ENR 1.7  Altimeter setting procedures

1  Introduction

The altimeter setting procedures in use generally conform to those contained in ICAO Doc 8168, Vol. I, Part 6 and are given in full below. Differences are shown in quotation marks.

Transition altitudes are given on the instrument approach charts and also in AD 2.

QNH reports and temperature information for use in determining adequate terrain clearance are provided in MET broadcasts and are available on request from the air traffic services units. QNH values are given in hectopascals.

The ICAO Standard altimeter settings procedures are in use throughout the African-Indian Ocean Region. The basic principles of the systems applicable in Somalia are:

  1. For terrain clearance purposes, a QNH altimeter setting is used wherever possible.
  2. For vertical separation on enroute, a system of flight levels is used. These flight levels are related to a pressure datum of 1013.2 hpa (Standard Atmospheric Pressure) and are separated by a nominal distance of 500ft.
  3. The transition from flight levels to altitudes is affected by means of a horizontal transition layer above which aircraft are flown at flight levels and below which aircraft are flown at altitudes.
  4. A flight level indicator or an altimeter set to 1013.2 hpa is used to indicate flight levels, and an altimeter set to a QNH setting is used to indicate altitudes.

2  Basic altimeter setting procedures

2.1  General
2.1.1 A transition altitude is specified for each aerodrome. No transition altitude is less than 450 m above an aerodrome.
2.1.2 At the coastal aerodromes within Somalia, namely: Berbera, Bosaso, Mogadishu, Kismayo and all other coastal aerodromes within Somalia, the transition altitude will be 3000 feet AMSL.
2.1.3 At Hargeisa International Airport, the transition altitude will be 8000 feet AMSL.
2.1.4 At Borama and Kalabeyed aerodromes, the transition altitude will be 8000 feet AMSL.
2.1.5 At Burao aerodrome, transition altitude will be 7000 feet AMSL.
2.1.6 At Gardo aerodrome, transition altitude will be 6000 feet AMSL.
2.1.7 Vertical positioning of aircraft when at or below the transition altitude is expressed in terms of altitude, whereas such positioning at or above the transition level is expressed in terms of flight levels. While passing through the transition layer, vertical positioning is expressed in terms of altitude when descending and in terms of flight levels when ascending.
2.1.8 Flight level zero is located at the atmospheric pressure level of 1 013.2 hPa (29.92 in). Consecutive flight levels are separated by a pressure interval corresponding to 500 ft (152.4 m) in the standard atmosphere.

Note: Examples of the relationship between flight levels and altimeter indications are given in the following table, the metric equivalents being approximate:

Flight level number Altimeter indication
Feet Metres
5500150
101 000300
151 500450
202 000600
505 0001 500
10010 0003050
15015 0004550
20020 0006100
2.2  Take-off and climb
2.2.1 A QNH altimeter setting is made available to aircraft in taxi clearance prior to take-off.
2.2.2 Vertical positioning of aircraft during climb is expressed in terms of altitudes until reaching the transition altitude above which vertical positioning is expressed in terms of flight levels.
2.3  Vertical separation — en route
2.3.1 Vertical separation during en-route flight shall be expressed in terms of flight levels at all times “during an IFR flight and at night”.
2.3.2 IFR flights, and VFR flights above 900 m (3 000 ft), when in level cruising flight, shall be flown at such flight levels, corresponding to the magnetic tracks shown in the following table, so as to provide the required terrain clearance:
000˚-179˚180˚-359˚
IFRVFRIFRVFR
Flight level number1020
30354045
50556065
70758085
9095100105
..........etc...........etc.
270280
290310
330350
etc.etc.

Note: Some of the lower levels in the above table may not be usable due to terrain clearance requirements.

2.4  Approach and landing
2.4.1 A QNH altimeter setting is made available in approach clearance and in clearance to enter the traffic circuit.
2.4.2 QFE altimeter settings are not available.
2.4.3 Vertical positioning of aircraft during approach is controlled by reference to flight levels until reaching the transition level below which vertical positioning is controlled by reference to altitudes.
2.5  Missed approach
2.5.1 The relevant portions of 2.1.2, 2.2 and 2.4 shall be applied in the event of a missed approach.

3  Procedures applicable to operators (including pilots)

3.1  Flight planning
The levels at which a flight is to be conducted shall be specified in a flight plan:
  1. in terms of flight levels if the flight is to be conducted at or above the transition level, and
  2. in terms of altitudes if the flight is to be conducted in the vicinity of an aerodrome and at or below the transition altitude.

Note: 1.— Short flights in the vicinity of an aerodrome may often be conducted only at altitudes below the transition altitude.

Note: 2.— Flight levels are specified in a plan by number and not in terms of feet or metres as is the case with altitudes.

