Probable Cause #45: Out of Position
This article originally appeared in IFR Refresher, Dec. 2006.It's not too difficult to understand the theory of the ILS approach. The pilot is required to fly a horizontal radio beam while referring to a cockpit indicator that tells him whether he is left or right of the course. At the same time he must fly a vertical radio beam by looking at a second needle in the same instrument that will inform him of his position above or below it. When the weather is good and there is plenty of outside reference to the ground it can be very easy to fly. But take the weather down to IFR minimums in fog and the pilot's workload increases dramatically. Now, his eyes must dance across the instrument panel taking pictures of what each of the flight and navigation instruments is telling him. His brain must meld all of the images into a coherent mental reference of where the airplane is relative to the approach he is flying. Then, he must do it again and again and again. Flying a good approach requires constant practice and the pilot must be current and proficient at all phases of instrument flight. After all, flying an approach to minimums is the most demanding instrument flying a pilot is likely to do in normal, everyday operations. If he is lacking any of the basic skills, he will have problems with the ILS.