Grizzled bush pilot Apeneck Sweeney's converted Swordfish aircraft has a true air speed of 150 knots and an estimated heading of 45°. The Swordfish is also being buffeted by a headwind of 40 knots from a bearing of 25°. What is the actual ground speed and course of the Swordfish?
The course and ground speed are equal to the sum of the instrument vector (150 knots, 45°) and the wind vector (-40 knots, -25°), but since the wind vector opposes the instrument vector the result is a vector subtraction. (North becomes the x-coordinate so that the problem corresponds with navigational convention.)
The vectors are converted to rectangular coordinates and summed using the g and D keys. Using the f g key the result of the vector arithmetic is recalled from storage registers R.₁ (Σx) and R.₃ (Σy) and placed in the X and Y registers. The new summed rectangular coordinates are then converted back to polar coordinates to give the vector of the actual ground speed and course, (113.24 knots, 51.94°).
To run, enter ¦ 0.