1.7.1 Introduction

1.7.1.1. 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 heavy black type.

1.7.1.2. The transition altitude ( TA ) is given:

in the AD 2.17 tabulation, for the aerodrome but only for those aerodromes outside the Jeddah FIR which are , therefore, non standard (see 1.7.2.1.1 below); and
on all instrument approach charts.

1.7.1.3. QNH and temperature data, for use in determining adequate terrain clearance, are included in ATIS broadcasts, where provided, or are available on request from the appropriate ATS unit. QNH values are given in hectopascals (millibars), rounded down to the nearest whole unit.

1.7.2 Basic altimeter setting procedures

1.7.2.1 General

1.7.2.1.1. A common TA of 13 000 FT and a fixed transition level (TL) of FL 150 are established for the whole of Jeddah FIR airspace.

Note 1 : The altitude equivalent of FL 150, calculated from the lowest known MSL pressure in Saudi Arabia (986 HPA), is 14 265 FT and, therefore, a minimum of 1 000 FT of vertical separation exists in the transition layer under all surface atmospheric pressure conditions; thus, simultaneous flight at both TA and TL is always permissible, but level flight within the layer is prohibited.

Note 2 : The classification of the airspace within the transition layer assumes the classification of the airspace within which it resides.

1.7.2.1.2. The vertical position of aircraft is expressed in terms of:

altitude, when at or below the TA and when descending through the transition layer; and
flight level, when at or above the TL and when climbing through the transition layer.

1.7.2.1.3. Flight level zero is located at the atmospheric pressure level of 1 013.2 HPA. Consecutive flight levels are separated by a pressure interval corresponding to 500 FT (152.4 M) in the ICAO International Standard Atmosphere ( ISA ).

1.7.2.2 Take-off and climb

1.7.2.2.1. A QNH altimeter setting is available either:

in routine departure information, by ATIS ( where applicable ) or RTF, at aerodromes with ATS units; or
from Jeddah ACC , Dammam Approach , Abha APP, Riyadh Approach or Tabuk APP, as appropriate, for aerodromes without ATS units.

1.7.2.2.2. Vertical position of aircraft during climb is controlled by reference to altitude until reaching the TA, and by reference to flight level above the TA.

1.7.2.3 Vertical separation enroute

1.7.2.3.1. Vertical separation of aircraft enroute is controlled by reference to:

altitude, when at and below the TA; and
flight level, when at and above the TL.

1.7.2.3.2. Vertical separation is applied by requiring aircraft to fly at the appropriate hemispherical level prescribed in ICAO Annex 2, Appendix 3, according to the magnetic track of the aircraft, except that non hemispherical levels are also assigned on one way airways if necessary to improve traffic flow or avoid double level changes, as shown below:

IFR ALTITUDES 13 000 FT AND BELOW

359°
	000°
EVEN
	ODD
2 000
4 000
6 000	1 000
8 000	3 000
10 000	5 000
12 000	7 000
	9 000
	11 000
	13 000
180°
	179°

IFR FLIGHT LEVELS FL 150 UP TO FL 290

359°
	000°
EVEN
	ODD
160
180
200	150
220	170
240	190
260	210
280	230
	250
	270
180°
	179°

VFR ALTITUDES BELOW 13 000 FT

359°
	000°
EVEN
	ODD
2 500
4 500
6 500	1 500
8 500	3 500
10 500	5 500
12 500	7 500
	9 500
	11 500
180°
	179°

IFR FLIGHT LEVELS (FL290 - FL410) INCLUSIVE IN RVSM AIRSPACE "APPLY 2000 INTERVALS"

359°
	000°

EVEN
300	ODD
320	290
340	310
360	330
380	350
400	370
430	390
470	410
510	450
550	490
590	530
	570

180°
	179°

Note 1 : Aircraft operating on ATS routes above FL 600 or below ALT 11 500 FT will be outside controlled airspace and, therefore, will be provided with flight information service only.

Note 2 : Since VFR is not permitted above FL 150, the highest usable VFR level is ALT 12 500 FT.

Note 3 : Some of the lower levels shown above may not be usable due to terrain clearance requirements.

