Runway Visual Range (RVR)

What Is Runway Visual Range#

Runway Visual Range (RVR) is the distance a pilot can see down the runway surface during approach and landing. It is measured in feet (North America) or meters (most other regions). Unlike a weather observer's general estimate, RVR is an instrument-based measurement taken by certified equipment right at the runway.

RVR matters most during instrument approaches and low visibility procedures. When fog, rain, or snow reduces flight operations visibility, pilots depend on runway lighting and the instrument landing system to navigate to the runway. RVR tells them exactly how much of that environment they can expect to see.

This measurement applies specifically to the runway environment. It differs from prevailing visibility, which describes conditions across the entire airport. That distinction is central to safe decision-making, and we will explore it in detail below.

How RVR Is Measured and Reported#

RVR measurement relies on specialized sensors called transmissometers. These devices emit a beam of light across a known distance near the runway. A receiver on the other side measures how much light arrives. The more light lost (attenuated), the lower the visibility.

Airports install transmissometers at up to three positions along the runway:

• Touchdown zone (TDZ): Most critical for landing decisions.
• Midfield (MID): Indicates conditions along the runway's center section.
• Rollout (RO): Covers the far end, relevant for deceleration and turnoff.

RVR values appear in METAR reports and ATIS broadcasts. A typical METAR entry looks like this: R24L/2000VP6000FT. This means Runway 24 Left has an RVR varying between 2,000 and 6,000 feet. The "VP" notation signals variability. For a deeper look at decoding these reports, the guide How to Read a METAR walks through each field step by step.

During low-visibility conditions, RVR updates frequently. Values are reported in discrete increments, not continuous readings. In North America, expect feet. Internationally, expect meters. Knowing which unit your destination uses prevents dangerous conversion errors during dispatch.

Understanding RVR vs. Prevailing Visibility#

This is where pilots most often get tripped up. Prevailing visibility is a human observer's estimate of horizontal visibility across the airport. RVR is a precise instrument reading at a specific runway. They measure different things in different ways.

Fog, for example, may hug the ground near the runway surface while conditions at the observation tower look much better. A pilot could check the METAR, see 5 statute miles prevailing visibility, and assume the approach will be straightforward. Then, on short final, the touchdown zone RVR reads 1,200 feet because a shallow fog bank has settled over the runway.

These two numbers are not interchangeable. Low-visibility approach minimums (the legal floor for attempting a landing) are based on RVR, not prevailing visibility. Confusing them leads to landing attempts in conditions below published minimums. The guide Aviation Weather Explained covers how various weather phenomena create these localized visibility differences.

For preflight planning and go/no-go decisions, always check both values. Prevailing visibility tells you the big picture. RVR tells you what you will actually see when it matters most.

RVR Minimums and Landing Regulations#

RVR minimums define the lowest visibility at which a pilot may legally attempt a landing. These are set by regulation and depend on several factors:

• Approach type: An instrument landing system (ILS) CAT I approach typically requires RVR 1,800 or 2,400 feet. CAT II drops to 1,200 feet. CAT III can go as low as 300 feet or zero.
• Aircraft category: Faster aircraft (Categories C and D) often need specific runway configurations and lower RVR capability.
• Crew qualification: CAT II and CAT III approaches require specialized training and currency.
• Aircraft certification: Autoland capability allows operations at the lowest RVR values, but only when the system is certified and operational.

Under 14 CFR Part 91, a pilot may begin an approach regardless of weather. However, continuing below the decision altitude or minimum descent altitude requires the runway environment in sight and RVR at or above the published minimum. Parts 121 and 135 add dispatch restrictions. An air carrier cannot even dispatch to a destination unless forecast conditions meet specific visibility requirements for landing.

Every instrument approach plate publishes the RVR minimum for that procedure. Check it during preflight planning, not on short final. If you are reviewing terminal forecasts, the guide How to Read a TAF explains how to interpret forecast visibility groups for dispatch purposes.

RVR Variability and Weather Trends#

RVR is not static. During low-visibility events, it can swing hundreds of feet in minutes. A fog bank drifts, rain intensifies, or a clearing trend stalls. The "VP" (variable) notation in the METAR signals this instability.

Different weather types produce different RVR behavior:

• Advection fog (warm air moving over a cold surface) tends to produce stable, uniformly low RVR.
• Radiation fog (ground cooling on calm, clear nights) often shows rapid improvement after sunrise.
• Precipitation-induced low visibility (heavy rain, snow) can cause RVR to fluctuate wildly.

