Optical illusion.  A misleading visual image. For the  purpose of this handbook, the term refers to the brain’s  misinterpretation of features on the ground associated  with landing, which causes a pilot to misread the spatial  relationships between the aircraft and the runway. NTSB.  See National Transportation Safety Board. Primary flight display (PFD).  A display that provides  increased situational awareness to the pilot by replacing the  traditional six instruments used for instrument flight with  an easy-to-scan display that provides the horizon, airspeed,  altitude, vertical speed, trend, trim, and rate of turn among  other key relevant indications. Residual risk.  Risk left over after system safety efforts  have been fully employed. It is not necessarily the same as  acceptable risk. Residual risk is the sum of acceptable risk  and unidentified risk. This is the total risk passed on to the  user. Risk.  The future impact of a hazard that is not eliminated  or controlled. Risk assessment.  An approach to managing uncertainty.  Risk assessment is a quantitative value assigned to a task,  action, or event. Orientation.  Awareness of the position of the aircraft and of  oneself in relation to a specific reference point. Personality.  The embodiment of personal traits and  characteristics of an individual that are set at a very early  age and extremely resistant to change. PFD.  See primary flight display. PIC.  See pilot in command. Pilotage.  Navigation by visual reference to landmarks. Pilot error.  An accident in which an action or decision made  by the pilot was the cause or a contributing factor that led  to the accident. Pilot in command (PIC).  The pilot responsible for the  operation and safety of an aircraft. Pilot report (PIREP).  Report of meteorological phenomena  encountered by aircraft. Pilot’s Operating Handbook/Airplane Flight Manual  (POH/AFM).  Published by the airframe manufacturer, FAA- approved documents that list the operating conditions for a  particular model of aircraft. PIREP.  See pilot report. POH/AFM.  See Pilot’s Operating Handbook/Airplane  Flight Manual. Risk elements.  There are four fundamental risk elements  in aviation: the pilot, the aircraft, the environment, and the  external pressures that comprise any given aviation situation. Risk management.  The part of the decision-making process  which relies on situational awareness, problem recognition,  and good judgment to reduce risks associated with each  flight. Single-pilot resource management (SRM).  The ability  for a pilot to manage all resources effectively to ensure the  outcome of the flight is successful. Situational awareness.  Pilot knowledge of where the  aircraft is in regard to location, air traffic control, weather,  regulations, aircraft status, and other factors that may affect  flight. Spatial disorientation.  The state of confusion due to  misleading information being sent to the brain from various  sensory organs, resulting in a lack of awareness of the aircraft  position in relation to a specific reference point. SRM.  See single-pilot resource management. Stall.  A rapid decrease in lift caused by the separation of  airflow from the wing’s surface, brought on by exceeding  the critical angle of attack. A stall can occur at any pitch  attitude or airspeed. Stress.  The body’s response to demands placed upon it. Poor judgment chain.  A series of mistakes that may lead  to an accident or incident. Two basic principles generally  associated with the creation of a poor judgment chain are: (1) one bad decision often leads to another; and (2) as a string  of bad decisions grows, it reduces the number of subsequent  alternatives for continued safe flight. ADM is intended to  break the poor judgment chain before it can cause an accident  or incident.  G-4