Boston Logan Airport Noise Study
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IFR AIRPORT - An airport with an authorized instrument approach procedure.

IFR CONDITIONS - Weather conditions that require aircraft to be operated in accordance with instrument flight rules.

IFR MINIMUMS AND DEPARTURE PROCEDURES (FAR PART 91) - Prescribed takeoff rules. For some airports, obstructions or other factors require the establishment of nonstandard takeoff minimums or departure procedures, or both, to assist pilots in avoiding obstacles during climb to the minimum en route altitude.


IMPACT - In environmental studies, the word "impact" is used to express the extent or severity of an environmental problem, e.g., the number of persons exposed to a given noise environment. As indicated in CEQ 1500 (Section 1508.8), impacts and effects are considered to be synonymous. Effects or impacts may be ecological, aesthetic, historic, cultural, economic, social, or health related, and they may be direct, indirect, or cumulative.

INCOMPATIBLE LAND USE - Residential, public, recreational, and certain other noise-sensitive land uses that are designated as unacceptable within specific ranges of cumulative (DNL) noise exposure as set forth in FAR Part 150, Appendix A, Table 2.

INDEPENDENT CONSULTANT (IC) - Independent Consultant. For the BONS project, the Independent Consultant is Landrum & Brown, Inc.


INSTRUMENT APPROACH - An aircraft approach to an airport, with intent to land, by a pilot flying in accordance with an IFR flight plan, when the visibility is less than 3 miles and/or when the ceiling (see also) is at or below the minimum initial approach altitude.

INSTRUMENT APPROACH RUNWAY - A runway served by an electronic air navigation aid providing at least directional guidance adequate for a straight in approach.

INSTRUMENT FLIGHT RULES (IFR) - Rules specified by the FAA for flight under weather conditions that do not meet the minimum requirements for visual flight rules (VFR). Under these conditions the pilot must rely on instruments to fly and navigate.

INSTRUMENT LANDING SYSTEM (ILS) - A system that provides, in the aircraft, the lateral and longitudinal (localizer), and vertical (guidance) electronic guidance necessary for an instrument landing. A precision instrument approach system which normally consists of the following electronic components and visual aids: (1) LOCALIZER- the component of an ILS which provides course guidance to the runway, (2) GLIDESLOPE- provides vertical guidance for aircraft during approach and landing, (3) OUTER MARKER- A marker beacon at or near the glideslope intercept altitude of an ILS approach, and is normally located four to seven miles from the runway threshold on the extended centerline of the runway, and (4) MIDDLE MARKER- A marker beacon that defines a point along the glideslope of an ILS normally located at or near the point of decision height (ILS Category I). ILS Category II/III relates to the lowest approach minima authorized by the FAA. Provided specific criteria are met, appropriately certified aircrews may conduct: (1) an ILS Category II approach procedure to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet, (2) a category IIIA approach without a decision height minimum and with runway visual range of not less than 700 feet, a category IIIB approach procedure without a decision height minimum and with runway visual range of not less than 150 feet, and (4) a category IIIC approach with no decision height minimum and without runway visual range.


INSTRUMENT OPERATION - An aircraft operation in accordance with an IFR flight plan or an operation where IFR separation between aircraft is provided by a terminal control facility or air route traffic control center (see also).

INSTRUMENT RUNWAY - A runway equipped with electronic and visual air navigation aids and for which a straight in (precision or nonprecision) approach procedure has been approved or is planned.

INTEGRATED NOISE MODEL (INM) - A computer model developed by the FAA and required by the FAA for use in environmental assessments, environmental impact statements, and FAR Part 150 studies for developing existing and future aircraft noise exposure maps.

LANDRUM & BROWN, Inc. - Landrum & Brown, Inc. is responsible on this project for peer review, working with the Community Advisorty Committee (CAC), and acting as a technical resource. Another team (see Project Consultant)is the consultant to the Federal Aviation Administration (FAA) and Massport.



LAND AND HOLD SHORT OPERATIONS - These operations include landing and holding short of an intersecting runway, an intersecting taxiway, or some other predetermined point on the runway other than on a runway or taxiway. Previously, SOIR, the acronym for “simultaneous operations on intersecting runways,” was used exclusively to describe simultaneous operations on two intersecting runways – either two aircraft landing simultaneously or one aircraft landing and another one departing. The term LAHSO incorporates SOIR and is expanded to include holding short of a taxiway and holding short of predetermined points on the runway.

LAND USE COMPATIBILITY - The compatibility of land uses surrounding an airport with airport activities and particularly with the noise from aircraft operations.

LAND USE CONTROLS - Controls established by local or state governments to implement land use planning. The controls include zoning, subdivision regulations, land acquisition (in fee simple, lease back, or easements), building codes, building permits, and capital improvement programs (to provide sewer, water, utilities, or other service facilities).

LAND USE PLANNING - Comprehensive planning carried out by units of local government, for all areas under their jurisdiction, to identify the optimum uses of land and to serve as a basis for the adoption of zoning or other land use controls.

LOCALIZER (LOC) - Navigational equipment that provides electronic course guidance. The ground-based equipment sends two signals, which, when received and receded by airborne equipment with equal intensity, indicate that the aircraft is on course. If the received and receded signals have unequal intensity, then the aircraft is off course. A localizer is the part of an ILS (see also) that provides lateral and longitudinal course guidance to the runway.

LOCALIZER-TYPE DIRECTIONAL AID (LDA) - A navigational aid used for nonprecision instrument approaches with utility and accuracy comparable to a localizer; however, it is not part of a complete ILS and its signal is not typically aligned with the runway.

LOUDNESS - The judgment of the intensity of a sound by a person, loudness depends primarily on the sound pressure of the stimulus. Over much of the loudness range, it takes about a threefold increase in sound pressure (approximately 10 decibels) to produce a doubling of loudness.

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