Traffic Management and Snow Removal

from The WATCH - Fall 2022

Hot Air

Traffic Management and Snow Removal

By Sean Fortier, TCMP Acting Traffic Management Officer

Snow removal can be an impactful constraint on an airport and the ATC system, and the Traffic Management Units (TMUs) at the ATC System Command Center (ATCSCC), Air Route Traffic Control Centers (ARTCCs), Terminal Radar Approach Controls (TRACONs), and Air Traffic Control Towers are a critical part of assisting ATC Specialists in ensuring the safe, orderly and expeditious handling of air traffic services during a snow event.

When a snow event is known well in advance, especially if it is expected to be very impactful, conference calls are scheduled to discuss what the impacts will be, and what plans will be enacted. These calls include stakeholders from the National Weather Service, Airport Operations, Airlines, ATCSCC, and local ATC facility TMU and Operational personnel. Topics that are discussed include:

1. Storm impact expectations such as timing and intensity

2. Airline Schedule considerations

3. Snow removal plan based on snow rates and wind impacts

4. Runway configurations expected

5. Runway and Taxiway closures expected

6. Airport Arrival Rate (AAR) and Airport Departure Rate (ADR) expected

7. Traffic Management Initiatives (TMIs) expected

With all of these considerations, the group will put together a collaborative strategic plan for the event. As the event develops, Airport Operations will continue to coordinate with ATC facilities regarding the tactical plan for snow removal, consulting with the NationalWeather Service as necessary to inform their decisions. The ATCSCC and each facility’s Traffic Management Unit will have a part to play in the management of the plan, and they will work together to keep the system moving in the safest and most efficient manner.

TMU Equipment and Traffic Management Initiatives –

The ATCSCC and each of the facility TMUs use components of the Time Based Flow Management (TBFM) system, and the Traffic Flow Management System (TFMS) to monitor and control the flow of traffic to the affected airport. Some examples of the TBFM and TFMS products that are employed to mitigate snow removal are:

Time Based Flow Management (TBFM) – Assigns delay to arrivals to an airport based on Airport Arrival Rate (AAR).

Flight Schedule Monitor (FSM) – Displays forecast arrival and departure traffic.

NAS Monitor – Displays sector/position volume expected.

National Traffic Management Log (NTML) – Used to communicate, approve, and log information and Traffic Management Initiatives (TMIs) in the NAS.

TBFM and TFMS equipment is then used to determine what types of TMIs need to be employed in order to manage the flow of traffic to a constrained airport. Some examples of TMIs employed to mitigate snow removal are:

Miles in Trail (MIT) Spacing – Spacing required between successive arrivals to manage flow.

Ground Stop (GS) – Departures are held on the ground to manage flow.

Ground Delay Program (GDP) – Departures delayed on the ground to maintain a rate of arrivals over an extended period of constraint at a destination.

Departures are controlled with an Expect Departure Clearance Time (EDCT), and must be released within +/- 5 minutes of this time.

ATCSCC Role –

The ATCSCC has been granted the authority to direct the entire operation of the Traffic Management system. All TMUs assist the ATCSCC to ensure system efficiency and effectiveness without compromising safety.

The ATCSCC coordinates and communicates continuously with all of the Traffic Management Units and the stakeholders, and oversees all aspects of traffic flow throughout the NAS. Every 2 hours the ATCSCC conducts a Strategic Planning Webinar to communicate the plan, and provide an opportunity for any questions and concerns. The ATCSCC also holds an Advanced Planning Webinar each day to provide an outlook of future impacts and constraints. Between these webinars, ATCSCC specialists participate in tactical discussions with the facilities across the NAS, and monitor and approve TMIs on a real time basis.

When needed, facilities coordinate with ATCSCC specialists to institute Ground Stops, Ground Delay Programs, or other regional and national route programs to mitigate constraints in the NAS such as snow removal activity.

ARTCC Traffic Management Unit –

Through communication and coordination with the Tower and TRACON, the ARTCC will utilize TFMS equipment described above to evaluate and deliver the TRACON an appropriate amount of aircraft to meet the AAR.

For Centers that utilize TBFM equipment, the AAR will be programmed into the system, and TBFM will distribute delay times to arrivals within the area of jurisdiction. The TBFM system will also delay departures into the arrival stream within the jurisdiction of the system. TBFM can be programmed to reflect a runway closure period, and will adjust metering delays to accommodate the change in the AAR leading up to and out of the closure.

For Centers that don’t utilize TBFM, MIT restrictions will be utilized to prevent exceeding the AAR at the airport.

If demand exceeds capacity at the airport, the Center may coordinate with the ATCSCC to institute a Ground Stop to prevent excessive holding, or possible diversions.

If demand exceeds capacity at the airport for an extended period of time, the Center may coordinate with the ATCSCC to institute a Ground Delay Program in order to equitably distribute delay to the affected aircraft arriving during that period.

TRACON Traffic Management Unit –

The TRACON will coordinate with the Tower and communicate to the ARTCC what the effective AAR and ADR will be based upon the spacing on final approach required. Additionally, the TRACON will work to balance arrivals between the available runways, and delay aircraft as necessary to prevent overloading the airport.

As conditions deteriorate and a runway closure is expected, the TRACON will participate in the communication between the facilities and Airport Operations to coordinate a plan for the closure. The TRACON will then adjust the flow of traffic to optimize the use of the runway before it closes, and plan to begin arrivals as soon as it is to be opened.

Tower Traffic Management Unit –

The Tower will have the most up to date information on the impact that snow is having on the field as they observe the snowfall and receive braking action reports and PIREPs. Additionally, the Airport Operations personnel will be conducting friction testing to monitor for the need to treat a runway.

As runway conditions deteriorate, the Tower will require additional Mile in Trail spacing from the TRACON in order to accommodate longer landing roll and exit times while clearing aircraft for departure between successive arrivals and runway crossings.

When it is determined by ATC or Airport Operations that a runway can no longer be used for arrival or departure due to braking action reports or friction testing, Airport Operations will initiate a call with the facilities to inform them that they will be closing the runway, and how long the closure will be expected to last.

The Tower will then need to adjust their plans for taxi and departure as well as any other movement area that may be impacted by the surface closure.

Stakeholder Engagement –

Stakeholders such as Airline, International Air Transport Association (IATA), and National Business Aviation Association (NBAA) representatives participate in Strategic Planning Webinars and local conference calls as necessary to provide input and collaborate on possible solutions when constraints limit the capacity of the airport. These solutions can include delaying or cancelling flights, substituting departures, or prioritizing certain arrivals. Stakeholder input is also an especially important piece of the review of the operation post event.