1.7.2.3.3. Current QNH reports are used to determine the terrain clearance for flights operating at or below the TA. The chart on page ENR 6.11 Altimeter Setting Observing Stations - Index Chart depicts the network of observing stations, which report QNH hourly; these reports are provided direct to ATS units established at aerodromes and, in the form of an hourly METAR bulletin, to Jeddah ACC, Dammam Approach, Abha Approach , Riyadh Approach and Tabuk APP.

1.7.2.4 Approach and landing

1.7.2.4.1 A QNH altimeter setting is available either:

in routine approach and landing information, by ATIS (where applicable) or RTF, at aerodromes with ATS units ; or
from Jeddah ACC, Dammam Approach, Abha Approach, Riyadh Approach or Tabuk APP, as appropriate, for aerodrome without ATS units.

Note: At present there is no observing station at Jubail; the Dammam QNH is authorized for remote use.

1.7.2.4.2. A QFE altimeter setting is available on request at aerodromes with ATS units; QFE is NOT readily available at other aerodromes. Where available, the QFE reference datum is either:

runway threshold elevation - for all precision runways and those non-precision runways with a threshold elevation 7 FT or more below aerodrome elevation; or
aerodrome elevation - for all other runways.

1.7.2.4.3. Vertical positioning of aircraft during approach is controlled by reference to flight levels until reaching the TL, and by reference to altitude below the TL. However, this does not preclude pilots from using either:

QNH setting from top of descent, provided that level flight above the TA is neither indicated nor anticipated; or
QFE setting, where available, for terrain clearance purposes during final approach to the runway.

1.7.2.5 Missed approach

The relevant portions of the preceding paragraphs apply in all cases of missed approach.

1.7.3 Description of altimeter setting region

The altimeter setting regions are shown on the Altimeter Setting Observing Stations Index Chart ENR 6.11.

1.7.4 Procedures applicable to operators (including pilots)

1.7.4.1 Flight planning

1.7.4.1.1. The levels at which a flight is to be conducted shall be specified in a flight plan in terms of:

flight level, when the flight is to be operated at or above the TL; and
altitude, when the flight is to be operated at or below the TA.

1.7.4.1.2. The levels selected should:

ensure adequate terrain clearance for the entire route; and
satisfy ATC requirements; and
be compatible with those shown in paragraph 2.3.2.

Note 1 : The information required to determine the lowest level which will ensure adequate terrain clearance may be obtained from the appropriate services unit, e.g. ATS, AIS or MET.

Note 2 : The levels selected will depend upon the accuracy with which the vertical position of such levels relative to the terrain can be estimated which, in turn, is dependent upon the type of meteorological information available. A lower level may be used with confidence when its position is based on current information relevant to the particular route to be flown and when it is known that amendments to this information will be available in flight; but a higher level will be needed when based on information less relevant to the particular route to be flown and the time at which the flight is to be conducted. See chart on page ENR 6.11.

Note 3 : Flights over level terrain may often be conducted at one level, whereas flights over mountainous terrain may require several changes in levels to account for changes in the elevation of the terrain. The use of several levels may also be needed in order to comply with ATS requirements.

1.7.4.2 Pre-flight operational test

1.7.4.2.1. The following test should be performed by flight crew members prior to take-off; the purpose of this test being to establish whether or not the altimeter readout is within the permissible range for that instrument.

1.7.4.2.2. With the aircraft at a known elevation on the aerodrome, set the altimeter pressure scale to the appropriate current value (QNH or QFE). Vibrate the instrument by tapping unless a mechanical vibration is provided. A serviceable altimeter will indicate either:

QNH - the elevation of the point selected plus the height of the altimeter above this point; or
QFE - the height of the altimeter in relation to the QFE reference datum;

within a tolerance of plus/minus 60 FT or 80 FT for altimeters with test ranges up to 30 000 FT or 50 000 FT respectively.

Note 1 : When the altimeter does not indicate the reference elevation or height exactly, but is within the specified tolerance, no adjustment of this indication should be made either by means of the pressure adjustment knob or other adjustment on the altimeter at any stage of a flight. Furthermore, any error that is within tolerance, noted during pre-flight check on the ground, should be ignored by the pilot during flight.

Note 2 : The tolerances specified above are considered acceptable for aerodrome elevations up to 3 500 FT ISA. The tables below indicate the permissible range for different aerodrome elevations and when pressure is lower than ISA.

