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"Aimable Frag Clusters" -- munitions

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AlanStarcher
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2012/03/01 19:19:14 (permalink)
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"Aimable Frag Clusters" -- munitions

While researching 308th BG records, I've located the first reference to a new weapon employed by B-24s operating out of bases in China.
 
On December 23, 1944, two B-24s set out on a mission to "attack and harass motor convoys along the Siang River Valley."   Each plane was loaded with 10 x 500 lb.  "aimable frag clusters."
 
A notation penciled in above the typewritten line reads "M18  (M69)  Inc. 500 Lb." which was probably added by a clerk after the report was written, as there are several pencil notes tallying the bomb tonnage and numbers and types used on each mission report.   Four truck convoys were attacked but the results of the bombing were undetermined as the target areas were partially covered by overcast.
 
Referencing a modeling magazine article that details the various bomb types, I located a listing of a "M69 6-lb. incendiary bomb," used in the '40s and '50s.  The small units were only deployed in clusters;  the M19 aimable cluster unit contained 38 M69s and weighed in at 500 pounds.  The penciled-in note is likely an error and the bomb unit used was the M19.  The small bomb unit is an incendiary explosive rather than a fragmentation bomb -- the notes on the bomb type state that its designation varies depending on the ingredients of the explosive charge.  The M69X contained a half-pound of Tetryl in its formulation "to discourage firefighting" and the 500-lb. cluster unit was then named M21.  

 

 
-- Alan
Nephew of Kenneth S. Starcher, B-24 Liberator pilot 42-73309 "Trouble Maker," 308th BG/373rd BS, 14th AF, CBI
(KNB May 28, 1944 - Kweilin, China)

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    tonystro
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/02 00:15:03 (permalink)
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    Alan,
     
    I can't help with the annotated numbers.  I did find this information on "aimable 500-lb cluster" --
     
    Aimable cluster M17 consisted of an adapter, M10, and 110 4-pound bombs. The total weight was 490 pounds. The adapter was similar to the quick-opening type, but was streamlined by being enclosed in a cylindrical case, and by attachment of a tail fin and round nose. A time fuze adjustable from six to ninety-three seconds regulated the distance that the cluster fell before opening. The fuze detonated a strand of primacord, enclosed in a long tube running the length of the cluster, and the exploding primacord burst the steel straps binding the cluster. Later, on recommendation of the Joint Aircraft Committee, the CWS modified the adapter so that the cluster could be used on British and Navy aircraft.
    The modified cluster, designated as Model AN-M17A1, was used throughout the remainder of the war.
     
    (edited to adjust font for numeral '1')
    post edited by tonystro - 2012/03/02 15:24:48

    Tony Strotman, MSgt (ret.), USAF
    Son of T/Sgt Francis E. Strotman, Engineer-Gunner,
    491st Bm Sq / 341st Bm Gp (M), Yangkai, China
    "USAAF in CBI Tribute" http://www.usaaf-in-cbi.com
    omega7
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/02 14:42:34 (permalink)
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    > A notation penciled in above the typewritten line reads "M18  (M69)  Inc. 500 Lb." which was probably added by a clerk after the report was written………..The penciled-in note is likely an error and the bomb unit used was the M19.
     
    The penciled notation is likely accurate.
     
    M18’s were initially used, but unsatisfactory reports from combat theaters were found to be factual when Chemical Warfare Service retested the M18 aimable incendiary cluster at the Dugway Proving Grounds.  The majority of these field squawks centered on the M18 cluster’s problematic opening.  Testing revealed an average 3 percent airburst ignition of a considerable number of individual M69 bombs caused from the shock of cluster opening, while another 6 percent of the clusters failed to open at all.
     
    The resultant redesign included a new tail cone in order to accommodate a redundant fuze.  This twin fuze arrangement made cluster opening practically fail-safe.  Assigned test nomenclature for the redesigned cluster was E46, and while it met the 59 inch length requirement dictated by the forty 500 pound bomb stations of B-29 and B-32 airplanes, its weight increased 75 pounds per cluster over that of the existing M18’s, resulting in a corresponding decrease in the host airplane’s range/loiter. Chemical Warfare Service accepted and standardized this redesign, and the E46 went on to become the widely used M19 Incendiary Cluster.
    -ADRIAN   Ω07
     
     
    ramc181
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/02 15:11:13 (permalink)
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    T4E4 aka AN-M26 500lb Fragmentation Cluster (20 x M41 frag bombs) perhaps?
     
    I have seen photos of these in their shipping drums at AAF bases in China, so it does put them in theatre at the time.
     
    All the best,
    PB

    Paul Bellamy 

    401st BG Association
    401st BG Historical Society (UK)
    1st Air Division HQ Historical Society (UK)
    Alconbury ARG/AIX Archive
    AlanStarcher
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/02 23:47:12 (permalink)
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    tonystro

    Alan,

    I can't help with the annotated numbers.  I did find this information on "aimable 500-lb cluster" --  {snip} The modified cluster, designated as Model AN-M17A1, was used throughout the remainder of the war.

