Instrument Flight Rules (IFR)

Article Information
Category:	General
Content source:	SKYbrary
Content control:	SKYbrary

Description

Instrument Flight Rules (IFR) are rules which allow properly equipped aircraft to be flown under Instrument Meteorological Conditions (IMC).

IFRs are detailed in International Civil Aviation Organisation (ICAO) Annex 2: Rules of the Air, Chapter 5: Instrument Flight Rules and, under the European aviation safety regulations, in Commission implementing regulation (EU) No 923/2012 of 26 September 2012 laying down the common rules of the air and operational provisions regarding services and procedures in air navigation (the Standardised European Rules of the Air, or SERA).

IFR requirements in the SERAs are SKYbrary a transposition of the requirements of chapter 5 of ICAO Annex 2 in the European regulatory environment and they are articulated into three main categories as per the articulation of the requirements in chapter 5 of ICAO Annex 2: articulated into three main categories: rules applicable to all IFR flights (SERA.5015), rules applicable to IFR flights within controlled airspace (SERA.5020), and rules applicable to IFR flights outside controlled airspace (SERA.5025).

Rules applicable to all IFR flights

SERA.5015 requires that aircraft be equipped with suitable instruments and with navigation equipment appropriate to the route to be flown and in accordance with the applicable air operations legislation.

In terms of minimum levels, except when necessary for take-off or landing or when specifically authorised by the competent authority, according to SERA.5015, an IFR flight shall be flown at a level which is not below the minimum flight altitude established by the State whose territory is overflown, or, where no such minimum flight altitude has been established:

(1) over high terrain or in mountainous areas, at a level which is at least 600 m (2,000 ft) above the highest obstacle located within 8 km of the estimated position of the aircraft;

(2) elsewhere than as specified in (1), at a level which is at least 300 m (1,000 ft) above the highest obstacle located within 8 km of the estimated position of the aircraft.

When identifying which the highest obstacles within 8 km of the estimated position of the aircraft, the estimate will need to take account of the navigational accuracy which can be achieved on the relevant route segment, with regard to the navigational facilities available on the ground and in the aircraft.

With regard to change from IFR flight to visual flight rules (VFR) flight, SERA.5015 requires that an aircraft electing to change the conduct of its flight from compliance with the IFRs to compliance with the VFRs shall notify the appropriate air traffic services unit specifically that the IFR flight is canceled and communicate thereto the changes to be made to its current flight plan. SERA.5015 also requires that when an aircraft operating under IFRs is flown in or encounters visual meteorological conditions it shall not cancel its IFR flight unless it is anticipated, and intended, that the flight will be continued for a reasonable period of time in uninterrupted visual meteorological conditions. According to SERA.5015, change from IFR flight to VFR flight shall only be acceptable when a message initiated by the pilot-in-command containing the specific expression ‘CANCELING MY IFR FLIGHT’, together with the changes, if any, to be made to the current flight plan, is received by an air traffic services (ATS) unit. No invitation to change from IFR flight to VFR flight shall be made by ATS either directly or by inference. No reply, other than the acknowledgment ‘IFR FLIGHT CANCELLED AT ... (time)’, should normally be made by an ATS unit.

Rules applicable to IFR flights within controlled airspace

SERA.5020 requires that IFR flights comply with the provisions of the air traffic control (ATC) service section of the SERAs (section 8) when operated in controlled airspace, i.e., an airspace of defined dimensions within which ATC service is provided in accordance with the airspace classification (airspace Classes A, B, C, D and E for IFR flights).

An IFR flight operating in cruising flight in controlled airspace, according to SERA.5020, shall be flown at a cruising level, or, if authorised by ATS unit to employ cruise climb techniques, between two levels or above a level, selected from the table of cruising levels of the SERAs, except that the correlation of levels to track prescribed therein shall not apply whenever otherwise indicated in ATC clearances or specified by the competent authority in aeronautical information publications.

Rules applicable to IFR flights outside controlled airspace

SERA.5025 requires that an IFR flight operating in level cruising flight outside of controlled airspace be flown at a cruising level appropriate to its track as specified in the table of cruising levels of the SERAs, except when otherwise specified by the competent authority for flight at or below 900 m (3,000 ft) above mean sea level. Although an IFR flight operating in level cruising flight outside controlled airspace is to be flown at a cruising level appropriate to its track, as specified in the table of cruising levels, this does not preclude the use of cruise climb techniques.

According to SERA.5025, an IFR flight operating outside controlled airspace but within or into areas, or along routes designated by the competent authority shall maintain an air-ground voice communication watch on the appropriate communication channel and establish two-way communication, as necessary, with the ATS unit providing flight information service.

An IFR flight operating outside controlled airspace and required by the competent authority to maintain an air-ground voice communication watch on the appropriate communication channel and to establish two-way communication, as necessary, with the air traffic services unit providing flight information service, shall report position. Aircraft electing to use the air traffic advisory service whilst operating under IFR within specified advisory airspace are expected to comply with the provisions of the ATC service section of the SERAs (section 8), except that the flight plan and changes thereto are not subject to clearances and that two-way communication will be maintained with the unit providing the air traffic advisory service.

IFR rules in 14 CFR

Subpart B of 14 CFR Part 91, which prescribes rules governing the operation of aircraft in the United States, deals with flight rules and contains IFR requirements. The Part 91 requirements relate to both operating and rules of the air aspects and deal with such topics as fuel requirements for flight in IFR conditions, IFR flight plan, VHF omnidirectional radio range VOR equipment check for IFR operations, Air Traffic Control (ATC) clearance and flight plan required, take-off and landing under IFR. Additionally, the Part-91 IFR requirements cover straight-in landing operations below decision altitude (DA)/decision height (DH) or minimum descent altitude (MDA) using an enhanced flight vision system (EFVS) under IFR, minimum altitudes for IFR operations, IFR cruising altitude or flight level, operations within airspace designated as ‘reduced vertical separation minimum’ (RVSM) airspace, course to be flown, IFR communications, IFR operations: two-way radio communications failure, operation under IFR in controlled airspace: malfunction reports, category II and III operations: general operating rules, category II and category III manual, certificate of authorization for certain category II operations.

Related Articles

• Instrument Meteorological Conditions (IMC)
• Visual Flight Rules (VFR)

Further Reading

• Easy Access Rules for Standardised European Rules of the Air (SERA), European Union Aviation Safety Agency, 19 Dec 2018