B-17G with a 20 mm cannon onboard!

Discussion in 'Aviation' started by seesul, Jul 1, 2008.

  1. seesul

    seesul Active Member

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    One of 8 B-17´s shot down on August 29, 1944 in our area had a 20 mm cannon onboard! B-17G, serial # 42-31885,MACR8099, crash site Vyskovec.
    A friend of mine found 20 mm shells at the crash site last year, then we noted a strange gun on the historical picture (attached) and this week I´ve found out this cannon still exist (pic attached, taken from Fragmenty z B-17G – Detektor web.cz detektory kovù!!!

    More at 20 mm cannon aboard a B-17G???
     

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  2. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Wild stuff Roman - this is from the site you referenced...
     

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  3. Milos Sijacki

    Milos Sijacki Member

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    This is something completely new for me. That thing probably recoiled so much that it actually didn't do any good.
     
  4. comiso90

    comiso90 Active Member

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    Definition of helpless:
    Sitting still in a B-17 armed with .50 cals and while a German fighter closes in popping off 20mm rounds and waiting till your .50s are in range.

    arrgghhh!

    .
     
  5. renrich

    renrich Active Member

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    Comis, I think you would find that a 50 BMG has a longer effective range than most 20 mms although not as destructive with a hit.
     
  6. comiso90

    comiso90 Active Member

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    I wonder where I picked that up then?..
    seems like i heard a B-17 gunner saying it..
    oh well thanks for the correction.
     
  7. seesul

    seesul Active Member

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    Renrich,

    this is what you can find at mentioned discussion at ArmyAirForces.com posted by Martyjhawk:

    Hi Roman,
    From what I have read and been told, the few planes with the 20-mm guns flew the tail end charlie positions in their formations because the planes in this position were often attacked by fighters with guns of greater range than the 50's normally installed in the tail position. The fighters could lag behind the bombers and shoot at them, but the bombers lacked guns of effective range to shoot back...
     
  8. seesul

    seesul Active Member

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    Joe,

    we believe this cannon was mounted in tail. This aircraft was the last in the formation...I know this version did exist, but don´t have any pics. Don´t you have any?
     
  9. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    I have no pics of this Roman but it would seem to me despite the photo of the nose mounted cannon, the tail would seem like the best place. I'll look around for some more information.
     
  10. seesul

    seesul Active Member

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    This is what I´ve found on Internet:
    - 42-38090 340BS/97BG 'MISS WINDY CITY' was one of five B17Gs from 97th BG which had a similar 20mm cannon fitted in their tails
    - The 99th BG also had at least one B-17 with the 20mm gun in the tail. Aircraft was 42-32046, LIL ABNER, according to Dick Drain's 5th Wing History of Aircraft Assigned.
    - According to Roger Freeman's book The B-17 Flying Fortress Story, B-17's with these tail cannon were flown at the rear of formations, and the weapon was considered more of psychological than destructive value.'....

    Anyway, the mentioned B-17G, 42-31885, was transfered to 2ndBG from 99thBG, see the copy taken from the database at Second Bomb Group
    Assigned to 99th BG Feb 44. Transfer to 2nd BG 28 Mar 44 after 14 missions. MIA Moravska Ostrova 29 Aug 44 on its 49th mission, total 63. Attacked by fighters, crashed near Vsetin. Merrill Prentice crew, Heath, McVey, Laux, Goldstein, Ellis, Balcerzak, Johnson, Petrey, Fitch. McVey POW, rest KIA.
     
  11. seesul

    seesul Active Member

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    A friend of mine is going to scan the pics with the tail cannon mounting and send them to me. I´ll post them as soon as I get them...
     
  12. renrich

    renrich Active Member

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    If I was a gunner with a pair of 50 mgs confronted by a fighter with a pair of 20 mms, I would probably feel overmatched. I doubt that the gunners were too familiar with ballistic tables or the ballistic properties of the 50 BMG. In the Pacific the Wildcats liked the headon shot against the Zero not only because they had a more rugged fighter but because the flat trajectory of their 50s let them open fire before the Zero pilot had a good chance of hitting with a more rainbow trajectory of his 20 mm Oerlikons.
     
