Section 1, Chapter 4 - Flow Regulation

Question 1

What are the responsibilities and procedures regarding Air Traffic Flow Management (ATFM) for IFR traffic under UK Reg (EU) No 255/2010?

Answer 1

The responsibilities and procedures regarding Air Traffic Flow Management (ATFM) for IFR traffic are as follows:

• Subject to ATFM Measures: All IFR traffic that has filed a flight plan may be subject to ATFM measures as per UK Reg (EU) No 255/2010.
• Flow Control Bulletins: Sectors and destinations within ECAC States may or may not be subject to restrictions, as published in Flow Control bulletins on the AFTN.
• Operator Responsibility: Operators are responsible for communicating flow-related messages to the Central Flow Management Unit (CFMU).
• ATC Assistance: ATC may assist local operators who are unable to communicate such messages directly.

Question 2

What are the responsibilities of Aircraft Operators and Air Traffic Service Providers in managing Estimated Off-Block Times (EOBTs) for flights departing UK aerodromes?

Answer 2

Responsibilities in managing EOBTs for flights departing UK aerodromes include:

EOBT Change Notification:

• Any change in an EOBT of more than 15 minutes (+ or -) must be notified to the CFMU through IFPS.
• Operators should not modify EOBTs to a later time due to ATFCM delays.

Aircraft Operators’ Responsibility:

• Ensure the EOBT in a flight plan is accurate.
• If a non-regulated aircraft is not ready within EOBT +/- 15 minutes, ATS will not permit pushback/start until the EOBT is modified via a DLA or CNL message and acknowledged by IFPS.
• Update EOBTs if ATFCM measures are applied and then canceled.
• Cancel flight plans promptly if the flight schedule is disrupted and the flight may not depart.

Air Traffic Service Providers’ Responsibility:

• Modify the EOBT if an aircraft, ready to start on time, is delayed by ATS.
• Apply ATFCM measures during major disruptions (e.g., increasing taxi times or departure flow regulation).
• When ATFCM measures are canceled, ensure Aircraft Operators update EOBTs as necessary.

Question 3

How are take-off times and slots managed for departing flights, particularly in restricted and non-restricted sectors/destinations?

Answer 3

The management of take-off times and slots for departing flights includes:

Slot Messages:

• Slot messages are received from IFPS via AFTN and displayed on the Departure Slot Monitor (DSM).
• Types of messages include DLA, REA, DEP, ARR, and SMM.
• ATC may cancel and re-file a flight plan to generate an earlier OBT if requested by the captain.

Departures to Non-Restricted Sectors/Destinations:

• These flights will not be issued with a CTOT (Calculated Take-Off Time).

Departures to Restricted Sectors/Destinations:

• These flights will be issued with a CTOT.
• Flights can depart within an ATC tolerance of -5/+10 minutes from their CTOT.
• For earlier departures than EOBT, a CNL message followed by a refile with the new EOBT is required for a new CTOT.
• For delays, ATC can send a REA (Ready) message via DSM if the flight is ready to depart on schedule after EOBT. A new CTOT will be issued if available.
• Changes to CTOTs are issued as a Slot Revision Message (SRM).
• Slot Missed Messages (SMM) are normally processed by operators, but ATC may assist.

Sending EOBT Delay via EFPS:

• The minimum delay that can be successfully sent via EFPS is 15 minutes.
• Delays of less than 15 minutes should be sent via AFTN.

Question 4

How are departures flow restrictions managed when there is excessive workload demand from a single airfield?

Answer 4

When there is excessive workload demand from a single airfield, departures flow restrictions are managed by:

Increased Departure Separation:

• Considering increased departure separation as an alternative or supplement to regulation.

Consultation and Agreement:

• Consulting and agreeing with the airfield and PC Ops Supervisor when a high proportion of departures are on a single route.
• Managing an ADI/MDI to allow more flexibility than extended periods of ATFM regulation.

Traffic Volumes Coordination:

• The SCOD coordinates with PC to adjust traffic volumes based on circumstances.

Suggested Traffic Volumes (SSR Only for e.g.):
* An overall restriction of 15 departures every 60 minutes
* A maximum of 8 departures every 15 minutes
* This helps in managing sector workload and maintaining operational efficiency.

