Airspace: ACS Task E in Full

Class A runs from 18,000 feet MSL up to and including FL600. The AIM: "Generally, that airspace from 18,000 feet MSL up to and including FL 600, including the airspace overlying the waters within 12 nautical miles off the coast of the 48 contiguous States and Alaska" 1. There is no VFR in Class A. The rule: "each person operating an aircraft in Class A airspace must conduct that operation under instrument flight rules (IFR)," and "Operations may be conducted only under an ATC clearance received prior to entering the airspace" 2. The equipment is a transponder with Mode C and ADS-B Out: "no person may operate an aircraft within Class A airspace unless that aircraft is equipped with the applicable equipment specified in § 91.215, and after January 1, 2020, § 91.225" 2.

Class B

Class B surrounds the busiest airports from the surface to about 10,000 feet MSL. The AIM: "Generally, that airspace from the surface to 10,000 feet MSL surrounding the nation's busiest airports in terms of IFR operations or passenger enplanements. The configuration of each Class B airspace area is individually tailored and consists of a surface area and two or more layers" 3. Each Class B is different. The shelves are on the terminal area chart.

Entry requires an ATC clearance before the boundary. The rule: "The operator must receive an ATC clearance from the ATC facility having jurisdiction for that area before operating an aircraft in that area" 4. The AIM: "Regardless of weather conditions, an ATC clearance is required prior to operating within Class B airspace" 5.

Three things are not a clearance:

• two-way radio contact
• a squawk code
• flight following.

The clearance is the words "cleared into the Class Bravo airspace," and the pilot stays outside until the controller says them.

The equipment and the certificate

Class B takes three pieces of equipment:

• a two-way radio
• a transponder with Mode C
• ADS-B Out.

The rule: "For all operations. An operable two-way radio capable of communications with ATC on appropriate frequencies for that Class B airspace area" 6, and "The applicable operating transponder and automatic altitude reporting equipment specified in § 91.215," and "After January 1, 2020, the applicable Automatic Dependent Surveillance-Broadcast Out equipment specified in § 91.225" 4.

The pilot in command must hold at least a private pilot certificate, or be a student with the training and endorsement. The rule: "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" 4.

Twelve Class B primary airports admit no student solo at all. The rule: "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" 4. Appendix D, section 4 lists them: "solo student, sport, and recreational pilot operations are not permitted at any of the following airports," and the twelve are:

• Atlanta
• Boston
• Joint Base Andrews
• Chicago O'Hare
• Dallas/Fort Worth
• Los Angeles
• Miami
• Newark
• Kennedy
• LaGuardia
• San Francisco
• Reagan National 7.

San Francisco is on the list. No endorsement permits a student solo there.

Separation inside Class B

A VFR airplane inside Class B receives separation from ATC. The AIM: "An ATC clearance is required for all aircraft to operate in the area, and all aircraft that are so cleared receive separation services within the airspace," and "VFR aircraft are separated from all VFR/IFR aircraft which weigh 19,000 pounds or less by a minimum of: (a) Target resolution, or (b) 500 feet vertical separation, or (c) Visual separation" 8. That separation is why the Class B cloud clearance is only clear of clouds. The separation does not cancel see and avoid.

The Mode C veil

The veil is a 30-mile circle around each Class B primary airport, from the surface to 10,000 feet MSL. The rule requires the transponder with Mode C "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" 9, and ADS-B Out "within 30 nautical miles of an airport listed in appendix D, section 1 to this part from the surface upward to 10,000 feet MSL" 10. The veil appears as a thin solid magenta ring on the sectional. The veil rule applies to airplanes that never enter Class B.

One class of airplane is exempt inside the veil. The rule: "any aircraft which was not originally certificated with an engine-driven electrical system or which has not subsequently been certified with such a system installed, balloon or glider may conduct operations in the airspace within 30 nautical miles," but only "Outside any Class A, Class B, or Class C airspace area" and "Below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport or 10,000 feet MSL, whichever is lower" 11. A Cub with no electrical system can fly under the shelves. It cannot enter the Class B.

