Instrument flight rules ( IFR ) is one of two sets of regulations governing all aspects of civil aviation aircraft operations ; the other is visual flight rules ( VFR ).

FAA's Instrument Flying Handbook defines IFR as: " Rules and regulations established by the FAA to govern flight under conditions in which flight by outside visual reference is not safe.

It is also a term used by pilots and controllers to indicate the type of flight plan an aircraft is flying, such as an IFR or VFR flight plan.

Visual flight rules are much simpler than IFR, and require significantly less training and practice.

However, any aircraft operating under VFR must have the required equipment on board, as described in FAR Part 91. 205 ( which includes instruments necessary for IFR flight ); but the view outside of the aircraft is the primary source for keeping the aircraft straight and level ( orientation ), flying where you intended to fly ( navigation ), and for not hitting anything ( separation ).

It is essential to differentiate between flight plan type ( IFR or VFR ) and weather conditions ( VMC or IMC ).

For example, an IFR flight that encounters VMC en route does not automatically change to a VFR flight, and the flight must still follow all IFR procedures regardless of weather conditions.

In controlled airspace, air traffic control ( ATC ) separates IFR aircraft from obstacles and other aircraft using a flight clearance based on route, time, distance, speed, and altitude.

In the United States, a flight operating under IFR is required to provide position reports unless ATC advises a pilot that the plane is in radar contact.

IFR flights in controlled airspace require an ATC clearance for each part of the flight.

Despite the protection offered by flight in controlled airspace under IFR, the ultimate responsibility for the safety of the aircraft rests with the pilot in command, who can refuse clearances.

Any time a flight is operating in VMC, the crew is responsible for seeing and avoiding VFR traffic ; however, since the flight is conducted under Instrument Flight Rules, ATC still provides separation services from other IFR traffic.

VFR flight into IMC is distinct from " VFR-on-top ," an IFR procedure in which the aircraft operates above IMC but remains in contact with ATC, and " VFR over the top ," a VFR procedure in which the aircraft takes off and lands in VMC but flies above an intervening area of IMC, both of which are legal in the United States.

During flight under IFR, there are no visibility requirements, so flying through clouds ( or other conditions where there is zero visibility outside the aircraft ) is legal and safe.

The most important concept of IFR flying is that separation is maintained regardless of weather conditions.

A significant amount of IFR flying is conducted in Visual Meteorological Conditions ( VMC ).

ATC is especially important for aircraft flying under Instrument flight rules ( IFR ), where they may be in weather conditions that do not allow the pilots to see other aircraft.

The techniques used for navigation in the air will depend on whether the aircraft is flying under the visual flight rules ( VFR ) or the instrument flight rules ( IFR ).

The techniques used for navigation in the air will depend on whether the aircraft is flying under the visual flight rules ( VFR ) or the instrument flight rules ( IFR ).

VOR is a more sophisticated system, and is still the primary air navigation system established for aircraft flying under IFR in those countries with many navigational aids.

The check ride is divided into an oral component to verify that the applicant understands the theory of instrument flying and an actual flight to ensure the pilot possesses the practical skills required for safe IFR flight.

For most private pilots, the most significant value of flying under IFR is the ability to fly in instrument meteorological conditions ( such as inside clouds ).

Pilots flying IFR are not subject to this requirement.

If flying under instrument flight rules ( IFR ) conditions, and VFR conditions exist or are encountered after the failure, the flight should be continued in VFR conditions and the pilot shall land as soon as practicable.

In most countries, flight plans are required for flights under IFR, but may be optional for flying VFR unless crossing international borders.

Support for IFR flying and approach vectoring is included.

It is important not to confuse IMC with IFR ( Instrument flight rules ) – IMC describes the actual weather conditions, while IFR describes the rules under which the aircraft is flying.

Aircraft can ( and often do ) fly IFR in clear weather, for operational reasons, or when flying in airspace where flight under VFR is not permitted ; indeed by far the majority of commercial flights are operated solely under IFR.

When flying in these conditions, pilots follow instrument flight rules ( IFR ).

The majority of IFR navigation is given by ground-and satellite-based systems, while radar vectors are usually reserved by ATC for sequencing aircraft for a busy approach or transitioning aircraft from takeoff to cruise, amongst other things.

Departures are described in an IFR clearance issued by ATC prior to takeoff.

Instrument approach procedure charts ( or approach plates ) are published for each ILS approach, providing pilots with the needed information to fly an ILS approach during instrument flight rules ( IFR ) operations, including the radio frequencies used by the ILS components or navaids and the minimum visibility requirements prescribed for the specific approach.

* Ideal final result ( IFR )-the ultimate idealistic solution of a problem when the desired result is achieved by itself ;

All IFR clearances are given by Denver center.

In many respects this is similar to VFR flight planning except that the task is generally made simpler by the use of special charts that show IFR routes from beacon to beacon with the lowest safe altitude ( LSALT ), bearings ( in both directions ) and distance marked for each route.

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For IFR flights, flight plans are used by air traffic control to initiate tracking and routing services.

SIDs and STARs are procedures and checkpoints used to enter and leave the airway system by aircraft operating on IFR flight plans.

In Canada, unlike the United States, unless specifically exempted by a company Operating Certificate, IFR flight plans require an alternate airport, regardless of the forecast destination weather.

IFR is distinguished by a nuclear fuel cycle that uses reprocessing via electrorefining at the reactor site.

The U. S. Department of Energy built a prototype ( the Experimental Breeder Reactor II ), but the IFR project was canceled by the US Congress in 1994, three years before completion.

IFR is cooled by liquid sodium or lead and fueled by an alloy of uranium and plutonium.

* Breeder reactors ( such as the IFR ) could in principle extract almost all of the energy contained in uranium or thorium, decreasing fuel requirements by nearly two orders of magnitude compared to traditional once-through reactors, which extract less than 0. 65 % of the energy in mined uranium, and less than 5 % of the enriched uranium with which they are fueled.

The goals of the IFR project were to increase the efficiency of uranium usage by breeding plutonium and eliminating the need for transuranic isotopes ever to leave the site.

The IFR fuel cycle's reprocessing by pyroprocessing ( in this case, electrorefining ) does not need to produce pure plutonium free of fission product radioactivity as the PUREX process is designed to do.

Like any fast reactor, by changing the material used in the blankets, the IFR can be operated over a spectrum from breeder to self-sufficient to burner.