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Airport - Collaborative Decision Making

A-CDM in summary

Airport CDM is about partners (airport operators, aircraft operators/ground handlers, ATC and the Network Operations) working together more efficiently and transparently in the way they work and share data. One of the main outputs of the CDM process will be greater accuracy in Target Take Off Times which can be used to improve en route and sector planning of the European ATM Network

Accurate departure times have a dual benefit, they:

  • allow all airport partners to use their assets more efficiently,
  • enable better utilisation of European airspace, and
  • improved information to the Network which results in dynamic improvement of regulation slots (CTOT's).

At thirty minutes before departure we use the Target Off-Blocks Time (TOBT) to create a 'virtual place' for the aircraft on the runway and provide visibility of an expected Target Start-up Approval Time (TSAT). We also use your TOBT to calculate a Target Take-Off Time (TTOT) that is communicated to the Network Manager (NMOC) in Eurocontrol. This TTOT is used in the management of European airspace.

Ground operations

Target Off-Blocks Time (TOBT) must be updated to an accuracy of +/- 5 minutes. If your TOBT is changing please take a minute to think through the reason the time is changing and decide on a new time that is realistic. Late, small, and repeated incremental changes are to be avoided as this creeping delay creates a phantom requirement for a runway place.

Remember, your pilot can still call up within +/- 5 minutes of TOBT so there is a ten minute window available.

Flight operations

Estimated Off-Blocks Time (EOBT) must be aligned to within +/-10 minutes of the TOBT.


Pilots should call Delivery at TOBT +/-5 minutes.

A-CDM in winter

During the winter season, A-CDM has a ‘snow mode’ that accommodates the process changes that occur during periods of mass de-icing.

When this mode is enabled, the AO/GH requests de-icing through A-CDM and their contracted De-icing Service Provider (DSP) will allocate one or more rigs. By completing these activities, ATC are made aware that de-icing is taking place and will receive an updated time relating to the end of de-icing activities.

When in ‘snow mode’ remember the following:

  • TOBT must still be maintained to an accuracy of +/- 5 minutes
  • Pilots must call ATC within the TOBT window to confirm ready to start de-icing
  • ATC will confirm the TSAT, which the Pilot should communicate to their DSP
  • The DSP will de-ice/anti-ice the aircraft
  • Pilot must call ATC to confirm completion and receive start-up approval

A-CDM newsletter

We publish a newsletter every two weeks, containing seasonal updates, system information, process reminders, and any other news we believe will be useful to the community.

When you request A-CDM access, you are automatically added to the mailing list. However, if you are not receiving our emails, please contact lhracdm@heathrow.com and we will be pleased to add you to the list.

Our most recent newsletters are:

A-CDM Newsletter Issue 23 - 29 Apr. 2015 (296KB PDF)
A-CDM Newsletter Issue 22 - 2 Apr. 2015 (337KB PDF)
A-CDM Newsletter Issue 21 - 19 March 2015 (315KB PDF)

A-CDM developments

During the first six months of 2015, the team is working on decommissioning a legacy system, UltraSIS, and incorporating some of its features into the Heathrow A-CDM system.

The following training documents are available, depending on the level of knowledge you have about the A-CDM system currently in use at Heathrow:

A-CDM update for current users (1MB PDF) – if you are an experienced user of A-CDM already, this pack will detail the changes being made.

A-CDM for UltraSIS users  (2MB PDF) – if you are transitioning over from UltraSIS, this pack covers how to use A-CDM to complete many of the tasks you do today.

Contact us

If you have any questions, please contact the A-CDM team at lhracdm@heathrow.com. The mailbox is monitored during weekday office hours and a member of the team will respond as soon as possible. If you have a technical issue, please contact the IT Service Desk via itservicedesk@heathrow.com, or call 020 8745 5355 if the matter is urgent.

Request access to A-CDM

Airplane taking off

Download the access request form (66KB PDF)