Beneath the shelf

Flying beneath a Class B shelf requires no clearance. The airplane is outside Class B, in the Class E or G below the floor. The veil's equipment rules still apply there, because the rule defines the veil by distance from the airport, not by the shelf 9. A Warrior under the San Francisco shelf needs its transponder with Mode C and its ADS-B Out. It does not need the words "cleared into the Class Bravo." The speed limit under the shelf is 200 knots 12.

Class C surrounds airports with a tower and a radar approach control. The AIM: "Generally, that airspace from the surface to 4,000 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower, are serviced by a radar approach control, and that have a certain number of IFR operations or passenger enplanements" 13. The usual shape is two rings: "a 5 NM radius core surface area that extends from the surface up to 4,000 feet above the airport elevation, and a 10 NM radius shelf area that extends no lower than 1,200 feet up to 4,000 feet above the airport elevation" 13.

The chart prints Class C and Class D altitudes in MSL, but the definition of each is a height above the airport. The AIM says "4,000 feet above the airport elevation (charted in MSL)" for Class C 13 and "2,500 feet above the airport elevation (charted in MSL)" for Class D 14. The chart number is MSL. The design number is AGL at the airport. A Class C around an airport at 1,300 feet reaches about 5,300 feet MSL, and the chart prints 53.

The callsign

The controller establishes two-way communications by saying your callsign. 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 C airspace." A reply without the callsign establishes nothing: "if the controller responds to the initial radio call without using the aircraft identification, radio communications have not been established and the pilot may not enter the Class C airspace" 15. After "Aircraft calling Norcal approach, standby" the airplane stays outside.

Equipment, certificate, and the outer area

Class C takes three pieces of equipment:

• a two-way radio
• a transponder with Mode C
• ADS-B Out.

The AIM: "(a) Two-way radio; and (b) Unless otherwise authorized by ATC, an operable radar beacon transponder with automatic altitude reporting capability and operable ADS−B Out equipment" 16. The rule: "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" 17.

No certificate rule applies to Class C or Class D. The AIM for both: "Pilot Certification. No specific certification required" 16. A student pilot on a solo cross-country can land at a Class C airport with an endorsement for that airport under 61.95.

The outer area is a 20-mile procedural ring that is not on the chart. The AIM: "Class C airspace areas have a procedural Outer Area. Normally this area is 20 NM from the primary Class C airspace airport," and "(This outer area is not charted.)" The services are the same and the choice is the pilot's: "Pilot participation is voluntary within the outer area and can be discontinued, within the outer area, at the pilot's request" 18. A pilot 15 miles out who calls approach gets Class C services there. A pilot who does not call is legal until the 10-mile ring.

Above the ceiling

Above the ceiling of a Class B or Class C area, the transponder and ADS-B rules continue up to 10,000 feet. The rule requires them for "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" 9, and ADS-B Out "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" 10. An airplane at 6,000 feet over a Class C with a ceiling of 5,300 feet is in Class E. It still needs Mode C and ADS-B Out.

Class D surrounds airports with an operating control tower. The AIM: "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" 14. Each Class D has its own shape, and most are a circle of about four miles with extensions for the instrument approaches.

Class D requires only a two-way radio. The AIM: "Pilot Certification. No specific certification required," and "Equipment. Unless otherwise authorized by ATC, an operable two−way radio is required" 19. The class rule itself requires no transponder and no ADS-B. A Class D inside a Mode C veil takes the veil's equipment, from the veil, not from the class. The entry rule is the same callsign test as Class C, in 91.129 20.

When the tower closes

A part-time Class D reverts to Class E or Class G when the tower closes. The AIM: "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" 14. The overlying airspace is usually the Class E transition area at 700 or 1,200 feet AGL. At Salinas after the tower closes, the surface is Class G up to 700 feet, and Class E starts there. The Chart Supplement says which class each airport becomes.

