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. 

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. 

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. 

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. 

Hypoxia. A state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs. 

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. 

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. 

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. 

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. 

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. 

NAVAID.  Navigational aid. 

NM.  Nautical mile. 

NOTAM.  See Notice to Airmen. 

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. 

