Study Guide:Low Visibility Procedures

Definition

Low visibility procedures exist to support Low Visibility Operations at Aerodromes when either surface visibility is sufficiently low to prejudice safe ground movement without additional procedural controls or the prevailing cloud base is sufficiently low to preclude pilots obtaining the required visual reference to continue to landing at the equivalent of an ILS Cat 1 DH/DA. [[1]]

Terminology: RVR/CAT

RVR = Runway Visual Range (Landebahnsicht)

RVR is being measured at three points along the runway: "Touchdown Zone", "Mid Point" and "Stop End".

ILS-Category	Minimum RVR	Decision Height (DH)
Cat I	550 meters or visibility 800 meters	200ft
Cat II	300 meters	100ft
Cat IIIa	200 meters	100 - 0ft
Cat IIIb	75 - 50 meters	50 - 0ft
Cat IIIc	keine RVR Begrenzung	nil

Terminology: Vertical Visibility

Vertical visibility is given in ft AGL. For LVP only BKN, OVC or VV are relevant. The latter being general vertical visibility with sufficient reduction of visibility not based on a specific cloud type. The values given in the metar are rounded down to the lowest 100ft value. OVC002 therefore means OVC between >200 and ≤300.

As of November 2020, in real life only RVR is considered in the decision making process whether LVP is being activated or not. This does not apply to VATSIM operations due to various factors, including but not limited to the depiction of visibility in various simulator-weather-addons. [[2]]

Decision Making Process (LOWW)

In order to determine whether ot not LVP has to be used, two factors have to be considered: Ceiling (lowest OVC or BKN cloud layer or vertical visibility) and RVR.

For exact criteria refer to LVP Criteria For Airports

Procedures

ATIS

Pilots need to be informed about the activity of LVP. To do this, add „&lvp“ at the end of the Uniatis-String. This will result in the following text to be recieved by the pilots:

LOW VISIBILITY PROCEDURES IN OPERATION

Landing Clearance

During LVP Landing Clearances should be given:

• Arriving A/C 2 NM Final
• In exceptional circumstances at 1 NM Final

Note: They "should" be given - this is not a requirement per se, but rather considered as guidance for the ATCO.

Sequencing On Final

Lower visibilities require enlarged separation minima on final depending on the actual conditions:

• CAT II radar separation on final: 4nm
• CAT III radar separation on final: 6nm

Considerations For Takeoff

• During LVP Stage 2 or 3, departing TFC should be cleared for takeoff before the next inbound for the same runway is closer that 6nm from threshold.

Phraseology

As soon as the METAR indicates an RVR value e.g: R16/P1500N you are required to transmit this value

In real life the controller will be provided with 3 RVR values: Touchdown Zone, Mid-Point, Stop-end.

Takeoff Clearance

AUA94, RVR 550, 650, and 800 meters, wind 250 degrees 6 knots, RWY 29 cleared for takeoff.

RVR Above maximum measurable value (1500m)

R16/P1500N

RVR 1500 meters or more, RWY 16 Cleared for takeoff

The words "or more" are induced by the preceeding "P" which indicates an RVR value ABOVE 1500m. (It is not possible to measure an RVR greater than 1500m)

VATSIM vs. Real Life

As the VATSIM METAR only provides one RVR Value (Touchdown Zone RVR) you may choose to add the remaining two values at your discretion.

"AUA26, 250 deg 6 kts, RVR 550, 500 and 650 Meters RWY 16 Cleared to land.

It should be noted that only dictating value is indicated in the METAR string - It defines the Touchdown Zone RVR, and thus should be used as a reference when applying the above mentioned procedure.

The same applies to Takeoff Clearances:

"AUA25, 250 deg 6 kts, RVR 550, 500 and 650 Meters, RWY 29 cleared for takeoff"

Or:

"AUA25, 250 deg 6 kts, RVR above 1500 meters, RWY 29 cleared for takeoff"

No distinction is being made upon clearing an aircraft for an ILS approach in regard to the LVP-stage.

LVP Criteria For Airports

LOWW

Available CAT III runways: 16 & 29.

NO LVP or CAT I

RVR 600m or more AND ceiling 200 feet or above.

LVP CAT II (LVP Stage 2)

RVR less than 600m OR ceiling less than 200 feet.

LVP CAT III (LVP Stage 3)

LVP CAT II conditions prevail AND RVR less than 350m.

LOWL

Available CAT III runway: 26.

NO LVP or CAT I

RVR 600m or more AND ceiling 200 feet or above.

LVP CAT II (LVP Stage 2)

RVR less than 600m OR ceiling less than 200 feet.

LVP CAT III (LVP Stage 3)

LVP CAT II conditions prevail AND RVR less than 350m.

LOWK

Available CAT II runway 28R

CAT III requires authorization from authority (MA-climb 4,7%)

NO LVP or CAT I

RVR 800m or more AND ceiling 300 feet or above.

LVP CAT II (LVP Stage 2)

N/A

LVP CAT III (LVP Stage 3)

RVR less than 800m OR ceiling less than 300 feet.

LOWI

Available CAT II or CAT III runways: none.

No explicit procedures for arriving traffic are published. Use best judgement and consider minima-values published on approach plates.

Also check further information in the LOWI_Primer.

LOWG

Available CAT III runways: 35C.

NO LVP or CAT I

RVR 600m or more AND ceiling 200 feet or above.

LVP CAT II (LVP Stage 2)

RVR less than 600m OR ceiling less than 200 feet.

LVP CAT III (LVP Stage 3)

LVP CAT II conditions prevail AND RVR less than 350m.

LOWS

Available CAT II runway: 16.

CAT III requires authorization (see special chart)

NO LVP or CAT I

Visibility and RVR 1500m or more AND ceiling 600 feet or above.

LVP CAT III (LVP Stage 2)

N/A

LVP CAT III (LVP Stage 3)

Visibility or RVR less than 1500m OR ceiling less than 600 feet.