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AIRCRAFT-LAUNCHED SMOKE AND FLAME MARKING DEVICES - 14313_113
REVIEW NUMBER 2 ANSWERS - 14313_115

Aviation Ordinanceman - Aviation theories and other practices
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MK 25 MODS 2 AND 3 MARINE LOCATION MARKER The Mk 25 Mods 2 and 3 (fig. 4-7) marine location markers are launched from aircraft or surface craft. They are launched from aircraft to provide day or night reference points for marking the course of enemy submarines in antisubmarine warfare operations. They are suitable for any type of sea-surface reference-point marking that calls for both smoke and flame for a period of 10 to 20 minutes. Mods 2 and 3 function identically. The only significant difference is that Mod 2 contains two seawater-activated batteries and two related squibs while Mod 3 contains a single battery and squib. Physical Description The  Mk  25  marker  consists  of  a  cylindrical  outer tube about 18.5 inches long and 2.9 inches in diameter. A valve assembly is fitted into the projecting chimney at  the  marker's  nose  end.  The  smoke  and  flame  are emitted  from  this  opening.  At  the  opposite  end  is  a heavier  aluminum  base  assembly  to  which  the  outer tube is crimped. The heavy base end causes the marker to float in the water with the chimney out of the water and the base in the water. Within   the   base   assembly   is   a   Mk   72   Mod   0 seawater-activated battery (two batteries in the Mod 2). The battery is shielded from water contact by two plugs fitted into 1/2-inch holes on two opposite sides of the base  assembly.  A  rigid  cover  (arming  plate),  held  in place by a retainer ring, is recessed into the base end. An arrow in the center of the arming plate indicates its safe or armed position. The words SAFE and ARMED are stamped into the base rim. Also, a machined notch in the rim at the armed position helps during night use. When   the   arming   plate   is   in   the   safe   position,   it physically  blocks  the  base  plugs  internally  to  prevent them  from  being  accidentally  pushed  in.  When  in  the armed position, the arming plate no longer blocks the base   plugs,   allowing   them   to   be   pushed   in   at   the appropriate time. A black rubber G-ring circles the base assembly   approximately   1/4   inch   from   the   crimp, which holds the outer case. Functional Description To activate the seawater battery, the base plugs are pushed  in  before  the  marker  is  actually  launched.  An electric squib ignites the marker, and the seawater-activated   battery   (two   batteries   and   two squibs  in  Mod  2)  supplies  power.  When  the  marker enters the water, seawater enters the battery cavity and serves as an electrolyte, causing the battery to produce a current  that  activates  the  squib.  The  squib  ignites  the starter mix, which, in turn, ignites the red phosphorous pyrotechnic composition. Gas buildup forces the valve assembly  from  the  chimney  in  the  nose,  and  yellow flame   and   white   smoke   are   emitted.   Burning   time averages 13.5 to 18.5 minutes. Although this marker is normally  used  in  seawater,  it  can  be  used  in  inland bodies of fresh water by using table salt and following the   procedures   outlined   in   Pyrotechnic, Screening, Marking, and Countermeasure Devices,   NAVSEA SW050-AB-MMA-010/NAVAIR 11-15-7. 4-8 Figure 4-7.—Mk 25 marine location marker.







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