Departing a satellite airport

Departing a satellite airport without a tower inside Class C or D, the pilot calls ATC as soon as practicable after takeoff. The Class D rule: "From a satellite airport without an operating control tower, must establish and maintain two-way radio communications with the ATC facility having jurisdiction over the Class D airspace area as soon as practicable after departing" 21. The Class C rule reads the same 22. The airplane is inside the airspace from the moment it lifts off, so the call comes after takeoff, not before.

Class E is all controlled airspace that is not A, B, C, or D. The AIM: "Class E airspace is controlled airspace that is designated to serve a variety of terminal or en route purposes" 23. Above the vignette floors, most of the country is Class E. Where no lower Class E floor exists, Class E starts at 14,500 feet MSL: "The airspace extending upward from 14,500 feet MSL to, but not including, 18,000 feet MSL overlying the 48 contiguous states, the District of Columbia and Alaska" 23. Class E ends at, but does not include, 18,000 feet, where Class A begins.

The floors on the chart

A magenta vignette means Class E begins at 700 feet AGL. A blue vignette means 1,200 feet AGL. The AIM: "Class E transition areas extend upward from either 700 feet AGL (shown as magenta vignette on sectional charts) or 1,200 feet AGL (blue vignette) and are designated for airports with an approved instrument procedure" 24. The transition areas are permanent: "The 700-foot/1200-foot AGL Class E airspace transition areas remain in effect continuously, regardless of airport operating hours or surface area status" 24.

A dashed magenta line is a Class E surface area. The AIM: "Surface area designated for an airport where a control tower is not in operation. Class E surface areas extend upward from the surface to a designated altitude, or to the adjacent or overlying controlled airspace. The airspace will be configured to contain all instrument procedures" 25. A surface area extends controlled airspace to the ground, so the 91.155 surface area rules apply there.

No entry requirement

VFR flight in Class E has no entry or communication requirement. The AIM: "Arrival or Through Flight Entry Requirements. No specific requirements," and "Separation for VFR Aircraft. No separation services are provided to VFR aircraft" 26. The control in Class E is for IFR separation. A VFR pilot in Class E has no duty to contact ATC and receives no service from ATC, unless the pilot asks for flight following.

Federal airways

A Victor airway is a Class E corridor from 1,200 feet AGL up to but not including 18,000 feet. The AIM: "Federal airways and low-altitude RNAV routes are Class E airspace areas and, unless otherwise specified, extend upward from 1,200 feet AGL to, but not including,18,000 feet MSL," and "VOR Federal airways are based on VOR/VORTAC facilities and are identified by a 'V' prefix" 27. The width is 4 nautical miles each side of the centerline. The Instrument Procedures Handbook: "The primary obstacle clearance area has a protected width of 8 NM with 4 NM on each side of the centerline" 28. The airway widens past 51 miles from the VOR, where the 4.5-degree lines pass the 4-mile boundary.

Class G is uncontrolled airspace. The AIM: "Class G airspace (uncontrolled) is that portion of airspace that has not been designated as Class A, Class B, Class C, Class D, or Class E airspace" 29. ATC exercises no control over VFR airplanes in Class G. The VFR minimums in 91.155 and the right-of-way rules in 91.113 are the rules that separate VFR traffic there 30. No one separates traffic in Class G. See and avoid is the only separation.

The Class G rows

Class G has five rows in the 91.155 table for airplanes. Two rows apply at or below 1,200 feet AGL. Three rows apply above 1,200 feet AGL:

• above 1,200 feet AGL and below 10,000 feet MSL, day: "1 statute mile 500 feet below. 1,000 feet above. 2,000 feet horizontal."
• above 1,200 feet AGL and below 10,000 feet MSL, night: "3 statute miles 500 feet below. 1,000 feet above. 2,000 feet horizontal."
• above 1,200 feet AGL and at or above 10,000 feet MSL: "5 statute miles 1,000 feet below. 1,000 feet above. 1 statute mile horizontal." 31

By day above 1,200 feet, the visibility stays 1 mile and the cloud distances apply. At night the visibility becomes 3 miles. At 10,000 feet the row becomes the same as Class E at 10,000 feet.

