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Encyclopedia > Instrument flight rules
It has been suggested that Air traffic control#Instrument Flight Rules (IFR) be merged into this article or section. (Discuss)

Instrument flight rules (IFR) is a set of regulations and procedures for flying aircraft without the assumption that pilots will be able to see and avoid obstacles, terrain, and other air traffic; it is an alternative to visual flight rules (VFR), where the pilot is primarily or exclusively responsible for see-and-avoid. Image File history File links Please see the file description page for further information. ... Air Traffic Control Towers (ATCTs) at Schiphol Airport Air Traffic Control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and in the air. ... Airbus A380 An aircraft is any machine capable of atmospheric flight. ... Visual flight rules (VFR) are a set of aviation regulations under which a pilot may operate an aircraft, if weather conditions are sufficient to allow the pilot to visually control the aircrafts attitude, navigate, and maintain separation with obstacles such as terrain and other aircraft. ... An aviator is a person who flies aircraft for pleasure or as a profession. ...



The most important concept of IFR flying is that it allows continued flight operations in reduced visibility, during which time the ability of a pilot to physically see and avoid collision with other aircraft or obstacles is severely reduced, or even impossible. The distance that is achieved when avoiding obstacles or other aircraft is termed separation. In controlled airspace, air traffic control (ATC) separates IFR aircraft from obstacles and other IFR aircraft by applying separations based on time, distance, and altitude differences between aircraft, by relying either on radar or reports of aircraft positions traditionally sent as voice radio transmissions, but increasingly as electronic data exchanges. Generally, in most controlled airspaces, IFR aircraft require an ATC clearance for each part of the flight, typically providing a heading or route, altitude, and clearance limit (the farthest the aircraft can fly without a new clearance). In very busy areas, typically near major airports, clearances may also be required for VFR aircraft, and ATC may also provide separation between IFR and VFR aircraft or even between VFR aircraft. In uncontrolled airspace, IFR aircraft do not require clearances, and they separate themselves from each other by using charted minimum altitudes to avoid terrain and obstacles, standard cruising altitudes to avoid aircraft flying in different directions, and radio reports over mandatory locations. In the United States and Canada, all airspace from 18,000 to 60,000 feet (5,586 to 18,288 meters) is designated as Class A, requiring all aircraft to operate under IFR. It should be noted however that in the United States even when on a filed IFR flight plan, if conditions permit the pilot is ultimately responsible for see and avoid. Controlled airspace exists in areas where air traffic control is capable of providing traffic separation. ... Air Traffic Control Towers (ATCTs) at Schiphol Airport Air Traffic Control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and in the air. ... M*A*S*H , see Corporal Walter (Radar) OReilly. ...


One advantage of IFR is the ability to fly an aircraft in instrument meteorological conditions (IMC), weather conditions that do not meet the minimum visibility requirements for VFR. In such conditions the pilot will control the attitude of the aircraft by watching the flight instruments, and will rely entirely on ATC for separation (though large airliners and, increasingly, smaller aircraft now carry their own terrain- and collision-avoidance systems such as TCAS). It is important, however, not to confuse IFR with IMC: the vast majority of IFR flying is done under visual meteorological conditions (VMC), and in many cases, the pilot will be controlling the aircraft primarily by outside visual references, as with VFR. Under VMC in some types of airspace, ATC will not provide separation between IFR and VFR aircraft (in fact, in areas with limited radar coverage, ATC may not know the location of VFR aircraft), so pilots are responsible for seeing and avoiding other traffic just as they would be under VFR. Instrument meteorological conditions (IMC) are weather conditions that require aircraft pilots to fly primarily by reference to instruments rather than outside visual references, as they could in Visual meteorological conditions (VMC). ... Six basic instruments in a light twin engine aircraft Most aircraft are equipped with a standard set of flight instruments which give the pilot information about the aircrafts attitude, airspeed, and altitude. ... TCAS and IVSI Indicator The Traffic Collision Avoidance System (or TCAS) is a computer system installed on board many large aircraft, designed to prevent mid-air collisions. ... In aviation, visual meteorological conditions (or VMC) are those in which visual flight rules (VFR) flight is permitted—that is, conditions in which pilots have sufficient visibility to fly the aircraft without reference to instruments and can maintain visual separation from terrain and other aircraft. ...