  13. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Thanks Roman, I'd love to see them.
     
  14. Erich

    Erich the old Sage
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    Roman the range in this case for aerial combat of the 20mm oerlikon (sp ?) was just plain terrible to the effectiveness of the .50cal besides being lighter they could of course rain out more destructive power than the US 20mm cannon - heavy, slow to operate and probably just a plain nuisance and not even having the overall range by using a heavier hand held weapon.

    E ~
     
  15. seesul

    seesul Active Member

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    yes, as they say:''the weapon was considered more of psychological than destructive value"
    btw, have you ever seen a pic of B-17 with that Hispano in tail?
    I´d like to know how many B-17´s had this instalation...
     
  16. Erich

    Erich the old Sage
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    no Roman I have not, the experimental --------- is it YB-40 supposed to be an heavy fighter killer equipped with over 17 mg and cannons. I may have the designation incorrect - circa 1943
     
  17. seesul

    seesul Active Member

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    yes, I know YB-40, they were too heavy and slow, lagged behind the formation...
     
  18. Erich

    Erich the old Sage
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    to be truthful Roman I think they were complete fantasy and never flew in action, a believed myth by single-engine LW fighter pilots during mid-war.

    by the way ~ nice signature ~

    E ~
     
  19. Micdrow

    Micdrow “Archive”
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    Here is a picture of a YB-40 for those that do not know what it looked like. Though if I remember right none of them had the 20mm tail cannon. Not to get off subject but some may find the bottom picture is of interest also. Dont remember where I got it but if I remeber right the B-17 was modified around 1949. It was a failure because of the movement of the wing which made the gunner more subsitable to air sickness.
     

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  20. HoHun

    HoHun Active Member

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    Hi Renrich,

    >Comis, I think you would find that a 50 BMG has a longer effective range than most 20 mms although not as destructive with a hit.

    I once asked Tony Williams (author of "Rapid Fire" and the "Flying Guns" books) for the formal definition of the term "maximum effective range". To my surprise, he pointed out that it was a rather poorly defined term without a clear way to arrive at the figures you usually find quoted under this headline.

    This has some relevance to the question of comparable effective ranges as we have to establish what it is what we'd like to compare :)

    I believe that the mention of "effectivness" in the term is decisive for a definition. It's not "efficiency", which would mean we'd have to compare effort spent to results achieved, but plain effect - results achieved regardless of the means.

    If I'd make an attempt at a definition, it would be something like:

    "Maximum effective range is the range at which a battery of guns, spending the full amount of ammunition that it has available, has a chance of destroying its target with a certain probability in an engagement of a certain duration."

    The probability mentioned in that definition should be comparatively low so that a target beyond maximum effective range could feel fairly safe from destruction - one might say 1% for example. (It's assumed that destructiveness decreases with increasing range.)

    This definition is interesting because it leads to a number of unusual conclusions:

    - Maximum effective range depends on

    ... the number of barrels installed,

    ... the amount of ammunition carried,

    ... the destructive power of the round,

    ... the durability of the target,

    ... the duration of the engagement.

    Of course, it also depends on the "traditional" characteristics of a gun, such as hit probability at the range in question, but the unusual aspect is that maximum effective range is not a property of the gun alone, but rather one of the entire weapons system. For example, if one has already used up half of one's original ammunition supply, the maximum effective range drops for the rest of the mission.

    I think this definition can be used to explain why a rear gunner can feel out-ranged by attacking fighters even if his rearward-firing 12.7 mm machine gun has a much flatter trajectory than the fighter's forward firing 20 mm cannon.

    (It can also be used to explain how Sorley arrived at the conclusion that the RAF fighters would need an eight-gun battery :)

    By the way, the Luftwaffe often used cannon in forward firing positions even when the rear guns were rifle-calibre only because combat experience showed that these guns would have only very short periods during which they could engage the enemy. The greater effect from cannon shells was more important than the added weight of the gun - this could be compensated by supplying it with a smaller number of (heavier) rounds.

    I figure the idea behind the B-17 nose cannon was similar!

    Regards,

    Henning (HoHun)
     
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