APP/ACC
Key Definitions
Throughout the following sections, several important terms will be used. Below are their definitions to ensure clarity.
Upstream and Downstream Sectors
- Upstream Sector: The airspace sector an aircraft is coming from before entering the current sector.
- Downstream Sector: The airspace sector an aircraft is heading toward after leaving the current sector.
For example, if an aircraft is transitioning through sectors A → B → C, then from the perspective of sector B:
- Sector A is the upstream sector.
- Sector C is the downstream sector.
Coordination Point (COP)
A Coordination Point (COP) is typically a designated waypoint close to a sector boundary where aircraft are handed off between controllers. This reference point helps both the transferring and receiving controllers manage traffic more efficiently.
In many operational setups:
- COPN (Entry COP) marks the handoff point for aircraft entering the sector.
- COPX (Exit COP) marks the point where an aircraft leaves the sector.
When coordinating handoffs, controllers should refer to recognizable waypoints, VORs, or major aerodromes rather than obscure landmarks that may not be known to the receiving controller. In a simulated environment like VATSIM, specifying the aircraft’s exact location can be useful since pre-planned coordination may be less structured.
Transfer of Control
The transfer of control refers to the moment when responsibility for issuing flight instructions—such as altitude changes, heading adjustments, or speed restrictions—shifts from one controller to another.
Unless otherwise specified in verbal agreements or a Letter of Agreement (LoA), control is transferred once the aircraft enters the new sector and has reached at least half of the required minimum separation distance from the sector boundary.
For example, if the required separation is 3 NM, the aircraft should maintain at least 1.5 NM from the boundary on each side. This ensures that both sectors collectively maintain the full separation requirement without requiring additional coordination.
Silent Transfer of Control
In some cases, silent transfer of control is defined within LoAs. This means that under specific conditions, an aircraft can be handed off to the receiving controller without requiring additional verbal coordination. These agreements streamline operations by allowing controllers to focus on active conflicts rather than routine handovers.
Transfer of Communication (≠ Transfer of Control)
A transfer of communication occurs when an aircraft is instructed to switch to a new ATC frequency. This does not necessarily mean that control of the flight is being transferred at the same time. Communication and control can be transferred separately based on operational requirements.
Controller Initials
In real-world air traffic control centers, each controller is identified by a unique set of initials, typically formed from the first letter of their first and last name.
During coordination calls, initials serve as a form of acknowledgment—signaling that both controllers agree on the discussed handover. The conversation is only concluded once both parties state their initials, effectively marking the coordination as finalized.