ICAO Doc 8168 Volume I: Flight Procedures - Vocabulary

Vocabulary and definitions flashcards covering flight procedure design, operational limitations, instrument approach segments, departures, arrivals, holding patterns, and helicopter criteria from ICAO Doc 8168 Volume I.

Aerodrome elevation

The elevation of the highest point of the landing area.

Airborne collision avoidance system (ACAS)

An aircraft system based on secondary surveillance radar ($\text{SSR}$) transponder signals which operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft that are equipped with $\text{SSR}$ transponders.

Area minimum altitude (AMA)

The minimum altitude to be used under instrument meteorological conditions ($\text{IMC}$), that provides a minimum obstacle clearance within a specified area, normally formed by parallels and meridians.

Area navigation (RNAV)

A method of navigation which permits aircraft operation on any desired flight path within the coverage of station-referenced navigation aids or within the limits of the capability of self-contained aids, or a combination of these.

Balked landing

A landing manoeuvre that is unexpectedly discontinued at any point below the $\text{OCA/H}$.

Base turn

A turn executed by the aircraft during the initial approach between the end of the outbound track and the beginning of the intermediate or final approach track, where the tracks are not reciprocal.

Continuous descent final approach (CDFA)

A technique, consistent with stabilized approach procedures, for flying the final approach segment of a non-precision instrument approach procedure as a continuous descent, without level-off, from an altitude/height at or above the final approach fix altitude/height to a point approximately $15\,m$ ($50\,ft$) above the landing runway threshold or the point where the flare manoeuvre should begin.

Decision altitude (DA) or decision height (DH)

A specified altitude or height in a 3D instrument approach operation at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.

Minimum descent altitude (MDA) or minimum descent height (MDH)

A specified altitude or height in a 2D instrument approach operation or circling approach operation below which descent must not be made without the required visual reference.

Obstacle clearance altitude (OCA) or obstacle clearance height (OCH)

The lowest altitude or the lowest height above the elevation of the relevant runway threshold or the aerodrome elevation as applicable, used in establishing compliance with appropriate obstacle clearance criteria.

Minimum sector altitude (MSA)

The lowest altitude which may be used which will provide a minimum clearance of $300\,m$ ($1\,000\,ft$) above all objects located in an area contained within a sector of a circle of $46\,km$ ($25\,NM$) radius centred on a significant point, the aerodrome reference point ($\text{ARP}$), or the heliport reference point ($\text{HRP}$).

Terminal arrival altitude (TAA)

The lowest altitude that will provide a minimum clearance of $300\,m$ ($1\,000\,ft$) above all objects located in an arc of a circle defined by a $46\,km$ ($25\,NM$) radius centred on the initial approach fix ($\text{IAF}$), or on the intermediate fix ($\text{IF}$) where there is no $\text{IAF}$, delimited by straight lines joining the extremity of the arc to the $\text{IF}$, accounting for an area of $360^\circ$ around the $\text{IF}$.

Primary area and Secondary area

The primary area is a defined area symmetrically disposed about the nominal flight track in which full minimum obstacle clearance ($\text{MOC}$) is provided ($\frac{1}{2}$ of total width). The secondary area consists of areas on each side ($\frac{1}{4}$ of total width each) in which $\text{MOC}$ reduces linearly from full value at the inner edge to zero at the outer edge.

Fly-by waypoint

A waypoint which requires turn anticipation to allow tangential interception of the next segment of a route or procedure.

Flyover waypoint

A waypoint at which a turn is initiated in order to join the next segment of a route or procedure.

Constant radius arc to a fix (RF) turn

A curved flight path segment used in performance-based navigation ($\text{PBN}$) procedures that follows a circular arc of constant radius around a defined arc centre point between two waypoints.

Procedure design gradient (PDG)

The climb gradient used by procedure designers to identify critical obstacles in a departure procedure; the standard assumed nominal value is $3.3\%$ for aeroplanes and $5.0\%$ for Category H.

Standard instrument departure (SID)

A designated instrument flight rule ($\text{IFR}$) departure route linking the aerodrome or a specified runway of the aerodrome with a specified significant point, normally on a designated $\text{ATS}$ route, at which the en-route phase of a flight commences.

Standard instrument arrival (STAR)

A designated instrument flight rule ($\text{IFR}$) arrival route linking a significant point, normally on an $\text{ATS}$ route, with a point from which a published instrument approach procedure can be commenced.

Fixed radius transition (FRT)

A constant radius turn applied at fixes between area navigation route segments on the en-route structure, authorized for use with Advanced $\text{RNP}$, $\text{RNP 4}$, and $\text{RNP 2}$ navigation specifications.

