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Meteorology

Question

  • Why the sky is blue?
  • What are the weather minimums for IFR flight?
  • What is fog?
  • What are the weather minimums for VFR flight?

Answer

Sunlight contains all of the colors of our visible spectrum.  These colors combined together appear white. 

Red light has the longest wavelength and, therefore, the least amount of energy in the visible spectrum. Wavelength decreases and energy increases as you move from red to violet light across the spectrum in the following order: red, orange, yellow, green, blue, and violet.

The sky is blue because of the scaterring of the wavelength passing thru the molecules of the air. The scattering caused by these tiny air molecules known as Rayleigh scattering increases as the wavelength of light decreases.

Violet and blue light have the shortest wavelengths and red light has the longest. Therefore, blue light is scattered more than red light and the sky appears blue during the day.

Being instrument rated and flying an IFR flight does not mean to operate aircraft during 0 visibility and 0 vertical visibility/cloud base.

Unless otherwise required by the local regulations and approved by authority, minimum required visibility for take-off is 800m.

For landing, it is always mandatory to meet the minimum visibility latest by passing 1000ft Above Aerodrome Elevation (or Runway threshold). 

The system minimums for ICAO CATI are:

  • general visibility 800m
  • Runway Visual Range (RVR) touch down zone: 550m
  • Runway Visual Range (RVR) midpoint: 125m
  • Runway Visual Range (RVR) touch down zone: 75m
  • Decision height: 200ft AGL

Above mentioned minimums can be lowered provided the crew, aircraft and airport is authorized for such operation (e.g. CATII or CATII approaches). They may also be increased due to degraded performance or equipment of an aircraft or obstacles in the vicinity. 

Fog is a weather phenomena which reduces vertical and horizontal visibility. There are different kinds of fog based on its origin. The fog is the condensate water vapor caused by thermal processes in atmosphere.

One of the most common reason of forming the fog is the air is being cooled down to the temperature of dew point after sunset.

In aviation fog is reported whenever the horizontal visibility is reduced below 2000m. The density of fog is reported in so-called runway visual range, which reports the horizontal visibility thru the fog along the runway.

Abbreviation used to report fog in aviation meteorological reports and forecasts is “FG”.

There are different VFR meteo minimum requirements based on the airspace. Meteorological minimums for VFR Flight are always described as a minimum cloud base clearance over terrain and minimum forward visibility.

Minimum required VFR weather is generally 5km of forward visibility and flying out of the clouds.

When preparing the flight, we have to take into the consideration that reporting weather conditions are applicable for the vicinity of observation station only. Reported fair weather at the observation station does not necessarily mean the fair weather couple of miles off the station.

 

Question

  • Why the sky is blue?

    Answer

    Sunlight contains all of the colors of our visible spectrum.  These colors combined together appear white. 

    Red light has the longest wavelength and, therefore, the least amount of energy in the visible spectrum. Wavelength decreases and energy increases as you move from red to violet light across the spectrum in the following order: red, orange, yellow, green, blue, and violet.

    The sky is blue because of the scaterring of the wavelength passing thru the molecules of the air. The scattering caused by these tiny air molecules known as Rayleigh scattering increases as the wavelength of light decreases.

    Violet and blue light have the shortest wavelengths and red light has the longest. Therefore, blue light is scattered more than red light and the sky appears blue during the day.

  • What are the weather minimums for IFR flight?

    Answer

    Being instrument rated and flying an IFR flight does not mean to operate aircraft during 0 visibility and 0 vertical visibility/cloud base.

    Unless otherwise required by the local regulations and approved by authority, minimum required visibility for take-off is 800m.

    For landing, it is always mandatory to meet the minimum visibility latest by passing 1000ft Above Aerodrome Elevation (or Runway threshold). 

    The system minimums for ICAO CATI are:

    • general visibility 800m
    • Runway Visual Range (RVR) touch down zone: 550m
    • Runway Visual Range (RVR) midpoint: 125m
    • Runway Visual Range (RVR) touch down zone: 75m
    • Decision height: 200ft AGL

    Above mentioned minimums can be lowered provided the crew, aircraft and airport is authorized for such operation (e.g. CATII or CATII approaches). They may also be increased due to degraded performance or equipment of an aircraft or obstacles in the vicinity. 

  • What is fog?

    Answer

    Fog is a weather phenomena which reduces vertical and horizontal visibility. There are different kinds of fog based on its origin. The fog is the condensate water vapor caused by thermal processes in atmosphere.

    One of the most common reason of forming the fog is the air is being cooled down to the temperature of dew point after sunset.

    In aviation fog is reported whenever the horizontal visibility is reduced below 2000m. The density of fog is reported in so-called runway visual range, which reports the horizontal visibility thru the fog along the runway.

    Abbreviation used to report fog in aviation meteorological reports and forecasts is “FG”.

  • What are the weather minimums for VFR flight?

    Answer

    There are different VFR meteo minimum requirements based on the airspace. Meteorological minimums for VFR Flight are always described as a minimum cloud base clearance over terrain and minimum forward visibility.

    Minimum required VFR weather is generally 5km of forward visibility and flying out of the clouds.

    When preparing the flight, we have to take into the consideration that reporting weather conditions are applicable for the vicinity of observation station only. Reported fair weather at the observation station does not necessarily mean the fair weather couple of miles off the station.

     

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