- Visual flight rules
Visual flight rules (VFR) are a set of regulations which allow a pilot to operate 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. If the weather is worse than VFR minimums, pilots are required to use instrument flight rules.
To avoid collisions, the VFR pilot is expected 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. Near busier airports, and while operating within certain types of airspace, VFR aircraft are required (not in the United States) to have a transponder to help identify the aircraft on radar. 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.
From a regulatory perspective, airspace is categorized as controlled and uncontrolled. In controlled airspace known as Class B for example (note that Class B does not exist in the UK), Air Traffic Control (ATC) will separate VFR aircraft from all other aircraft. In most other types of controlled airspace, ATC is only required to maintain separation to aircraft operating under instrument flight rules (IFR), but workload permitting will assist all 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—usually placing a pilot in simulated IMC environment using a view limiting device and recency of experience, equipment, and inspection requirements for both the pilot and 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.
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.
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:
500ft provision An aircraft must not fly closer than 500ft to any person, vessel, vehicle, building or structure.
1000ft 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 1000ft above the highest fixed object within 600m of the aircraft.
- Australian VFR rules—published by CASA (Civil Aviation Safety Authority)
- See FAA regulation 7110.65
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