Section 3, Chapter 3 - Runway Visual Range Flashcards
What is the purpose of the Runway Visual Range (RVR) system?
The RVR system provides a localized assessment of visual range for a specific runway when meteorological visibility is less than 1,500 meters. It indicates the range over which a pilot on the runway centerline can see the runway surface markings and lights delineating or identifying the runway centerline.
What are the methods and reporting standards for assessing Runway Visual Range (RVR) at suitably equipped aerodromes in the UK?
The two methods of RVR assessment are:
- Instrumented RVR, using electronic equipment.
- Human Observer Method.
The UK standard for reporting RVR ranges from zero to 1,500 meters, in the following steps:
- 0 to 400 meters in 25-meter steps.
- 400 to 800 meters in 50-meter steps.
- 800 to 1,500 meters in 100-meter steps.
Not all systems can report all increments. The maximum reportable RVR value must be included in the UK AIP if it is less than 1,500 meters. Observed values are rounded down to the nearest lower step. Reports should indicate RVR as less than 50 meters or more than 1,500 meters if they fall outside these limits.
How does the Instrumented Runway Visual Range (IRVR) system work and what are its key features?
The IRVR system provides an automatic and continuous display of RVR values to ATC using transmissometers to measure atmospheric opacity. Key features include:
- Transmissometers: Placed at fixed points alongside the runway, typically three units per system (one at each runway end and one at the midpoint).
- Data Transfer and Processing: Transmissometers are linked to a central processor that computes and displays RVR values in digital form to ATC.
- Locations: The positions are known as “Touchdown,” “Mid-Point,” and “Stop End” for RTF transmission purposes.
- Runway Edge Light Intensity: The system adjusts for light intensity settings. The DEO should be informed of any discrepancies.
When are IRVR systems operational, and who notifies of any changes to their availability?
IRVR systems are operational at all times unless notified otherwise by the Duty Engineering Officer (DEO).
When is IRVR reporting to aircraft started?
IRVR reporting to aircraft is started:
- Whenever the aerodrome meteorological report shows visibility less than 1,500 meters.
- Whenever the IRVR display indicates an RVR value equal to or less than the system’s maximum.
- Whenever shallow fog is reported and during a period it is forecast.
What are the protocols for IRVR indications and reporting values at UK aerodromes?
- Some IRVR systems automatically reduce or suppress the display of mid-point and/or stop-end readings when not operationally significant.
- Unless specifically requested by a pilot, only values displayed at full intensity are transmitted in RVR reports.
- The touchdown position value is always displayed at full intensity and, if no other values are at full intensity, only the touchdown value needs to be reported.
- A description of the equipment and its use, along with liaison with the DEO, is included in MATS Part 2.
What are the protocols for transmitting IRVR values to aircraft during landing and take-off?
- IRVR values must be passed to aircraft at the beginning of each approach for landing and whenever there is a significant change (one increment or more) until landing.
- The current RVR value must be passed to aircraft before take-off, even if it was already received via ATIS broadcast.
- When reporting all three positions, the values for touchdown, mid-point, and stop-end are given as three numbers (e.g., “RVR runway [designator] 650 — 500 — 550 meters”).
- If only two values are reported, they must be individually identified (e.g., “RVR runway [designator] Touchdown 650 — Stop End 550 meters”).
- A high degree of priority should be given to ensure timely delivery of current RVR information to pilots.
What actions should be taken when a transmissometer in the IRVR system becomes unserviceable?
- Touchdown Transmissometer Failure: If the touchdown transmissometer fails but the system is still serviceable, use the mid-point value and stop-end value (if available). Inform the pilot about the failure (e.g., “RVR runway [designator] Touchdown not available — Mid-Point 600 — Stop End 400 meters”).
- Two Transmissometers Failure: If two transmissometers fail and the remaining one is not the stop-end, use the remaining value. If the stop-end value is the only one available, the system is unserviceable for that runway. Changing the runway direction might restore serviceability.
- Complete IRVR System Failure: If the IRVR system is entirely unserviceable, revert to Human Observer RVR or the reported meteorological visibility. Inform pilots of the meteorological visibility and that the IRVR system has failed.
What are the key procedures for determining RVR using the Human Observer Method?
- Detailed procedures for human observer RVR methods are in CAP 168 and MATS Part 2.
- RVR must never be assessed from a position on the runway.
- The number of visible runway edge lights is used with a conversion table to obtain the RVR value.
- MATS Part 2 includes detailed calculation procedures for specific aerodromes.
When should the assessment of RVR by human observer commence and what should be done if an RVR measurement cannot be made?
- The assessment and reporting of RVR by human observer should commence when the official meteorological visibility is reported as less than 1,500 meters.
- This assessment continues until the official meteorological visibility is 1,500 meters or more and the RVR is in excess of the maximum reportable value.
- If an RVR measurement cannot be made, the pilot should be given the meteorological visibility and informed that RVR is not available.
What is the frequency of RVR assessment by human observers, and when should reports be made at aerodromes with continuous versus intermittent traffic?
- At aerodromes with continuous traffic, RVR assessments are made at half-hourly intervals or whenever there are significant changes (one increment or more).
- At aerodromes with intermittent or light traffic, RVR is assessed before an aircraft departs and 15 minutes before the ETA of an arriving aircraft. Significant changes are reported until the aircraft lands.
- RVR reports should not be used or passed after the observer has been stood down, unless included in a full meteorological report with a time of origin.
When and how should RVR values and significant changes be transmitted to aircraft?
- RVR values and significant changes should be passed to inbound aircraft before the commencement of approach until landing.
- For departing aircraft, RVR values should be passed until the commencement of take-off.
- These broadcasts should be given high priority to ensure pilots receive current RVR information with minimal delay.
What are the limitations on passing RVR values to aircraft?
- Only RVR incremental values up to the maximum reportable value should be passed to aircraft. The maximum reportable value for a particular runway is indicated in MATS Part 2.
- If the assessed value exceeds the maximum reportable value, controllers should state, “RVR is greater than (number) meters.”
- If no lights are visible, controllers should state, “RVR less than (number) meters,” using the value corresponding to one light.
How should controllers handle discrepancies between reported RVR values and visibility conditions observed by pilots or from the aerodrome control tower?
- Controllers must not pass information to pilots that suggests visibility is better than the reported RVR, whether assessed by IRVR or human observer.
- If a pilot’s report or observation from the aerodrome control tower indicates worse visibility conditions, this information should be passed with subsequent RVR reports for as long as the condition is considered to exist, using the phraseology in CAP 413.
What are the guidelines for RVR observations regarding runway edge light intensity settings?
- All RVR observations must be made with runway edge lights set at an intensity appropriate to prevailing conditions.
- Some IRVR equipment only displays readings when runway lights are set at an intensity of 10% or more. Settings below 10% may result in readings being replaced by zeros. Pilots requesting a light setting below 10% should be informed that an RVR reading may not be available.
- Human observer RVR assessments should not be made with lights set at an intensity for which there is no conversion table. If a pilot requests a light setting without a corresponding conversion table, they should be advised that RVR is not available at that setting.