4  Tables of cruising levels

The cruising levels to be observed when so required are as follows:
  1. in areas where, on the basis of regional air navigation agreement and in accordance with conditions specified therein, a vertical separation minimum (VSM) of 300 m (1 000 ft) is applied between FL 290 and FL 410 inclusive:∗
    TRACK∗∗
    From 000 degrees to 179 degreesFrom 180 degrees to 359 degrees
    IFR FlightsVFR FlightsIFR FlightsVFR Flights
    FLAltitudeFLAltitudeFLAltitudeFLAltitude
    MetresFeetMetresFeetMetresFeetMetresFeet
    -90–––0–––
    103001 000–––206002 000–––
    309003 000351 0503 500401 2004 000451 3504 500
    501 5005 000551 7005 500601 8506 000652 0006 500
    702 1507 000752 3007 500802 4508 000852 6008 500
    902 7509 000952 9009 5001003 05010 0001053 20010 500
    1103 35011 0001153 50011 5001203 65012 0001253 80012 500
    1303 95013 0001354 10013 5001404 25014 0001454 40014 500
    1504 55015 0001554 70015 5001604 90016 0001655 05016 500
    1705 20017 0001755 35017 5001805 50018 0001855 65018 500
    1905 80019 0001955 95019 5002006 10020 0002056 25020 500
    2106 40021 0002156 55021 5002206 70022 0002256 85022 500
    2307 00023 0002357 15023 5002407 30024 0002457 45024 500
    2507 60025 0002557 75025 5002607 90026 0002658 10026 500
    2708 25027 0002758 40027 5002808 55028 0002858 70028 500
    2908 85029 0003009 15030 000
    3109 45031 0003209 75032 000
    33010 05033 00034010 35034 000
    35010 65035 00036010 95036 000
    37011 30037 00038011 60038 000
    39011 90039 00040012 20040 000
    41012 50041 00043013 10043 000
    45013 70045 00047014 35047 000
    49014 95049 00051015 55051 000
    etc.etc.etc.etc.etc.etc.
    ∗ Except when, on the basis of regional air navigation agreements, a modified table of cruising levels based on a nominal vertical separation minimum of 300 m (1 000 ft) is prescribed for use, under specified conditions, by aircraft operating above FL 410 within designated portions of the airspace.
    ∗∗ Magnetic track, or in polar areas at latitudes higher than 70 degrees and within such extensions to those areas as may be prescribed by the appropriate ATS authorities, grid tracks as determined by a network of lines parallel to the Greenwich Meridian superimposed on a polar stereographic chart in which the direction towards the North Pole is employed as the Grid North.
  2. in other areas:
    TRACK∗∗
    From 000 degrees to 179 degreesFrom 180 degrees to 359 degrees
    IFR FlightsVFR FlightsIFR FlightsVFR Flights
    FLAltitudeFLAltitudeFLAltitudeFLAltitude
    MetresFeetMetresFeetMetresFeetMetresFeet
    -90–––0–––
    103001 000–––206002 000–––
    309003 000351 0503 500401 2004 000451 3504 500
    501 5005 000551 7005 500601 8506 000652 0006 500
    702 1507 000752 3007 500802 4508 000852 6008 500
    902 7509 000952 9009 5001003 05010 0001053 20010 500
    1103 35011 0001153 50011 5001203 65012 0001253 80012 500
    1303 95013 0001354 10013 5001404 25014 0001454 40014 500
    1504 55015 0001554 70015 5001604 90016 0001655 05016 500
    1705 20017 0001755 35017 5001805 50018 0001855 65018 500
    1905 80019 0001955 95019 5002006 10020 0002056 25020 500
    2106 40021 0002156 55021 5002206 70022 0002256 85022 500
    2307 00023 0002357 15023 5002407 30024 0002457 45024 500
    2507 60025 0002557 75025 5002607 90026 0002658 10026 500
    2708 25027 0002758 40027 5002808 55028 0002858 70028 500
    2908 85029 0003009 15030 0003109 45031 0003209 75032 000
    33010 05033 00034010 35034 00035010 65035 00036010 95036 000
    37011 30037 00038011 60038 00039011 90039 00040012 20040 000
    41012 50041 00042012 80042 00043013 10043 00044013 40044 000
    45013 70045 00046014 00046 00047014 35047 00048014 65048 000
    49014 95049 00050015 25050 00051015 55051 00052015 85052 000
    etc.etc.etc.etc.etc.etc.etc.etc.etc.etc.etc.etc.
    ∗Magnetic track, or in polar areas at latitudes higher than 70 degrees and within such extensions to those areas as may be prescribed by the appropriate ATS authorities, grid tracks as determined by a network of lines parallel to the Greenwich Meridian superimposed on a polar stereographic chart in which the direction towards the North Pole is employed as the Grid North.