Q: What are the provisions for non-CAT airports including stall airport?
A: All depends on whether the aerodrome concerned is an official ICAO international aerodrome listed in the Regional Air Navigation Plan. If it is not an official international aerodrome, then it is fully up to the ICAO Contracting State (i.e. the Country) concerned to decide the level of the facilities and services. A number of States do, nevertheless, try to follow the international provisions also at their non-international aerodromes. If the aerodrome is an international aerodrome then of course ICAO Annex 3 provisions are applicable. In this specific case (i.e. an aerodrome with non-CAT runways only), you do not have any formal obligation to use automatic systems. However, in practice, it is difficult, if not impossible, to comply with the ICAO Annex 3 requirements concerning the display at the ATC units, averaging and reporting variability, at least as far as the surface wind, visibility, RVR and height of cloud base are concerned. In conclusion, it is strongly suggested that integrated automatic systems be used for the acquisition, display and dissemination of 1) surface wind; 2) visibility; 3) RVR; 4) height of cloud base; 5) air and dewpoint temperatures; and 6) atmospheric pressure at all international aerodromes.
Q: What would be the parameter background luminance?
A: When calculating RVR during nighttime, the Runway Lights seen by a pilot should exceed the visual threshold of illumination. This is defined to be (ICAO Doc 9328): “The visual threshold of illumination (E¡) of the eye that is required for a point source or small light to be visible. This is related to the measured or assumed luminance of the background against which the light is viewed.” The background luminance is measured by a sensor, for example Vaisala Background Luminance Sensor LM21 www.vaisala.com/en/products/visibilitysensors/Pages/default.aspx.
Q: For the fully automated systems that you have installed to date, what has been the response/feedback from airlines, airport operators, Air Traffic Control etc. - particularly where conditions are close to the limit of operations (Cat 1 cloud base, visibility etc.)?
A: The response has been positive after training and information sharing. It is very important to communicate the differences between weather observations done by a fully automatic system and a human observer. The information sharing should include also pilots and air traffic controllers.
Q: For the results shown for the freezing rain detection algorithm, this showed a 100% detection rate. But were there any false alarms (where automation showed Freezing, but observer said non-freezing)?
A: The rate of false alarms was less than 1% during the whole year. It should also be emphasized that the detection rate of human observations is not 100%.
Q: What is the minimum recommended number of present weather sensors for Vaisala PW algorithm?
A: Vaisala Present Weather algorithm typically uses one or two present weather sensors and the detection is then improved using other sensors at the airport, like visibility, cloud height temperature and humidity sensors.
Q: What kind of AWOS algorithms has Vaisala developed?
A: Vaisala has developed the following AWOS algorithms:
- Sky condition algorithm using multiple ceilometers
- Multi-instrument present weather algorithm
- Prevailing visibility using multiple visibility sensors
- Low Level Windshear Alert − algorithm
- Over 100 METAR weather cross-checker algorithms
- RVR (Visibility, Background luminance, Runway-In-Use connection and Light setting interface)
- Lightning detection algorithms
In addition, Vaisala is constantly improving these algorithms and creating new ones.