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1 ACS Report 0908 TERMS AND DEFINITIONS USED IN AIRPORT CAPACITY STUDIES Edited version of document for ACL reference

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3 Airport Capacity Studies Operational Analysis NATS Ltd. ACS REPORT 0908 TERMS AND DEFINITIONS USED IN AIRPORT CAPACITY STUDIES Revision of ACS Report 0801; March 2008 SUMMARY This paper defines the terms and definitions used in the studies made by the Airport Capacity Team concerning demand and delays at airports and projected Runway Capacities. This report supersedes ACS Report NATS Ltd. November

4 NATS Ltd The information contained herein is for the sole use of the addressee and may not be communicated to any third party in any medium in whole or in part without the prior written permission of the Head of Capacity & Environmental Analysis, NATS Ltd. 2

5 Publication History Issue Month/Year Change made in this Author issue CS Report 9536 October 2004 First issue John Dow ACS Report 0801 March 2008 Major upgrade to align with Operational Summary definitions ACS Report 0908 November References to wake vortex changed to wake turbulence. - Change to wake turbulence and service rate definitions. - Correction of PRT definition to align with Operational Summary definition. - Correction in index reference to Wheels Roll Time - Inclusion of publication history. - Inclusion of Airport Experience -Times for Crossers moved into individual section Nicola Cavanagh, Norliza Nordeen Norliza Nordeen Katherine Marren Scott Alexander Dominic Nortney 3

6 CONTENTS PUBLICATION HISTORY... iii GLOSSARY INTRODUCTION AIRPORT ENVIRONMENT AIRCRAFT AND MOVEMENT CATEGORIES TIMES FOR ARRIVALS TIMES FOR DEPARTURES TIMES FOR CROSSERS DEMAND, UTILISATION AND TRAFFIC MIX RUNWAY CAPACITY ASSESSMENTS

7 GLOSSARY Times Times stated in minutes UTC have seconds truncated, e.g signifies all times from 0729 up to, but not including, Abbreviations ACS...Airport Capacity Studies ACL...Airport Co-ordination Limited AIP...Aeronautical Information Publication ARIES...Air Traffic Real-Time Integrated Evaluation System ATC...Air Traffic Control BASIS...British Airports Stand Information System CAVOK...Cloud And Visibility OK CFMU...Central Flow Management Unit CTOT...Calculated Take-Off Time ETOT...Expected Take-off time FIR...Flight Information Region FL...Flight Level IATA...International Air Transport Association ICAO...International Civil Aviation Organisation IFR...Instrument Flight Rules LVPs...Low Visibility Procedures MATS...Manual of Air Traffic Services MDI...Minimum Departure Interval MTWA...Maximum Take-off Weight Authorised OA...Operational Analysis PLOG...Planned LOG R/T...Radio Telephony SID...Standard Instrument Departure SSR...Secondary Surveillance Radar SVFR...Special Visual Flight Rules TMA...Terminal Control Area UTC...Universal Co-ordinated Time UKFDB...United Kingdom Flight Data Base VFR...Visual Flight Rules 5

8 1. INTRODUCTION 1.1 This report contains definitions of the statistics and terms used by the Airport Capacity Studies Team. The principal (recurring) studies in which these terms and definitions are used are capacity assessment studies. 1.2 Should the reader have any comments or questions on the information presented they should be addressed to ACS directly, either by telephone on +44 (0) , by fax on +44 (0) or in writing to: Airport Studies Team, Mailbox 9, NATS CTC, 4000 Parkway, Whiteley, Fareham, Hampshire, UK PO15 7FL 1.3 Terms printed in Italics in the text are defined elsewhere in this report. 6

