Section 3 Chapter 3 RVR Flashcards
The RVR indicates
the range over which the pilot of an aircraft on the
centreline of a runway can expect to see the runway surface markings,
the lights delineating the runway or identifying its centreline.
The two methods of RVR assessment available at suitably equipped
aerodromes are:
- Instrumented RVR, using electronic equipment;
2. Human Observer Method.
The UK standard for reporting RVR extends from zero to 1500 metres in
the following steps:
0 to 400 metres in 25 metre steps
400 to 800 metres in 50 metre steps
800 to 1500 metres in 100 metre steps.
3.4 Not all RVR systems are able to report all increments from zero to 1500
metres. Where the maximum reportable RVR value for a system and
runway combination is less than 1500 metres this information shall be
included in the UK AIP.
3.5 Note that any observed value, which does not fit the reporting scale,
shall be rounded down to the nearest step lower in the scale. It is
recommended that 50 metres be regarded as the lower limit and 1500
metres be regarded as the upper limit for assessments of RVR. Outside
of these limits, reports should indicate that RVR is less than 50 metres
or more than 1500 metres.
Instrumented RVR (IRVR)
This method gives an automatic and continuous display of RVR values
to ATC.
Transmissometers are used to
measure atmospheric opacity from fixed
points alongside a runway, the number of units in any system being
determined by the category of the ILS or MLS installation and runway
length. In a three transmissometer system the units are linked by an
associated data transfer system to a central processor. The processor
computes the RVR for each transmissometer position and displays it
in digital form to ATC. The three transmissometers are located one at
each end of the runway adjacent to the touchdown zone and the third
near the runway mid- point area. For RTF transmission purposes the
locations will be known as “Touchdown”, “Mid-Point” and “Stop End”
and RVR values will relate to these positions.
IRVR reporting to aircraft is started:
- whenever the aerodrome meteorological report shows the visibility
to be less than 1500 metres; - whenever the IRVR display is indicating an RVR value equal to or
less than the maximum for that system; - whenever shallow fog is reported and during a period for which it is
forecast.
IRVR values are to be passed to aircraft
at the beginning of each
approach for landing and, thereafter, whenever there is a significant
change in the RVR until the aircraft have landed. A significant change is
defined as a change in value of one increment or more. The current RVR
value is also to be passed to aircraft before take-off.
3.15 Even though a pilot may have received an IRVR value from the ATIS
broadcast, controllers must ensure that they pass the current value as
specified above.
3.16 When all three positions are to be reported to the pilot, they are to be
passed as three numbers relating to touchdown, mid-point and stop end
respectively, e.g.
“RVR runway (designator) 650 — 500 — 550 metres”.
3.17 If only two values are to be passed, they are to be individually identified,
e.g.
“RVR runway (designator) Touchdown 650 — Stop End 550 metres”.
3.18 A high degree of priority should be given to such broadcasts to ensure
that current RVR information is provided to pilots with the minimum
delay.
Transmissometer Unserviceability
If the touchdown transmissometer fails, the IRVR system may still be
serviceable provided that confirmation is received from the DEO to
this effect. In such circumstances the mid-point value is to be used to
determine the ATC procedure and is to be passed to the pilot together
with the stop end value, if this is available. It is imperative that the pilot
should be informed that the touchdown transmissometer has failed,
e.g.
“RVR runway (designator) Touchdown not available — Mid-Point 600
— Stop End 400 metres”.
3.20 If two transmissometers become unserviceable the RVR value for the
remaining instrument provided that it is not the stop end value, may
be used. If the RVR value for the stop end is the only one available, the
system is to be regarded as unserviceable for that runway. By changing
the direction of use of the runway it may become serviceable again with
the single available value representing the touchdown reading.
3.21 When the IRVR system is unserviceable, controllers should revert
to Human Observer RVR where provided, or to the reported
meteorological visibility to determine ATC procedures. In the latter
case, pilots should be passed the reported meteorological visibility and
advised that the IRVR system has failed.
Occasionally pilots of aircraft may report, or observations from the aerodrome control tower may indicate, that the visibility conditions on the runway are significantly different to those being reported
Under no circumstances is a controller to pass a pilot information which suggests that the visibility is better than the RVR reported, whether assessed by IRVR or a human observer. However, when a pilot’s report or an observation from the aerodrome control tower indicates a worse condition on the runway, this information is to be passed with subsequent RVR reports for as long as the condition is considered to exist according to the phraseology in CAP 413.
All RVR observations, including those for transmission in meteorological reports, are to be made with the runway edge lights
set at the intensity appropriate to the prevailing conditions.
3.36
However with some IRVR equipment, because of the design of the system, transmissometer readings may only be displayed when the runway lights are set at an intensity of 10% or more. Settings less than 10% may result in all three readings being replaced by zeros. If, during RVR conditions, a pilot requests a reduced runway edge light setting of less than 10%, he is to be advised that an RVR reading may not be available at this setting.
Aerodrome Operating Minima
A controller is not responsible for ensuring that pilots observe their
Aerodrome Operating Minima and is not to query the right of a pilot to
attempt a landing or take-off.
