Flight Milestones

1 Introduction

This document details the concepts and ideas supporting the definition of flight milestones..

2 Phases of a Flight

In a flight we can identify events that can help to monitor its evolution from a gate-to-gate perspective. Figure 2.1 shows a simplified diagram of a possible set of flight phases (white square boxes) and relevant events (Txy labels).

Figure 2.1: Flight phases and events.

In general we are interested in analyzing performance at gate-to-gate level so as to cover both the airborne and the ground phases of flights. To this extent we summarize a flight down to some of its fundamental milestones as in the following list (from departure to arrival):

1. Off-block (T06)
2. End of push back (T07)
3. Enter runway for take-off (T09)
4. Lift-off (T12), a.k.a. take-off
5. 40-nautical-miles intersection (T14 ?)
6. top-of-climb (T15)
7. top-of-descent (T18)
8. 40-nautical-miles intersection (T19 ?)
9. Touch-down (T22)
10. Runway vacated (T24)
11. Enter parking spot (T26)
12. on-block (T27)

Other interesting milestones could be

13. Holding start
14. Holding end
15. Leveled segment start
16. Leveled segment end
17. FIR crossing

Subsets of these milestones allow for the calculation of taxi-in (T24, T27) and taxi-out (T06, T09) times, runway utilization and sequencing (T12, T22), inefficiencies in the Terminal Maneuvering Area (TMA) (via holding patterns and leveled portions of the descent) … Additional ad-hoc milestones can be defined for specific needs, for example Flight Information Region (FIR) crossing milestones would be usefult to count Departure, Arrival, Internal, Overflight (DAIO) statistics.

3 Milestone

A flight milestone is conceptually defined by

• flight ID it belongs to
• 3D location (decimal degrees of longitude, latitude [in WSG84] and altitude [in feet]), i.e.  17.933996,59.653410,-203
• UTC timestamp, i.e. 2021-09-27 10:43:11.234 UTC
• milestone type, i.e. top-of-climb or off-block

Further useful attributes for business processing of the information are:

• the source of extraction of the milestone, i.e. apdf (when data provided by airport), osn (extracted by OpenSky Network (OSN)’s Automatic Dependent Surveillance–Broadcast (ADS-B) data), nm (as calculated by EUROCONTROL’s Network Manager (NM))
• contextual information, i.e. F33R as the relevant parking position for an off-block milestone or 26 as the runway ID for a take-off milestone. This field can be also useful to define a custom fomat for airspace crossing, for example for a milestone like x-fir we could have the info contain something like from:LFFF, to:LFRR to provide info about the transition order of airspace penetration.

4 Use Cases

A milestone-based representation of a flight is a way to reduce complexity for its representation and hence allow some (still useful) statistical analysis for performance monitoring.

4.1 Fuel consumption / Environmental emissions

Environmental emissions and climate impact are indicators more and more in news headlines and on the political agendas. With a milestone-based representation of a flight we can segment the phases of interest and calculated the relevant cumulative emissions.

For example we can split a flight in the following phases:

• cruise
• Landing and TakeOff (LTO) cycle

and calculate the fuel-burnt emissions by further splitting them.

LTO phases ([1] Figure 2.5).

For LTO we have four sub-phases:

• approach
• taxi-in
• taxi-out
• take-off
• climb-out

For example taxi-out sub-phase can be framed by the ground portion from off-block to rwy-entry milestones which with defined assumptions in term of aircraft & engine type, full thrust percentage and number of engines in use can be handled to an emission calculator to compute CO2, NOx, … emissions.

The selection of milestones to model the flight and the further assumptions of how the aircraft is operated between those milestones will produce results with different levels of accuracy and precision.

NOTE: add ER diagram for use case

4.2 Operational performance

A milestone-based modelling of a flight provides practical ways to extract operational indicators for the analysis of the operation performance at network, state, airport or airline level.

For example using the touch-down (T22 in Figure 2.1) with the contextual information we can calculate RWY utilization at each airport or inter-arrival times, etc.

4.3 Airspace profile

TODO: milestones line FIR crossing (x-fir) could be used to extract an flight airspace profile. For example we could have AUA crossing (x-aua) or even elementary airspace (x-esa) ones. The tricky thing is obviously having a non-overlapping airspaces (of the same type)

5 Milestones Definition

The milestone concept can be modeled in entity-relationship fashion as in Figure 5.2.

erDiagram
    MILESTONE {
        int id PK
        int flight_id FK
        string type
        timestamp event_time
        float longitude
        float latitude
        float altitude
        string source
        string version
        string info
    }
    MEASUREMENT {
        int id PK
        int milestone_id FK
        string type
        float value
        string version
    }
    FLIGHT {
        int id PK
        int ADEP FK
        int ADES FK
        int aircraft FK
        string profile_id FK
        timestamp DOF
    }
    OA_AIRPORTS {
        int id PK
        string ident
        string type
        string name
        double latitude_deg
        double longitude_deg
        int elevation_ft
        string continent
        string iso_country
        string iso_region
        string municipality
        string scheduled_service
        string gps_code
        string iata_code
        string local_code
        string home_link
        string wikipedia_link
        string keywords
    }
    OA_RUNWAYS {
        int id PK
        int airport_ref FK
        string airport_ident
        int length_ft
        int width_ft
        string surface
        boolean lighted
        boolean closed
        string le_ident
        double le_latitude_deg
        double le_longitude_deg
        int le_elevation_ft
        double le_heading_degt
        int le_displaced_threshold_ft
        string he_ident
        double he_latitude_deg
        double he_longitude_deg
        int he_elevation_ft
        double he_heading_degt
        int he_displaced_threshold_ft
    }
    AIRCRAFT {
        int id PK
        int icao24
    }
    PROFILE {
        int id PK
    }
    
    MILESTONE }|--|| FLIGHT : has
    FLIGHT    }o--|{ OA_AIRPORTS : has
    OA_AIRPORTS   }|--|{ OA_RUNWAYS : has
    FLIGHT ||--|{ AIRCRAFT : has
    FLIGHT ||--|| PROFILE : has 
    MEASUREMENT ||--|{ MILESTONE : has

Figure 5.1: Entity-Relationship diagram for Milestone and relevant concepts.

Figure 5.2: Entity-Relationship diagram for Milestone and relevant concepts.

In words, a milestone refers to a flight (via the foreign key flight_id) and has few attributes as described in Chapter 3 (namely, type, timestamp, lon, lat, alt, src, info.)

A flight is (simply) defined by the aerodrome of departure (ADEP) and destination (ADES) (which are are foreign keys to AIRPORT.id), its callsign, take-off and landing timestamps, and aircraft (a foreign key to AIRCRAFT.id.) [NOTE: this is still simplistic…how do we cater for AFIL, ZZZZ (these could be just special airport entries without lon/lat/elevation) or crashes (again another special entry?)]

A flight (point) profile is a 4D sequence of timestamp and 3D positions as flown (or calculated). A flight profiles links to the relevant flight via the foreign key flight_id.

For OSN a flight profile is a state vector.

6 Example data

TBD

7 List of Acronyms

ADS-B

Automatic Dependent Surveillance–Broadcast

DAIO

Departure, Arrival, Internal, Overflight

FIR

Flight Information Region

LTO

Landing and TakeOff

NM

Network Manager

OSN

OpenSky Network

TMA

Terminal Maneuvering Area

[1]

E. E. Agency and E. U. A. S. Agency, European aviation environmental report 2016. Publications Office of the European Union, 2016.