ATC provides trending information during approaches. Phrases like "RVR Runway 28L, touchdown 1,400, trending up" help pilots decide whether to continue or divert. Understanding seasonal and geographic patterns (coastal fog, valley inversions, lake-effect snow) reduces surprise and supports better dispatch decisions.

Always treat a variable RVR as a warning. The lower value in the range is the one that might greet you at decision height.

Using RVR in Pre-Flight Planning and Dispatch#

Good preflight planning treats RVR as a hard constraint, not a suggestion. Here is a practical workflow:

1. Check current RVR at the destination and alternate airports during your weather briefing. Do not assume conditions will improve by arrival time.
2. Cross-reference the approach plate. Find the RVR minimum for the approach you plan to fly. Compare it against reported and forecast conditions.
3. Verify your qualifications. Can you legally fly the approach that matches the expected RVR? Is your aircraft certified for it?
4. Pick a strong alternate. Choose an alternate with forecast weather well above minimums. Do not pair a borderline destination with a marginal alternate.
5. Assess the trend. Is RVR improving, steady, or deteriorating? Factor fuel reserves accordingly.

Review reporting units carefully. A destination reporting RVR in meters and an approach plate listing feet creates a conversion trap under pressure. Handle it on the ground, not in the cockpit.

Common RVR Scenarios in Low-Visibility Operations#

Morning radiation fog. RVR reads 1,200 feet at 0600 local. The forecast calls for improvement to 2,000 feet by 0800. Crews time their approaches to arrive in the improvement window. A solid alternate is filed in case the fog lingers.

Convective activity with variable RVR. A rain shower drops RVR from 2,000 feet to 1,000VP2,000FT. Crews monitor trends and coordinate with ATC. If conditions are marginal at decision height, a go-around is the safe call.

CAT II/III landing with autoland. RVR sits at 600 feet. The crew holds CAT II currency, and the aircraft's autoland system is certified and serviceable. Dispatch proceeds with the appropriate low visibility procedure in effect at the airport.

Alternate selection under pressure. Destination RVR is 1,600 feet, forecast to improve. The alternate sits at 5,000 feet and stable. That stable alternate provides the safety margin. Never let an optimistic trend at the destination substitute for a reliable backup.

Common Myths About Runway Visual Range#

Myth: RVR and prevailing visibility are the same thing. RVR is an instrument measurement at the runway. Prevailing visibility is a human observation across the airport. They often differ by thousands of feet.

Myth: If prevailing visibility is 5 miles, I can always land regardless of RVR. Landing minimums are based on RVR, not prevailing visibility. You must meet the RVR minimum on the approach plate.

Myth: RVR only matters for CAT II and CAT III approaches. RVR affects all instrument approaches during marginal conditions. Even a standard ILS CAT I approach has published RVR minimums.

Myth: RVR stays stable throughout my approach. RVR can change rapidly during fog or precipitation. Monitor trends and be prepared to go around if conditions drop below minimums.

Frequently Asked Questions#

Key Takeaways#

• RVR is an instrument-based measurement of visibility at the runway, not a human estimate.
• Transmissometers measure RVR at touchdown, midfield, and rollout zones.
• RVR is reported in METAR and updated frequently during low-visibility events.
• RVR and prevailing visibility are different measurements that can differ significantly.
• Landing minimums are based on RVR, not prevailing visibility.
• RVR minimums depend on approach type, aircraft category, and crew qualifications.
• Variable RVR ("VP" notation) signals unstable conditions requiring extra caution.
• Always cross-reference RVR with approach plate minimums during preflight planning.
• Choose alternates with weather well above minimums when destination RVR is marginal.
• Monitor RVR trends from ATC to support go-around and diversion decisions.

Sources & References#

• FAA Aeronautical Information Manual (AIM), Chapter 7: Defines RVR measurement standards, reporting formats, and procedures for low-visibility operations. FAA AIM
• 14 CFR Parts 91, 121, and 135: Federal regulations governing operating minimums, dispatch requirements, and RVR-based landing criteria. eCFR Title 14
• ICAO Annex 3, Meteorological Service for International Air Navigation: International standards for RVR measurement, reporting intervals, and sensor placement. ICAO Publications
• ICAO Annex 14, Aerodromes: Specifications for transmissometer placement and runway visual range reporting at international airports.
• FAA Advisory Circular AC 120-118: Guidance on criteria for approval of CAT II and CAT III landing operations, including RVR thresholds and crew qualification standards.