THE FUTURE ROLE OF THE HUMAN PILOT

In an age where more and more of the aircraft control task is being devolved to automatic equipment (e. g. autopilots, blind landing systems, stability augmentation systems) the role of the human pilot will perhaps slowly change from that of an active element in the man/machine system to that of a manager overseeing the operation of the automatic controls. In this situation the pilot must monitor the performance of the equipment and be prepared to take over in the event of a failure. This philosophy quite rightly predicates that the human pilot should make the final decisions that determine the fate of the craft under his command. Moreover, human pilots are uniquely capable of assessing the meaning of complex data patterns which indicate the state of the vehicle under conditions that the automatic equipment has not been designed to handle (witness Apollo 13!). On the other hand, this modus o’perandi poses a serious problem for the pilot, for he is then expected to assume manual control of a vehicle at a critical time, following a system failure. If he is unable to make the transition from passive to active control with sufficient speed and precision, disaster could well be the result.

Thus it appears that if the pilot is expected to assume manual control at any time, the system should be so structured that he is either kept actively in the control loop at all times or is constantly made aware of the feel of the present aircraft configuration through some auxiliary task which he can practice on during critical phases of the flight. Research on the ability of pilots to control vehicles following stability augmentation system (SAS) failures has indicated that the resulting step change in vehicle dynamics can lead to an unstable man-machine system and loss of control (ref. 12.29). The mechanism behind this problem is as follows. With the SAS operating properly the vehicle dynamics are satisfactory and the pilot adopts a control technique to suit. The sudden SAS failure results in less satisfactory vehicle dynamics, which demands a much more concentrated effort on the part of the pilot in order to maintain control. Immediately following SAS failure, however, the pilot attempts to continue to employ the control technique he has been using previously with the SAS operative. This combination of man-machine dynamics can lead to an unstable system. If the system is to be fail-safe the pilot must be able to detect the change quickly and alter his control technique in time to recover from the upset. Consequently the advent of more automatic equipment does not diminish the need to study the role of man in the vehicle control loop. On the contrary, it generates new and more difficult problems requiring an even better understanding of the human pilot.