GM7 Safety performance indicator (SPI) for monitoring ATFM over-deliveries

Regulation (EU) 2019/317

A.      Definition

The purpose of this guidance is to explain the ATFM OVD SPI, its calculation and how it will be monitored.

The OVD SPI is defined in Annex I, Section 3, point 2.2 as:

‘The ATFM over-deliveries above the capacity limits of a sector declared by the air navigation service provider where ATFM regulations are imposed, calculated as follows:

(a) the ratio between the time that the number of flights exceeds by more than 10% the capacity limits of a sector declared by the air navigation service provider where ATFM regulations are imposed, and the total time where ATFM regulations are imposed, calculated for the whole calendar year and for each year of the reference period;

(b) for the purposes of this indicator, the regulated time is divided in overlapping hourly slices at every 20-minutes interval.’

An ATFM regulation is a traffic flow measure that aims to protect a node that may potentially be overloaded by limiting the maximum rate of aircraft entering the node. The ATFM regulation is requested by affected ANSPs whenever expected demand exceeds available capacity of the node and will affect a number of flights that enter the node in a time period. Flights entering a regulated sector during the regulation period are subject to that regulation and may be assigned ATFM slots by the Network Manager. An ATFM regulation is, therefore, characterised by a regulated time duration, by the acceptable rate of flights that enter the regulated sector, and the flights affected, also known as traffic volume (TV). 

The traffic volume is created based on either a sector in the airspace, in which case falls within the scope of the indicator definition, or a significant point in the airspace or an airport/group of airports, which falls/fall outside the scope.

In order to determine the total regulated time for an ATFM regulation applied on a traffic volume, the method considers the interval between the regulation start time and regulation end. The regulation end is defined as:

1.       either the last regulation end time indicated when a regulation is created and at subsequent extensions, if any, when the regulation is not cancelled;

2.       or the time at which the regulation was cancelled, when this happens before the declared regulation end time.

The regulated time is further divided in ‘overlapping hourly slices at every 20-minute intervals’.

For example, a regulation starting at 10:40 and ending at 11:40 will have 7 overlapping hourly slices defined as illustrated in Figure 2:

Figure 2: Example of hourly slices of 20-minute intervals of a regulated sector

The last slice is the first hourly slice reaching the regulation end; in the example above it is the 12:40 to 13:30 (this is the only slice that can be less than 1 hour).

B.      Example of the OVD calculation indicator

Figure 3 is an example of an ATFM regulation that was imposed over a certain sector with a regulated rate of 35 flights/hour. The ATFM regulation duration applied from 10:40 until 13:30. The orange bars in the graph depict 20-minute slices that were over-delivered, while the green bars depict 20-minute slices where the actual flight entries were below the regulated rate. In this example, the OVD indicator value is OVD = 3/7 = 42.9 %.

Figure 3: Example of over-deliveries in 20-minute intervals in a regulated sector

The number of actual flight entries in the TV for each 20-minute slice is calculated from the current tactical flight model (CTFM) profile generated by the NM system (whenever a flight fulfils that the CTFM entry time ≥ slice start time and the CTFM entry time < slice end time). To this, a correction will be applied for the airspace un-anticipated flights[40] that, although geographically are crossing the regulated sector, from an operational perspective are not under the control of that sector (non-operational un-anticipated traffic). The objective is to avoid ‘false positives’, i.e. situations when an over-delivery seems to have occurred while in reality there was none . This categorisation will be implemented in the NM reporting system during RP3.

The technical system of the NM generates and archives the data used for OVD monitoring:

1.       regulated TVs and associated reference locations;

2.       ATFM regulation start, end, and cancellation times;

3.       regulated rates;

4.       number of actual entries in the regulated TVs for each slice; the categorisation of non-operational un-anticipated traffic will be available during RP3.

C.      Level of aggregation of the OVD indicator

The OVD indicator can be determined for any combination of geographical areas (TV, ACC, SES area, NM area) or time intervals (daily, monthly, yearly). To aggregate the OVD indicator for the combination of geographical area and time interval, the total number of slices with over-delivery are divided by the total number of slices for the regulations within the reporting scope.