Table 1

Tolerances for altimeters
with test range up to
30 000 FT.

AD ELEV (FT)	Permissible Range (FT)
2 000	1 940 to 2 060
3 000	2 930 to 3 070
4 000	3 925 to 4 075
5 000	4 920 to 5 080
6 000	5 915 to 6 085
7 000	6 905 to 7 095

Table 2

Tolerances for altimeters
with test range up to
50 000 FT.

AD ELEV (FT)	Permissible Range (FT)
2 000	1 900 to 2 100
3 000	2 895 to 3 105
4 000	3 885 to 4 115
5 000	4 875 to 5 125
6 000	5 865 to 6 135
7 000	6 855 to 7 145

1.7.4.3 Take off and climb

1.7.4.3.1. Prior to take-off, one altimeter shall be set to the latest QNH available for the aerodrome.

1.7.4.3.2. During climb, all references to the vertical position of the aircraft in air-ground communications shall be expressed in terms of:

altitude, up to and while at the TA ; and
flight level, above the TA.

1.7.4.3.3. The reference to vertical position of the aircraft shall be changed from altitude ( QNH ) to flight level ( ISA 1 013.2 HPA ) when leaving or passing the TA.

1.7.4.4 Enroute

1.7.4.4.1. Vertical separation during enroute flight is accomplished as follows:

at or below the TA, aircraft shall be flown at altitudes and references to vertical position in air-ground communications shall be expressed in such terms; and
at or above the TL , aircraft shall be flown at flight levels and references to vertical position in air-ground communications shall be expressed in such terms.

1.7.4.4.2. It is essential that all aircraft operating in the same airspace segment use the same altimeter setting reference to ensure that vertical separation is not infringed and, therefore, aircraft flown entirely in accordance with paragraph 1.7.4.4.1 a) above shall set QNH as follows:

within a TMA, the QNH provided for the area by the controlling ATS unit except that aircraft destined to other aerodromes within that same TMA shall set the appropriate aerodrome QNH when entering the relevant ATZ or, where no ATZ is established, the aerodrome traffic circuit; or
elsewhere, the QNH for the nearest on track station, the changeover from the station QNH behind the aircraft to that ahead being made at the mid point between the two stations.

Note : This does not preclude aircraft using off-track QNH reports to assess terrain clearance in accordance with paragraph 1.7.4.4.3 below.

1.7.4.4.3. Terrain clearance shall be assessed using the latest and most appropriate QNH altimeter setting reports available.

1.7.4.4.4. Where the adequacy of terrain clearance cannot be assessed with an acceptable degree of accuracy by means of the QNH reports available, other information shall be obtained from the appropriate services unit for checking the adequacy of terrain clearance.

1.7.4.5 Approach and landing

1.7.4.5.1. Prior to descending below the TL, the latest QNH altimeter setting for the aerodrome shall be obtained.

1.7.4.5.2. On descending below the TL, the reference for vertical position shall be changed from flight level (ISA 1 013.2 HPA) to altitude (QNH) and, thereafter, the vertical position of the aircraft shall be expressed in terms of altitude.

Note : This does not preclude a pilot using either:

QFE for terrain clearance during final approach in accordance with 1.7.4.5.3 below; or
the change of reference for vertical position from flight level to altitude above the TL, when so cleared by the appropriate ATS unit, after approach clearance has been issued and the descent to land commenced, provided that level flight above the TA is neither indicated nor anticipated.

1.7.4.5.3. When an aircraft is cleared as number one to land and is completing its approach using QFE, vertical position shall be expressed in terms of height, above the aerodrome reference datum used in establishing OCH, during that portion of its flight for which QFE may be used.

The relevant portions of the preceding paragraphs apply in all cases of missed approach.

