Airspace: controlled, uncontrolled, special use and everything else

AGL is height above the ground directly beneath you. MSL is height above mean sea level. They are units of reference, not different quantities - the same object has a correct AGL value and a correct MSL value simultaneously.

Sectional charts label airspace in MSL because manned pilots fly MSL altimeters.

Airspace is DEFINED in AGL (Class C 4,000 ft, Class D 2,500 ft), so you convert by adding or subtracting the airport elevation.

Your drone's controller shows height above the LAUNCH POINT - a third reference that is neither true AGL nor MSL.

The AGL number is always smaller than the MSL number (above sea level).

Flight levels (FL180 = 18,000 ft) exist but never appear on sectionals or the exam.

Controlled airspace is airspace where ATC provides a SERVICE - principally traffic separation - to manned aircraft. Uncontrolled (Class G) has no such service.

Controlled does not mean someone is watching you. It means manned traffic is likely and is being separated.

Four families - controlled (A/B/C/D/E), uncontrolled (G), special use, and "other airspace".

There is no Class F in the United States.

18,000 ft MSL up to and including FL600. Irrelevant to sUAS operations.

Set around the nation's busiest airports. An inverted wedding cake, generally surface to 10,000 ft MSL, with lateral dimensions tailored per airport. Depicted with SOLID BLUE lines.

The 10,000 ft top is only "generally" - Phoenix tops at 9,000, Miami at 7,000, Orlando at 10,000. Read the chart, do not assume.

Defined and charted in MSL - unusual, since most airspace is defined in AGL.

Each segment shows two numbers, ceiling over floor, in hundreds of feet.

Only the SURFACE segment affects you; outer rings based at 3,000-8,000 ft are far above your 400 ft.

Manned aircraft need an explicit ATC clearance to enter - it is the most restrictive controlled airspace.

The layered shape exists to protect aircraft descending on approach.

A 30 NM ring around Class B marking where manned aircraft need a Mode C transponder. Drawn in the same magenta as Class C, which is why students misread it.

It is an EQUIPMENT requirement for manned aircraft, not an airspace class.

No effect on UAS operations. Not on the exam. Labelled "Mode C veil" on the chart.

Towered airports with significant IFR traffic. Two cylinders - an inner 5 NM radius from the SURFACE to 4,000 ft AGL, and an outer 10 NM radius from 1,200 ft AGL to 4,000 ft AGL. Depicted with SOLID MAGENTA lines.

Defined in AGL, charted in MSL - Albuquerque's 9,400 ft MSL top over a 5,355 ft airport is 4,045 ft AGL, matching the 4,000 ft definition.

Only the inner surface ring matters to you; the outer shelf starts at 1,200 ft.

Manned aircraft must establish two-way communication to enter.

Class C can abut Class B (Fort Lauderdale against Miami) and can be shared by two airports (Tucson with an Air Force base).

A single cylinder around a towered airport, typically 2,500 ft AGL tall, with a radius that varies by airport. Depicted with a DASHED BLUE line and a boxed ceiling number.

The ceiling number is in hundreds of feet MSL - "25" means 2,500 ft MSL, "75" means 7,500 ft MSL at 5,045 ft Prescott (still ~2,455 ft AGL).

Lateral dimensions are based on the INSTRUMENT APPROACH at that airport, which is why there is no standard radius.

Many Class D towers are part-time. When the tower closes the airspace reverts to Class E or Class G - the Chart Supplement says which.

A minus sign ("-30") means up to but NOT including that altitude, because another airspace sits on top.

Class E fills the remaining controlled airspace. Unless charted otherwise it begins at 1,200 ft AGL and extends to 18,000 ft. It may instead begin at 700 ft AGL, at the surface, at a charted zipper-line altitude, or at 14,500 ft MSL.

Chart depictions - dashed magenta = surface; shaded/faded magenta = 700 ft AGL; shaded blue = 1,200 ft AGL on the faded side and 14,500 ft MSL on the dark side; zipper line = the charted MSL figure.

The sectional legend states Class E exists at 1,200 ft AGL unless otherwise designated - and the exam gives you that legend.

By volume it is the largest airspace in the system, though Class G covers more of the map at the altitudes you fly.

All three are Class E beginning at the surface and all three are drawn with the SAME dashed magenta line. E2 is PRIMARY to its own airport. E3 is an extension off Class C. E4 is an extension off Class D. Only E2 requires authorization.

The test - does the dashed magenta area stand alone around an airport (E2, authorization required), or does it hang off a Class C or Class D shape (E3 / E4, no authorization)?

E1 is the 14,500 ft MSL variety; E5 is the 700 ft variety. Neither affects you.

Class E at the surface exists because instrument traffic descends there - so poor visibility is exactly when manned aircraft may be present.

A dashed magenta STRAIGHT line with numbers is the magnetic variation line, not airspace. The instructor uses this as a deliberate trick question.

Everything that is not A, B, C, D or E. No ATC service, and NO authorization required for UAS operations. Not depicted on charts - you identify it by the absence of anything else.

It runs from the surface up to but NOT including the base of the Class E above - so 0 to 699 ft under 700 ft Class E, or 0 to 1,199 ft under 1,200 ft Class E.

Where Class E starts at the surface there is no Class G at all.

Most of the country at the altitudes you fly is Class G.

LAANC (Low Altitude Authorization and Notification Capability) grants near-instant authorization to fly in controlled airspace at or below the ceiling shown in the UAS Facility Map grid for your location.

Grid squares carry a maximum altitude - 0, 100, 200, 300 or 400 ft. Fly at or below it and approval returns in seconds.

Airports not in LAANC require a request through FAADroneZone, quoted as up to 90 days but typically a week or two.

Requests ABOVE the grid figure go through the further-coordination path - roughly a week in the instructor's experience.

Departments should request a WIDE AREA AUTHORIZATION covering the whole grid rather than filing per flight.

Part 107 authorization and a public-safety COA are separate systems. Do not mix them.

Airspace separating civil traffic from special government activity. Prohibited (P), Restricted (R), Warning (W), Military Operating Areas, Alert areas (A), and Controlled Firing Areas.

PROHIBITED - security; entry never permitted, no approval possible. P-56 and P-73 over Washington DC.

RESTRICTED - hazardous activity (gunnery, missiles); may be active or inactive by published hours or NOTAM. Contact the controlling agency.

WARNING - same hazards but beginning 3 NM outside the US coast.

MOA - separates military training traffic; not prohibited, but expect fast low-level jets and helicopters.

ALERT - high volume of pilot training or unusual activity such as aerobatics; avoidance advised, not required.

CFA - activity STOPS when a spotter sees an aircraft, so it is NOT charted at all. You will never see one.

Chart symbology - P, R and W share a blue hairline comb; MOA and Alert share a magenta one. The letter tells you which.

The sectional's margin panel lists each area's altitudes, times of use and controlling agency.

Temporary prohibitions issued by NOTAM - disaster areas, wildfires, major incidents, VIP movement, and space operations. Not charted, because they are not known in advance.

STADIUM TFR (NOTAM FDC 7/4319) - 3 NM radius, surface to 3,000 ft AGL, from one hour before to one hour after the event, at stadiums seating 30,000 or more. Applies to MLB, NFL, NCAA Division I football, and NASCAR / Indy / Champ races.

DISNEY - a standing 'permanent temporary' flight restriction since 9/11 at both parks; 3 NM radius, below 3,000 ft AGL.

VIP TFRs travel with the protected person - they float.

Sources - tfr.faa.gov, 1-800-WX-BRIEF for a live briefer, or 1800wxbrief.com.

The residual category - everything not controlled, uncontrolled or special use.

MILITARY TRAINING ROUTES - VR (visual) and IR (instrument). FOUR digits means the route includes segments BELOW 1,500 ft AGL; three digits means above. Four digits is the one to watch.

PARACHUTE JUMP AREAS - a parachute symbol; details in the Chart Supplement.

VFR FLYWAYS and CLASS B VFR TRANSITION ROUTES - corridors through busy airspace, shown on Terminal Area Charts rather than sectionals; expect concentrated traffic.

NSA - national security areas; avoidance is REQUESTED, not required, unless a NOTAM prohibits it.

FRZ - flight restricted zone around the Capitol and White House. No flight.

ADIZ - air defense identification zone along the borders and coasts.

SFRA - fewer than ten nationally (Washington DC, Los Angeles, Hudson River, Grand Canyon, Luke AFB); each has its own rules, and DC has drone-specific training requirements.

SPECIAL MILITARY ACTIVITY areas contain military UAS, often shadowed by fast manned aircraft.

Drones may not be launched, landed or operated in national parks or designated wilderness areas - a drone counts as a motorised vehicle, which those areas prohibit.

Wilderness areas are drawn with a solid blue line dotted on the INSIDE.

Manned aircraft are merely REQUESTED to stay 2,000 ft AGL above them; the drone prohibition is a land-management rule, not an airspace one.

The instructor rejects the launch-from-outside-and-fly-in loophole outright.

The Grand Canyon is both an SFRA and a national park - two separate restrictions.

Tethered balloons on cables (e.g. Key West to 14,000 ft MSL) sit inside restricted areas; the cable is effectively invisible and has killed people.

Airspace questions follow a small number of shapes - identify the airspace over an airport, find a floor or ceiling, or work out how to check whether something is active.

Half the difficulty is FINDING the named airport in the figure.

Class G answers are phrased 'surface up to but not including' - the correct option names both the Class G band and the Class E above it.

Class C authorization - the exam wants 'receive ATC authorization'. Real life is LAANC or FAADroneZone.

The chart legend is provided in the exam supplement; use it rather than trusting memory on symbology.

Activity status of a MOA or restricted area is found via the margin panel's controlling agency, or by NOTAM.