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Weather & capacity

Bad weather reduces how many aircraft an airport can handle. This page explains which CDM tools help, and when.

First: check demand

Only use CDM measures when demand is higher than the reduced capacity. If traffic is light, bad weather alone is not a reason to regulate. Normal spacing, holding and coordination are enough.

Check the arrival and departure lists, or the CDM dashboard, for how many flights are expected per hour.

Departures: LVO rate

Each airport has a normal and a low-visibility (LVO) departure rate. See Airport CDM data.

  • Use the LVO rate only when low-visibility procedures are in force.
  • Strong wind, gusts or a low cloud base alone do not mean LVO. If departures need extra spacing in those conditions, agree it with the master.

Arrivals: arrival regulation

If more arrivals are expected than the airport can take, an arrival regulation can be set on the CDM dashboard by lowering the airport's arrival rate for a time period. The CDM server then gives CTOTs to inbound flights.

Arrival regulations only give CTOTs to flights departing from airports using CDM. Most long-haul traffic into BIKF (North America, much of Europe) departs from airports without CDM and will not be held on the ground.

For BIKF this means an arrival regulation helps a little, but you will still need:

  • Holding
  • Miles-in-trail or minutes-in-trail requested from the adjacent centre (Gander, Shanwick, Scottish, Bodø, etc.)
  • Speed control on arrival

Example: BIKF in strong crosswind

BIKF 14036G46KT 4000 DZRA BR OVC007 08/08 Q1005

  • Runway 10 is best for this wind (about 22 kt crosswind, gusting 28). Single runway operations.
  • A 700 ft cloud base with 4 km visibility is not LVO. Keep the normal departure rate.
  • Realistic arrival capacity is about 15–18 per hour instead of 26.
  • If fewer than about 15 arrivals per hour are expected: no regulation needed.
  • If arrivals start bunching above that: set an arrival regulation for BIKF of about 16 per hour on the dashboard for the affected period, and use holding or in-trail spacing for flights without CTOTs.

Who decides?

The CDM master, together with the APP/CTR controller, decides on LVO rates and arrival regulations. Inform the adjacent units when a regulation is in force.

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