1. ILS facilities in the United Kingdom conform to ICAO Annex 10 Standards appropriate to the pro-mulgated FACILITY PERFORMANCE CATEGORY unless otherwise indicated in the UK AIP. They can therefore be relied upon to provide naviga-tional information to the required accuracy provi-ding:

a) They are only used inside the specified coverage sectors
b) the signal-in-space is being adequately protected
c) due account is taken of any warnings or difference promulgated by NOTAM or contained in the UK AIP

2. ILS Localizers in the United Kingdom provide coverage in the following areas. From the centre of the Localizer antenna to distance of:
a) 25 nm within +/- 10° of the front course line
b) 17 nm between 10° and 35° from the front course line

2.1. Localizers paired with steep angle Glide Paths in the United Kingdom provide coverage in the following areas. From the centre of the Localizer to distance of:
a) 18 nm within +/- 10° of the front course line
b) 10 nm between 10° and 35° from the front course line

2.2 Flight crews are warned that use of the Localizer outside these areas can lead to false course and reverse sense indications being received. Such use should not be attempted. In particular it must be noted that there is no provision for Localizer “Back Beams” to be used in the United Kingdom and any indications from them must be ignored.

3. ILS Glide Paths in the United Kingdom provide coverage in the following areas:
a) Coverage sectors of 8° in azimuth each side of the Localizer centre-line to a distance of 10 nm from threshold
b) Steep angle Glide Path facilities provide coverage to a distance of 8 nm from threshold in a sector to 8° either side of the Localizer centre-line
c) Vertical Coverage is provided from 0,45Æ up to 1,7Æ above the horizontal where o is the promulgated Glide Path angle. This equates to coverage from 1,35 to 5,25 degrees above the horizontal for a 3 degrees Glide Path.

3.1 Flight crews are warned that use of the Glide Path outside these limits can lead to intermittent and incorrect indications being received. In particular, use of the Glide Path BELOW 0,45Æ, that is below 1500 ft QFE at 10 nm range, for a 3° glide path, should only be attempted when the Promulgated Gli-de Path intercept Procedure REQUIRES such use and then NEVER below 0,30Æ (0,9° for a 3° Glide Path), that is below 1000 ft QFE at 10 nm range. Where special approach procedures have been devised in which the glide Path may be joined from above, pilots must bear in mind that a false Glide Path may exist at an angle of about 2Æ. This false Glide Path must NOT be used for descent guidance. Establishment on the promulgated Glide path should be confirmed by the relationship between aircraft height and distance to runway threshold.

4. Certain Glide Paths in the United Kingdom do not exhibit correct deflection sensitivity to one side of the Localizer course line. This effect is caused by terrain or other problems and can lead to inadequate “FLY UP” indications being received. When this situation exists a warning will be promulgated by NOTAM and subsequently appear in the appropriate columns of the COM 2 section of the UK AIP.

5. The use of an ILS in its promulgated Category is subject to the “signal-in-space” being adequately protected from interference due to the reflection from objects “illuminated” by the Localizer or Glide Path beam. Moving objects, particularly large ones like aircraft manoeuvering in close proximity to the runway, may disturb the ILS guidance signals. ATC will apply increased separation and such other methods considered necessary to prevent interference particularly during Low Visibility operations. Such measures may also be applied, at the discretion of ATC, when requested by pilots wishing to use Low Visibility Procedures when meteorological condi-tions do not necessitate them.

5.1 Flight crews should be aware of the ILS interference effects that can occur while conducting autolands when Low Visibility Procedures (LVPs) are not in force. Included within LVPs is the protection of the ILS sensitive area from intrusion by aircraft and vehicles.

5.2 In Category I conditions or better, LVPs will not be in force unless specifically requested. Intrusion into the ILS critical and sensitive areas by taxiing aircraft, ground vehicles or overflight of the ILS localizer may cause interference to the ILS signal. This interference may result in deviations from the desired approach path and may be accompanied by a “LOC” warning flag appearing briefly.

5.3 When making autolands in conditions not requi-ring the introduction of LVPs, flight crews should closely monitor the flight path of their aircraft and be prepared to disconnect the autopilot immediately if excessive disturbances occur near to the ground.

6. Certain combinations of localizer beam characteristics and modern receiver/autopilot combinations can cause premature localizer capture. Flight crews should be alert to this possibility. Flight deck procedures should be designed to reduce the risk of this type of event by not allowing Flight Direc-tor/Autopilot capture modes to be armed too early. Flight crews are advised to confirm the validity of ILS capture by cross-checking with other sources of navigational information where available. Being alert to anomalous aircraft performance such as illogical heading or descent will also assist in guarding against premature capture.

7. When an ILS is undergoing maintenance or is radiating for test purposes only, The IDENTIFICATION coding will either be removed completely or replaced by a continuous tone. Under these conditions NO ATTEMPT should be made to use the ILS as completely erroneous indications may be received. Additionally, in some instances, because of an un-serviceable Glide Path, the ILS may be radiating for LOCALIZER APPROACHES ONLY, in which case the identification coding will be radiating. However, it is possible that the Glide Path may also be radia-ting for setting-up purposes or for flight inspection, it may be subject to interruptions and alterations without warning and may give erroneous indications. In this case ATC will warn all users of this fact and no attempt should be made to use the Glide Path.

8. Distance Measuring Equipments that are frequency paired with ILS channels are provided to supplement or replace the range information provided by ILS markers. All range information is zero referenced to the ILS runway threshold. The DME is protected from interference from other DME services only within the Localizer service area as described in paragraph 2 up to a height of 25.000 ft above threshold. Certain ILS paired DME support other promulgated approach and departure procedures, in these cases protection from interference from other DME is assured within the volume required by the procedures. Use of an ILS paired DME outside of a promulgated procedure may result in erroneous distance information and/or corrupt or erroneous identification co-ding.