Air Traffic Control Tower (ATCT) – A tower operated by the FAA at an airport to pro­vide for a safe, orderly and expeditious flow of traffic on and in the vicinity of the airport.

Auxiliary Power Unit (APU) – Equipment, either on-board an aircraft or on the ground, that is used to generate electric power for operating on-board equipment, or for engine starts, when the aircraft is at rest.

Avigation Easement – A right of overflight in the airspace above or in the vicinity of a par­ticular property including the right to create such noise or other effects as may result from the lawful operation of aircraft in such airspace and the right to remove any obstruc­tions to such overflight.

A-Weighted Sound (dBA) – A system for measuring sound energy that is designed to represent the response of the human ear to sound.  Energy at frequencies more readily de­tected by the human ear is more heavily weighted in the measurement, while frequencies less well detected are assigned lower weights.  A-weighted sound measurements are commonly used in studies where the human response to sound is the object of the analysis.

Day-Night Average Sound Level (DNL) – A noise measure used to describe the average sound level over a 24-hour period, typically an average day over the course of a year.  In computing DNL, an extra weight of 10 decibels is assigned to noise occurring between the hours of 10:00 p.m. and 7:00 a.m.

Daytime – For noise analyses, the hours from 7:00 a.m. to 10:00 p.m.

Decibel (db) – A measurement of sound energy or sound pressure.  The decibel scale is logarithmic.  A 10-decibel increase in sound is equal to a tenfold increase in sound energy.

Distance Measuring Equipment (DME) – A flight instrument that measures the line-of-sight distance of an aircraft from a particular point in nautical miles.

Downwind Path - A flight track followed by aircraft that are approaching the airport in the opposite direction from their final approach as such aircraft maneuver past the airport and then into position to make their turns onto final approach.

Environmental Impact Statement (EIS) – The final Environmental Impact Statement, dated November 2001, that was prepared by the FAA with respect to runway 5L/23R, the FedEx cargo facility and associated developments at the airport.  The EIS reviewed the anticipated environmental impacts of the project, including aircraft noise.

FAA – The Federal Aviation Administration.

Federal Aviation Regulations (FAR) – The body of Federal regulations relating to avia­tion.  Published as Title 14 of the Code of Federal Regulations.

Final Approach – A flight path for arriving aircraft that follows the extended runway centerline.

Geographic Information Systems (GIS) – An information system that is designed for storing, integrating, manipulating, analyzing, and displaying data referenced by spatial or geographic coordinates.

Glide Slope – The electronic signal on which arriving aircraft descend for their arrival runway under ILS approach procedures.

Ground Power Unit (GPU) – Equipment on the ground that is used to generate electric power for operating on-board equipment, or for engine starts, when the aircraft is at rest.

Head-to-Head Operations – The proposed operational procedure for the FedEx hub, to be followed when allowed by weather conditions, in which aircraft arrive on Runways 5R and 5L and subsequently depart on Runways 23L and 23R.

Incompatible Use – The use of a tract or parcel of land which, under the guidelines set forth in FAR Part 150, is not compatible with the noise exposure at that location.

Instrument Flight Rules (IFR) – That portion of the Federal Aviation Regulations (FAR Part 91) specifying the procedures to be used by aircraft during flight in instrument meteorologi­cal conditions.  These procedures may also be used under visual conditions and provide for positive control by ATC.  (See also VFR.)

Instrument Landing System (ILS) – An electronic system which helps to guide pilots to runways for landing during periods of limited visibility or adverse weather.

Integrated Noise Model (INM) – A computer model developed, updated and maintained by the FAA to calculate the noise exposure generated by aircraft operations at an airport.

Leq – Equivalent Sound Level.  The steady A-weighted sound level over any specified period of time (not necessarily 24 hours) that has the same acoustic energy as the fluctu­ating noise during that period (with no consideration of nighttime weighting).  It is a measure of cumulative acoustical energy.  Because the time interval may vary, it should be specified by a subscript (such as Leq 8 for an 8-hour exposure to noise).

Lmax – The highest A-weighted sound level occurring during a noise event.

Mean Sea Level (MSL) – The average height of the surface of the sea for all stages of the tide; used as a reference for elevations.

Nautical Mile – A measure of distance equal to one minute of arc on the earth's surface (6,076.1 feet or 1,852 meters).

New Stage 3 Aircraft – Aircraft that met the Stage 3 requirements of FAR Part 36 at the time of their original manufacture.

Nighttime – For noise analyses, the hours from 10:00 p.m. to 7:00 a.m.

Noise Contours – Lines on a map that connect points of equal noise exposure.

Noise Compatibility Program (NCP) – A program developed in accordance with FAR Part 150 that contains provisions for the abatement of aircraft noise through aircraft op­erating procedures, air traffic control procedures, or airport facility modifications.  It also includes provisions for land use compatibility planning and may include actions to miti­gate the impact of noise on incompatible land uses and recommendations for amending local land use con­trols to affect future land uses and development.

Noise Exposure Map (NEM) – A scaled, geographic depiction of an airport, its noise contours and surrounding area developed in accordance with FAR Part 150, and the accompanying documentation required by FAR Part 150.

One-Way Operations - A procedure in which aircraft arrive and depart on the same run­way heading.

Operation – A takeoff or landing by an aircraft.

Original Operations Forecast – See Section 1.2 of the Introduction to this Part 150 Study.

Profile – The position of the aircraft during an approach or departure in terms of altitude above the runway and distance from the runway end.

Record of Decision (ROD) – The Record of Decision issued by the FAA on December 31, 2001, based on the EIS, approving the federal actions required for the construction and operation of runway 5L/23R, the FedEx cargo facility and associated developments.

Retrofitted Stage 3 Aircraft – 727 aircraft and all other aircraft that met the Stage 3 re­quirements of FAR Part 36 through retrofit or engine replacement.

Sound Exposure Level (SEL) – A standardized measure of a single sound event, expressed in A-weighted decibels, that takes into account all sound above a specified threshold set at least 10 decibels below the maximum level.  All sound energy in the event is integrated over one second.

Updated Operations Forecast – See Section 1.2 of the Introduction to this Part 150 Study.

User Group  – The six categories of aircraft operations at the airport.  Air Carrier (larger aircraft) and Commuter (smaller aircraft) carry passengers for a fee.  Cargo (FedEx and Other) carry only cargo for a fee.  General Aviation is private aircraft of all types.  Military is military aircraft of all types.

Visual Approach – An approach conducted under Visual Flight Rules (VFR).

Visual Flight Rules (VFR) – Rules and procedures specified in FAR Part 91 for aircraft op­erations under visual conditions.  Aircraft operations under VFR are not generally under positive control by ATC.

Yearly Day-Night Average Sound Level – See DNL.

Abbreviations