Meteorological Aerodrome Reports (METARs) — Page 484, Lesson 456

I want to walk you through the Runway State Group — a special section that gets added to a METAR or a SPECI when there is significant contamination on the runway surface. This is critical information for you as a pilot because it tells you exactly what the runway condition is before you land or take off. The format is very specific: it starts with the letter R, then the runway designator, followed by an oblique (a forward slash), and then six digits that describe the contamination state in detail. Let's break down each part. First, the Runway Designator. This identifies which runway we're talking about. For example, R27 means Runway 27, and R27L means Runway 27 Left. There are also two special codes: R88 means "all runways," and R99 means "a repetition of the last message received because no new information received" — so if the tower hasn't got a fresh report, they repeat the previous one. Now, the six digits after the oblique. Each digit or pair of digits has a specific meaning. The 1st digit tells you the Runway Deposits — what is actually on the runway. Here is the full list: - 0 = Clear and dry - 1 = Damp - 2 = Wet or water patches - 3 = Rime or frost covered (depth normally less than 1 mm) - 4 = Dry snow - 5 = Wet snow - 6 = Slush - 7 = Ice - 8 = Compacted or rolled snow - 9 = Frozen ruts or ridges - / = Type of deposit not reported (for example, due to runway clearance in progress) The 2nd digit tells you the Extent of Runway Contamination — how much of the runway is covered. The codes are: - 1 = 10% or less - 2 = 11% to 25% - 5 = 26% to 50% - 9 = 51% to 100% - / = Not reported (again, due to runway clearance in progress) Notice the gaps in the numbering — there is no 3, 4, 6, 7, or 8. Those codes simply aren't used. The 3rd and 4th digits together give you the Depth of Deposit. This is the mean number of readings, or if operationally significant, the greatest depth measured. Let me walk through the scale: - 00 = less than 1 mm - 01 = 1 mm, and it goes up through to 90 = 90 mm - 91 = not used - Then it switches to centimetres: 92 = 10 cm, 93 = 15 cm, 94 = 20 cm, 95 = 25 cm, 96 = 30 cm, 97 = 35 cm, 98 = 40 cm or more - 99 = Runway(s) non-operational due to snow, slush, ice, large drifts or runway clearance, but depth not reported - // = Depth of deposit operationally not significant or not measurable So, to give you a concrete example, if you saw R27/4525//, that would mean Runway 27, deposit type 4 (dry snow), extent 5 (26% to 50% coverage), depth 25 (which would be 25 mm — wait, let me check the scale: 25 is not on the list, so that wouldn't be valid. Let me use a valid one: R27/4595// would be Runway 27, dry snow covering 26% to 50% of the runway, with a depth of 25 cm. And the double slash at the end means depth is not significant or not measurable — actually, in that example the depth is given, so the double slash wouldn't be there. Let me correct: R27/4595 would be Runway 27, dry snow, 26-50% coverage, 25 cm depth. The key takeaway is that this group gives you precise, coded information about runway contamination so you can make safe operational decisions.