Visual flight rules
Visual flight rules (VFR) are a set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than basic VFR weather minimums, as specified in the rules of the relevant aviation authority. The pilot must be able to operate the aircraft with visual reference to the ground, and by visually avoiding obstructions and other aircraft. [1]
If the weather is below VFR minimums, pilots are required to use instrument flight rules, and operation of the aircraft will primarily be through referencing the instruments rather than visual reference.
Requirements
VFR require a pilot to be able to see outside the cockpit, to control the aircraft's attitude, navigate, and avoid obstacles and other aircraft.[2] Governing agencies establish specific requirements for VFR flight, including minimum visibility, and distance from clouds, to ensure that aircraft operating under VFR are visible from enough distance to ensure safety.
Under Visual Meteorological Conditions the minimum visual range, distance from cloud, and heights to be maintained above ground vary by jurisdiction, and may also vary according to the airspace in which the aircraft is operating.
The VFR pilot is required to "see and avoid" obstacles and other aircraft. Pilots flying under VFR assume responsibility for their separation from all other aircraft and are generally not assigned routes or altitudes by air traffic control. Depending on the category of airspace in which the flight is being conducted, VFR aircraft may be required to have a transponder to help Air Traffic Control identify the aircraft on radar in order that ATC can provide separation guidance to IFR aircraft.
In the United States, a pilot operating VFR outside of class B airspace can request "VFR flight following" from ATC. This service is provided by ATC if workload permits it, but is an advisory service only. The responsibility for maintaining separation with other aircraft and proper navigation still remains with the pilot. In the United Kingdom, a pilot can request for "Deconfliction Service", which is similar to flight following.
Meteorological conditions that meet the minimum requirements for VFR flight are termed visual meteorological conditions (VMC). If they are not met, the conditions are considered instrument meteorological conditions (IMC), and a flight may only operate under IFR. IFR operations have specific training requirements and certification required of the pilot, and increased equipment requirements for the aircraft. Additionally, an IFR flight plan must usually be filed in advance. For efficiency of operations, some ATC operations will routinely provide "pop-up" IFR clearances for aircraft operating VFR, but that are arriving at an airport that does not meet VMC requirements. For example, in the United States, California's Oakland (KOAK), Monterey (KMRY) and Santa Ana (KSNA) airports routinely grant temporary IFR clearance when a low coastal overcast forces instrument approaches, while the rest of the state is still under visual flight rules.
In the United States and Canada, VFR pilots also have an option for requesting Special VFR when meteorological conditions at an airport are below normal VMC minimums, but above Special VFR requirements. Special VFR is only intended to enable takeoffs and landings from airports that are near to VMC conditions, and may only be performed during daytime hours if a pilot does not possess an instrument rating.
VFR flight is not allowed in airspace known as class A, regardless of the meteorological conditions. In the United States, class A airspace begins at 18,000 feet msl, and extends to an altitude of 60,000 feet msl.
Pilot certifications
In the United States and Canada, any certified pilot who meets specific recency of experience criteria may operate an airworthy aircraft under VFR.
Controlled visual flight rules
CVFR flight is used in locations where aviation authorities have determined that VFR flight should be allowed, but that ATC separation and minimal guidance are necessary. In this respect, CVFR is similar to Instrument flight rules (IFR) in that ATC will give pilots headings and altitudes at which to fly, and will provide separation and conflict resolution. However, pilots and aircraft do not need to be IFR rated to fly in CVFR areas, which is highly advantageous. An example of airspace where CVFR is common would be Canadian Class B airspace.[3]
The CVFR concept is used in Canada and certain European countries, but not in the U.S., where the Private Pilot certificate itself authorizes the pilot to accept clearances under VFR.
In Israel and the Palestinian territory, for example, VFR does not exist. All visual flights must be performed under CVFR rules.
Low Flying Rules
In the UK, the Rules of the Air define clearly in the principles of Low Flying Rules in Rule 5. The main principle is that an aircraft must always be able to perform an emergency landing in a case of engine failure. Hence these three criteria:
500 ft provision An aircraft must not fly closer than 500 ft to any person, vessel, vehicle, building or structure.
1000 ft provision If an aircraft is flying over a congested area (town, settlement, etc.) it must fly high enough so that in the case of an engine failure, it is able to land clear without being a danger to people or it must not fly less than 1000 ft above the highest fixed object within 600m of the aircraft.
See also
References
- ^ Section 91.155 14 CFR Part 91 - General Operating and Flight Rules - FAA
- ^ Annex 11 of the Convention on International Civil Aviation, 1/11/01, chap. 1, p. 6
- ^ AIM RAC 5.6 - CVFR Procedures
- Australian VFR rules—published by CASA (Civil Aviation Safety Authority)
- See FAA regulation 7110.65