Class D Airspace

AIM ¶ 3-2-5 Class D Airspace

AIM 3-2-5 explains Class D airspace dimensions, two-way radio entry requirements, speed limits, and part-time tower operations for pilot students.

In Plain English

Class D airspace surrounds airports with an operational control tower and generally extends from the surface up to 2,500 feet above airport elevation (charted in MSL). Each Class D area is individually tailored, and on charts it appears as a blue segmented line on Sectionals and Terminal charts.

Key requirements for student pilots:

  • Pilot certification: No specific rating required.
  • Equipment: An operable two-way radio (unless ATC authorizes otherwise).
  • Entry: You must establish two-way radio communications with the tower before entering. Communications are established when the controller responds using your callsign (e.g., "N123AB, standby"). If the controller says only "aircraft calling tower, standby," comms are NOT established and you may not enter.
  • If told to "remain outside the Class Delta airspace and standby," you must stay clear.
  • Speed limit: Max 200 knots indicated at or below 2,500 ft AGL within 4 NM of the primary airport.
  • No VFR separation services are provided.

Many towers are part-time. When closed, the airspace reverts to Class E or Class G per the Chart Supplement. This matters operationally because your communication and weather minimums change accordingly.

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AIM Source Text
FAA AIM ¶ 3-2-5
Definition. Generally, Class D airspace extends upward from the surface to 2,500 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower. The configuration of each Class D airspace area is individually tailored and when instrument procedures are published, the airspace will normally be designed to contain the procedures. Class D surface areas may be designated as full-time (24 hour tower operations) or part-time. Part-time Class D effective times are published in the Chart Supplement. Where a Class D surface area is part-time, the airspace may revert to either a Class E surface area (see paragraph 3-2-6 e 1 ) or Class G airspace. When a part-time Class D surface area changes to Class G, the surface area becomes Class G airspace up to, but not including, the overlying controlled airspace. Operating Rules and Pilot/Equipment Requirements: Pilot Certification. No specific certification required. Equipment. Unless otherwise authorized by ATC, an operable two-way radio is required. Arrival or Through Flight Entry Requirements. Two-way radio communication must be established with the ATC facility providing ATC services prior to entry and thereafter maintain those communications while in the Class D airspace. Pilots of arriving aircraft should contact the control tower on the publicized frequency and give their position, altitude, destination, and any request(s). Radio contact should be initiated far enough from the Class D airspace boundary to preclude entering the Class D airspace before two-way radio communications are established. Departures from: A primary or satellite airport with an operating control tower. Two-way radio communications must be established and maintained with the control tower, and thereafter as instructed by ATC while operating in the Class D airspace. A satellite airport without an operating control tower. Two-way radio communications must be established as soon as practicable after departing with the ATC facility having jurisdiction over the Class D airspace as soon as practicable after departing. Aircraft Speed. Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class D airspace area at an indicated airspeed of more than 200 knots (230 mph). Class D airspace areas are depicted on Sectional and Terminal charts with blue segmented lines, and on IFR En Route Lows with a boxed [D]. Surface area arrival extensions: Class D surface area arrival extensions for instrument approach procedures may be Class D or Class E airspace. As a general rule, if all extensions are 2 miles or less, they remain part of the Class D surface area. However, if any one extension is greater than 2 miles, then all extensions will be Class E airspace. Surface area arrival extensions are effective during the published times of the surface area. For part-time Class D surface areas that revert to Class E airspace, the arrival extensions will remain in effect as Class E airspace. For part-time Class D surface areas that change to Class G airspace, the arrival extensions will become Class G at the same time. Separation for VFR Aircraft. No separation services are provided to VFR aircraft.
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Oral Exam Questions a DPE Might Ask
Q1What are the standard vertical and lateral dimensions of Class D airspace, and how is it depicted on charts?
Per AIM 3-2-5, Class D generally extends from the surface up to 2,500 feet above airport elevation (charted in MSL), individually tailored to contain instrument procedures. It is depicted with blue segmented lines on Sectional and Terminal charts, and as a boxed [D] on IFR En Route Low charts.
Q2How do you know when two-way radio communications have been 'established' for entry into Class D airspace?
Per AIM 3-2-5, communications are established when the controller responds using your aircraft callsign — e.g., 'N123AB, standby' is sufficient to enter. A generic response like 'aircraft calling tower, standby' does NOT establish communications, and you may not enter. If told to 'remain outside,' you must stay clear until cleared in.
Q3What is the maximum airspeed in Class D airspace, and what happens to the airspace when the tower closes?
Per AIM 3-2-5, unless authorized by ATC, no person may operate above 200 knots indicated (230 mph) at or below 2,500 ft above the surface within 4 NM of the primary airport. When a part-time tower closes, the airspace reverts to Class E surface area rules or a combination of Class E (to 700 ft AGL) and Class G to the surface, per the Chart Supplement.
Related Paragraphs in Chapter 3
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