1.7.1   Introduction

The altimeter setting procedures in use conform to those contained in ICAO PANS-OPS Doc. 8168 - Volume III and are given in full below.

Transition altitudes are given in Sub-section 1.7.2 below and AD-2.17 for each aerodrome. In addition, transition altitudes are given on instrument approach charts.

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

1.7.2   Basic altimeter setting procedures

1. General

1.1 A transition altitude is specified for each aerodrome.

1.2 Vertical positioning of aircraft when at or below the transition altitude is expressed in terms of altitudes where as 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 level when ascending.

1.3 Flight level zero is located at the atmospheric pressure level of 1013.2 HPA (29.92 inHg). Consecutive flight levels are separated by a pressure interval corresponding to 500 feet (152.4 metres) in the Standard Atmosphere.

1.4 Lisboa FIR - Table of transition altitudes and levels

1.5 Santa Maria FIR - Table of transition altitudes and levels

2. Take-off and climb

QNH altimeter setting is made available to aircraft prior to take-off.

QFE altimeter setting shall be passed to aircraft on request.

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.

3. Vertical separation en-route

Vertical separation during en-route flight shall be expressed in terms of flight levels at all times.

4. Approach and landing

A QNH altimeter setting is made available in approach clearances and in clearances to enter the traffic circuit.

A QFE altimeter setting shall be passed to aircraft on request.

The transition level is made available in approach clearances.

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 altitudes.

5. Missed approach

The relevant portions of paragraphs 1.2, 2 and 4 and shall be applied to the case of a missed approach.

1.7.3   Altimeter setting region(s)

1.7.4   Procedures applicable to operators (including pilots)

Flight planning

The levels at which a flight is to be conducted shall be specified in a Flight Plan:

1. in terms of flight level 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.