This edition incorporates all amendments approved by the Council prior to 29 August 2018 and supersedes on 8 November 2018, all previous editions of Doc 8168, Volume I. INTERNATIONAL CIVIL AVIATION ORGANIZATION Doc 8168 Sixth Edition, 2018. PANS-OPS, (Doc 8168), Procedures for Air Navigation Services — Aircraft Operations Volume I — Flight Procedures Volume II— Construction of Visual and Instrument Flight Procedures PANS-OPS OAS Software PANS-TRG, (Doc 9868), Procedures for Air Navigation Services — Training.

Altimeter Temperature Error Correction

Icao Pans-ops Aircraft Operations Manual Doc 8168 Volume 1

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TEC

Definition

Altimeter Temperature Error Correction is applied to altimeters to compensate for error caused by deviation from ISA conditions.

Description

Pressure altimeters are calibrated to ISA conditions. Any deviation from ISA will result in error proportional to ISA deviation and to the height of the aircraft above the aerodrome pressure datum.

According to ICAO PANS OPS (Doc 8168) 'The calculated minimum safe altitudes/heights must be adjusted when the ambient temperature on the surface is much lower than that predicted by the standard atmosphere. In such conditions, an approximate correction is 4 per cent height increase for every 10°C below standard temperature as measured at the altimeter setting source. This is safe for allaltimeter setting source altitudes for temperatures above –15°C. For colder temperatures, a more accurate correction should be obtained according to the guidance provided in section 4.3 'Temperature corrections'.

When temperature is LESS than ISA an aircraft will be LOWER than the altimeter reading.

For example, if the OAT is - 40 °C then for a 2000 ft indicated altitude the true altitude is 1520 ft thus resulting in a lower than anticipated terrain separation and a potential obstacle-clearance hazard.

When To Apply Corrections

When the aerodrome temperature is 0°C32 °F <br />273.15 K <br />491.67 °R <br /> or colder, the temperature error correction must be added to:

• DH/DA or MDH/MDA and step-down fixes inside the final approach fix (FAF).
• All low altitude approach procedure altitudes in mountainous regions (terrain of 3000 ft914.4 m <br /> AMSL or higher)

According to ICAO PANS OPS Chapter 4 'Altimeter Corrections', the pilot-in-command is responsible for the safety of the operation and the safety of the aeroplane and of all persons on board during flight time (Annex 6, 4.5.1). This includes responsibility for obstacle clearance, except when an IFR flight is being vectored by radar.

When pilots intend to apply corrections to the FAF crossing altitude, procedure turn or missed approach altitude, they must advise ATC of their intention and the correction to be applied.

Pilots may refuse IFR assigned altitudes if altitmeter temperature error will reduce obstacle clearance below acceptable minima. However, once an assigned altitude has been accepted, it must not subsequently be adjusted to compensate for temperature error.

Publication of Cold Temperature Corrections

In accordance with Annex 15, Appendix 1 (Contents of Aeronautical Information Publication), States should publish in Section GEN 3.3.5, “The criteria used to determine minimum flight altitudes”. If nothing is published, it should be assumed that no corrections have been applied by the State.

Considering that, in ECAC airspace, most of the States are experiencing temperatures that require correction for minimum flight altitudes, it is recommended that such information is not omitted, and in case of no cold temperature correction applied, a clear statement to that effect is made in AIP GEN 3.3.5.

Determination of Temperature Corrections

When designing the structure of airspace where air traffic control is provided, an ATS authority will have to consider annual and seasonal variation of temperature when establishing the minimum flight altitudes.

The analysis of recorded meteorological data will be the basis for considering how the effect of cold temperatures should be mitigated in operations. Such an activity will indicate the magnitude of the correction required to operate within a given temperature range.

According to the airspace requirements and the surrounding environment, an airspace designer may consider a lower temperature as a reference for establishing the minimum flight altitudes.

The combination of concept of operations, airspace requirements and temperature range will indicate which of the following approaches would be appropriate for a given environment:

• Annual - In areas where the temperatures recorded are not too low, and the seasonal variation is minor, it would be possible to calculate the cold temperature correction in accordance with historical meteorological data and publish the resulting minimum levels accordingly in the AIP. All minimum altitudes should then include the cold temperature correction which would be known to pilots.

