Permanent Order No. 66
  Note for all "FAT" and "Lut" Boats  
  Secret  1)  Success in the use of "FAT" and "Lut" depends, in particular, on the correct distance, i.e. the correct adjustment of the preliminary setting.  
  2)  The great danger when estimating distance is that the whole FAT will run short if the range is underestimated, that is the torpedo will deviate from course before reaching its target, and will completely fail to fulfil its purpose.  Overestimation of the range of FAT at least makes full use of the preliminary setting of the torpedo, and has therefore the same chance of success as in normal direct fire.  
  3)  Experience has shown that nearly all captains underestimate the distance at night, especially great distances, i.e. approximately 2 to 3000 meters or more.  Miscalculations occur easily when distance of several thousand metres are involved.  
  4)  If, therefore, the estimated range is unreliable, particularly in the case of great distances, the preliminary setting should always be chosen as too great rather than too small, or the torpedo should be fired directly, dispensing with FAT.  
  5)  Flotilla S.O.'s (Fl.) issue fresh instructions to all boats fitted with FAT before leaving harbour.  
                                                                                    C.C. U-boats  2242/FS  
                                                                                5th U-boat Flotilla G 794  
                                                                                            Translated by C/W Watson  
                                                                                                                  C/W Robertson  



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