9 2. AIRPORT ENVIRONMENT 2.1 Departure Holding Point A location on the Manoeuvring Area of an aerodrome at which an aircraft is held before entering a Runway for take-off. 2.2 Departure Route The Departure Route of an aircraft for separation purposes is determined by the Standard Instrument Departure (SID) used. 2.3 Inner Cordon A circle centred on the centre of an airport. The Inner Cordon is used to provide a reference point for monitoring inbound delays. The Inner Cordon is chosen such that aircraft only cross it once (i.e. it is well before the Stacks). Operational Analysis (OA) has been using the Inner Cordon (mainly for Delay Monitoring) since Summer The Inner Cordons in current use are: Heathrow: a 40Nm radius circle, Manchester: a 30Nm radius circle, Gatwick: a 30Nm radius circle, Stansted: a 30Nm radius circle, Birmingham: a 30Nm radius circle. 2.4 Manoeuvring Area That part of an aerodrome provided for the take-off and landing of aircraft and for the movement of aircraft on the surface excluding the apron and any part of the aerodrome provided for the maintenance of aircraft (Ref 1). 2.5 Queue A continuous stream of aircraft demanding the use of the Runway such that the following aircraft in each pair may have had some delay imposed on it in order to achieve the required separation. 2.6 Runway A defined rectangular area on a land aerodrome prepared for the landing and take-off run of aircraft along its length. 2.7 Runway Crossing Point A location on the Manoeuvring Area of an aerodrome at which an aircraft is held while waiting to cross an active Runway. 7

10 2.8 Runway Threshold The beginning of that portion of the Runway usable for landing (Ref.1). On observations the point at which the aircraft flies over the end of the Runway is used. 2.9 Stack / SIDS Stack A specified location, identified by visual or other means, in the vicinity of which the position of an aircraft in flight is maintained in accordance with air traffic control clearances (Ref 1). The Stacks for the following airports are found in AIP. Standard Instrument Departure (SID) A standard routing for departures. "SVFR" - Special Visual Flight Rules - is used for a departing aircraft using an SVFR clearance, and not using a SID. "IFR" - Instrument Flight Rules - is used for a departing aircraft using an IFR clearance, but not using a SID. Ref 1 gives further information on clearances issued to aircraft. 8

11 3. AIRCRAFT AND MOVEMENT CATEGORIES 3.1 Callsign Alpha and numerical characters used for a specific flight in R/T communication between pilot and ATC. 3.2 CTOT Traffic Traffic subject to flow regulation administered by the Central Flow Management Unit (CFMU) - i.e. traffic having Calculated Take-Off Times (CTOTs), whether due to flow restrictions in the UK or in other countries. 9

12 3.3 Daily Flight Schedule The daily list of operations produced by the Airport operator. This is also known as the Mayfly as produced the day before the day of operation. 3.4 Haulage Category Short Haul Traffic that has a domestic, European or North African origin / destination. Long Haul All traffic that is not included in Short Haul. 3.5 Scheduled Movement An aircraft movement that is notified in the Daily Flight Schedule. 3.6 Scheduled Time The time an aircraft is scheduled to leave stand or arrive on stand. 3.7 Unscheduled Movement An aircraft movement that is not notified in the Daily Flight Schedule. 10

13 4. TIMES FOR ARRIVALS 4.1 Arrival Congestion Delay The outcome when Cross Threshold Time is subtracted from the Threshold Demand Time. If this parameter is negative, it is taken to be zero. 4.2 Arrival Runway Occupancy The time interval between an arriving aircraft crossing the Runway Threshold and exiting the Runway. 4.3 Arrival Schedule Shift The outcome when Scheduled Threshold Time is subtracted from the Threshold Demand Time, where a positive value indicates that the aircraft was late. Schedule shift is only defined for aircraft that appear in the Daily Flight Schedule. Flights that have a schedule shift of between -5 minutes and +5 minutes are categorised as having "No Shift". 4.4 Arrival-Arrival Separations (AA_Sep) The difference between the times at which two consecutive queued aircraft are observed, to cross the Runway Threshold. 4.5 Arrival-Departure-Arrival Separations (ADA_Sep) The difference between the times at which 2 arriving aircraft are observed to cross the Runway Threshold, where there is a single departure interleaved between the 2 queued arriving aircraft on the same Runway. 4.6 Arrival-Departure-Departure-Arrival Separations (ADDA_Sep) The difference between the times at which 2 arriving aircraft are observed to cross the Runway Threshold, where there are two departures interleaved between the 2 queued arriving aircraft on the same Runway. 4.7 Cross Cordon Bearing The bearing from the airport at which an aircraft crosses the Inner Cordon. 11

