WORLD WAR 2 FIGHTER ARMAMENT EFFECTIVENESS

Discussion in 'Aviation' started by syscom3, Apr 7, 2006.

  1. syscom3

    syscom3 Pacific Historian

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    I received this in an e-mail today.

    WORLD WAR 2 FIGHTER ARMAMENT EFFECTIVENESS
    © Anthony G Williams Emmanuel Gustin (with
    acknowledgements to Henning Ruch)

    Revised 28 June 2004

    The comparative effectiveness of fighter guns in the
    Second World War is a subject of perennial fascination
    (and a great deal of argument) among technical
    military historians. This is an attempt to take a
    fresh and objective look at the evidence in order to
    draw up comparative tables of cartridge
    destructiveness, gun power and gun efficiency. The
    effectiveness of typical day fighter armament fits is
    also considered.

    CARTRIDGE DESTRUCTIVENESS

    There are two types of energy that may be transmitted
    to the target; kinetic and chemical. The kinetic
    energy is a function of the projectile weight and the
    velocity with which it hits the target. This velocity
    in turn depends on three factors: The muzzle velocity,
    the ballistic properties of the projectile, and the
    distance to the target. There are therefore two fixed
    elements in calculating the destructiveness of a
    projectile, its weight and chemical (high explosive or
    incendiary) content, and one variable element, its
    velocity. The key issue is the relationship between
    these three factors.

    A high muzzle velocity will provide a short flight
    time, which is advantageous in increasing the hit
    probability and extending the effective range, and
    will also improve the penetration of AP rounds.
    However, it might not add much to destructiveness, as
    unless an AP projectile hits armour plate (and not
    much of the volume of an aircraft was protected by
    this), a higher velocity just ensures that a neater
    hole is punched through the aircraft; the extra
    kinetic energy is wasted. Also, if the projectile is
    primarily relying on HE blast or incendiary effect,
    the velocity with which it strikes the target is
    almost immaterial. Provided that it hits with
    sufficient force to penetrate the skin and activate
    the fuze, the damage inflicted will remain constant.
    In contrast, AP projectiles lose effectiveness with
    increasing distance.

    It is sometimes argued that a projectile with a high
    muzzle velocity and a good ballistic shape (which
    reduces the rate at which the initial velocity is
    lost) provides a longer effective range. To some
    extent this is true, but the greatest limitation on
    range in air fighting in the Second World War was the
    difficulty in shooting accurately. The problem of
    hitting a target moving in three dimensions from
    another also moving in three dimensions (and probably
    at a different speed and on a different heading)
    requires a complex calculation of range, heading and
    relative speed, while bearing in mind the flight time
    and trajectory of the projectiles. Today, such a
    problem can easily be solved by a ballistic computer
    linked to a radar or laser rangefinder, but at the
    time we are examining, the "radar" was the human
    eyeball and the "ballistic computer" the human brain.
    The range, heading and speed judgements made by the
    great majority of pilots were notoriously poor, even
    in training. And this was without considering the
    effects of air turbulence, G-forces when manoeuvring,
    and the stress of combat. These factors limited the
    effective shooting range to around 400 m against
    bombers (longer in a frontal attack) and against
    fighters more like 250 m.

    For all of these reasons muzzle energy (one half of
    the projectile weight multiplied by the square of the
    velocity) has not been used to calculate kinetic
    damage as this would overstate the importance of
    velocity. Instead, momentum (projectile weight
    multiplied by muzzle velocity) was used as an estimate
    of the kinetic damage inflicted by the projectile. It
    might be argued that even this overstates the
    importance of velocity in the case of HE shells, as
    noted above, but the effect of velocity in improving
    hit probability is one measure of effectiveness which
    needs acknowledging, so it is given equal weighting
    with projectile weight.

    Chemical energy is generated by the high explosive or
    incendiary material carried by most WW2 air-fighting
    projectiles. First, there is the difference between HE
    and incendiary material, which were often mixed (in
    very varying proportions) in the same shell. HE
    delivers instant destruction by blast effect (plus
    possibly setting light to inflammable material within
    its blast radius), incendiaries burn on their passage
    through the target, setting light to anything
    inflammable they meet on the way. The relationship
    between the effectiveness of HE and incendiary
    material is difficult to assess. Bearing in mind that
    fire was the big plane-killer, there appears to be no
    reason to rate HE as more important, so they have been
    treated as equal.

