Contaminated Runways — Page 241, Lesson 343

I want to walk you through contaminated runways — a critical topic for professional pilots operating in winter conditions. Let's start with the performance side. Part B of the Operations Manual contains type-specific information on procedures for take-off and landing on contaminated runways. That includes performance data and any wind limitations — specifically crosswind limits, tailwind limits, and possibly headwind gust limits. So the exact numbers depend on your aircraft type, and you'll find them in the Ops Manual. Now, SNOWTAMs. These are special NOTAMs issued by aerodromes where runway contamination is a common occurrence. As an ATPL student, you need to be familiar with several specific items on a SNOWTAM. Item (F) tells you the type of contaminant. Item (G) gives the depth of contaminant over each third of the runway, reported in millimetres. Item (H) gives the braking action on each third of the runway — this is stated either as a two-figure number to indicate a measured coefficient, or a one-figure number to indicate braking action. The validity of a SNOWTAM is up to 24 hours. Let me give you the contaminant codes, because you need to know these cold: NIL means clear and dry. 1 means damp. 2 means wet or water patches. 3 means rime or frost covered, with a depth normally less than 1 millimetre. 4 means dry snow. 5 means wet snow. 6 means slush. 7 means ice. 8 means compacted or rolled snow. 9 means frozen ruts or ridges. Now let's decode a real SNOWTAM example so you can see how it all fits together. Here's the first one: SWED0072 EDDM 12110810. That's SNOWTAM number 0072. Item (A) is EDDM — that's Munich airport. Item (B) is 12110810 — that means 11 December at 0810 Zulu time. Item (C) is 08L — runway 08 Left. Item (F) is 6/6/6 — over the whole runway, the contaminant is slush, code 6. Item (G) is 01/01/01 — the mean depth of slush is 1 millimetre over the entire length. Item (H) is 35/26/26 — these are friction measurements. The first third of the runway has a coefficient of 0.35, which is medium braking action. The second third is 0.26, medium/poor. The third third is also 0.26, medium/poor. Item (N) is 2,6 — the taxiway is contaminated with wet slush. Item (R) is 2,6 — the apron is contaminated with wet slush. Item (T) says the runway 08L is planned to be closed due to slush removal. Let me give you a second example so you see a different situation. SNOWTAM for EDDF — Frankfurt. Item (A) is Frankfurt. Item (B) is 11 December at 1215 Zulu. Item (C) is runway 07L. Item (F) is 1/1/1 — the runway is damp over the entire length. Item (G) is XX/XX/XX — the mean depth of the contaminant is not measurable. Item (H) is 5/5/5 — braking action over the entire length of the runway is good. Item (N) is 2/5/6 — the taxiway is contaminated with water patches, wet snow, and slush. Item (R) is 2/5/6 — the apron is contaminated with water patches, wet snow, and slush. Item (T) says taxiways and apron are slippery. One more important note: Item (D) on a SNOWTAM is the cleared runway length in metres. If that cleared length is less than the published runway length, you need to look at Item (T) for details. Item (T) describes in plain language any uncleared length in metres. That figure shows you the braking action code table — it's a quick reference for interpreting those two-figure and one-figure numbers on a SNOWTAM.