On the 30mm MK 103 and synchronization...

Discussion in 'Weapons Systems Tech.' started by riacrato, Mar 4, 2010.

  1. riacrato

    riacrato Member

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    this should give those who claim it wasn't possible some food for thought.

    source is:
    Harmann, Dietmar
    Focke-Wulf Ta 152: The Story of the Luftwaffe's Late-War, High-Altitude Fighter
    Schiffer Publishing Ltd.
    ISBN-10: 0764308602
    ISBN-13: 978-0764308604
     

    Attached Files:

  2. vanir

    vanir Banned

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    I may be ignorant but do not understand how any repeater could not be synchronised, mechanically speaking. The only prohibition I've read regarding the MK-103 was that it was at some point intended to be used as motorkanone in an Me-109K subtype but this was not possible because of its size and recoil concerns in the relatively light airframe and engine mount of the Messerschmitt (iirc it would rattle the engine too much but was tested on the ground).

    Given the Ta-152 were still in the development phase and could be effectively constructed around different armaments installations to suit, and weight on their side I don't see any reason the MK-103 would not be fitted. As I understand it the Ta-152B-5 was a proposal derived of the Jumo engine reconnaissance version that had its airframe in common with the Ta-152C, which was in effect derived of the Ta-152B series but with fitment of the DB-603, hence the Ta-152B-5 and C-3 with same equipment but DB-603 motor were to be produced alongside the Ta-152C-1, H-1 and the B-reconnaissance version. By this stage the later, more capable versions of the Fw-190D using various Jumo and DB-603 types would be helping fill out squadron numbers in conventional aircraft, on the don't put all your eggs in the jet basket rule.

    I realise that initially some work was required to perfect synchronisation for the MG-151 but I assume this involved as much sorting a reliable electrical interrupter to the wing roots of the Fw-190A, which could be readily adapted to any other electrically fired gun type. I don't think it was something specific to the MG-151 itself, just its type. Hence I can see no logical reason of a mechanical mind, that an MK-103 or any other repeater weapon cannot be interrupted for synchronisation given that a working linkage system for the gun placement is already developed previously. Both the MG-151 and MK-103 are electrically fired IIRC (the MK-103 basically an electrically fired version of the MK-101).
    So then the problems could only be ones of recoil concerns and weight distribution. I do not think these much of an issue with the Ta-152 because weight distribution was still being sorted for improved low speed stability, most particularly in rear fuselage equipment and fuel tankage which were unresolved. I should think heavier guns in the wing roots might've actually helped. As it was it seems the MW-50 installation was moved to replace the inner port-wing fuel tank and reduced in size to get rid of some weight in the rear fuselage, and pilots were told not to put fuel in the rear fuselage tank due to similar instability you get with a fully loaded Mustang. I believe the production Ta-152B/C was to have the rear fuselage fuel tank removed also, to leave only the front tank and wing tanks (where the Fw-190 series has no wing tanks but front/rear fuselage tanks).

    If someone was telling you it was impossible to synchronise the MK-103 the statement itself lacked credibility in the first place. I suggest they then attempted to confuse you by suggesting that "historically it was never done" which you have certainly proved wrong with good photographic evidence. Nicely done.

    I usually like to ask for a mechanical reason something can't be done and therefore was never done. I suggest postwar enthusiasts can be a little conservative about what has been tried out in wartime conditions and like to neatly categorise something inherently anarchistic to some degree. Regulations and guidelines are more often than not a work in progress and even retroactive to actual fitments and conditions unexpectedly performed in wartime, or tried out in the field on some combination of desperate inspiration.

