RAF ICAN Nav Comp - 6B/180 MK3 D*

A pristine RAF Navigation Aid for height, drift, airspeed etc, for a Navigator or Pilot with leg straps rather than pinpoints for a desk attachment, it provided a rapid means of solving problems involving the effect of wind on the track and ground speed of an aeroplane. These, together with interception problems, are solved geographically by constructing a vector triangle. Models are calibrated for either isothermal or I.C.A.N. The model letter suffix * indicates that the circular scale is rotated by grasping it. In the first configurations of the Mk III the scale was rotated by a knob at the side of the instrument, but this probably proved too complicated when wearing flying gloves at night. Models A,B,C and D were designed to be strapped onto the leg. A&B was for slower speeds, C&D for higher speeds. In each case the first (A & C) were based on an isothermal model of atmosphere and the second (B & D) on an ICAN atmosphere. This computor was worn on the knee of the user by two straps and has a Broad Arrow marking, retaining its original "Bound with any paper that is available" notebook. The "A M & Crown" was replaced by the Broad Arrow in 1944, when the Ministry of Defence was created to oversee the armed forces of Great Britain. Leg straps were dispensed with as standard with the introduction of the Model F. Only models A,B,C,and D. appear in the 1944 RAF manual of navigation; which, together with the other clues, suggests the date of this example is indeed 1944.  This MK3 D*  6B/180 is in wonderful original condition, extremely rare and very few are found as intact as this one.  
 
As found in the IWM.