CONFIDENTIAL  
     
 
ANALYSIS OF ANTI-SUBMARINE ACTION BY AIRCRAFT
     
  Unit:  VB-107                Unit Report No. 15                Incident No. 5510  
     
  Base of Operations:  Ascension Island  
     
  Squadron No. of Aircraft:  VB-107-B-3  
     
  Aircraft Type:  PB4Y-1  
     
  Aircraft Commander:  Lt. (j.g.) Carrel Ivan Pinnell, USN  
     
  Location of Attack:  Latitude:    10°35' S  
                                 Longitude:  23°16'N  
     
  Date:  6 February, 1944                Time:  1029 GCT  
     
  1.  WEATHER  
     
 
        Clear with scattered cumulus clouds at 2000' and 15 mile visibility.  Wind 14 knots from 110°.  Moderate sea.
 
 
 
  2.  MISSION  
     
          Anti-submarine sweep.  
     
  3.  CONTACT AND APPROACH  
     
          While flying on regular anti-submarine sweep at 2600' through scattered cumulus clouds, a PB4Y-1 sighted a fully surfaced submarine bearing 075° relative at a range of 12 miles.  The weather was clear with 15 mile visibility.  Radar was not being used.  The plane immediately turned toward the U-boat notifying 107-B-10, another plane on the two-plane sweep, of the contact by voice radio.  
     
          When the plane was about two miles away from the U-boat a moderate amount of heavy AA fire was noticed about 100 yards ahead and slightly to port.  As an evasive measure the plane went into a power glide for a few seconds and then pulled up to 1000' when about 3/4 mile from the U-boat.  
     
  4.        ATTACK  
     
 

The pilot then began his attack run (TA 345°) in a 15° dive dropping six Mark 47 depth bombs set at 25' and spaced by intervalometer at about 65'.  The bombs were released from 100 feet while the submarine was still fully surfaced and making an apparent attempt to submerge.  The plane's bow gun opened fire on the conning tower on the run-in silencing the AA fire, and after the plane passed over the U-boat 400 rounds were fired from the tail gun.

  
     
                                                                                                           Enclosure (A) to Cominch  
                                                                                                           conf. serial __01161__  
                                                                                                           dated _5 April 1944.___  
 
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  CONFIDENTIAL
     
  5.        REPORTED POSITION OF EXPLOSIONS  
     
          The bomb explosions straddled the U-boat just forward of the conning tower between bombs #5 and 6.  
     
  6.        REPORTED EVIDENCE OF DAMAGE  
     
          The plane immediately climbed to 800' and circled for another attack with the remaining three Mark 47 depth bombs.  Upon looking back, the pilot saw that "the submarine had completely disappeared beneath the surface, but noticed a large disturbance and the conning tower a few feet under the water".  
     
  7.        SECOND ATTACK  
     
          Since the submarine was still clearly visible the pilot decided to drop his remaining three bombs.  He estimates they exploded "well ahead of the conning tower".  
     
  8.        SUBSEQUENT ACTIONS OF AIRCRAFT  
     
          When the plane circled back after the second attack, survivors were seen in the water.  A life raft was dropped and then the plane climbed to 1000' and circled for one hour until relieved by another plane, when it returned to base.  
     
  9.        COMMENTS  
 
 
          This was a well executed and swiftly delivered attack.  
     
          The following remarks of the Squadron Commander are concurred in:  "The use of evasive tactics by varying the glide angle during the approach and the accuracy with which the bombs were dropped exemplifies the skill of the pilot."  
     
          The report of the action was for the most part complete and well prepared, but neglected to give any details of the second attack and did not state accurately the location of any of the depth bomb explosions.  
     
          The Commanding Officer comments, ". . . . . it is of some significance that no personnel were observed on deck although anti-aircraft fire was encountered throughout the attack."  Prisoners of war state that the first string of explosions blew all the personnel from the conning tower and caused such great damage that the submarine sank immediately.  Undoubtedly the guns were manned during the plane's approach although the personnel were probably hidden from view behind the gun shields.  
     
                                                                                                           Enclosure (A) to Cominch  
                                                                                                           conf. serial __01161__  
                                                                                                           dated _5 April 1944.___  
     
 
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