It could be that some isolated higher obstacles will be subject to special arrangements (providing a protection around the obstacle rather than raising overall the minimum flight altitudes).

This approach has the benefit of having one set of values for minimum vectoring altitudes^[1] applicable for the entire year.

• Seasonal - The low temperatures are normally recorded within a defined period of the year. When the low temperatures experienced are significantly low during this season, the buffer necessary to accommodate an annual application of cold temperature correction may lead to a less efficient use of the airspace. In such cases the appropriate ATS authorities may consider a dual set of minimum flight altitudes: one applicable during “warm season” and one during the “cold season”. The activation of one or the other set of values can be indicated in the State’s AIP such as: “from 1 December to 31 March the cold temperature values for minimum flight altitudes are applied”.

The set of values for minimum vectoring altitudes a controller must use in cases documented in ICAO Doc 4444, PANS-ATM, § 8.6.5.2 ^[2] would be provided/activated accordingly.

• Daily - The cold temperature corrections can also be updated on a daily basis using the coldest temperature forecast for the day as the baseline. The supervisor will use the table/methodology as provided by the appropriate ATS authority to ascertain the set of minimum vectoring altitudes a controller will use that day.
  • The State will publish in AIPs that correction for low temperature effect are applied, when necessary, by ATC.

• Tactical - When full integration of the methodology for cold temperature correction in the ATS system is performed, the controller will be provided with the appropriate information on the CWP.
  • The State will publish in AIP that correction for low temperature effect are applied, when necessary, by ATC.

A common aspect for the first two solutions is that they will not cover temperatures lower than those in the selected range. Therefore, they should be supplemented with specific procedures for temperatures lower than those in the selected range.

Minimum Sector Altitude

Currently, there is not a European-wide common procedure to deal with adjustments to Minimum Sector Altitudes (MSAs). Some regulators do not specify adjustments to MSAs and consequently ATC providers do not apply a temperature correction to published MSAs for cold temperatures. It is the flight crew reponsibility according to the provisions of ICAO PANS OPS referred above.

Some operators advise flight crews to add 1000 ft to the MSA when the temperature is - 30 °C or colder. (RAF FIH)

Minimum Vectoring Altitude

MVAs are established for use by the Air Traffic Controller (ATCO) when Air Traffic Control (ATC) provide a surveillance service (usually radar). Each MVA chart contains sectors large enough to accommodate the vectoring of aircraft within the sector at the MVA.The minimum vectoring altitude in each sector provides 1000 ft above the highest obstruction in non-mountainous areas and 2000 ft above the highest obstacle in designated mountainous areas.

According to ICAO PANS OPS, minimum vectoring altitudes shall be corrected for temperature. The temperature correction shall be based on seasonal or annual minimum temperature records. In turn, ATC authorities are required, as per ICAO PANS ATM, 8.6.5.2, Note 2, “to provide the controller with minimum altitudes corrected for temperature effect”.

Editor's notes:

1. ^ In cases where minimum vectoring altitudes are not established by the airspace designers and the controllers use (according to localprocedures) a specific set of minimum flight altitudes (AMA, minimum flight level en route) or surveillance minimum altitudes when vectoring aircraft, the ATS authority should provide the corrected values for such set of minimum altitudes.
2. ^ICAO Doc 4444, PANS-ATM, § 8.6.5.2:“When vectoring an IFR flight and when giving an IFR flight a direct routing which takes the aircraft off an ATS route, the controller shall issueclearances such that the prescribed obstacle clearance will exist at all times until the aircraft reaches the point where the pilot will resume ownnavigation. When necessary, the relevant minimum vectoring altitude shall include a correction for low temperature effect.
   Note 1.— When an IFR flight is being vectored, the pilot may be unable to determine the aircraft’s exact position in respect to obstacles in thisarea and consequently the altitude which provides the required obstacle clearance. Detailed obstacle clearance criteria are contained in PANSOPS(Doc 8168), Volumes I and II. See also 8.6.8.2.
   Note 2.— It is the responsibility of the ATS authority to provide the controller with minimum altitudes corrected for temperature effect.”
   ATM Procedures Development Sub-Group of EUROCONTROL Network Operation Team considers that “the controller shall issue clearances such that the prescribed obstacle clearance will exist at all times until the aircraft reaches the point where the pilot will re-join the flight planned route, or a published ATS route or instrument procedure”.

