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ACDM Guide

A-CDM Tool: https://vats.im/vdgs

Basic Definitions

EOBT – Estimated Off-Blocks Time
The time submitted with your flight plan.

TOBT – Target Off-Blocks Time
The time your aircraft must be ready for pushback and start-up. Missing TOBT +5 minutes will suspend your flight plan.

TSAT – Target Start-Up Approval Time
The time you can expect start-up clearance.

CTOT – Calculated Take-Off Time
Your assigned take-off time for traffic flow management.

Visual Timeline

EOBT Prefile on VATSIM
(Off-Block UTC HHMM)
→
TOBT Set on
vats.im/vdgs
→
TSAT Assigned by system
(based on TOBT)
→
PDC Request via Hoppie
~20 min before TSAT
→
START-UP Via voice on frequency
TSAT ±5 min
→
CTOT Calculated Take-Off Time
(flow management)

1. VATSIM Prefile (EOBT)

Create your flight in the VATSIM prefile. The time you enter here becomes your EOBT.

2. Check A-CDM Status

After connecting to VATSIM, check your A-CDM status and assigned times. This includes TOBT, TSAT and possible restrictions.

3. Set TOBT

If no TOBT is set, the system will prompt you to enter one. This is required to receive further sequencing.

4. Confirm TOBT

Confirm your EOBT as TOBT or enter a new value if needed. Make sure the time reflects when your aircraft will actually be ready.

Important: At TOBT, your aircraft must be fully ready for pushback.

This includes:
  • Boarding completed
  • GSX loading finished
  • Doors closed
  • Pushback clearance can be accepted immediately
Setting an unrealistic TOBT may result in delays or loss of your slot.

5. TSAT Assignment

The system will assign your TSAT and place you in the departure sequence. Monitor any changes and be prepared accordingly.

6. Request PDC

Approximately 20 minutes before TSAT, request your PDC (Pre-Departure Clearance) in the aircraft.

The PDC will contain your clearance and confirm the A-CDM procedure.

A step-by-step PDC guide is available here: View PDC Guide

7. Request Start-Up

Request start-up on your assigned frequency between TSAT -5 minutes and TSAT +5 minutes.

Use standard phraseology (e.g. “ready for start-up”).

Be ready on time. Missing your TSAT window may result in delays or suspension of your slot.

8. Missed TSAT / Suspension

If you fail to request start-up within your TSAT window (TSAT -5 to TSAT +5 minutes), your flight will be suspended.

Important: Once suspended, you will lose your departure sequence.

To continue, you must:
  • Request a new TOBT via the A-CDM tool
  • Re-enter the departure sequence
This may result in significant delays.
Flight suspended