Design Con 2015

Design hindsight from the tail-gunner position of a WWII bomber--Part two

Mort Hans -January 04, 2013

Editor's note: This part two of the two part article explains what went wrong in a seemingly good design. Take note designers, Mort Hans describes some of the pitfalls and things to watch out for in any design. Please be sure to read Part one for the introduction details.

The P-4 Computer

Acquisition & Identification

The P-4 computer and two periscopes were donated to the museum in the Spring of 2004 by Mr. Saul Leyton of Manhasset, NY without documentation or manuals, other than an inspection certification tag for one of the periscopes signed by a Sperry inspector.  The tag certifies that the periscope passed mechanical inspection and is dated June 21, 1943.  The periscope is identified as Part No. 647634 and Serial No. P4-88.  Neither periscope has a nameplate. The computer has an attached nameplate with the following information:  Sperry Gyroscope Company, Inc., Brooklyn, NY, P-4 Computer, Part 647823, Ser. 352, Cont(ract) 26160, Inspr AN167.

The third XB-29, which crashed in June 1943, was already equipped with the GE system so that the Sperry contract would logically have been cancelled before that date.  The Army Air Force Inspection Team didn’t recommend changes to the XB-32 armament until November 1943 so that Sperry in June of 1943 would have still been under contract to supply the Central Station Computer System for the XB-32 bomber. 

The first flight of the second XB-32 was on July 2, 1943, less than two weeks after the date on the inspection certificate so that based on both the excellent condition of the museum’s computer and the periscopes as well as the short interval between the inspection date and the second XB-32’s first flight, it is unlikely that the museum’s computer and periscopes were ever installed on board an aircraft.  More likely they were intended for the third XB-32 whose twin tail configuration was changed and whose armament system was also changed to turrets built by Martin and to Sperry ball turrets with 50 cal machine guns, probably with the “K” series automatic computing sights.

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