Manifiesto Comunista – Antología del Capital

3.1 Siting and Number of Runway Observation Positions

For RVR observations made in connection with Category I operations, one ROP giving an assessment of the RVR on the runway in the touchdown zone will generally be sufficient.

An ROP may be either a structure or vehicle and its location should be determined by the aerodrome operator in consultation with the CAA using the guidance material set out below.

3.1.1 Lateral Position

Ideally the ROP should be sited not more than 120 m laterally from the runway centreline. However, for safety reasons it must not be located:

a) within the runway cleared and graded area; b) within taxiway strips;

c) such that a profile of 1 in 10 slope originating at the runway centreline is infringed by the height of the structure or vehicle, including the observer in his observation position.

However, as an exception to b) above it is acceptable to locate the ROP on a taxiway that is inactive when measurements are being taken. Reference should be made to CAP 168 Chapter 3, paragraph 6 for details of the relevant specifications and criteria.

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3.1.2 Longitudinal Position

The touchdown zone ROP should be located approximately 300 m upwind of the runway threshold. On short runways it is preferable for the ROP to be sited abeam or downwind of the threshold so as to be able to increase the maximum reportable RVR. Care should be taken to ensure that the ROP does not constitute an obstacle infringing the relevant instrument approach surfaces specified in CAP 168.

3.1.3 Position of ROP relative to Lights/Marker Boards

The ROP should be sited so as to enable the lights used for assessing RVR to be clearly visible to the observer. The observer eye height should be 5 m above the runway level, this being the maximum practical height for a human observer. The most representative assessment of RVR will be made when counting lights on the opposite side of the runway to that of the ROP, but it is recognised that although this should be the aim, it will not be possible on some runways, for example on undulating runways or where there are many flush edge light fittings on the opposite side. In such cases the order of preference for the selection of lights to be used is shown in paragraph 4 below.

3.1.4 The ROP should be located so that the vehicle or structure does not obscure a pilot’s view of visual aids.

3.1.5 In order to ensure that the ROP does not affect the performance of electronic

navigation aids, advice on the siting should be sought from the aerodrome telecommunications officer.

3.2 Marking and Lighting

3.2.1 Whether the ROP is a fixed structure or parked vehicle it should be marked and

lighted as an obstacle as laid down in CAP 168, Chapter 4, paragraph 12.

3.2.2 In order to ensure that the observer makes his observation from the calibrated

position where the ROP is a parked vehicle, the parking position should be clearly and unambiguously marked, so that the vehicle may be correctly positioned each time it is deployed.

3.3 Equipment and Facilities

3.3.1 Communications

The ROP should have direct and preferably discrete communication with ATC in order to facilitate the rapid reporting of RVR changes. It is a requirement that the report reaches the pilot within 30 seconds of an observation being made.

3.3.2 Comfort

The ROP, whether permanent or mobile, should have a sufficient degree of comfort so that personnel are not affected by fatigue or poor working conditions.

3.3.3 Transparency of Glass Surfaces

Glass surfaces through which observations are made should be kept clear of precipitation and condensation.

3.3.4 Internal Lighting

Sufficient light should be available for reporting and recording the observations. Lighting within the ROP should be such that the taking of observations and the visual night acclimatisation of the observer are not adversely affected.

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3.3.5 ROP Construction

Where the ROP is a fixed structure, it should be of minimum dimensions and maximum frangibility consistent with its function.

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Lights

4.1 Selection of lights to be used for observations

4.1.1 The order of preference for selecting lights to be used for observations is, in

descending order:

opposite side runway edge lights opposite side special reference lights same side runway edge lights

same side special reference lights.

4.1.2 The CAA will advise the aerodrome operator which lights are to be used for each

runway and only that set of lights should be used for observations. Some runway edge light fittings may not be clearly visible to an observer at the side of the runway and a row of special reference lights of similar characteristics to the runway lights but beamed towards the ROP, may be needed. The intensity setting of these reference lights should be automatically set to the same intensity as the runway lights. Reference lights are to be arranged so as not to present a confusing or dangerous appearance to pilots.

4.1.3 So as to ensure the accuracy of the assessment it is necessary for the positions of the lights to be used to be accurately determined. Accordingly, they require to be included in the aerodrome survey, the requirements for which are contained in CAP 232, Chapter 5.

4.2 Creation of RVR Conversion Table

4.2.1 There are two methods available for creating the RVR Conversion Table, details for both are provided in CAP 746, Appendix C:

a) Use of the Gold Visibility Meter;

b) Use of a distance based methodology.

4.2.2 A new conversion table is required to be produced following any alterations or

changes to the system, for example when lights have been re-aligned or relocated, or changes made to supply voltages, or when the ROP has been changed. Any such change invalidates the previous conversion table and RVR reports are not to be passed until a new table is available.

