What is Transmissometer | RVR | Runway Visual Range

This page describes Transmissometer and RVR (Runway Visual Range). Transmissometer is used to measure RVR i.e. Runway Visual Range in aviation(Avionics) domain.

What is Runway Visual Range

• Visibility on the runway is extremely important for safe landing and safe take-off of aircraft or aeroplane.
• It is usually in the 50 to 2000 meter range.
• It is the distance from where pilot of aircraft can see runway surface marking which delineates runway or help to identify center line. Pilot should be on centerline of runway while sitting in the aircraft.
• This term RVR is used in aviation meteorology or avionics.

Transmissometer definition and features

Transmissometer: Visual range depends on several environmental factors viz. fog, rain, snow and storm. It is commonly measured as RVR (i.e. Runway Visual Range) or MOR (i.e. Meteorological Optical Range). MOR ranges from 10 to 10,000 meters.

The Transmissometer is known as transmittance meter as it is an instrument which is used to measure transmission coefficient of light passing through atmosphere and hence determine RVR and/or MOR.

Transmissometer for RVR measurement

Following are the typical components or modules of a transmissometer with their functions.
• Transmitter: Lamp with spectral characteristics same as lights on the runway.
• Receiver: Photo diode and suitable electronics are used in the design of receiver. The response is similar to human eye response.
• BLM: (Background luminance monitor), 2 to 40,000 candela per square meter, it covers range of night, twilight, normal day, bright day. It has measurement accuracy of about +/-10%.
• Software: The embedded software for operation of transmissometer and to provide interface with ATC (Air Traffic Control) tower.
• Communication with control tower: Either using wifi or using landline facility is equipped.

Transmissometer Vendors

Following are the vendors or manufactures of Transmissometer.
• WET Labs, USA
• Vaisala , Sweden
• MTECH Systems Pvt. Ltd.
• Bluefin Robotics

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