Man-Machine Systems and Interface. Aircraft Computer Visual Verification

An aircraft is an example of a man-machine system. Other examples are automobiles and boats. These machines have the common attribute of being driven by a human. Landau (1) defines man-machine systems as sets of manually performed and machine-performed functions, operated in conjunction to perform an operation.

The aircraft computer is constantly changing the role of the human in the aircraft machine. The earliest aircraft required the constant attention of the pilot. Improved flight control devices allowed the pilot freedom for leisure or for other tasks. Modern aircraft computers have continued the trend of making the aircraft more the machine and less the man system.

Human Factors of Aircraft Computers. Human factors is the science of optimal conditions for human comfort and health in the human environment. The human factors of aircraft computers include the positioning of the controls and displays associated with the aircrew’s workloads. They also provide monitoring and adjustment of the aircraft human environment, including temperature, oxygen level, and cabin pressure.

Man-Machine Interface. The man-machine interface is the place where man’s interactions with the aircraft coordinate with the machine functionality of the aircraft. An example of a man-machine interface is the API, which is where a person provides inputs to and receives outputs from computers. These types of interfaces include keyboards (with standard ASCII character representation), mouse pads, dials, switches, and many varieties of monitors.

A significant interface in aircraft comprises their associated controls and displays, which provide access to the flight controls, the sensor suite, the environmental conditions, and the aircraft diagnostics through the aircraft’s central computer. Control sticks, buttons, switches, and displays are designed based on human standards and requirements such as seat height, lighting, accessibility, and ease of use.

Voice-Activated Systems. Voice-activated systems are interfaces to aircraft controls that recognize and respond to aircrew’s verbal instructions. A voice-activated input provides multiple input possibilities beyond the limited capabilities of hands and feet. Voice-activated systems have specified sets of word commands and are trained to recognize a specific operator’s voice.

Aircraft Computer Visual Verification. Visual verification is the process of physically verifying (through sight) the correct aircraft response to environmental stimuli. This visual verification is often a testing requirement. It is usually done through the acceptance test procedure (ATP) and visual inspections ofdisplays through a checklist of system and subsystem inputs. Until recently, visual verification has been a requirement for pilots, who have desired the capability to see every possibility that their aircraft might encounter.

This requirement is becoming increasingly difficult to implement because of the growing complexity and workload of the aircraft’s computers and their associated controls and displays. In the late 1980s to early 1990s, it required about 2 weeks to visually verify the suite of an advanced fighter system’s avionics. This verification can no longer be accomplished at all with current verification and validation techniques. Several months would be required to achieve some level of confidence that today’s modern fighters are flight-safe.

Air Traffic Control. Air traffic control is the profession of monitoring and controlling aircraft traffic through an interconnected ground-based communication and radar system. Perry (23) describes the present capabilities and problems in air traffic control. He also discusses the future requirements for this very necessary public service. Air traffic controllers view sophisticated displays, which track multiple aircraft variables such as position, altitude, velocity, and heading.

Air traffic control computers review these variables and give the controllers continuous knowledge of the status of each aircraft. These computers continuously update and display the aircraft in the ground-based radar range. When potential emergency situations, such as collision, develop, the computer highlights the involved aircraft on the displays, with plenty of lead time for the controller to correct each aircraft’s position.