The 10,000-foot row and the terrain

The 10,000-foot row applies only above 1,200 feet AGL. The table's heading for the 5-mile row is "More than 1,200 feet above the surface and at or above 10,000 feet MSL" 31. Over high terrain, the low-altitude Class G rows can apply above 10,000 feet MSL. A pilot 1,000 feet above a 9,500-foot ridge, at 10,500 feet MSL, is in the "1,200 feet or less above the surface" row, which the table applies "(regardless of MSL altitude)" 31. That pilot needs 1 mile and clear of clouds by day.

The 5-mile rows begin at 10,000 feet, where the 250-knot limit ends. The rule: "no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots" 12. Above 10,000 feet a jet can close at 400 knots or more. More speed needs more seeing distance, so the visibility rises to 5 miles and the horizontal cloud distance to 1 mile.

An airplane in the pattern at night in Class G can operate with 1 mile and clear of clouds. The rule: "If the visibility is less than 3 statute miles but not less than 1 statute mile during night hours and you are operating in an airport traffic pattern within 1/2 mile of the runway, you may operate an airplane, powered parachute, or weight-shift-control aircraft clear of clouds" 32. The exception is for Class G below 1,200 feet, within half a mile of the runway, and nowhere else.

The night rows apply from the end of evening civil twilight, not from sunset. The 1.1 definition: "Night means the time between the end of evening civil twilight and the beginning of morning civil twilight, as published in the Air Almanac, converted to local time" 33. The 91.155 table says "Night" and "Day" without its own definition, so the 1.1 definition governs. Between sunset and the end of civil twilight, the day rows apply.

The surface area rules

The rule prohibits VFR flight beneath a ceiling below 1,000 feet inside a surface area. The rule: "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" 34. Takeoff, landing, and the pattern under VFR inside a B, C, D or E surface area need 3 miles of ground visibility. The rule: "Unless ground visibility at that airport is at least 3 statute miles; or (2) If ground visibility is not reported at that airport, unless flight visibility during landing or takeoff, or while operating in the traffic pattern is at least 3 statute miles" 34. Special VFR is the exception to both rules.

The base altitude

An airplane exactly at the base of a Class E shelf is in the airspace below it. The rule: "an aircraft operating at the base altitude of a Class E airspace area is considered to be within the airspace directly below that area" 35. An airplane at exactly 1,200 feet AGL under a blue vignette is in Class G. The rule decides which row of the table applies at the boundary.

The flight of N4891F

On August 31, 1986, at 11:52 in the morning, a Piper Archer and an Aeromexico DC-9 collided over Cerritos, California. The collision was inside the Los Angeles Terminal Control Area, the airspace now called Class B. The NTSB: "Fifty-eight passengers and 6 crewmembers on flight 498 were killed as were the pilot and 2 passengers on the Piper. The wreckage and postimpact fires destroyed five houses and damaged seven others. Fifteen persons on the ground were killed" 36. Eighty-two people died. The sky was clear and the visibility was 14 miles.

The Piper departed Torrance eleven minutes earlier for Big Bear. The NTSB: "According to the flight plan, his proposed route of flight was direct to Long Beach, California, then direct to the Paradise, California, VORTAC, and then direct Big Bear. The proposed enroute altitude was 9,500 feet" 36. The route crossed the TCA. "The on board transponder was active with a 1200 code. Postaccident investigation revealed that as the Piper proceeded on its eastbound course, it entered the Los Angeles Terminal Control Area (TCA) without receiving clearance from ATC" 36.

The pilot was careful. The NTSB: "Friends, relatives, and colleagues who had flown with the Piper PA-28 pilot described him as a conscientious and careful pilot" 36. He asked about the airspace before the flight: "The pilot discussed the route to Big Bear with another pilot, who advised him on how to stay out of the TCA. This pilot was intimately familiar with the area's freeway complex and relied on these underlying highways as landmarks" 36. He bought the terminal area chart, "which was found opened in the cockpit wreckage" 36.

