The IPC-1 for multiple Navigation and Instrument Flying calculations. A circular 115mm diameter calculator. Circular Slide Rule side is that of the CRP-1 without a cursor. For calculation and conversion of Temperature, Time, Distance Volume, Altitude and Density Altitude, Speed, Weight, Fuel, Multiplication and Division, 1 in 60 rule etc. Procedure side incorporates a cursor with colour defined Wind Speed procedures. A simple movement of the cursor and procedure disc enables calculations to be completed for Head and Tail Wind components, correct Sector join procedures and turns for holding patterns etc