    For example even aircraft model variants are only a general guideline, every aircraft is individual and a more accurate classification is by production series then individual modifications and flight condition, inevitably one arrives at the point that each specific tail number really represents a unique aircraft and many were freely modified in the field or by the factory to various squadron specifications at various times, differing fuel qualities and servicing facilities, etc.
    Just to proclaim "all aircraft of this model had these specifications" is I think a mistake, let alone that something quite mechanically sound, possible and available was never done even if only loose references suggest it might've been.
    To form such an absolute argument you'd have to track the history and records of each individual aircraft in the series. People who say which modifications were and were not performed seem to rarely have gone to these lengths in my experience.
     
  3. riacrato

    riacrato Member

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    I remember the argument was that with a shell as large as that of the MK 103, the variations in gunpowder charge and thus ignition sequence of the round were too large to allow for a synchronized gun firing safely through the prop disc.

    So the mechanical reasoning behind the argument was there, but it lacked any first hand sources or evidence. And this particular prototype certainly suggests otherwise. We don't know how it fared as the whole Ta 152 B project was put on hold in favor of the other subtypes, but it certainly seems it was in general considered to be possible to fire the MK 103 though the prop disc.
     
  4. vanir

    vanir Banned

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    Well you forced me to review some of my PDF files saved to disc and it appears the final Zerstörer version of the Ta-152 mooted for production during 1945 development of the Ta-152 prototypes fitted with later series engines was to have four MG-151/15 with AP loadouts and an MK-103(M) only as motorkanone.
    These were to be Ta-152C variants since by then the Jumo versions had already been passed over due to reliability and performance issues with the 213 on B4 fuel, which are numerous and worthy of their own discussion. The Daimler by comparison had been found to be virtually trouble free and wtih a far higher torque output in the base engine on B4 for the same weight and external dimensions. Ta-152B combat variants were mooted back in December 1943 when only the DB-603G was available for testing alongside Jumo 213A and E prototypes, but I believe by 1945 the Daimler had clearly drawn ahead in preference due to the absolutely remarkable performance of the DB-603EB/EC versions in the Ta-152C prototypes (easily cracking 600km/h at low altitude in combat condition). Hence I believe the Ta-152B was finally to enter production using surplus Jumo engines in tactical reconnaissance versions only, whilst the Ta-152C-3 was to take the reigns of the Zerstörer role with the Daimler engine.
    It would appear to be a decision unrelated to armament packages.

    The synchronisation argument of the MK-103 could be sound if any evidence can be discovered attesting to a highly varied rate of fire with the gun normally. I do have some documentation for various ammunition used by MK-101/103 guns (440g, 455g and 255g projectiles). Figures like around 75mm penetration at 90-degrees from 100-300m are impressive for APSD. MG-151/15 also have impressive penetration and unusually were available with tungsten ammo.

    Everything I can find so far on the MK-103 reports a fairly reliable 420rpm-cyclic as opposed to something like the Oerlikon 2cm which tends to vary between 480-550rpm (higher averages for the later version). Obviously the Oerlikon would be unsuitable for synchronisation. My bibliography here is simply a basic websearch however, which does include Tony Williams but also just whatever plastered on the browser, so my only real point is general media reports a fairly reliable 420rpm for the MK-103 where variation can clearly be found for types like the Oerlikon, for whatever that's worth.

    I would suggest the decision to go with four MG-151/15 and an MK-103M was more related to a higher ammo load for similar overall weight and penetration/damage capabilities of three MK-103, rather than synchronisation issues with the heavier gun. With a gas mechanism, electrical firing and pretty refined munitions production it seems by all accounts to be a reliable and functionary weapon, with only weight and recoil issues to worry about as an aircraft gun. Certainly other contemporaries might not have been as good, perhaps the argument is more related to they.
     
  5. Erich

    Erich the old Sage
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    out of correctness for the above author: his name is properly spelled Dietmar Hermann not ............... harmann
     
  6. CharlesBronson

    CharlesBronson Well-Known Member

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    That person was me, no problem I am already wiping miself with an barber steel wire for making that mistake ( auch..it hurts ¡¡¡¡ :) )

    Now seriously: Thanks for the information, but ( there is always a but) my claim was related to a ventral pod used in FW190A/F series wich may not be the same as this, this picture is 1945 that MIGHT mean the problems earlier posted were corrected.
     