The airplane had a transponder without Mode C. The NTSB: "N4891F was equipped with a NARCO Model AT-50A transponder without a mode C altitude encoder. Given this transponder configuration, N4891F could provide position but not altitude information to Los Angeles Approach Control" 36. The controller could not tell whether the 1200 target was under the floor or inside the TCA.

The Piper climbed through the floor. The NTSB: "the last available proper VFR altitude for flight below the floor of the TCA was 5,500 feet. The Piper would have reached 5,500 feet 1 minute before entering the TCA and 2 minutes before reaching the collision altitude" 36. The Board's finding: "the pilot intended to avoid the TCA but that he probably misidentified his navigational checkpoints and entered the TCA inadvertently" 36. The collision was at 6,560 feet.

The probable cause: "the limitations of the air traffic control system to provide collision protection, through both air traffic control procedures and automated redundancy. Factors contributing to the accident were (1) the inadvertent and unauthorized entry of the PA-28 into the Los Angeles Terminal Control Area and (2) the limitations of the 'see and avoid' concept to ensure traffic separation under the conditions of the conflict" 36. The Board's recommendation to the FAA: "Require transponder equipment with mode C altitude reporting for operations around all Terminal Control Areas (TCAs)" 36. The Mode C veil in 91.215(b)(2) requires what the Board recommended.

Where the pilot could have prevented the accident

A careful pilot with the terminal chart open in the cockpit climbed into Class B without a clearance, in clear air, and 82 people died. Each decision below carries the PAVE category that applied to it.

Special VFR lets a pilot operate below basic VFR minimums inside a surface area. The rule: "special VFR operations may be conducted under the weather minimums and requirements of this section, instead of those contained in § 91.155, below 10,000 feet MSL within the airspace contained by the upward extension of the lateral boundaries of the controlled airspace designated to the surface for an airport" 37. It applies inside the lateral bounds of the B, C, D or E surface area, and nowhere else. The AIM: "ATC does not provide separation after an aircraft leaves the Class B, Class C, Class D, or Class E surface area on a special VFR clearance" 38.

The clearance and the minimums

Special VFR requires an ATC clearance, and the pilot must ask for it. The rule's first condition: "With an ATC clearance" 37. The AIM: "A VFR pilot may request and be given a clearance to enter, leave, or operate within most Class D and Class E surface areas and some Class B and Class C surface areas in special VFR conditions" 38. ATC never offers it. The request goes to the tower where there is one, and "In a Class E surface area, a clearance may be obtained from the nearest tower, FSS, or center" 38.

The minimums are 1 statute mile flight visibility and clear of clouds. The rule: "(2) Clear of clouds; (3) Except for helicopters, when flight visibility is at least 1 statute mile" 37. To take off or land, the ground visibility must be 1 mile: "Unless ground visibility is at least 1 statute mile; or (2) If ground visibility is not reported, unless flight visibility is at least 1 statute mile" 39.

Night, the prohibited airports, and the student

Special VFR between sunset and sunrise requires an instrument-rated pilot and an IFR-equipped airplane. The rule: "between sunrise and sunset (or in Alaska, when the sun is 6 degrees or less below the horizon) unless— (i) The person being granted the ATC clearance meets the applicable requirements for instrument flight under part 61 of this chapter; and (ii) The aircraft is equipped as required in § 91.205(d)" 37. The time limits here are sunset and sunrise, not civil twilight.

Some Class B and Class C surface areas prohibit Special VFR for fixed-wing airplanes. The AIM: "Special VFR operations by fixed−wing aircraft are prohibited in some Class B and Class C surface areas due to the volume of IFR traffic. A list of these Class B and Class C surface areas is contained in 14 CFR part 91, Appendix D, Section 3. They are also depicted on sectional aeronautical charts" 38. San Francisco, Los Angeles, Seattle and Portland are on the list 40. The chart prints NO SVFR beside the airport name.

Special VFR does not change the limits on a student solo. The student limits in 61.89 still apply: a student must not act as pilot in command "With a flight or surface visibility of less than 3 statute miles during daylight hours or 5 statute miles at night" 41. A Special VFR clearance changes the airspace rule. It does not change the student's own rule.

