britain also had explosive ammunition, called De Wilde, in their 0.303 Brownings.

 

Given the reduction in rate of fire because of synchronisation, arguments suggesting X nose mounted guns were worth X+ wing guns have to be treated with a considerable pinch of salt.

 

Most successful fighter pilots only fired at close range anyway, where the problems of convergence were minimal.  Early in the war the RAF pilots argued for convergence at a closer range than the prewar standard, and this was generally adopted.  Apparently the FAA carried out a survey of results later in the war that demonstrated the reverse, and FAA guns were reset to meet at a greater distance.  Presumably much the same as that prewar, but I can't confirm the precise distance.  As for convergence being more important than deflection: I think this is rather difficult to prove and would doubt it, given the importance given to deflection training by successful pilots (for example, JE Johnson would insist on pilots going on game bird shoots) and the reported gains from the late-war gyro gunsight..

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Hello Graham

Yes, but de Wilde ammunition was more an incendiary type than explosive, and would only burst upon impact. Germans had various types of 13-mm ammo, which could be set to self-destruct at certain distance. Otherwise I agree with you, with so many arguments pro and contra it is difficult to reach a definite conclusion. For example, gyro sights improved results of average shots, but marksmen preferred regular sights as gyros required target distance input and than several seconds of tracking before providing useful deflection distance. In most cases tracers were helpful but novices sometimes attempted to ˝hose down˝ opponents instead of aiming through gunsights. And there is plenty more questions ... Cheers

Jure

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This is a fascinating topic that I really enjoy talking about.

 

2 hours ago, Graham Boak said:

The other argument against wing guns is that in a turning fight the wings will be flexing, and so the guns will no longer be firing along the expected lines.  

 

This was countered by moving the guns as close to the fuselage as possible.  Most US fighters like the P-47 and F6F where extremely robust. The Hurricane and Typhoon where also pretty structurely sound.  Flexing was an issue but not as big of one as you would think for the allied fighters.  Flexing was more an issue with Axis aircraft, especially those not designed for such heavy wing armaments.

 

2 hours ago, Jure Miljevic said:

Take a look at Bf 109 G-6/U4 weapons manual here and check ballistic curves on page 29. One can only imagine how difficult was to actually hit something if MK 108s in the wing had been replaced with MG 151 or 21-cm rockets.

 

Ballistic variables are a HUGE deal, your right. But if you'll notice outside of Germany this practice of mixing guns almost goes away entirely.  Only the Yaks and Spitfires are still using it on the Allied side. (Although  there are some late war twins that go against this philosophy) Again older planes still being manufactured. The Mig-15 is the only single engined mass manufactured post war fighter I can think of that mixed ballistics. I'm sure there's more.

 

2 hours ago, Jure Miljevic said:

 Several early USAAC and USAAF types also had machine guns (P-36, P-39, P-40), firing through propeller arc and I doubt pilots complained much because of that. 

 

 

Actually the exact opposite is true. Ammerican pilots hated synchronized guns. So did American designers. That is why there are no fighters by late war in the USAAC with the feature. Going as far as to move the guns out on the P-40.

 

1 hour ago, Graham Boak said:

 

Given the reduction in rate of fire because of synchronisation, arguments suggesting X nose mounted guns were worth X+ wing guns have to be treated with a considerable pinch of salt.

 

 

It's not so much an x vs y issue as much as it is a design decision. I have these tools available to me, how do I get the best performance out of them?  The US, the UK and Japan tended to move the guns out P-51, F4U, Typhoon, Sea Fury, Jack and George.  The Germans and the USSR tended to move them in Ta 152, La-7 and Do 335. Like I said earlier jets made the whole argument pointless. 

Edited by Thud4444
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20 hours ago, Thud4444 said:

A big issue not mentioned so far here is convergence and rate of fire. 

 

When you sit on your guns like in a Me-109, Yak-9 or La-5 convergence isn't a issue. Just point your nose at the other plane and the bullets should land where your aiming. The trade off is a slower rate of fire because of the interrupter gear.  In other words more accurate, less lead going down range. 

     When you move the guns out into the wings, convergence (sometimes called harmonisation) becomes a huge issue. Here your guns are no longer aimed dead center and each gun must be kicked in so that your shots can connect easier. (this is an even bigger deal during deflection) So the guns are set a particular angle so that they all converge.  Here is an pic from an RAF training manual showing what I mean on a 8 gun Hurricane:

 

238px-Hurricane_gun_harmonisation_-_not_

    

Convergence could be changed for different pilots or staggered to create a "shotgun" effect. The total effect here is less accuracy, but with way more lead going down range. For example, an American 6 gun fighter has the  same rate of fire as a Vulcan gatling gun.

 This is why most twin engine fighters from that era (P-38, Me-110, Whirlwind, etc..) have their guns in the nose, it's the best of both words.  This can also be applied to jet fighters.

    There are also the problems of what kind of guns where available at the time of the aircraft's manufacture. 

   The Germans had a great LMG and a great HAC. The Orelikon was not a great gun nor was the available HMG. It made sense to move the guns into the nose to not only increase performance, but to increase lethality.  Later when the heavily built US aircraft where more common in theater, this layout became inadequate. Thus the reinstallation of the  wing guns into underslung gondolas because the wings  had been redesigned for maximum performance. 