14 4.8 Cross Inner Cordon Time The time at which an aircraft is found to cross the Inner Cordon. 4.9 Cross Threshold Time The time at which an aircraft is found to cross the Runway Threshold. This term may be qualified to indicate the source of the data- i.e. ARIES Cross Threshold, SMR Cross Threshold, ATC Cross Threshold Inbound Route The route in which arriving aircraft approaches the Runway. It is dependent on a number of factors, including the aircraft s origin and Stack Instack Time The Cross Inner Cordon Time plus the Standard Flying Time From Inner Cordon To Stack Inter Cordon Delay The Cross Inner Cordon Time less Cross Extended Cordon Time, less the Standard Flying Time from Extended Cordon to Inner Cordon Queued Arrival A continuous stream of arrival aircraft demanding the use of the Runway such that the following aircraft may have some delay imposed on it in order to achieve the required separation Scheduled Arrival Time The time, as notified in the Daily Flight Schedule, that an aircraft is planned to arrive at its designated stand Scheduled Threshold Time The Scheduled Arrival Time less the Standard Arrival Taxi Time (i.e. when an aircraft would have had to cross the Runway Threshold in order to achieve the Scheduled Time of arrival at the stand). 12

15 4.16 Standard Arrival Taxi Time A defined value representing the typical time taken for aircraft from Cross Threshold Time to reaching the stand Standard Flying Time From Inner Cordon To Threshold A typical time for aircraft to fly from the Inner Cordon to the Runway Threshold (i.e. Cross Threshold Time - Cross Inner Cordon Time) when they suffer no delay. This is dependant on the Cross Cordon Bearing and Runway direction Threshold Demand Time The Cross Inner Cordon Time plus the Standard Flying Time from Inner Cordon to Threshold (i.e. the time that an aircraft would have crossed the Runway Threshold if it had had no delay). 13

16 5. TIMES FOR DEPARTURES 5.1 Airborne Demand Time The time the departure would have become airborne had there been no Departure Measured Delay. This time is estimated by taking the Airborne Time minus the Departure Measured Delay. Or Leave Stand Time plus Standard Departure Taxi Time. 5.2 Airborne Time The time an aircraft is observed as becoming airborne (ie aircraft begins to rotate off the Runway). 5.3 Cleared Take-Off Time The time when the pilot reads back their clearance to take-off issued by the controller. 5.4 CTOT (Calculated Take-Off Time) The approved Airborne Time of departure, given after flow regulation has been applied by the CFMU. There is a "window" around the CTOT in which departures are permitted to become airborne, this is 5 minutes before to 10 minutes afterwards. 5.5 CTOT Delay The outcome of the time asked for in the aircraft's final request to become airborne, subtracted from the earlier of (a) the initial CTOT that is applied to this request, and (b) the Airborne Time. 5.6 Departure Join Holding Point Time The time when an aircraft has arrived at the holding point, or if a preceding aircraft is already at the holding point, then it is when it joins the queue for the holding point. 14

17 5.7 Departure Line-up Effective Time The time the aircraft is observed to start lining up, examples: a) If Queued behind an arrival then, when the arriving aircraft passes the queuing aircraft s holding point. b) If Queued behind a departure at the same holding point then, when the departing aircraft s Wheels Roll Time c) If not Queued then, when the aircraft reaches the holding point. 5.8 Departure Line-up Time The time an aircraft takes to manoeuvre from the Holding Point to become lined up on the Runway. 5.9 Departure Measured Delay For CTOT Traffic the Departure Measured Delay is the sum of the Holding Point Delay and the CTOT Delay. For non-ctot Traffic the Measured Departure Measured Delay is the sum of Holding Point Delay and Start-up Delay. 15

18 5.10 Departure-Departure Separations The time interval between a departure immediately followed by another departure on the same Runway (i.e. Airborne Time to Airborne Time for Queued traffic) Leave Stand Time The time an aircraft is observed to start push back from the stand Lined-up Time The time an aircraft is pointing down the centre line of the Runway. The aircraft may be classed as lined up before it has stopped manoeuvring into position Minimum Departure Interval (MDIs) A Minimum Time Interval is the minimum time required between successive departures on the same Standard Instrument Departure (SID) route. 16

