AIM ¶ 3-5-6 — Terminal Radar Service Area
AIM 3-5-6 explains Terminal Radar Service Areas (TRSAs): non-Part 71 airspace, voluntary VFR participation, Class D primary airport, and chart depiction.
A Terminal Radar Service Area (TRSA) is a leftover from the original Terminal Radar Program. Because TRSAs were never created through the rulemaking process, they are not regulatory airspace — they don't appear in 14 CFR Part 71, and there are no TRSA operating rules in Part 91. As a result, TRSAs do not fit into any of the standard U.S. airspace classes (A, B, C, D, E, or G).
Key points to remember:
- The primary airport inside a TRSA is Class D airspace.
- The rest of the TRSA overlies other controlled airspace, typically Class E starting at 700 or 1,200 feet AGL, used to transition between the en route and terminal environment.
- Pilot participation is voluntary for VFR pilots, but ATC encourages you to contact radar approach control to receive TRSA Services (additional radar services like sequencing and separation).
- On VFR sectional and terminal area charts, the TRSA boundary is drawn with a solid black line with altitudes for each segment, and the Class D portion uses a blue segmented (dashed) line.
Operationally, flying through a TRSA is a great opportunity to use radar advisories — but you're not legally required to participate.
Five FAA-written-style questions. Instant explanations, every answer cites its source — no account needed.
What is required before you may operate an aircraft within Class B airspace?