The pilot will usually navigate by using electronic navigation equipment and, in areas of radar coverage, by receiving vectors (compass headings assigned by ATC). While weather conditions can be worse than those allowed for VFR flight, there are still minimum conditions that must be present in order for the aircraft to take off or land. These will vary according to the type of electronic navigation aids available, the location and height of terrain and obstructions in the vicinity of the airport, and according to qualifications of the crew and aircraft.


There are three stages to an IFR flight: departure, en route, and approach. For each stage, there are standard, published procedures to allow IFR aircraft to move in a safe, orderly way, from the moment the wheels leave the runway to the moment they touch down again. These procedures also allow an IFR aircraft to complete a flight predictably in the case of lost communications with ATC (lost-comms), with default altitudes and headings for every stage.

Departures are described by simple departure procedures (DP), normally providing an initial heading and altitude, or (for busier airports) by standard instrument departures (SID) providing more detailed instructions, often accompanied by diagrams or charts. En route flight is described by IFR charts showing navigation aids, fixes, and standard routes called airways with minimum safe altitudes for each segment. Approaches are described by terminal procedures (often called approach plates), describing a series of steps and segments to make the transition from en route flight to a position where the aircraft can complete a landing visually (often from a low altitude and close to the airport). All instrument approaches have minimum altitudes: if it is not possible to complete a landing visually from the specified altitude (decision height) and location, the pilot must commence a missed approach and return to en route flight. Busy airports may also have standard terminal arrivals (STARS) providing an additional connection between en route flight and the final approach. In aviation, an airway is a designated route in the air. ...


To fly under IFR, a pilot must have an instrument rating, and must meet recency of experience requirements. In the United States, these recency of experience requirements include six instrument approaches, navaid intercepting and tracking, and holding procedures in the past six months. The aircraft must also be equipped and type-certified for instrument flight. Instrument Rating refers to the qualifications that a pilot must have in order to fly under Instrument Flight Rules (IFR). ... An instrument approach is a type of air navigation that allows an aircraft to land in weather restricting visibility, or to reach visual conditions permitting a landing. ... A hold is an aeronautical maneuver that keeps an aircraft in a predetermined safe area while waiting for a clearance, weather, traffic, or any other delays. ...

The UK differs from pilot licensing practice in the U.S. In the UK any pilot can decide to which flight rules he adheres given that the meteorological conditions for those rules are met. The pilot does need an instrument rating to fly in instrument meteorological conditions, and under IFR in controlled airspace. The upshot of this is that non-instrument qualified pilots can elect to fly under IFR in visual meteorological conditions outside controlled airspace. Compared to the rest of the world the UK's flight crew licensing regime is somewhat unusual in this respect by licensing for meteorological conditions and airspace, rather than flight rules.

See also

  Results from FactBites:
The Instrument Rating (205 words)
Along with new maneuvers go new regulations governing instrument flight rules that must be learned in along with flying.
The same place you got your initial private license, almost all flight schools, big or small, can provide the instruction and the properly equipped aircraft for flight under instrument flight rules.
Instrument training and flying is considered one of the most challenging but yet most rewarding phases of your flight training.
Visual flight rules - Wikipedia, the free encyclopedia (396 words)
Visual flight rules (VFR) are a set of aviation regulations under which a pilot may operate an aircraft, if weather conditions are sufficient to allow the pilot to visually control the aircraft's attitude, navigate, and maintain separation with obstacles such as terrain and other aircraft.
If they are not met then the flight must be flown under instrument flight rules (IFR), the pilot must have an instrument rating and meet recency of experience requirements pertaining to instrument flight, and the aircraft must be equipped and type-certified for instrument flight.
In some types of airspace, generally at higher altitudes, a flight must be flown under IFR regardless of the meterological conditions, as aircraft fly at high speeds at higher altitudes and the "see and avoid" method of avoiding conflicting traffic is less successful.
  More results at FactBites »



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