19 5.17 Pilot Reaction Time (PRT) This is either: or a) If the aircraft is already lined up on the Runway, PRT is the outcome of subtracting Cleared Take-Off Time from the Wheels Roll Time. b) If the aircraft was cleared for take-off before it was lined-up on the Runway, PRT is the outcome of subtracting Lined-up Time from the Wheels Roll Time 5.18 Pre-departure Delay Delay experienced by an aircraft due to congestion at its arriving airport and therefore is held at its departure airport until it is cleared through to its arrival airport Queued Departure A continuous stream of departing aircraft demanding the use of the Runway such that the following aircraft may have some delay imposed on it in order to achieve the required separation Scheduled Airborne Time The Scheduled Departure Time plus the Standard Departure Taxi Time Scheduled Departure Time The time listed in the Daily Flight Schedule when an aircraft is planned to depart from its stand Standard Departure Manoeuvring Time Calculation used within ACS, it is the defined value representing a typical time taken for push-back, taxi, line-up and roll to airborne. The Standard Departure Manoeuvring Time varies depending on stand, aircraft type and Runway. (Used to calculate the HP delay.) 5.23 Standard Departure Taxi Time A defined value representing the typical time taken for aircraft from leaving the stand to becoming airborne. (Used to calculate the Scheduled Airborne Time.) 17

20 5.24 Start-up Delay The time interval between an aircraft requesting start-up and it being given permission to start-up Wheels Roll Time The time after Lined-up Time and Cleared Take-off Time, on the Runway in the direction of take-off the aircraft first moves to begin the take-off roll. 18

21 6. TIMES FOR CROSSERS 6.1 Cross Runway Effective ( Clear Cross ) When an aircraft is given their clearance to cross the Runway, it is either: or or a) If an aircraft had reached the STOP bar, and there is no arrival or departure using the Runway (i.e. the Runway is clear). Then it is the time when the aircraft is issued clearance. b) If an aircraft has reached the STOP bar, and there is an arrival or departure using the Runway (i.e. the Runway is not clear). Then if the aircraft has been given a conditional clearance, it is the time when the arriving or departing aircraft passes the crossing point. c) If an aircraft has not yet reached the STOP bar, and has been given clearance. Then it is the time when the aircraft reaches the STOP bar. Note: This is a time issued only at Manchester Airport for capacity study reporting. 19

22 8. DEMAND, UTILISATION AND TRAFFIC MIX 8.1 Actual Utilisation The number of aircraft with an observed Cross Threshold Time or Airborne Time in a given interval. 8.2 Scheduled Airborne Demand The number of aircraft having a Scheduled Airborne Time in a given interval. 8.3 Scheduled Threshold Demand The number of aircraft having a Scheduled Threshold Time in a given interval. 8.4 Stack Utilisation The number of aircraft having an Instack Time in a given interval. 8.5 Undelayed Airborne Demand The number of aircraft having an Airborne Demand Time in a given interval. 8.6 Undelayed Threshold Demand The number of aircraft having a Threshold Demand Time in a given interval. 8.7 Wake Turbulence Traffic Mix The proportions of Heavy, Medium, Small and Light Wake Turbulence Category aircraft having a Cross Threshold Time or an Observed Airborne Time in a given interval. For Heathrow, Gatwick, Manchester and Stansted arrivals, the Arrival Medium Wake Turbulence Category is split into Upper Medium and Lower Medium. (See section 3.10) 20

23 9. RUNWAY CAPACITY ASSESSMENTS 9.1 Average Cumulative Delay The Average Delay to all aircraft which have operated up to a specified time of day. 9.2 Average Delay The Average Delay to all aircraft in a particular period. 9.3 Busy Period For an airport, the Busy Period are defined periods at which traffic demand is close to the Runway Capacity as defined by airport ATC in conjunction with the airport operator and ACL. 9.4 Declared Capacity The Runway Capacity as declared by the airport operator for the purposes of Runway slot allocation. This declaration is based on advice provided by the ACS assessment of Runway Capacity (Ref. 8). 21

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