Bristol Industrial & Research Associates Ltd (BIRAL)

Aviation Meteorology - Aerospace & Air Transport - Airports

SWS and VPF sensors are used in airports throughout the world as part of aviation ground control and meteorological monitoring systems. Our visibility and ambient light sensors form the core of Runway Visual Range monitoring systems used to control the safe landing of aircraft in reduced visibility conditions. Our present weather sensors provide automated precipitation classification and monitoring that forms a vital part of the METAR signals broadcast to aircraft in the airport vicinity. The detection and reporting of thunderstorms is important in the aviation industry supporting both the safety of ground operations and the provision of meteorological data to aircraft and forecasting authorities. Our BTD-300 Thunderstorm Detector has been developed to be compliant with FAA regulations for lightning detection systems used at airfields.


Runway Visual Range RVR

The term Runway Visual Range or RVR refers to the estimation of the distance a pilot can see whilst approaching or departing from a runway. Historically RVR values were provided by trained observers stationed at defined locations on the airfield; these observers have now largely been replaced by automated systems due to cost and reliability considerations. To calculate RVR an automated system must measure the local visibility, the ambient or background brightness and the intensity of the runway lights. The calculation of RVR is described by ICAO publication 9328, Manual of Runway Visual Range Observing and Reporting Practices. ICAO 9328 details the requirements of the components of a RVR system and the data processing requirements. All Biral visibility and present weather sensors are compliant with the requirements of ICAO 9328, as is the ALS-2 Ambient Light Sensor which is used to measure the background luminance.

The accreditation of a RVR system is generally undertaken by an agency of the national government of the country where the system is installed. Such agencies often rely on a combination of international standards and local regulations when accreditation a system. Biral products are compliant with a wide range of internationally applied standards and regulations including EC Regulation 552/2004, ICAO Annex 3, CAP 746, ICAO Annex 5 and WMO 8 Part I Chapters 9 and 14. Declarations of conformity with a range of standards are available on request for Biral sensors.

Biral sensors are used in many RVR systems around the world from small independently operated grass airstrips to major international airports with UK CAA Category III (CAT III) approval.


METAR is a standard form for the reporting of weather commonly used in aviation with a format controlled by ICAO. The reports are typically produced at hourly or 30 minute intervals and originate from observing sites at airfields, military bases and other observing stations. The information is typically produced by automated weather observing systems (AWOS) with checking by meteorologists prior to transmission to aircraft and forecasting groups.

A wide range of weather types can be encoded in a METAR including visibility, precipitation and thunderstorm activity. Biral visibility and present weather sensors fulfil the ICAO requirements for the automated observation of a number of METAR parameters as specified in ICAO Annex 3, ICAO Annex 5, and WMO 8 Part I Chapters 9 and 14.