Global Navigation Satellite System (GNSS).  Satellite  navigation system that provides autonomous geospatial  positioning with global coverage. It allows small electronic  receivers to determine their location (longitude, latitude, and  altitude) to within a few meters using time signals transmitted  along a line of sight by radio from satellites.  Instrument flight rules (IFR).  Rules and regulations  established by the Federal Aviation Administration to govern  flight under conditions in which flight by outside visual  reference is not safe. IFR flight depends upon flying by  reference to instruments in the flight deck, and navigation is  accomplished by reference to electronic signals. Instrument landing system (ILS).  An electronic system that  provides both horizontal and vertical guidance to a specific  runway, used to execute a precision instrument approach  procedure. Global positioning system (GPS).  Navigation system  that uses satellite rather than ground-based transmitters for  location information. GLS.  See GPS Landing System. GNSS.  See Global Navigation Satellite System. GPS.  See Global Positioning System. Hazard.  A present condition, event, object, or circumstance  that could lead to or contribute to an unplanned or undesired  event, such as an accident. It is a source of danger. For  example, a nick in the propeller represents a hazard. Instrument meteorological conditions (IMC). Meteorological conditions expressed in terms of visibility,  distance from clouds, and ceiling less than the minimums  specified for visual meteorological conditions, requiring  operations to be conducted under IFR. Judgment.  The mental process of recognizing and analyzing  all pertinent information in a particular situation, a rational  evaluation of alternative actions in response to it, and a timely  decision on which action to take. Mean sea level.  The average height of the surface of the  sea at a particular location for all stages of the tide over a  19-year period.  Hazardous attitudes.  Five aeronautical decision-making  attitudes that may contribute to poor pilot judgment:  anti-authority, impulsivity, invulnerability, macho, and  resignation. Hazardous Inflight Weather Advisory Service (HIWAS).  Service providing recorded weather forecasts broadcast to  airborne pilots over selected VORs. MFD.  See multifunction display. MSL.  See mean sea level. Multifunction display (MFD).  Small screen (CRT or LCD)  in an aircraft that can be used to display information to the  pilot in numerous configurable ways. Often an MFD will be  used in concert with a primary flight display. Human behavior.  The product of factors that cause people  to act in predictable ways. Human factors.  A multidisciplinary field encompassing the  behavioral and social sciences, engineering, and physiology,  to consider the variables that influence individual and  crew performance for the purpose of optimizing human  performance and reducing errors. National Transportation Safety Board (NTSB).  A United  States Government independent organization responsible for  investigations of accidents involving aviation, highways,  waterways, pipelines, and railroads in the United States.  NTSB is charged by congress to investigate every civil  aviation accident in the United States. Hypoxia.  A state of oxygen deficiency in the body sufficient  to impair functions of the brain and other organs. NAVAID.  Navigational aid. NM.  Nautical mile. NOTAM.  See Notice to Airmen. Identified risk.  Risk that has been determined through  various analysis techniques. The first task of system safety is  to identify, within practical limitations, all possible risks.  IFR.  See instrument flight rules. IMC.  See instrument meteorological conditions. Notice to Airmen (NOTAM).  A notice filed with an aviation  authority to alert aircraft pilots of any hazards en route or at  a specific location. The authority in turn provides means of  disseminating relevant NOTAMs to pilots. G-3