   The US and the UK had access to very good LMGs. The US had an exceptional HMG. While the UK had (IMHO) the best LAC. This made placing the guns into the wings of their fighters, even though it had a effect on accuracy, the best choice to achieve maximum lethality.  It not only provides a greater rate of fire, it also meant you didn't have some crazy convergence issues like in the Fw-190 and the Ki-61. Placing low hitting guns in the nose was grossly ineffective; see most Italian fighters as an example. (I'm looking at you C.202)

   The Russians had an entirely different set of problems. They had an excellent LAC, so you would think they would get the same answers as the US and UK. But they didn't.  The excellent LAC the Russians were using was made out of softer materials than the British gun. That gave it a shorter service life. The best use of said gun was to put it in the nose. To slow down it's rate of fire and make it more accurate. This would help extend its short service life. (Before anybody points out that the Yak's cannon didn't fire through the propeller, all the Yaks had a crazy small magazine. Which not only addressed the cannon's issues but was more inline with the Red Air Force's tactical footing.)

  

 

 

 

 

The use of two 12.7mm guns in the nose of Italian fighters was the result of some conservative views by the Air Force high commands that were however based on experience.

The CR.32 had introduced wing mounted MGs in addition to the standard nose mounted ones a good few years before but the experience was not positive. The presence of these guns affected the manouverability of the aircrafts, something that in an Air Force that placed this feature very highely in their combat philosophy was a serious problem. The CR.32 installation was also not particularly reliable and the wing mounted weapons were removed quickly.

There was also the ever present problem of weight: until the "Serie 5" aircrafts most Italian fighters suffered from lack of power and excessive weight. The MC.202 itself could carry 2 7.7mm MGs in the wings (apart from the very first production series) but these were very rarely installed and most pilots preferred to leave them off their aircrafts. he Re.2001 on the other hand commonly retained the wing mounted MGs.

The Serie 5 aircrafts were a different story and the 3 X 20mm plus 2 X12.7 armament of the G.55 was a massive improvement over the older types.

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 I don't know man, the Italians are weird. It's almost like they where constantly resistant to change. Even their late war stuff still used prewar layouts. While every one else was evolving they just installed bigger guns into the same layouts. Ive always been amazed at how successful they where, considering the tools they where working with. I always thought the C205 was a nice plane though. And all the series 5 planes where lookers IMHO. Thank God they didn't build more of them.

 

I've always thought the maximizing roll rate and maneuverability arguments against wing guns to be a red herring.  I mean didn't the two best roll rate fighters both have wing guns? (Fw-190 and F-4U) The Spitfire was no slouch in the maneuverability department,  plus it got better not worse as it evolved. Unlike the 109 and Zero. The Japanese also had a maneuverability obsessed aerospace industry. But they still managed to install wing guns in almost all their late war designs. 

 

On 4/20/2018 at 4:45 PM, Graham Boak said:

Early jets?  Attacker?  Meteor 11/12/14?  I suspect there were others...   But the drive to thin wings had perhaps at least as much to do with the trend.

 

Wasn't the Attacker basically a jet with Spitfire wings? And those Meteors only moved the guns out to make room for the radar. Basically everybody knew that placing the guns in the nose is the optimum solution. Almost every twin engined fighter followed this layout because, just like early jet fighters, shooting through the propeller was a non issue.

 

 

Holy crap I just remembered that the P-59 mixed bullet ballistics like the Mig-15. 

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10 hours ago, Thud4444 said:

 I don't know man, the Italians are weird. It's almost like they where constantly resistant to change. Even their late war stuff still used prewar layouts. While every one else was evolving they just installed bigger guns into the same layouts. Ive always been amazed at how successful they where, considering the tools they where working with. I always thought the C205 was a nice plane though. And all the series 5 planes where lookers IMHO. Thank God they didn't build more of them.

 

 

It was not a matter of being weird and the high commands changed a lot of their views based on the experience of the war. Simply in some aspects they continued to follow paths that had been proven to be satisfactory. Nose mounted armament have pros and cons and the same apply to wing mounted armament, the Italians kept a mix of the two simply because they found this to be succesful.

There is another aspect that however explains why certain layouts were retained and this is the evolution of the various designs within the design teams. The MC.205 is an example: this aircraft did indeed retain several features of the MC.200 but this was due to the fact that the 205 was little more than a re-engined MC.202, in itself an advanced derivative of the MC.200. A good number of structural components were carried through from one design to the other and so was the overall layout of the 3 aircrafts

Edited by Giorgio N
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15 hours ago, Thud4444 said:

 

I've always thought the maximizing roll rate and maneuverability arguments against wing guns to be a red herring.  I mean didn't the two best roll rate fighters both have wing guns? (Fw-190 and F-4U) The Spitfire was no slouch in the maneuverability department,  plus it got better not worse as it evolved. Unlike the 109 and Zero. The Japanese also had a maneuverability obsessed aerospace industry. But they still managed to install wing guns in almost all their late war designs. 

 

 How about the Yak 3?

 

If you can explain how sticking sizeable lumps of weight into a wing are NOT going to increase the rolling inertia and hence make the aircraft less agile, I think that you are going to have to argue the point with greater authorities than me.  It is purely a matter of physics.  (What's your opinion on gravity?)  Just try waving your arms about with and without dumbbells in your hands.

 

The maximum roll rate is more a matter of how good the ailerons were, and does vary a lot with speed, but agility is more a measure of how quickly you could reach that roll rate.  The Spitfire had a very good roll rate at low speeds, as did the Fw190, but the Fw190 could roll and pull away and leave a conventional-winged Spitfire struggling to catch up.  Hence the clipped wing.  Other aircraft, such as the F4U and F6F, were considerably slower in roll at low speed but better at higher speeds.

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