AIM Text
- An ATC clearance must be obtained prior to operating within a Class B, Class C, Class D, or Class E surface area when the weather is less than that required for VFR flight. 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, traffic permitting, and providing such flight will not delay IFR operations. All special VFR flights must remain clear of clouds. The visibility requirements for special VFR aircraft (other than helicopters) are:
- At least 1 statute mile flight visibility for operations within Class B, Class C, Class D, and Class E surface areas.
- At least 1 statute mile ground visibility if taking off or landing. If ground visibility is not reported at that airport, the flight visibility must be at least 1 statute mile.
- The restrictions in subparagraphs 1 and 2 do not apply to helicopters. Helicopters must remain clear of clouds and may operate in Class B, Class C, Class D, and Class E surface areas with less than 1 statute mile visibility.
- When a control tower is located within the Class B, Class C, or Class D surface area, requests for clearances should be to the tower. In a Class E surface area, a clearance may be obtained from the nearest tower, FSS, or center.
- It is not necessary to file a complete flight plan with the request for clearance, but pilots should state their intentions in sufficient detail to permit ATC to fit their flight into the traffic flow. The clearance will not contain a specific altitude as the pilot must remain clear of clouds. The controller may require the pilot to fly at or below a certain altitude due to other traffic, but the altitude specified will permit flight at or above the minimum safe altitude. In addition, at radar locations, flights may be vectored if necessary for control purposes or on pilot request.
- Special VFR clearances are effective within Class B, Class C, Class D, and Class E surface areas only. 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.
- 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.
- ATC provides separation between Special VFR flights and between these flights and other IFR flights.
- Special VFR operations by fixed-wing aircraft are prohibited between sunset and sunrise unless the pilot is instrument rated and the aircraft is equipped for IFR flight.
- Pilots arriving or departing an uncontrolled airport that has automated weather broadcast capability (ASOS/AWOS) should monitor the broadcast frequency, advise the controller that they have the “one-minute weather” and state intentions prior to operating within the Class B, Class C, Class D, or Class E surface areas.
Source: FAA Aeronautical Information Manual · current edition · paragraph 4-4-6.
Research Notes
AIM 4-4-6 covers IFR clearances for off-airway routes — the procedure for IFR aircraft requesting routes that aren't along published airways.
The off-airway scenario: Pilot wants to fly direct from one waypoint to another using GPS, avoiding the published airway structure. ATC clearance permits this when traffic and radar coverage support it.
The clearance format: "Cleared direct ZULU, then direct destination" — direct to a fix, then direct to the next.
Off-airway altitude requirements (§ 91.177): When operating IFR off published airways, the pilot must maintain at least 1,000 feet above the highest obstacle within 4 NM of the course (in non-mountainous areas), or 2,000 feet above (in designated mountainous areas).
Required equipment: Off-airway IFR generally requires RNAV (GPS) capability. Conventional VOR/DME navigation cannot reliably fly off-airway routes due to the navigation receiver limitations.
Reference: § 91.177 (minimum altitudes IFR); AIM 4-4-6; AC 90-100B (RNAV operations).