Vat (Speed at threshold)

The indicated airspeed at the runway threshold based on $1.3$ times stall speed $V_{so}$ or $1.23$ times stall speed $V_{s1g}$ in the landing configuration at maximum certificated landing mass, which determines aircraft categorization.

Aircraft Categories (A, B, C, D, E)

Classification of aeroplanes based on $V_{at}$: Category A ($< 169\,km/h$ / $< 91\,kt$), Category B ($169\text{--}223\,km/h$ / $91\text{--}120\,kt$), Category C ($224\text{--}260\,km/h$ / $121\text{--}140\,kt$), Category D ($261\text{--}306\,km/h$ / $141\text{--}165\,kt$), and Category E ($307\text{--}390\,km/h$ / $166\text{--}210\,kt$).

Segments of an instrument approach procedure

The five distinct phases that may form an approach: arrival route, initial approach segment, intermediate approach segment, final approach segment ($\text{FAS}$), and missed approach segment.

Final approach fix (FAF)

A designated facility or fix on the final approach track of a non-precision approach procedure where alignment and descent for landing are commenced.

Final approach point (FAP)

A point in space on the final approach track of a precision or vertically guided approach where the intermediate approach altitude/height intercepts the nominal glide path or vertical path angle.

Missed approach point (MAPt)

That point in an instrument approach procedure at or before which the prescribed missed approach procedure must be initiated in order to ensure that the minimum obstacle clearance is not infringed.

Step down fix (SDF)

A fix incorporated in some non-precision approach procedures that permits descent to a lower $\text{OCA/H}$ when the fix is positively identified during the approach.

Visual manoeuvring (circling)

The phase of visual flight after an instrument approach has been completed which brings an aircraft into position for landing on a runway not suitably located or aligned for a straight-in approach.

Missed approach phases

The three successive segments of a missed approach: initial phase (from $\text{MAPt}$ to start of climb ($\text{SOC}$), no turns), intermediate phase (from $\text{SOC}$ to first point achieving $50\,m$ ($164\,ft$) clearance, maximum $15^\circ$ turn), and final phase (where $50\,m$ obstacle clearance is maintained and procedure turns may be executed).

Holding pattern entry sectors

The three designated angular sectors relative to the inbound track used for entering a holding pattern: Sector 1 (parallel entry, $110^\circ$), Sector 2 (offset entry, $70^\circ$), and Sector 3 (direct entry, $180^\circ$), with a $5^\circ$ flexibility zone on either side.

Holding buffer area

An additional airspace area extending $9.3\,km$ ($5.0\,NM$) beyond the boundary of the holding area ($3.7\,km$ / $2\,NM$ for helicopters below $1\,830\,m$) where significant obstacles are considered in determining the minimum holding level.

Cross-track tolerance (XTT) and Along-track tolerance (ATT)

Performance-based navigation ($\text{PBN}$) fix tolerances where $\text{XTT}$ is measured perpendicularly to the nominal track ($\text{XTT} = \text{TSE}$) and $\text{ATT}$ is measured along the nominal track ($\text{ATT} = 0.8 \times \text{TSE}$).

Shuttle

A descent or climb conducted in a holding pattern, normally prescribed when the altitude change required between initial approach and final approach exceeds standard maximum descent rates.

Point-in-space (PinS) departure

A departure procedure designed for helicopters only that consists of a visual segment from a heliport or landing location to an initial departure fix ($\text{IDF}$), followed by an instrument segment.

Point-in-space (PinS) approach

An instrument approach procedure designed for helicopters only flown to a point in space ($\text{MAPt}$), containing either a 'proceed visually' or 'proceed VFR' instruction to reach the landing location.

Direct visual segment (Direct-VS)

A visual segment in a helicopter $\text{PinS}$ procedure designed as a leg direct from the $\text{MAPt}$ to the landing location (or via a descent point), or as a straight leg from the landing location to the initial departure fix ($\text{IDF}$).

Manoeuvring visual segment (Manoeuvring-VS)

A visual segment in a helicopter $\text{PinS}$ procedure protected for visual manoeuvres from the $\text{MAPt}$ around the landing location to land from a direction other than directly from the $\text{MAPt}$, or for take-off in a direction other than directly to the $\text{IDF}$.

Procedure altitude/height

A published altitude/height used in defining the vertical profile of a flight procedure, at or above the minimum obstacle clearance altitude/height where established, developed to support a stabilized $5.2\%$ ($3.0^\circ$) descent gradient.