Prohibited areas ban flight for security. The AIM: "Prohibited areas contain airspace of defined dimensions identified by an area on the surface of the earth within which the flight of aircraft is prohibited. Such areas are established for security or other reasons associated with the national welfare" 42. They carry P-numbers on the chart. There is no clearance into one.

Restricted areas

Restricted areas contain invisible hazards. The AIM: "Restricted areas denote the existence of unusual, often invisible, hazards to aircraft such as artillery firing, aerial gunnery, or guided missiles. Penetration of restricted areas without authorization from the using or controlling agency may be extremely hazardous to the aircraft and its occupants" 43. Entry when the area is active requires the controlling agency's authorization. The chart carries the R-number, and the chart margin carries the hours, the altitudes, and the controlling agency.

An inactive restricted area is open to flight through it. The AIM: "If the restricted area is not active and has been released to the controlling agency (FAA), the ATC facility will allow the aircraft to operate in the restricted airspace without issuing specific clearance for it to do so" 43. The pilot asks the controlling agency or Flight Service whether the area is active. The chart's printed hours are a schedule, not a status.

Warning areas

Warning areas carry restricted-area hazards over the water. The AIM: "A warning area is airspace of defined dimensions, extending from three nautical miles outward from the coast of the U.S., that contains activity that may be hazardous to nonparticipating aircraft. The purpose of such warning areas is to warn nonparticipating pilots of the potential danger" 44. They carry W-numbers. The United States cannot prohibit flight over international waters, so the area is a warning, not a restriction.

Military operations areas

A MOA separates military training from IFR traffic. The AIM: "MOAs consist of airspace of defined vertical and lateral limits established for the purpose of separating certain military training activities from IFR traffic," and the activities include "air combat tactics, air intercepts, aerobatics, formation training, and low−altitude tactics" 45. VFR flight can enter a MOA. The AIM: "Pilots operating under VFR should exercise extreme caution while flying within a MOA when military activity is being conducted," and "pilots should contact any FSS within 100 miles of the area to obtain accurate real-time information concerning the MOA hours of operation" 45. The fighters inside are exempt from the 250-knot limit.

Alert areas mark high volumes of training or unusual activity. The AIM: "Alert areas are depicted on aeronautical charts to inform nonparticipating pilots of areas that may contain a high volume of pilot training or an unusual type of aerial activity" 46. An alert area needs no clearance, and the pilots share the responsibility: "pilots of participating aircraft as well as pilots transiting the area must be equally responsible for collision avoidance" 46. They carry A-numbers.

Controlled firing areas

Controlled firing areas do not appear on the chart, because the firing stops when an airplane approaches. The AIM: "its activities are suspended immediately when spotter aircraft, radar, or ground lookout positions indicate an aircraft might be approaching the area. There is no need to chart CFAs since they do not cause a nonparticipating aircraft to change its flight path" 47. The controlled firing area is the one special use airspace that is not on the chart. The reason is the spotter.

National security areas

In a national security area, the FAA requests voluntary avoidance. The AIM: "Pilots are requested to voluntarily avoid flying through the depicted NSA. When it is necessary to provide a greater level of security and safety, flight in NSAs may be temporarily prohibited by regulation under the provisions of 14 CFR section 99.7. Regulatory prohibitions will be issued by System Operations Security and disseminated via NOTAM" 48. A request becomes a prohibition by NOTAM.

Getting the status

The chart margin prints the special use airspace's times, altitudes, and controlling agency. The Chart Users' Guide: "All are supplemented with altitude, time of use and the controlling agency/ contact facility, and its frequency when available" 49. Live status comes from three places:

• the using or controlling agency, on the frequency in the chart margin
• Flight Service
• the FAA SUA website.

The AIM: "Pilots can request the status of SUA by contacting the using or controlling agency. The frequency for the controlling agency is tabulated in the margins of the applicable IFR and VFR charts," and "Special use airspace scheduling data for preflight planning is available via the FAA SUA website" 50.