Question 5

What are the three forms of time-based separation that can be considered to manage departures flow restrictions?

Answer 5

The three forms of time-based separation to manage departures flow restrictions are:

ARDS (Airfield Reasonable Departure Spacing):

• Manages departures on a specific route during a specified time period to minimize bunching in the enroute environment.
• Does not include a specific departure interval.
• Provides the Airfield Tower Departure Controller with tactical freedom while ensuring that the departure sequence minimizes bunching in a busy sector.

ADI (Average Departure Interval):

• The average time between three successive departures should be no less than the rate applied.
• For example, an ADI of 1 per 5 allows a 4-minute gap followed by a 6-minute gap.
• Provides flexibility in arranging departures while maintaining an average interval.

MDI (Minimum Departure Interval):

• The rate applied must be strictly adhered to with no less than the minimum time stated between departures.
• Ensures a strict adherence to the specified minimum interval to manage departures precisely.

Question 6

What is the “Take Off Not Before” procedure, and when is it applied?

Answer 6

The “Take Off Not Before” procedure is applied under the following circumstances and guidelines:

Purpose:

• Used when a small number of aircraft from a single source or multiple airfields generate a disproportionate workload during a busy period, making ADI/MDI ineffective.

Procedure:

• Specific aircraft are delayed and not allowed to depart before a specified time.
• Requests for such delays should be made directly between the requesting unit and the concerned airfield.
• Delays should not normally exceed 15 minutes.
• The requesting unit should record details of flights delayed in this manner.

Considerations:

• The most appropriate measure depends on the exact circumstances at the time.
• The impact on the airfield should always be considered.
• Measures should be the minimum level of intervention necessary to achieve the desired result.
• MDIs should only be applied when it is critical that there is no variation in the minimum time between departures.

Question 7

What are the operating parameters for notifying and applying ADI/MDI procedures?

Answer 7

The operating parameters for notifying and applying ADI/MDI procedures are:

Notification Timing:

• Should be carried out no later than 30 minutes and no earlier than 90 minutes prior to the start of the ADI/MDI.

Duration:

• ADI/MDIs should be applied for a period not exceeding 45 minutes.
• May be extended beyond 45 minutes only with agreement from the relevant Watch Manager.

Interval Between Departures:

• The interval requested between successive departures should be no greater than 6 minutes.

Planning and Implementation:

• Sufficient information is usually available to plan ADI/MDIs well in advance.
• Parameters allow for the late application of ADI/MDI when unforeseen circumstances arise, necessitating short notice intervention.

Question 8

How should ADI/MDIs be applied in comparison to ATFM slots, and what steps should be taken if excessive delays occur?

Answer 8

The application of ADI/MDIs in comparison to ATFM slots and steps for managing excessive delays are:

ADI/MDIs vs. Slots:

• ADI/MDIs should be used as an alternative to a regulation within UK airspace.
• Airfields should disregard any UK ATFM slot when an aircraft is subject to ADI/MDI, except for communicated exceptions.
• Flights regulated outside of the UK should adhere to their ATFM slot but depart according to the ADI/MDI (i.e., not earlier than their slot).
• Airfields unsure of a flight’s status should seek clarification from London FMP.

Excessive Delay:

• If the application of an ADI/MDI results in delays exceeding 20 minutes, the Watch Manager should inform the PC Ops Supervisor.
• The Watch Manager should consider revising the ADI/MDI if appropriate.

Recording of ADI/MDIs:

• A note of ADI/MDIs should be made in the left-hand page of the ATC Log.
• Any significant delays must also be recorded.

Question 9

What are the procedures for implementing arrival flow measures at Belfast TMA?

Answer 9

The procedures for implementing arrival flow measures at Belfast TMA include:

Current Traffic Levels:

• Flow control measures are not normally applied and are at the discretion of the WM/DWM.

Implementing Flow Control Measures:

• If circumstances require flow control measures, contact GS Scotland Lower at 01294 655 230 to enforce restrictions.
• The restriction applied is referred to as the EGAA/C/D Traffic Volume.

Applicability:

• The EGAA/C/D Traffic Volume applies to all IFR arrivals to:
• EGAA (Belfast International Airport)
• EGAC (George Best Belfast City Airport)
• EGAD (Newtownards Airport)