A system for presenting steering information during visual flight (the head-up display): Part 1: the effect of location of the instrument display on combined instrument and visual flying

It is possible to distinguish between the (manual) control of aircraft based entirely on visual information from the external world and control entirely by looking at flight instruments. In fact, it is not always possible to separate these control modes absolutely, and it is desirable for the pilot to be able to attend both to the external visual world and to the flight instruments. He is thus required to carry out a (dual) task based on visual information presented concurrently in two fields. Three possible alternatives to the conventional location of flight instruments are considered in relation to the effect on performance of the pilot's dual task. It is shown in the laboratory that these three methods give equivalent performance capabilities for simplified tasks. But the particular method of bringing the two relevant fields of information together, by collimation, is preferabIe because the eyes are used in a natural way and because the infornmtion capacity of the instrument presentation is increased. With more elaborate tasks, it is shown that collimated presentation is superior to the conventional method because there is then negligible interference between the two types of task. The dual task capability is examined in real flight, with satisfactory results, but with some interference. An additional laboratory experiment is used to show that the information in both the external visual field and the collimated instrument presentation may together be interpreted critically. The overall effect of altering the location of the instrument presentation is to alter significantly the performance of the total visual task, without serious effect on component parts of the task (performed separately).