A TFR is a NOTAM. It never appears on the printed chart. The rule: "The Administrator will issue a Notice to Airmen (NOTAM) designating an area within which temporary flight restrictions apply and specifying the hazard or condition requiring their imposition" 51. The AIM: pilots "should check appropriate NOTAMs during flight planning" 52. A chart printed in March cannot show a fire in July.

The three purposes of 91.137

A 91.137 TFR protects three things. The rule lists them:

• "Protect persons and property on the surface or in the air from a hazard associated with an incident on the surface"
• "Provide a safe environment for the operation of disaster relief aircraft"
• "Prevent an unsafe congestion of sightseeing and other aircraft above an incident or event which may generate a high degree of public interest" 51.

Entry into a hazard TFR is limited to the relief effort. The rule: "no person may operate an aircraft within the designated area unless that aircraft is participating in the hazard relief activities and is being operated under the direction of the official in charge of on scene emergency response activities" 53. A fire TFR under (a)(2) admits a few more. Two of them are an airplane on an IFR flight plan and a flight direct to an airport inside the area. The NOTAM says which paragraph applies.

Stadiums and the President

Large sporting events carry a standing security TFR. The figures commonly taught are 3 nautical miles and 3,000 feet AGL over a major stadium event, from an hour before to an hour after. Those figures are not in a regulation. They are in the current FDC NOTAM, issued under the special security instructions of 99.7, which binds "Each person operating an aircraft in an ADIZ or Defense Area" to "special security instructions issued by the Administrator in the interest of national security" 54. The pilot reads the current NOTAM for the terms, because a NOTAM can change and the chart cannot show it.

Presidential and VIP TFRs move with the person. The rule: "No person may operate an aircraft over or in the vicinity of any area to be visited or traveled by the President, the Vice President, or other public figures contrary to the restrictions established by the Administrator and published in a Notice to Airmen (NOTAM)" 55. A pilot who enters one can meet an armed escort and an FAA enforcement action.

The TFR check

Checking TFRs is part of each preflight. The rule: "Each pilot in command shall, before beginning a flight, become familiar with all available information concerning that flight" 56. The check has two parts:

• the briefing output, which lists the TFRs on the route
• tfr.faa.gov, the FAA's own list.

The overlay on the tablet helps, and it can lag. A TFR issued after the app last refreshed is not on the screen. The briefing and the FAA list are the record. The overlay is a convenience.

Entering an Air Defense Identification Zone requires a filed and activated flight plan. The rule: "No person may operate an aircraft into, within, or from a departure point within an ADIZ, unless the person files, activates, and closes a flight plan with the appropriate aeronautical facility," and "The pilot shall designate a flight plan for VFR flight as a DVFR flight plan" 57. The coastal ADIZ begins a few miles off the California shore. A flight to the Channel Islands can cross it.

The ADIZ equipment and the five minutes

An ADIZ flight requires a working two-way radio with a continuous listening watch. The rule: "A person who operates a civil aircraft into an ADIZ must have a functioning two-way radio, and the pilot must maintain a continuous listening watch on the appropriate aeronautical facility's frequency" 58. It requires a transponder with altitude reporting: "no person may operate a civil aircraft into or out of the United States into, within, or across the contiguous U.S. ADIZ unless that aircraft is equipped with a coded radar beacon transponder and automatic pressure altitude reporting equipment" 59.

A DVFR departure must take place within 5 minutes of the estimate. The rule: "The aircraft departs within five minutes of the estimated departure time contained in the flight plan" 58. The flight plan carries "the time and point of ADIZ penetration" 58. An airplane that departs late without amending the plan is an unknown target where the plan said a known one would be.

The Washington airspace

Flying VFR within 60 miles of the Washington VOR requires the FAA's special awareness training. The rule: "no person may serve as a pilot in command or as second in command of an aircraft while flying within a 60-nautical mile radius of the DCA VOR/DME, under VFR, unless that pilot has completed Special Awareness Training and holds a certificate of training completion" 60. The training is free on the FAA's site. The DC SFRA itself is a 30-mile circle, "from the surface to, but not including, FL 180, within a 30-mile radius" of the DCA VOR 61, with the Flight Restricted Zone inside it. The AIM lists the three rules for it: 93.339, the 91.161 training, and the 99.7 security NOTAMs 62.