    (edited to adjust font for numeral '1')

    Actually, that was a great help, Tony.  As I continued on through the mission reports, I came across more references to the "M18 incendiary cluster" in reports from January through April 1945 -- the M17 makes its first appearance on Mission 518, 30 January 1945 raid on the Hankow docks.   By the 10 April 1945 mission, no. 552, it was being listed in the report by its proper name, "M-17-A-1," an aimable cluster bomb containing 110 of the 4-lb. M50 incendiary bombs.
     


    Photo  © Copyright Harrington Aviation Museum Society 2001 - 6
    Website: http://www.harringtonmuseum.org.uk/CarpetbaggerMuseumHomePage.htm
     
     
    I had to search a bit harder for the M18 and located a few references to B-29s carrying this particular munition, listed as a 350-lb. M-18 IB cluster. 
     
    omega7The penciled notation is likely accurate.

    M18’s were initially used, but unsatisfactory reports from combat theaters were found to be factual ... {snip}  ... and the E46 went on to become the widely used M19 Incendiary Cluster.
    -ADRIAN Ω07

     
    And that was the missing piece of the puzzle.  You can find all kinds of references to the M19 cluster munition (containing the M69 subunit) but not the M18, except for those early mission report excerpts. 
     
    -- Alan
     
    [EDIT to add copyright and web source of graphic]
      
      
      
     
    post edited by AlanStarcher - 2012/03/03 08:47:45

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    butterfly
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/05 16:25:03 (permalink)
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    Interesting thread. I looked in the manual (TM 9-1980   Bombs for Aircraft   November 1944)  and there is no mention of the M18, references go as far as the M17 shown above.
    The M69 is a 6lb incendiary oil bomb. The AN- M13 and AN-M17 were both 500lb aimiable clusters for the M69 - I think the printing of this manual is too early to include any reference of an M18 container and Adrian may have the answer in his earlier post.
    I will look at other references to see if I can dig out any more info.
     
    regards Kev
    omega7
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/06 16:58:26 (permalink)
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    >...........and AN-M17 were both 500lb aimiable clusters for the M69..............
     
    I was left with the impression that the M-17 cluster series contained 110 AN/M-50 magnesium bombs on an M10 adapter.
     
    During WWII, magnesium became a strategic material used chiefly for lightweight forgings and castings used in aircraft components.  Most industrial belligerents entered the war years with poorly developed magnesium industries.  With the rapid expansion of their air arms, they began to encroach on their magnesium stockpile reserves by the end of 1943, resulting in the quest for alternative incendiary media that led the U.S. to the M69 “oil bomb” used in the M18/M19 clusters.  -Adrian   Ω7
    AlanStarcher
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/07 07:17:06 (permalink)
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    butterfly
    The AN- M13 and AN-M17 were both 500lb aimiable clusters for the M69 - I think the printing of this manual is too early to include any reference of an M18 container and Adrian may have the answer in his earlier post.

     
    And yet another piece falls into place! 
     
    During a mission preceding the December 1944 sortie where I found mention of the M-18, some aircraft carried "M-13 500-lb. incendiaries" in addition to the M-18s on a bombing raid on Hankow on September 22, 1944, Mission No. 252.  The report states that the 23 planes that reached the target "dropped their mixed load of bombs consisting of about 80% incendiaries and 20% frag clusters."   The planes on this mission carried "M-26 500-lb. frag clusters, M-47 100-lb. incendiaries, M-18 500-lb. incendiary clusters and M-13 500-lb. incendiaries" (clusters).  Three aircraft also carried M-46 "photo flash bombs" on this night mission.

    Eleven M-18s were returned when their aircraft turned back; these may have been part of the munitions used by the two planes that attacked the convoys on December 24.
     
    -- Alan
    post edited by AlanStarcher - 2012/03/07 09:15:33
    AlanStarcher
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/07 09:04:53 (permalink)
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    Double post
     
    25Kingman49
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/12 01:14:06 (permalink)
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    Although it looks as though the "M-17-A-1," inquiry has been solved.  Here are a few additional ordnance sites for the tool kit. The first two would be my favorites and the second two give some good individual bomb stencil identifications.
    [1] http://www.ibiblio.org/hy...ef/TM/pdfs/TM3-400.pdf 
    [2] http://www.468thbombgroup...p;tabid=36&mid=467 
    [3] http://www.ammunitionpage...egories.php?cat_id=167 
    [4] This is an incomplete and brief introduction to US bombs but an ...  The attached photos are of [1] B-29 mission using M-69's [2] M-69 detail [3] M-69's on Tinian.
    Scott M.

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    25Kingman49
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    Re:"Aimable Frag Clusters" -- munitions 2012/03/12 04:31:22 (permalink)
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    Video of M-69 production and test, if you’re a B-25 fan you’ll like this film.
    Scott M.

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