Winter season preparation

Published on Thursday 4 January 2018

Airlines are associated to the preparation of winter season plans at local or national level. It starts by a yearly national consultation organized by DGAC.

This meeting aims at :

  • agreeing on high level objectives to manage operations if a significant winter weather episode was to disrupt either one of the French platforms,
  • defining the high level method to anticipate and best manage the potential disruption,
  • presenting and explaining the procedure leading to a flight cancellation decision on any impacted airports if the forecasted weather disruptions were to be significant.

When a snow episode arises, the primary objective of a winter plan is to maintain a safe traffic flow to and from either one of the concerned French airports while ensuring that the flight program of each airline is the least impacted. The step-by-step approach followed relies on a weather forecast regularly updated by the national MET office and a thorough information process to all involved parties, particularly emphasized in A-CDM airports.

Lyon St Exupery, at the heart of the French Alps

The 4 major gateways into the French Alps share the same airspace. The Lyon approach (APP) operational unit handles all traffic to Lyon St Exupery and Grenoble. It is also a feeder for Chambery/Annecy APP while managing all its departures.

Lyon St Exupéry
Crédits : Tous droits réservés - DGAC

Lyon APP and its satellite airfields are frequently subject to various kinds of snow episodes during the winter season. Managing the traffic in such cases follows well identified processes.

During the ski season, the traffic significantly increases and particularly towards the satellite airfields. Between Chambery/Annecy and Grenoble, 300 additional flights concentrate on 17 week-ends and come in addition to the usual traffic at Lyon Saint Exupéry. On Saturdays, the traffic pattern reverses and the pressure is mostly applied on Grenoble, Chambery and Annecy subject to limited capacity. Air traffic intensifies, complexity increases with 3 simultaneous approaches to manage and sometimes conflicting arrival/departure trajectories to integrate.

If the trend were to be confirmed with a continuous increase of the traffic demand to Grenoble and Chambéry during the 17 week-ends of the ski season, the current air traffic system of the Lyon Terminal Manoeuvring Area (TMA) will evolve to be more consistent and efficient in dealing with this mixed traffic.

The different platforms being so close from each other, Air Traffic Management (ATM) during snow episodes has to consider the airspace as a whole, as such event may impact the 3 airfields at the same time. The traffic flow segregation usually applied turns out to be inefficient during critical conditions.
Therefore, the role of Lyon St Exupery tower manager is crucial. He must decide on the best ATM strategy to apply between Grenoble, Lyon and Chambery to ensure safe operations to these platforms with a minimum of disruptions. He must coordinate with local partners and adjacent centres at all times, particularly with the Geneva approach which traffic is particularly important during the winter season and potentially impacting if severe weather events arise.

Traditional weather alternates for Lyon St Exupery are Geneva, Marseille and Paris. Grenoble may be chosen as a short time waiting platform if the forecast is accurate enough and shows rapid signs of improvement.

Crédits : Tous droits réservés - DGAC

Highlights of the Lyon St Exupery snow plan

From coordination processes to suspending operations

Updated every year, Lyon snow plan covers the winter season from mid-November to mid-April. It details the roles and responsibilities of all the involved actors on the airside and the groundside areas. It thus provides guidance in regards to the different coordination levels and processes to follow between the Air Traffic Services of Lyon (from the tower manager to the ops manager on duty), the airport operator (Aeroport De Lyon - ADL), the safety units, the Met service provider (Meteo France). For example, when snow episodes are forecasted, at J-1 the airport operator has to warn the staff dedicated to specific tasks for such cases (snow clearing, de-icing) and has to make sure that all vehicles and equipment is operative.
Besides, the snow plan lists the real time actions to be undertaken according to various weather statuses such as potential risk of snow, snowfalls beginning and heavy snowfalls in progress. It notably shows the snow clearing priorities on the manoeuvring area (i.e. standard snow clearing circuits : preferential runway and key taxiways to be cleared in priority) and on the different aprons. This plan provides all involved actors with a clear picture of what to expect.

Remember that clearing a runway and assessing its condition before giving it back to operations may take up to one hour and may cause ATS disruptions such as single runway operations or compulsory runway exit taxiways.

SNOWTAM : When warranted, a SNOWTAM will be issued by the airport authority to notify users of the presence of, or the removal of, hazardous conditions due to snow, ice, slush or the resulting standing water on the movement surfaces of the aerodrome. The maximum validity period for a SNOWTAM is 24 hours and a new SNOWTAM will be issued whenever there is a significant change in conditions.

A-CDM Lyon : A-CDM processes will complement the actual snow plan and the existing coordination procedures. It shall notably strengthen the pre tactical phase by a face to face meeting with all involved actors including airline operators, airport operators and assistance. The objective is to reach the same level of knowledge and understanding of the situation. Critical ops information such as the implementation of preventive regulations can thus be shared and agreed upon by all.

Ultimately, if the real time situation worsens and/or is expected to last, leading to measures that jeopardize the operational management of the platforms (both runways needing to be simultaneously cleared, heavy snow falls, etc.) suspending the operations may be decided.


What about the massive diversion plan for the south-east quarter?

In case of significant weather disruption on one of the major airports of the south east quarter that could lead to massive diversions by aircraft operators, a plan is followed to anticipate this critical phase for all first line actors. Marseille ACC will gather the stand availabilities and associated aircraft types on all airport subject to accommodate the diverting flights in order to best help air crews in their choice of the most suitable weather alternate.


A-CDM: enhanced ATC tools for improved recovery phase

The A-CDM concept is based on the sharing of flight-related information and the integration of all the constraints of the partners working in collaboration (airlines, airports, ground handling agents and the ATS unit).
The Pre-Departure sequencing System (PDS) calculates an off-block departure sequence, providing an optimized off-block departure time for each flight. It is connected to DSNA Departure MANager tool (DMAN) that shows the departure sequence to the tower controller as computed, and ensures a timely communication of take-off times to Eurocontrol’s Network Manager.

These tools turn out to be particularly useful when weather events occur as they make key information available to all involved actors. The tower manager can change the runway capacity status according to the real time situation and set it within a time frame of 2 hours. This input will automatically update the Target Start Up Approval Times (TSAT) for each aircraft, letting everybody know their new position in the departure sequence according to the disruption.
When a runway is snowbound and needs clearing (i.e. 1 hour notice), the D-MAN will indicate the time at which it would be returned to operations, thus improving the predictability of the recovery phase.

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