4.3 Calibration of runway lights

4.3.1 High intensity runway lights with a beamed element, directed along the runway

towards the pilot, will result in the intensity of light directed towards the ROP being less than the intensity directed towards the pilot. Consequently a calibration of the lights used will be necessary. This will be carried out from the ROP and from the runway centreline in order to prepare a conversion table. From this table an assessment of the RVR to be experienced by the pilot can be read against the number of lights observed from the ROP. The aerodrome operator should ensure that re- calibrations are carried out at the agreed intervals and that a new table is issued. A re- calibration is to be carried out immediately following any alterations or changes to the system, for example when lights have been re-aligned, or changes made to supply voltages, or when the ROP site has been changed. Any such change invalidates the previous conversion table and RVR reports are not to be passed until a new table is available.

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4.4 Maintenance of RVR reference lights

Where special reference lights are used they should be maintained to the same standard as the corresponding runway lights so that RVR observers and pilots are viewing lights which have a comparable performance.

4.5 Inspection of lights

The lights used for RVR observations should be regularly inspected from the ROP, at the correct eye height, through binoculars in clear daylight with the lights set at maximum intensity. This visual inspection should check for subsidence, damage, mis- alignment, ageing of bulbs/lenses and obscuration by grass. It is recommended that this inspection is carried out at least monthly.

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The Observer

5.1 Selection and function of the observer

The function of the observer needs no particular skill since it consists of identifying and counting lights and reporting this count to ATC. However, since assessment of RVR has a direct bearing on safety and regularity of aircraft operations, observers should be mature and with the ability to carry out their duties conscientiously at all times. The aerodrome operator should ensure that observers understand the importance of correct RVR observations and appreciate that extra vigilance is required when fog is forming or dissipating so that changes are detected and reported as they occur.

5.2 Time on duty

Duty periods for RVR observers should be arranged so that long periods without an adequate break are avoided. Periodic visits should be made by supervisors to an active ROP to check that the correct procedures are being used and the log is being correctly maintained when this is required of the observer.

5.3 Eyesight and Hearing Requirements

5.3.1 Personnel selected for RVR observer duties should have the necessary eyesight

(visual acuity and colour perception) and hearing requirements required for them to operate on the manoeuvring area. Correcting spectacles or contact lenses should be worn when required.

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Operating Procedures

6.1 Periods when RVR reporting is required

The ROP should be manned in accordance with an alerting procedure based on meteorological reports and forecasts which will ensure that a continuous service can be given throughout any operational period during which the meteorological visibility is reported to be 1500 m or less. Assessment and reporting may cease when meteorological visibility is greater than 1500 m and the RVR is greater than the maximum value that can be reported. At some less busy aerodromes it may be sufficient to report RVR only during those periods commencing 15 minutes prior to and during aircraft movements. However, consideration should be given to the need for pilots intending to depart from another aerodrome to have a recent destination RVR report available to them. Under no circumstances should an RVR report be used or passed after the standing down of the observer except when that report is quoted as part of a full meteorological report which includes a time of origin.

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6.2 Reporting Procedures

6.2.1 Standardisation

The UK standard for reporting RVR extends from zero to 1500 m in the following steps:

0 to 400 m in 25 m steps 400 to 800 m in 50 m steps 800 to 1500 m in 100 m steps

Where a system is unable to report the full range of RVR as outlined above, the limitations of the system should be published in the AIP at GEN 3.5.3.

6.2.2 The Count

The number of lights that can be seen (the count) should be reported to ATC, for example 'Four lights'. The report should be read back to the observer by ATC. The count is converted to RVR using the relevant conversion table. An immediate report is to be made whenever there is a change in the count, but if there are no changes, confirmatory reports should be made at 30 minute intervals, or when requested. Similar reports and read-backs should be made if the count is converted to RVR at the ROP.

6.2.3 Low/High RVR values

If the RVR is so low that no lights are visible to the observer, he should report this. The RVR in these circumstances should be reported to a pilot as 'less than... metres', the actual RVR value quoted being the equivalent of one light. If the visibility is sufficient to enable the observer to see an object at ground level at a distance greater than the light which defines the maximum reportable RVR value, a report of 'RVR greater than... metres' should be given.

6.2.4 Effect of light intensity on reporting

RVR observations, including those for transmission in meteorological reports, should be made with the lights set at the intensity appropriate to the prevailing conditions. RVR should not be assessed with the lights set at an intensity for which there is no conversion table. If a pilot requests that the lights be reduced in intensity and this results in a setting for which there is no conversion table, the pilot should be advised that RVR is not available at this requested setting.

6.3 ATS functions

ATS aspects of RVR are described in general terms in Part 1 of the Manual of Air Traffic Services (MATS). Air Traffic Service Units should ensure that aspects specific to their aerodromes are described in their Part 2 of MATS or Local Instructions. 6.4 Changes to procedures

RVR should be observed and reported strictly in accordance with the laid down procedures. However, where local conditions require a departure from the standard procedures, the proposed change should be cleared with the CAA before operational use.

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