The effect of the roll index (sky pointer) on roll reversal errors

This study examines the effect of the placement of the roll index (also known as the "sky pointer") in artificial horizons on roll reversal errors. Roll reversal errors (steering the wrong way, i.e. making a bank angle steeper rather than recovering from it) have been known to contribute to loss of control accidents in aviation. We assessed the roll recovery performance of 13 commercial pilots on a total of 390 trials, using an experimental set-up that tested three different sky pointer configurations: one commercial (roll index on top, slaved to the horizon), one General Aviation (roll index on top, slaved to the aircraft), and one military (roll index at bottom, slaved to the horizon). Performance on the commercial artificial horizon was almost five times worse than on the other two. The results point to the primacy of the control-display compatibility principle as mechanism for producing the great performance difference, and raises serious safety concerns with respect to commercial-type artificial horizons now being introduced (via LCD screens) to General Aviation aircraft.