US Bomb, 100 lb Chemical, M47 Series, AN-M47 Series
The M47 series of bombs was developed to meet the requirements of the Air Force for a chemical bomb for "bombardment" purposes. It was a thin case bomb whose design and construction was such as to provide maximum efficiency after release from the bomb bay of the plane.
The 100 pound AN-M47 series included the AN-M47A2, which could be filled with H, WP, or gasoline gel; the M47A2 Gas, Chemical, Smoke, or Incendiary; the M47A1 Gas, Smoke, or Incendiary; the M47 Chemical; the AN-M743A Incendiary; and the AN-M47A4 Incendiary.
The bodies of these bombs were made of 1/32-inch sheet metal rolled and lap welded into a cylindrical shape eight inches in diameter. The nose was hemispherical and welded to the body as was the box type tail fin assembly that formed the tail taper of the bomb body. The burster well was screwed into the bomb body by means of pipe threads to make a gastight seal at the nose. It was held in place at the tail of the bomb body by an attached cone in the inner side of the fin assembly. It was internally threaded to receive a sleeve that had a groove in its lower portion to seat the fuze, which was pressed in place. The pipe threads were coated with either white lead-in-oil, red lead-in-oil, or varnish shellac before the burster was inserted to make a leak tight joint. Around the bomb body were two suspension bands 14 inches apart, which provided suspension lugs for horizontal suspension. One blade of the fixed box type tail assembly was in line with the suspension lug.
The M47A1 bomb was designed to replace the 100-pound M47. The 100-pound M47 was found to have too thin a wall section, and in handling and storage, it developed leaks due to corrosion and rough treatment. Consequently, the wall thickness was increased from 1/32 inch to 1/16 inch, and the case was protected by coating inside with acid proof black paint. However, H was still found to leak from the bomb case and the only standard fills were WP and PT.
The M47A2 bomb was designed to be able to receive the chemical filler H without leaking. It was coated on the inside with a special oil that proved, in theoretical tests, to be resistant to filler pressure having a resistance of 400-pound pressure. It did not differ from the 100-pound M47A1 in any appreciable way. It was found; however, that this bomb was also subject to leaking, but not to such an extent as its predecessors. H was still to be loaded into this bomb as a temporary emergency filler. It could also be filled with HD, WP, gelled gasoline, or NP.
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