Hi! I was flying to Princess Juliana from the southeast as part of the calendar event, and San Juan Oceanic Center as well as TNCM approach was online. Initially, I thought I would only contact center to check in and request descent, but looks like everyone on freq had requested approach? I was planning on just waiting until I was in range for approach and then request approach from them. So now, I’m not rly sure what each freq is for, in general. What is center for apart from checking in? and how do I know when these different roles take effect?
This was also on expert so I assume the controller knew what they were doin.
When airspaces are busy, especially with larger airports or busy events, it’s not uncommon to see Center and Approach or even 2 approach frequencies to split the load. In this case, they are requesting approach as Center will likely vector them closer to TNCM before handing them off to approach. Cheers
To understand the difference between these two frequencies in the simulation air traffic control (such as Infinite Flight on the Expert server, which you mention by the calendar event), the key is in the airspace and the phase of the flight that each one handles.
Key differences between Center and Appr Control Role Rank and Altitude Main Function Center
(Center / On Route) Very wide (Covers entire oceanic countries or regions at high altitude). Controls the cruise flight, authorizes the initial descent and organizes the flow of traffic that comes from far to the airports.
Function of the FIR Center
The FIR Center (Flight Information Region) is the facility responsible for providing air traffic services within a designated Flight Information Region. Its main objective is to ensure that aircraft operate safely, orderly, and efficiently.
Main responsibilities:
Provide Flight Information Service (FIS).
Provide alerting services in case of emergencies.
Monitor and coordinate aircraft operating within the FIR.
Coordinate the transfer of aircraft between different ATC sectors and facilities.
Provide air traffic control services where applicable.
Disseminate relevant information such as weather conditions, NOTAMs, and traffic information.
Maintain safe and efficient traffic flow within its area of responsibility.
Approach Reduced (Generally a radius of 30–50 miles around the airport). Separate and sequence the planes in the final phase, giving them vectors (directions) to align them with the runway. Authorizes the approach (Approach request).
Initially, it would be like this: ATIS, Ground, Tower, Departure, Approach (some airports work like this) and then Centre. (the same in vice versa without the contact of departures, it would be: Centre, Approach Control, Tower and Ground)
Generally centre is used to ensure there’s no conflicts between aircraft but also to ensure that traffic flow is managed at busy hubs before aircraft reach approach airspace, which may include things like holds.
Edit: centre can/may provide approach service if an airport doesn’t have a live approach frequency.
You’re right to wait until you’re within distance/altitude for approach; I suspect many didn’t know what they’re doing with centre frequency so were requesting approaches as soon as they could; I’ve heard people request approaches to airports thousands of miles away as soon as they take off…
Here’s some more useful topics that may also help: