Airspace Applied: Charts, Entry, VFR Minimums

The chart draws Class B as solid blue rings. Each shelf label is the ceiling over the floor in hundreds of feet MSL. The Chart Users' Guide: "The MSL ceiling and floor altitudes of each sector are shown in solid blue figures with the last two zeros omitted" 1. A shelf labeled 100 over 40 runs from 4,000 to 10,000 feet MSL. The Pilot's Handbook: Class B "consists of a surface area and two or more layers (some Class B airspace areas resemble upside-down wedding cakes)" 2.

Class C

Class C is a core and a shelf. The Pilot's Handbook: "the airspace usually consists of a surface area with a five NM radius, an outer circle with a ten NM radius that extends from 1,200 feet to 4,000 feet above the airport elevation" 3. On the chart the rings are solid magenta, "shown in solid magenta figures with the last two zeros eliminated" 1.

Class D

Class D is a dashed blue circle with a boxed ceiling figure in hundreds of feet MSL. The Pilot's Handbook: "Class D airspace is generally airspace from the surface to 2,500 feet above the airport elevation (charted in MSL)" 4. A boxed 25 at a sea level field is 2,500 feet MSL. A boxed 47 at a field with an elevation of 2,200 feet is the same 2,500 feet above the field.

A minus sign before the boxed figure means up to but not including that altitude. The Chart Users' Guide: "A minus in front of the figure is used to indicate 'from surface to, but not including...'" 1. The minus appears where the Class D's top meets the floor of a Class B or C shelf above it. An airplane at exactly the boxed altitude is in the shelf, not the Class D.

The airport's color

Airport symbol color shows whether the airport has a control tower. The Chart Users' Guide: "Airports with Control Towers (CT) and their related data are shown in blue. All other airports and their related data are shown in magenta" 5. A blue airport has a tower. A magenta airport has none, and its frequency is a CTAF. The pilot reads the color before dialing the frequency.

The chart draws Class E to the surface as a dashed magenta circle around the airport. The Chart Users' Guide: "Class E Surface (SFC) Airspace is symbolized with a magenta dashed line" 6. Class E to the surface extends the controlled airspace rules to the runway at an airport with no tower, usually one with an instrument approach.

The vignette

Inside the magenta vignette, the shaded band, Class E begins at 700 feet AGL. Outside it, Class E generally begins at 1,200 feet AGL. The Chart Users' Guide: "Class E Airspace exists at 1200' AGL unless designated otherwise," and "Controlled airspace floors of 700' above the ground are defined by a magenta vignette" 6. The Pilot's Handbook: "In most areas, the Class E airspace base is 1,200 feet AGL. In many other areas, the Class E airspace base is either the surface or 700 feet AGL" 7. The soft edge of the shading is the side where the floor is 700 feet.

Class G

Below the Class E floor is Class G. The Pilot's Handbook: "Class G airspace extends from the surface to the base of the overlying Class E airspace" 8. At most airports it is a thin layer, 700 or 1,200 feet deep. In the mountain West it can be thicker, where the chart shows a blue vignette or a floor number. The Chart Users' Guide says Class G "extends up to 14,500' Mean Sea Level" where nothing lower is designated 6.

Class A

Class A begins at 18,000 feet MSL everywhere. The Pilot's Handbook: "Class A airspace is generally the airspace from 18,000 feet mean sea level (MSL) up to and including flight level (FL) 600," and "Unless otherwise authorized, all operation in Class A airspace is conducted under instrument flight rules (IFR)" 9. Entry requires an IFR clearance and an instrument rating. There are no VFR operations in Class A. The chart does not draw Class A. The Chart Users' Guide: "While visual charts do not depict Class A, it is important to note its existence" 1.

Class G has no ATC communication requirement. Section 91.126 governs the airport rules there, sets the pattern direction, and requires nothing on the radio. Self-announcing on the CTAF is procedure and good sense. The AIM's traffic advisory practices are recommendations: "Pilots of inbound traffic should monitor and communicate as appropriate on the designated CTAF from 10 miles to landing" 10. The call is not a legal requirement. Module 1-10 teaches the pattern.

Class E en route

Class E en route has no communication requirement for a VFR airplane. Section 91.127 applies the Class G airport rules to an airport in Class E: "each person operating an aircraft on or in the vicinity of an airport in a Class E airspace area must comply with the requirements of § 91.126" 11. Away from an airport, a VFR pilot in Class E does not need to contact ATC. The pilot can request flight following.

Class D

Class D entry requires two-way radio communications established before entering and maintained inside. Section 91.129: "Each person must establish two-way radio communications with the ATC facility (including foreign ATC in the case of foreign airspace designated in the United States) providing air traffic services prior to entering that airspace and thereafter maintain those communications while within that airspace" 12. The AIM adds the timing: "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" 13. North Aero's call is ten miles out, well before the dashed line.

The callsign test

The controller's use of the callsign establishes communications. The AIM: "If the controller responds to a radio call with, '[aircraft callsign] standby,' radio communications have been established and the pilot can enter the Class D airspace" 13. The other case: "if the controller responds to the initial radio call without using the aircraft callsign, radio communications have not been established and the pilot may not enter the Class D airspace," as in "Aircraft calling Manassas tower standby" 13. "Warrior three four five, standby" is established. "Aircraft calling, standby" is not. The pilot who hears the second reply stays outside the dashed line.

Class C entry takes the same established-communications test as Class D, plus the equipment. Section 91.130: "Each person must establish two-way radio communications with the ATC facility ... providing air traffic services prior to entering that airspace and thereafter maintain those communications while within that airspace," and "no person may operate an aircraft within a Class C airspace area designated for an airport unless that aircraft is equipped with the applicable equipment specified in § 91.215, and after January 1, 2020, § 91.225" 14. Entry requires the callsign and the equipment. The equipment is an altitude-reporting transponder and ADS-B Out.

Class B needs the words

Class B entry requires an explicit ATC clearance. Section 91.131: "The operator must receive an ATC clearance from the ATC facility having jurisdiction for that area before operating an aircraft in that area" 15. Hearing the callsign is not enough. The AIM: "Regardless of weather conditions, an ATC clearance is required prior to operating within Class B airspace" 16.

The words are "cleared into the Class Bravo." Without those words the airplane stays out. Vectors, a squawk, and flight following are not a clearance. The AIM: "It is the responsibility of the pilot to ensure that ATC clearance or radio communication requirements are met prior to entry into Class B, Class C, or Class D airspace. The pilot retains this responsibility when receiving ATC radar advisories" 17.

Who can fly in Class B

Class B requires at least a private pilot certificate, or an endorsed student. Section 91.131(b): the pilot in command "holds at least a private pilot certificate," or "The aircraft is operated by a student pilot who has met the requirements of § 61.94 or § 61.95 of this chapter, as applicable" 15. Section 61.95 sets the student's terms: ground and flight training "on that Class B airspace area," and a logbook endorsement "dated within the 90-day period preceding the date of the flight in that Class B airspace area" that "specifies that the student pilot has received the required ground and flight training, and has been found proficient to conduct solo flight in that specific Class B airspace area" 18. The endorsement names the Class B. An endorsement for one Class B does not cover another.

The busiest twelve

A short list of the busiest Class B airports bars student solos entirely. Section 91.131(b)(2): "no person may take off or land a civil aircraft at those airports listed in section 4 of appendix D to this part unless the pilot in command holds at least a private pilot certificate" 15. The list is twelve airports, from Atlanta to Washington National, and includes San Francisco International 19. A student with a valid endorsement cannot land at any of them.

Class A, B, and C require an altitude-reporting transponder and ADS-B Out. The rule also covers the airspace at and above 10,000 feet MSL, except within 2,500 feet of the ground. Section 91.215(b): "In Class A, Class B, and Class C airspace areas," and "at and above 10,000 feet MSL, excluding the airspace at and below 2,500 feet above the surface" 20. Section 91.225(d) lists the same airspace for ADS-B Out 21.

The Mode C veil

The Mode C veil is the 30-mile circle. Section 91.215(b)(2): "In all airspace within 30 nautical miles of an airport listed in appendix D, section 1 of this part from the surface upward to 10,000 feet MSL" 20. The AIM: within the veil, "aircraft operating within this airspace must be equipped with an operable radar beacon transponder with automatic altitude reporting capability and operable ADS-B Out equipment" 16. The chart draws the veil as "a solid magenta line" 22. The veil applies under the shelves and outside them. An airplane at 1,500 feet under the lowest shelf, 25 miles from the primary airport, is inside the veil.

Above the ceiling

Section 91.215 still requires the equipment above the ceiling of a Class B or C, within the lateral boundaries, up to 10,000 feet MSL. Section 91.215(b)(4): "All aircraft in all airspace above the ceiling and within the lateral boundaries of a Class B or Class C airspace area designated for an airport upward to 10,000 feet MSL" 20. Section 91.225(d)(3) says the same for ADS-B Out 21. Over the top of a Class C, between its ceiling and 10,000 feet, the transponder is on and reporting.

ADS-B Out's own rings

The ADS-B Out airspace is the transponder airspace plus two Class E areas. Section 91.225(d): "Class E airspace within the 48 contiguous states and the District of Columbia at and above 10,000 feet MSL, excluding the airspace at and below 2,500 feet above the surface," and "Class E airspace at and above 3,000 feet MSL over the Gulf of Mexico from the coastline of the United States out to 12 nautical miles" 21. The Warrior carries both a transponder and ADS-B Out. The list matters when a unit fails. Without the unit, the airplane cannot enter the listed airspace.

Without the equipment

Entering the listed airspace without the equipment requires an ATC authorization arranged in advance. Section 91.215(d): "Requests for ATC authorized deviations must be made to the ATC facility having jurisdiction over the concerned airspace within the time periods specified" 20. For ADS-B, section 91.225(g): "For operation of an aircraft that is not equipped with ADS-B Out, the request must be made at least 1 hour before the proposed operation" 21. The FAA's online tool for that request is ADAPT. The pilot does not make the request airborne at the boundary.

The speed cap below 10,000 feet MSL is 250 knots indicated. Section 91.117(a): "no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.)" 23. The Warrior cannot reach that speed. The rule matters to the Warrior because each faster airplane must obey it. That limit keeps closure rates below 10,000 feet survivable.

Two hundred near the primary airport

At or below 2,500 feet AGL within 4 miles of a Class C or D primary airport, the cap is 200 knots. Section 91.117(b): "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 C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph). This paragraph (b) does not apply to any operations within a Class B airspace area" 23.

Two hundred under the shelf

Under a Class B shelf and in a VFR corridor through Class B, the cap is 200 knots. Section 91.117(c): "No person may operate an aircraft in the airspace underlying a Class B airspace area designated for an airport or in a VFR corridor designated through such a Class B airspace area, at an indicated airspeed of more than 200 knots (230 mph)" 23. VFR traffic that stays out of the Class B gathers under the shelf. The cap keeps that traffic slow.

The flight of N4252G

On June 9, 2016, at 1:09 in the afternoon, a Cirrus SR20 stalled and spun into a hardware store parking lot. The lot was half a mile north of runway 35 at Houston Hobby. The pilot, a 46-year-old private pilot with 333 hours, and her two passengers died. She flew from Norman, Oklahoma, on a VFR flight plan, into "a high-volume air carrier airport surrounded by Class B airspace" 24.

The tower cleared her to land on runway 4 behind a Boeing 737 on a 3-mile final. Two minutes later, "The local controller directed the pilot to maintain maximum forward airspeed due to a Boeing 737 on a 9-mile final approach that was trailing the airplane and traveling 80 knots faster." Two minutes after that instruction, "Due to the trailing Boeing 737, which was overtaking the airplane, the local controller directed the pilot to go around and fly runway heading" 24.

The next eleven minutes included these events:

• a right base to runway 35
• a traffic call for another 737
• a left turn of 30 degrees
• an offer to follow the 737 to runway 4
• a turn back to runway 35
• a climb to 1,600 feet
• a straight-in the pilot said she was not lined up for
• a second go-around because she was too high
• a third approach.

At 1:08 she was over runway 35 and called a go-around. The new controller's reply was a 16-second transmission, then a 23-second one that ended "ma'am, ma'am, uh, straighten up, straighten up!" 24. She raised the flaps at 58 knots in a left turn. The airplane stalled, spun, and struck a parked car.

The NTSB on the workload: "compliance with ATC instructions greatly increased the pilot's workload as it led to an extended period of close-in maneuvering at a Class B airport due to the larger and faster airplanes converging on the airport. During this extended period of maneuvering the pilot did not assert the responsibilities that accompany being a pilot-in-command and did not offload the workload by either requesting to be re-sequenced, telling the controller to standby, or stating 'unable'" 24. The probable cause was the go-around with the flaps raised early. The NTSB continued: "Contributing to the accident were the initial local controller's decision to keep the pilot in the traffic pattern, the second local controller's issuance of an unnecessarily complex clearance during a critical phase of flight. Also contributing was the pilot's lack of assertiveness" 24.

Where the pilot could have prevented the accident

A 333-hour private pilot chose a Class B air carrier airport. Each decision below is marked with the PAVE category that applied to it.

The everyday minimums are 3 miles and 500, 1,000, 2,000. Section 91.155's table for Class C, Class D, and Class E below 10,000 feet: "3 statute miles" and "500 feet below. 1,000 feet above. 2,000 feet horizontal" 25. The school's shorthand is "three, one-five-two": 3 miles, 500 below, 1,000 above, 2,000 beside. That shorthand covers most of a Warrior's flying.

Class B: clear of clouds

Class B takes 3 miles and clear of clouds. The table: "Class B 3 statute miles Clear of Clouds" 25. The exception exists because each pilot inside holds an ATC clearance and the controller separates each airplane. The AIM: "The cloud clearance requirement for VFR operations is 'clear of clouds'" 16.

Class G by day

Class G by day, at or below 1,200 feet AGL, takes 1 mile and clear of clouds. The table: "1,200 feet or less above the surface (regardless of MSL altitude)," "Day," "1 statute mile," "Clear of clouds" 25. This lower minimum applies in a thin layer over most of the country.

Class G at night

Class G at night takes 3 miles and 500, 1,000, 2,000. The table: "Night," "3 statute miles," "500 feet below. 1,000 feet above. 2,000 feet horizontal" 25. Night removes the lower Class G minimum. The clouds that a pilot can see at a mile by day are not visible at night, so the cloud distances apply again.

At and above 10,000 feet

At and above 10,000 feet MSL the minimums rise to 5 miles and 1,000, 1,000, 1 mile. The table for Class E: "At or above 10,000 feet MSL," "5 statute miles," "1,000 feet below. 1,000 feet above. 1 statute mile horizontal" 25. The reason is the speed rule: the 250-knot cap of 91.117 ends at 10,000 feet 23. Above that altitude the traffic is faster and closure rates double. The pilot needs more distance to see and avoid.

Under a ceiling below 1,000 feet, VFR flight inside a surface area is not legal. Section 91.155(c): "no person may operate an aircraft beneath the ceiling under VFR within the lateral boundaries of controlled airspace designated to the surface for an airport when the ceiling is less than 1,000 feet" 26. The surface area is the dashed blue or dashed magenta circle. Under a 900-foot overcast inside that circle, there is no VFR.

Three miles on the ground

Ground visibility must be at least 3 miles to take off, land, or enter the pattern under VFR inside a surface area. The rule covers Class B, C, D, and E surface areas. Section 91.155(d): "no person may take off or land an aircraft, or enter the traffic pattern of an airport, under VFR, within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport" unless "ground visibility at that airport is at least 3 statute miles," or, if ground visibility is not reported, flight visibility is at least 3 26.

The preflight use of 91.155

The preflight use of 91.155 is a comparison. The pilot sets the destination's METAR and TAF ceiling and visibility against the surface area rule. The two numbers are 1,000 feet and 3 miles. A ceiling of 1,000 feet or more and a visibility of 3 miles or more make the field enterable under VFR. Either number below its minimum closes the field to VFR, and the pilot plans for an alternate or does not go. The pilot makes the comparison at the desk, where the numbers are, and not in the pattern, where the ceiling is.

Why the buffers exist

The cloud clearance buffers exist for see-and-avoid. The Pilot's Handbook: the rules include "the FAA's important 'see and avoid' mandate" and "provide the historical foundation of the FAA regulations governing the aviation system and the individual classes of airspace" 27. An IFR airplane can come out of that cloud on a clearance, unable to see a VFR airplane until it is clear of the cloud. Five hundred below, 1,000 above, and 2,000 beside give both pilots time to react.

Special use airspace prints on the sectional with hatched borders and a label:

• R for restricted
• P for prohibited
• A for alert
• MOA.

The Chart Users' Guide: "The areas are identified by type and identifying name/number, and are positioned either within or immediately adjacent to the area" 28. The chart-edge panel gives the rest: "All are supplemented with altitude, time of use and the controlling agency/contact facility, and its frequency when available. Users need to be aware that a NOTAM addressing activation will NOT be issued to announce permanently listed times of use" 29. The pilot identifies each area on the route and checks the panel. Module 3-5 covers the operating rules inside each area.

TFRs are not on the chart

TFRs never print on the sectional. They appear in NOTAMs and current EFB overlays. The AIM: pilots "should check appropriate NOTAMs during flight planning" for temporary flight restrictions 30. A TFR "restrict[s] entrance to a certain airspace at a certain time" 31. Section 91.103's all available information includes TFRs 32. The NOTAM check is an airspace check.

The numbers are MSL

Shelf floors and ceilings are MSL numbers. The Chart Users' Guide: "The MSL ceiling and floor altitudes of each sector are shown in solid blue figures" 1. The pilot converts against the terrain before flying under a shelf. A 3,000-foot floor over a 2,200-foot plateau is 800 feet above the ground. Under that shelf the airplane is at pattern altitude over houses.

The Class E floor is a minimums boundary

The Class E floor is also a minimums boundary. Below the vignette's floor the pilot holds Class G minimums, 1 mile and clear of clouds by day. Above 700 or 1,200 feet AGL, the three, one-five-two applies. The table's Class G row is "1,200 feet or less above the surface," and the Class E row is "Less than 10,000 feet MSL" 25. A pilot at 1,000 feet AGL under a 1,500-foot overcast outside a vignette is legal in Class G. The same pilot at 1,300 feet is 200 feet under a cloud in Class E, and 300 feet short of legal.

Airspace risk is a position problem. A ring is a risk only when the pilot does not know the airplane is inside it. Before flight the pilot fixes each boundary to a landmark or to the GPS overlay:

• the highway along the Class C's edge
• the lake under the shelf's corner
• the distance ring on the moving map.

The Pilot's Handbook includes airspace in the route check: "The course and areas on either side of the planned route should be checked to determine if there is any type of airspace with which the pilot should be concerned" 33. A pilot who knows the boundary by a landmark does not need a moving map to see the boundary.

After a possible deviation

After a possible airspace deviation, the order is:

• fly the airplane
• comply with ATC
• file a NASA Aviation Safety Reporting System report within 10 days.

The FAA: "The FAA considers the filing of a report with NASA concerning an incident or occurrence involving a violation of 49 U.S.C. subtitle VII or the 14 CFR to be indicative of a constructive attitude," and "neither a civil penalty nor certificate suspension will be imposed if" the violation "was inadvertent and not deliberate" and the pilot filed the report "within 10 days after the violation, or date when the person became aware or should have been aware of the violation" 34. The report's purpose is safety data. The sanction protection comes with the report, once in five years, for a mistake and not for a choice.