Part 93

Each special flight rules area carries its own rules in part 93. The AIM: "Airspace of defined dimensions, above land areas or territorial waters, within which the flight of aircraft is subject to the rules set forth in 14 CFR part 93, unless otherwise authorized by air traffic control," and "Each person operating an aircraft to, from, or within airspace designated as a SATR area or SFRA must adhere to the special air traffic rules set forth in 14 CFR part 93" 63. Washington and the Grand Canyon are the two a private pilot hears about. The pilot reads the subpart before going near either.

In a TRSA, ATC offers voluntary radar service to VFR airplanes. A TRSA is not an airspace class. The AIM: "TRSAs do not fit into any of the U.S. airspace classes; therefore, they will continue to be non−part 71 airspace areas where participating pilots can receive additional radar services," and "participation is voluntary on the part of the pilot" 64. The TRSA appears in solid black on the chart. The Class D inside it appears in dashed blue, and the Class D rules apply there.

Military training routes

Military training routes are IR and VR routes, flown fast and low. The AIM: "MTRs are established below 10,000 feet MSL for operations at speeds in excess of 250 knots," and "MTRs with no segment above 1,500 feet AGL must be identified by four number characters; e.g., IR1206, VR1207. (b) MTRs that include one or more segments above 1,500 feet AGL must be identified by three number characters; e.g., IR206, VR207" 65. A four-digit route number means no segment above 1,500 feet AGL. The route width is not the line on the chart. It "can extend several miles on either side of the charted MTR centerline" 65.

The transponder airspace

The rule requires a transponder with Mode C at and above 10,000 feet MSL in the 48 states, except within 2,500 feet of the ground. The rule: "In all airspace of 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" 9. The transponder rule covers five areas:

• Class A, B, and C
• the 30-mile veil to 10,000 feet
• above a B or C ceiling to 10,000 feet
• at and above 10,000 feet MSL, except within 2,500 feet of the ground
• the 10-mile ring around an appendix D section 2 airport, a list now empty.

The ADS-B Out rule covers the same five areas and adds two. The rule adds "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" 10. Class D, and Class E below 10,000 feet outside any veil, require neither a transponder nor ADS-B 9.

The failed transponder

ATC can authorize an airplane with a failed transponder to continue. The rule: "For operation of an aircraft with an inoperative transponder to the airport of ultimate destination, including any intermediate stops, or to proceed to a place where suitable repairs can be made or both, the request may be made at any time" 66. An airplane with no transponder at all asks earlier: "For operation of an aircraft that is not equipped with a transponder, the request must be made at least one hour before the proposed operation" 66. The request goes to the ATC facility that controls the airspace.

The airspace boundary is where the airplane is, not where the pilot thinks it is. The pilot of N4891F thought he was under the floor. The NTSB found that "he probably misidentified his navigational checkpoints and entered the TCA inadvertently" 36.

The fix comes before the line, each time. Under a shelf, the pilot names the landmark that marks the boundary and holds the altitude until the landmark is behind the airplane. The GPS overlay shows the line. The landmark proves the position.

The whole route

The riskiest airspace is the airspace the pilot did not know was there. The preflight covers the whole route's airspace, including what a diversion would enter. The rule: "Each pilot in command shall, before beginning a flight, become familiar with all available information concerning that flight" 56. The airspace preflight lists:

• each class boundary the route crosses, with its entry rule and its equipment
• each special use area near the route, with its hours and its controlling agency
• each TFR on the route from the briefing and tfr.faa.gov
• the airspace at each alternate, because a diversion enters airspace the route did not.

A pilot who diverts around weather into a Class C without the callsign test flies an unplanned route. The same applies to a pilot who diverts into a restricted area that became active at noon. The plan covers the diversion before the diversion is needed.