  7. Shortround6

    Shortround6 Well-Known Member

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    The problem isn't so much the firing rate of the gun, which is actually controlled in a synchronized gun by the synchro mechanism, but by the variation in timing between primer initiation and projectile leaving the barrel.

    A variation of 1/100 of a second isn't going to mean much to the cycle rate of the gun or even that much to the muzzle velocity of the projectile but it can mean a great deal to the position of the propeller blade.

    As a for instance, if the gun is 2 feet from the propeller shaft and the prop is turning 1350rpm the part of the prop in front of the gun is moving at 283ft/sec with a prop blade (for a 3 bladed prop) passing in front of the gun 67.8 times a second.

    The rate of acceptable "hang fires" in 7.9mm or even 13mm ammunition is going to be much different than the acceptable rate for 30mm ammunition. A 7.9mm or 13mm bullet hitting a prop blade, while annoying the ground personnel (and the pilot) is hardly going to lead to the immediate loss of the aircraft. If 1 round in a hundred is slow a gun with 2 synchro-ed 30mm cannon with 50rpg will shoot itself down every time it empties it's guns:lol:

    Even if things are nowhere near that bad, say one bad round per 1000 you loose one plane for every 10 that empties it's guns.

    Large volume cases show more variation in "burn time" or time between primer initiation and projectile muzzle exit than smaller cases.
     
  8. Milosh

    Milosh Well-Known Member

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    The dust cover for his Ta152 book spells his name 'Harmann' while his Dora book spells his name 'Hermann'.
     
  9. davebender

    davebender Well-Known Member

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    MG 151 cannon - Wikipedia, the free encyclopedia
    MG151/20 weight = 42 kg.
    4 x MG151/20 weigh 168 kg.

    MK 103 cannon - Wikipedia, the free encyclopedia
    MK103 3cm cannon weight = 145 kg.

    Why not arm the Fw-190D9 with a single Mk103 cannon firing through the prop shaft? Total weapon weight is less then for the Fw-190A series armed with 4 x 20mm cannon. You get the accuracy advantages of centerline mounting and high muzzle velocity. When combined with the new gyro stabilized gun site you should be able to hit B-17s from outside bomber defensive fire range.
     
  10. CharlesBronson

    CharlesBronson Well-Known Member

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    There were problems with the MK 103 wide and general size ( there is a complete post of it in my topic of Luftwaffe guns by T Williams) that why is wasnt used so much, I think also it was seen mostly as an twin engined aircraft canon due the weight.

    Is not the problem the rate, that for sure, also the fact that some weapons fired at open bolt does not incapacitate them for synchronization if they had a way to control the firing pin. The gun with fixed firing pin strike timing like the oerlikons, Scotti, and someother could no be synchronized.
     
  11. davebender

    davebender Well-Known Member

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    The U.S. managed to fit an even larger 37mm cannon in the relatively small P-39.
     
  12. riacrato

    riacrato Member

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    The Oldsmobile M4 is actually a tad shorter and significantly lighter than the MK 103. Also the P39 was kind of specifically designed around it. Apart from it (P-39), I don't think there is much application in operational aircraft except for prototypes. So both cannons were only limited in overall success.
     
  13. davebender

    davebender Well-Known Member

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    Why not design the Fw-190D9 specifically for the Mk103 3cm cannon?

    The P39 engine was mounted behind the pilot. You could do something similiar with the Fw-190D9. Mount the heavy cannon and ammunition in the rear to balance the front mounted engine. The cannon barrel would be in a tube which runs under the pilot seat.
     
  14. Milosh

    Milosh Well-Known Member

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    Do you even look at the feasibility of what you suggest before you suggest?:)

    [​IMG]
     
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