RTC – MOD-08 – Pt.05 – Clouds

Clouds are a significant factor in flying, they can determine if the takeoff and/or landing will have to be conducted IFR or VFR, they determine cruise levels, whether you’re likely to suffer icing en route, A-G, BVR and WVR tactics, potential future weather. They can have a lot to answer for, so it’s important that you are able to understand how to read cloud reports.

This will not cover things such as types of clouds, cloud recognition, or naming, which is far beyond the scope of this module. What you do need to know however are the 5 ways to describe the amount of clouds at a particular level.

When describing the amount of clouds, you report them in octas. In other words, the sky over the reporting airfield is observed, and the percentage of cloud cover is expressed in eights (1/8) of the area. Depending on whether 3 or 7 of those octas are filled with cloud depends on the reporting word.

The “reporting words” are as follows:

• 0 octas are known as sky clear, or SKC
• 1-2 octas are known as Few, or FEW
• 3-4 octas are known as Scattered, or SCT
• 5-6 octas are known as Broken, or BKN
• 7-8 octas are known as Overcast, or OVC
• Occasionally you may also see clouds reported as NSC or No Significant Cloud which mean no cloud below 5000ft and no CB/TCU (rain clouds or thunderstorm clouds, I said I wouldn’t get too technical.

Next in the report on the cloud layer, you will see its height QFE from the observation point. This is given in 3 digits in 100’s of feet (same format as FL, but height). So:

BKN050

Will mean Broken cloud layer at 5000ft QFE

In the old (pre-2.7) system, DCS cloud layer’s quantity is measured out of 10 instead of 8, so some creative maths will need to be done to work out exactly how it’s reported. In the new 2.7 weather system, the presets are named according to the octa system. Also to report on its height QFE, you will need to subtract the aerodrome elevation, from the DCS Cloud altitude, to get its height above the aerodrome.