Met

Question 1

What are the 3-letter groups that describe cloud cover and what do they signify?

Answer 1

FEW - 1-2 oktas
SCT - 3-4 oktas
BKN - 5-7 oktas
OVC - 8 oktas

CAP 746 Met Obs at Aerodromes, Ch 4, Para 8

Question 2

What is CAVOK?

Answer 2

• Visibility 10km or more, no visibility.
• No Cloud below 5000ft (or highest min. sector altitude, whichever is higher)
• No significant Weather at/in the vicinity of the aerodrome
• No CB or TCU present anywhere

Question 3

What is RVR?

Answer 3

• The range over which the pilot of an aircraft on the centreline of a runway can expect to see
the runway surface markings, the lights delineating the runway or identifying its centreline
• Included in METAR when vis <1500m
• Minimum Value 50m

Question 4

How is RVR measured?

Answer 4

• Human observer method - by counting visible runway lights and comparing against a table of
values.
• Instrumented RVR (IRVR) - Photo-optical sensors (transmissometers) measure amount of
light received from RWY lights for each 1/3rd of the RWY (requires 10% RWY lighting)

Question 5

Definitions/differences between Haze, Fog and Mist

Answer 5

• Fog (FG) - Suspension of water droplets giving a visibility of <1000m
• Mist (BR) - suspension of water droplets giving a visibility of not <1000m
• Haze (HZ) - Suspension of solid particles (smoke/dust) reducing vis to not <1000m(humidity
is <95%)

Question 6

When vis is below 5km, what must be reported?

Answer 6

• Any obscuration (FG / BR / DU / SA / FU / HZ / VA / PY)

Speed Limit.?