Related Articles

Further Reading

EUROCONTROL
Cold Temperature Correction Guidance and Tool

• Cold Temperature Correction Tool - This electronic tool (Excel Workbook) provided in conjunction with the Guidelines for Cold Temperature Corrections by ATS is intended to assist airspace designers and ATS authorities, in general, to assess how temperature correction can be most effectively accommodated in the airspace design, to identify which temperature ranges would provide the most efficient utilization of a given volume of airspace. The tool provides three spreadsheets where the user may calculate the value of the correction required for a given set of parameters, the possibility to calculate the effect of the cold temperature on the minimum vectoring altitude and the possibility to assess a the correction for temperature banding.

Others

• Royal Air Force Flight Information Handbook
• IFALPA Briefing Leaflet: Cold Temperature Corrections, December 2014
• see also ICAO Doc 8168 - PANS-OPS, Volume 1, Chapter 4 and associated tables.

An aircraft approach category is a grouping which differentiates aircraft based on the speed at which the aircraft approaches a runway for a landing.

Categories[edit]

Specifically the V_Ref,of a given aircraft, at the maximum certificated landing weight (if V_Ref is not specified, the approach speed is given as the V_S0multiplied by 1.3) . V_Ref, V_S0, and the maximum certificated landing weight are those values as established for the aircraft by the certification authority of the country of registry. An aircraft shall fit in only one category. If it is necessary to maneuver at speeds in excess of the upper limit of a speed range for a category, the minimums for the next higher category should be used. For example, an aircraft which falls in Category A, but is circling to land at a speed in excess of 90 knots, should use the approach Category B minimums when circling to land.^[1] The categories are as follows:

• Category A: Speed 90 knots or less.
• Category B: Between 91 and 120 knots.
• Category C: Between 121 and 140 knots.
• Category D: Between 141 knots and 165 knots.
• Category E: Speed 166 knots or more.

Category E contains only certain Military Aircraft.

Another category is H used only for helicopters but without specific V_Ref. See performancecategory in ADEXP 3.1 (link provided below).

Aircraft Approach Category (ICAO)[edit]

While the speed ranges used to determine an aircraft's approach category are identical to 14 CFR 97.3 (ICAO Doc 8168 PANS-OPS Vol 1, Section 4, Paragraph 1.3.5), the maximum permitted speed for visual maneuvering is significantly higher. The method used for determining the approach category speed is slightly different: V_AT = speed at threshold based on 1.3 times V_S0 or 1.23 times V_s1g at maximum certificated weight. Additionally, speed ranges are specified for other segments of the approach: (ICAO Doc 8168, Vol 1, Section 4, Table I-4-1-2).

The following ICAO table indicates the specified range of handling speeds (IAS in Knots) for each category of aircraft to perform the maneuvers specified. These speed ranges have been assumed for use in calculating airspace and obstacle clearance for each procedure.^[2]

V_AT —Speed at threshold based on 1.3 times stall speed in the landing configuration at maximum certificated landing mass.

Icao Pans Ops Doc 8168 Volume 1

'*' Maximum speed for reversal and racetrack procedures.

Category E contains only certain Military Aircraft and is usually not included on commercial aeronautical charts.

Examples[edit]

References[edit]

Icao Pans Ops Doc 8168 Pdf

1. ^14 CFR Part 97.3
2. ^ICAO Doc 8168 PANS-OPS Vol 1
3. ^'FAA Reference Code and Approach Speeds for Boeing Aircraft'(PDF). Boeing. 30 March 2016.

External links[edit]

• Eurocontrol standard ADEXP 3.1