    The comparison between kinetic and chemical energy is
    the most difficult and complicated subject to tackle.
    This complexity is revealed by the example of a strike
    by a delay-fuzed HEI cannon projectile. This will
    first inflict kinetic damage on the target as it
    penetrates the structure. Then it will inflict
    chemical (blast) damage as the HE detonates. Thirdly,
    the shell fragments sent flying by the explosion will
    inflict further kinetic damage (a thin-walled shell
    will distribute lots of small fragments, a
    thick-walled shell fewer but larger chunks), and
    finally the incendiary material distributed by the
    explosion may cause further chemical (fire) damage.

    There will therefore always be a degree of
    arbitrariness in any attempt to compare kinetic and
    chemical energy, as it all depends on exactly where
    the projectile strikes, the detail design of the
    projectile and its fuze, and on the type of aircraft
    being attacked. To allow a simple comparison, we will
    reduce all these factors to an increase in
    effectiveness directly proportional to the chemical
    content of the projectile. We assign to projectiles
    that rely exclusively on kinetic energy an
    effectiveness factor of 100%. For projectiles with a
    chemical content, we increase this by the weight
    fraction of explosive or incendiary material, times
    ten. This chosen ratio is based on a study of many
    practical examples of gun and ammunition testing, and
    we will see below that it at least approximately
    corresponds with the known results of ammunition
    testing.

    To illustrate how this works: a typical cannon shell
    consists of 10% HE or incendiary material by weight.
    Multiplying this by ten gives a chemical contribution
    of 100%, adding the kinetic contribution of 100% gives
    a total of 200%. In other words, an HE/I shell of a
    given weight that contains 10% chemicals will generate
    twice the destructiveness of a plain steel shot of the
    same weight and velocity. If the shell is a
    high-capacity one with 20% chemical content, it will
    be three times as destructive. If it only has 5%
    content, the sum will be 150%, so it will be 50% more
    destructive, and so on.
     
  2. the lancaster kicks ass

    the lancaster kicks ass Active Member

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    a very interesting read and something to think about, i don't know enough to say if that theory works or nut but one thing bugged me when i read it

    that sounds missleading, it should be multiplied by the velocity squared (V^2), "the square of the velocity" means the square root (V^0.5), i know it's small it just bugged me :lol:
     
  3. lesofprimus

    lesofprimus Active Member

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    Thats not really brand new information.... Many of us understand the ballistics portion of combat arms....

    Is it the summation at the bottom that ur wishing to discuss???
    If so, I can agree with the article...
     
  4. wmaxt

    wmaxt Active Member

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    You might want to check out this site:
    http://www.geocities.com/CapeCanave...ox and tack on html to get it to work. wmaxt
     
  5. Gnomey

    Gnomey World Travelling Doctor
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    Interesting stuff.
     
  6. Twitch

    Twitch Member

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    What I love unendingly is the fact the we muse over ballistics unceasingly and guys in combat simply put whatever ordnance they were supplied with on target and killed enemies. Every cartridge used in the conflict was sufficient to kill enemies with the exception of .30 cals. and even then watch out if you have an old hand on you because he is capable of pinpointing them into your canopy which will not deflect them.
     
  7. MacArther

    MacArther Active Member

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    Precisely! It may matter what caliber is hitting the actual plane body, but I think that any bullet going throught the cockpit will hurt. In that case, I don't think the pilot would be worrying about what caliber guns are shooting at him.
     
  8. syscom3

    syscom3 Pacific Historian

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    There is a big difference between the ammunition and to pretend they're similar is a big mistake.

    Think about this..... what would you rather have hit your cockpit. A .50 that would just put a hole in whatever it strikes, or a 20mm that would explode and throw fragments around?

    Erich had a great thread several months ago showing how even the 20mm had different lethality depending on the type.
     
  9. Twitch

    Twitch Member

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    As I mentioned elsewhere 20s should have been THE standard fighter vs fighter round of WW 2. My gripe with armchair ballistics experts is that they completely discount the .50 API round as totally ineffective and nothing could be farther from the truth with many thousands of kills to its credit. Rounds in the thirty caliber category were completely worthless unless a great shooter could precisely lay them into your cockpit.
     
  10. KraziKanuK

    KraziKanuK Banned

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    Sys, are all these e-mails from the same person?

    Sounds like it is some of Tony Williams work.

    http://www.quarry.nildram.co.uk/

    Twitch, there is a guy on this forum, http://www.tgplanes.com/Public/snitz/forum.asp?FORUM_ID=1 that thinks the .30s/7.92s were good enough to hold off Mossies. see the Mossie vs 110 thread

     
  11. syscom3

    syscom3 Pacific Historian

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    I dont think so. The e-mail I received was obviously passed around the 'net for quite some time.

    The e-mails that I get, if they have an identifying author, I always include that in my post.
     
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