Plath manual navigation computer

During WW2 the Luftwaffe used assorted mechanical and electrical radio directional aids, primitive radars and precision target detection equipment. Flight personnel were given basic training in manual navigation and map reading. 

Personnel who had elected to, or had been chosen to become flight observers undertook further blind-flight and navigational training. Along with the mechanical and electrical radio directional aids, two different models of manual flight navigation computers to assist in navigational calculations which were basically circular slide rules. 

From the auction listing;

 The flight navigation computer device consists of discs roughly 15 cm in diameter, dual sided, multi piece, molded black and white bakelite construction attached with aluminum rivets. One side features a static, molded black bakelite outer circle with impressed white, 360 degree numerical compass markings with the four major cardinal directional points of N, S, O and W (North, South, East and West) and the four intercardinal points of NO, SO SW and NW. (Northeast, Southeast, Southwest & Northwest) This outer circle encompasses a movable, molded white bakelite inner circle which also has impressed black and red 360 degree numerical compass markings, and the outline of an aircraft with directional arrow. Mounted on top of both of these circles is a clear moulded moveable arm with an additional blue directional arrow. The inner circle and arm can both be turned to align with the outer circle to determine the approximate computations. 

The other side of the computer features moulded white bakelite movable inner and outer circles with a static moulded black bakelite circular ring in between the two. The central, movable circle has the addition of a moulded clear bakelite movable arm with a directional arrow. All three circles also have impressed, black, red and white, numerical degrees, temperature and kilometer markings. Both the inner and outer circles and the arm can be turned to align with the static, in-between circle to determine the appropriate computations. The computer also has impressed green script which includes the model designation. "Dreieckrechner Baumuster DR2", Computer Construction Model DR2) "Gerat Nr. 127 107 B". ( Equipment number 127 107 B) "Anforderz. Fl 23825. ( Flight Requisition number FL 23825). "Hersteler. Dennert & Pape Hamburg, Altona". (Manufacturer and Location),and "Fertigstellung Sept 1940 "(Completion date Sept 1940).

The whole system is a mystery to me, how any aircraft could navigate and return to their base after a mission is a thing of marvel to me and although I did learn the basics of a slide rule in high school, how the two can be combined to make an effective workable tool is amazing. 

 More here. 

Lots of detail here. 

History of the Plath company here.

Of note; the Luftwaffe used a specific Map, Degree Network Reference System (Gradnetzmedeverfahren) navigation system system that was based on the Greenwich longitude/latitude degree system to pointpoint a precise location. The Luftwaffe's Gradnetzmedeverfahren differed slightly from the systems used by the Army and Navy.

Thanks, Rolf!