1.7.5 Tables of cruising levels

The cruising levels to be observed when so required are as follows:

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:*

TABLE A

TRACK**

From 000 degrees to 179 degrees						From 180 degrees to 359 degrees
IFR Flights			VFR Flights			IFR Flights			VFR Flights
Altitude			Altitude			Altitude			Altitude
FL	Metres	Feet	FL	Metres	Feet	FL	Metres	Feet	FL	Metres	Feet
-90			--	--	--	0			--	--	--
10	300	1000	--	--	--	20	600	2000	--	--	--
30	900	3000	35	1050	3500	40	1200	4000	45	1350	4500
50	1500	5000	55	1700	5500	60	1850	6000	65	2000	6500
70	2150	7000	75	2300	7500	80	2450	8000	85	2600	8500
90	2750	9000	95	2900	9500	100	3050	10000	105	3200	10500

110	3350	11000	115	3500	11500	120	3650	12000	125	3800	12500
130	3950	13000	135	4100	13500	140	4250	14000	145	4400	14500
150	4550	15000	155	4700	15500	160	4900	16000	165	5050	16500
170	5200	17000	175	5350	17500	180	5500	18000	185	5650	18500
190	5800	19000	195	5950	19500	200	6100	20000	205	6250	20500

210	6400	21000	215	6550	21500	220	6700	22000	225	6850	22500
230	7000	23000	235	7150	23500	240	7300	24000	245	7450	24500
250	7600	25000	255	7750	25500	260	7900	26000	265	8100	26500
270	8250	27000	275	8400	27500	280	8550	28000	285	8700	28500
290	8850	29000				300	9150	30000

310	9450	31000				320	9750	32000
330	10050	33000				340	10350	34000
350	10650	35000				360	10950	36000
370	11300	37000				380	11600	38000
390	11900	39000				400	12200	40000

410	12500	41000				430	13100	43000
450	13700	45000				470	14350	47000
490	14950	49000				510	15550	51000
530	16150	53000				550	16750	55000
570	17350	57000				590	18000	59000
etc.	etc.	etc.				etc.	etc.	etc.

* Except when, on the bases of regional air navigation agreements, a modified table of cruising levels based on a nominal vertical separation minimum of 300 M ( 1000 FT ) is prescribed for use, by aircraft operating above FL 410 within designated portion 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 stereo graphic chart in which the direction towards the North Pole is employed as the Grid North.

***Except where, on the basis of regional air navigation agreements, from 090 to 269 degrees and from 270 to 089 degrees is prescribed to accommodate predominant traffic dircetions and appropriate transition procedures to be associated therewith are specified.

TABLE B

TRACK**

From 000 degrees to 179 degrees						From 180 degrees to 359 degrees
IFR Flights			VFR Flights			IFR Flights			VFR Flights
Altitude			Altitude			Altitude			Altitude
FL	Metres	Feet	FL	Metres	Feet	FL	Metres	Feet	FL	Metres	Feet
-90			--	--	--	0			--	--	--
10	300	1000	--	--	--	20	600	2000	--	--	--
30	900	3000	35	1050	3500	40	1200	4000	45	1350	4500
50	1500	5000	55	1700	5500	60	1850	6000	65	2000	6500
70	2150	7000	75	2300	7500	80	2450	8000	85	2600	8500
90	2750	9000	95	2900	9500	100	3050	10000	105	3200	10500

110	3350	11000	115	3500	11500	120	3650	12000	125	3800	12500
130	3950	13000	135	4100	13500	140	4250	14000	145	4400	14500
150	4550	15000	155	4700	15500	160	4900	16000	165	5050	16500
170	5200	17000	175	5350	17500	180	5500	18000	185	5650	18500
190	5800	19000	195	5950	19500	200	6100	20000	205	6250	20500

210	6400	21000	215	6550	21500	220	6700	22000	225	6850	22500
230	7000	23000	235	7150	23500	240	7300	24000	245	7450	24500
250	7600	25000	255	7750	25500	260	7900	26000	265	8100	26500
270	8250	27000	275	8400	27500	280	8550	28000	285	8700	28500
290	8850	29000				300	9150	30000

310	9450	31000				320	9750	32000
330	10050	33000				340	10350	34000
350	10650	35000				360	10950	36000
370	11300	37000				380	11600	38000
390	11900	39000				400	12200	40000

410	12500	41000				430	13100	43000
450	13700	45000				470	14350	47000
490	14950	49000				510	15550	51000
490	14950	49000				510	15550	51000
530	16150	53000				550	16750	55000
etc.	etc.	etc.				etc.	etc.	etc.

* Except when, on the bases 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, by aircraft operating above FL410 within designated portion of the airspace.

ENR 1.7 ALTIMETER SETTING PROCEDURES