GACA eAIP

ENR 1.7 ALTIMETER SETTING PROCEDURES

1. Introduction

1.1. The altimeter setting procedures in use generally conform to those contained in PANS-OPS ICAO Doc 8168-OPS/611 Volume I, section 2, and only differences are stated.
1.2. Transition Altitude (TA) is given on the instrument approach charts.

1.3 Definitions

• QNH — Altimeter setting indicating altitude above mean sea level (AMSL) in ISA
• QFE — Altimeter setting indicating height above a specific reference datum (normally aerodrome or threshold elevation)
• Standard Pressure Setting —  1013.25 hectopascals (hPa)

2. BASIC ALTIMETER SETTING PROCEDURES

2.1 General
2.1.1 System of flight levels
2.1.1.1. Flight level zero is located at the atmospheric pressure level of 1013.25 hPa (29.92 IN inches Hg). Consecutive flight levels  are separated by a pressure interval corresponding to 500 FT in the Standard Atmosphere

2.1.1.2. Flight levels shall be numbered according to the standard ICAO Table of cruising levels.
2.1.2. Transition Altitude (TA)

2.1.2.1. Damascus FIR Transition Altitude (TA) is common and specified as 13000 FT.

2.1.2.2. Transition Altitude (TA) is published in Aeronautical Information Publications and shown on the instrument approach charts.

2.1.3 Transition level (TL)

2.1.3.1. Damascus FIR Transition level (TL) is common and specified as FL 150.

2.1.4 References to vertical position

2.1.4.1. The Vertical positioning of aircraft operating at or below the TA shall be expressed in terms of Altitude (ALT).

2.1.4.2. The Vertical positioning of aircraft operating at or above the TL is expressed in terms of Flight Levels (FL).

2.1.4.3. Vertical positioning of aircraft while passing through the Transition Layer shall be expressed in terms of:

a) altitude when descending and,

b) flight levels when climbing.

2.1.5 The terminology TA/TL applies during:

a) climb;

b) en route flight; and

c) approach and landing

2.2 Take-off and climb.

2.2.1 A QNH altimeter setting is made available to aircraft in taxi clearance before take-off.

2.2.2 During climb, all references in A/G communication to vertical position shall be in terms of:

a) FL when at or above TA; or

b) ALTs when at or below TA.

2.2.3 The altimeter subscale setting shall be changed from QNH to  1013.25 hPa (ISA) on leaving or passing the TA.

2.3 Enroute

2.3.1 Vertical separation en route is assessed in terms of:

a) ALT, when at and below the TA; and

b) FL, when at and above the TL.

2.3.2 Terrain clearance
2.3.2.1 Terrain clearance shall be assessed based on the latest Regional QNH obtainable from ATC.

2.4 Approach and landing

2.4.1 A QNH altimeter setting shall be made available to aircraft in approach clearance and in clearance to enter the traffic circuit.

2.4.2 A QFE altimeter settings are clearly identified by ATS for AD ELEV and THR ELEV if 7 ft or more below AD ELEV. They are available in approach and landing clearances on request.

NOTE: QFE is the isobaric surface pressure at the reference point. At other altitudes, the altimeter will give an indication of the height above that reference point. With the aerodrome QFE set in the subscale, your altimeter will read zero on the highest point on the runway, and at other altitudes will read the height above the airfield elevation. For precision approach runways or for instrument runways when the threshold is 7 ft or more below aerodrome elevation, the QFE may be based on the threshold elevation [ICAO Doc 4444, 4.10.1.2]. With the runway threshold QFE set in the subscale, your altimeter will read zero on the runway threshold.

2.4.3 Vertical positioning of aircraft during approach is controlled by reference to:

a) FL, until reaching the TL; and

b) ALT, when below the TL.

Note: This does not preclude a pilot using either:

a) QNH setting from the top of descent when cleared for uninterrupted descent to a level below TL; or

b) QFE setting for terrain clearance purposes during final approach to the runway.

2.5 Missed approach
2.5.1 The relevant parts of 2.1.4, 2.2, “Take-off and climb”, and 2.4, “Approach and landing” shall be applied in the event of a missed approach.

3. ALTIMETER SETTING REGIONS (ASR).

• QNH shall be used during all operations in the aerodrome vicinity and for all take-offs
• Arriving aircraft shall set QNH upon passing the transition level or as directed by ATC
• QFE may be used upon a specific pilot request
• Standard pressure ( 1013.25 hPa) shall be set when climbing through the transition altitude and maintained for all flight levels

3.1Transition Altitude, Level, and Layer

• Transition Altitude (TA) — Fixed altitude for each aerodrome, published in the AD section
• Transition Level (TL) — Lowest FL above TA, determined by ATS based on prevailing QNH
• Transition Layer — Airspace between TA and TL

4. PROCEDURES APPLICABLE TO OPERATORS (Including Pilots).

4.1 Flight planning

4.1.1 The levels at which a flight is to be conducted shall be specified in a flight plan in terms of :
a) Flight Levels (FL) if the flight is to be conducted at or above the Transition Level (TL) (or the lowest usable flight level, if applicable); and
b) Altitudes (ALTs) if the flight is to be conducted in the vicinity of an aerodrome and at or below the Transition Altitude (TA).
4.1.2 The altitudes or flight levels selected for flight should:
a) ensure adequate terrain clearance at all points along of the entire route; and
b) be compatible with the table of cruising levels as shown on page ENR 1.7-1. satisfy ATC requirements; and
c) be compatible with the table of cruising levels as shown in Table 4.2

.2 Table of cruising levels
4.2.1 The cruising levels to be observed when so required are as follows:

a) In areas where, based on a regional air navigation agreement and in accordance with conditions specified therein, a vertical separation minimum (VSM) of 300 m (1000 ft) is applied between FL290 and FL 410 inclusive.

References

• ICAO Annex 4 — Aeronautical Charts
• ICAO Annex 15 — Aeronautical Information Services