Air to Ground
As Santa and his reindeer prepared for their journey south, they pushed ahead the cold arctic winds. Everyone in the northern two-thirds of the U.S. simultaneously wished for a blanket of white to decorate the year and refresh the farmlands, while preparing to fight the limitations it imposes. Santa and relatively few Alaskan and Canadian aircraft can land happily on a long strip of ice and snow, the rest of us prefer some kind of drier surface. Airports fill tanks with de-icing liquids and sharpen the blades of the snowplows. Airport managers make sure that the phone number to the flight service NOTAM desk is on speed dial.
Snow-NOTAMS or Snotams, as ATC calls them, are issued every time field conditions change at any airport. By far the airports that issue the most are in the Great Lakes region. Cleveland, Chicago, Detroit, Buffalo and the hundreds of smaller airports in the vicinity may call every hour of the day and night reporting snow and ice accumulation, runway and taxiway closures and braking action. Lockheed Martin Flight Service gears up whenever they see lake effect snow beginning to fall by tripling or quadrupling the number of people assigned to NOTAM dissemination. Managers can call, fax or input the Snotams into the E-Notam program. One of the most confusing Snotams is the MU values (mew, like a cat, not moo like cow). Runway braking action can be described in one of two ways. The old fashioned way is where a Piper Cherokee lands, goes “Wahoo!” while sliding down the runway then just telling the manager if he stopped (braking action good), slipped in patches (braking action fair), took all of a two-mile runway (braking action poor), or ended up backwards on top of a taxiway sign (braking action Nil). These are abbreviated BRAG – as in bragging how good his landing was, BRAF, BRAP, and BRAN-as in “glad I ate my Wheaties this morning”.
Sometimes these relatively easy to remember terms are wrapped up in the technological rhetoric associated with a friction-measuring device used at larger airports. The numbers used are actually percentages of 100 or full stop ability. During the initial tests in Sweden, it was determined that 40 per cent friction was enough for an aircraft to come to a full stop in a crosswind. The NOTAMs will drop the decimal point, and report the values as whole numbers. The lower the number, the less friction there is for the tires to grab.
In general you can equate MU values in this manner:
40 percent or greater Good - BRAG
30 to 40 percent Fair - BRAF
20 to 30 percent Poor – BRAP
20 percent or less Nil – BRAN
The NOTAM will show three MU values in a row. These correlate to the beginning, middle and ending thirds of the runway. It will also indicate what type of friction measuring device was used to get the values. In the following NOTAM, RFT means Runway Friction Tester, a specific type of equipment.
!DCA DCA 18 RFT MU 40/30/38 WEF 0912291030.
All runway NOTAMS must contain a WEF (with effect) time. This tells the pilot how long ago the condition was reported by the airport manager. Airports serving air carriers are required to update their runway conditions frequently, and will issue separate NOTAMs for each runway, taxiway and ramp area, sometimes hourly. Smaller facilities may simply issue a NOTAM for the whole airport that is updated at irregular intervals. If a NOTAM is left in the system for a couple days, or you are pretty sure that the condition has changed, let a flight service specialist know this so that he or she can call the manager to verify it.
The Snotams are categorized by surface with the first indicator listed after the location: RWY (runway), TWY (taxiway), AD (whole airport), or RAMP. Here are contractions you can expect to see in Snotams:
SN Snow
IR Ice on Runway
SIR Snow and Ice on Runway
SLR Slush on Runway
PTCHY Patchy
THN Thin
ICE Ice
SCT Scattered
WSR Wet Snow on Runway
BERM Snowbanks
LSR Loose Snow on Runway
ALTNLY Alternately
Snow and ice are measured in inches and quarters of inches. Anything below a quarter of an inch is thin. Here are a few examples.
!IAD 12/029 IAD RWY ALL RWYS ALTNLY CLSD SNOW REMOVAL WEF 0912051800 !EKN 12/030 2G4 RWY 9/27 1/2 IN SIR BRAN WEF 0912051820
!DCA 12/083 GAI AD PTCHY ICE WEF 0912060220
!COS 12/078 COS RAMP PTCHY THN LOOSE SN OVR PTCHY THN ICE WEF 0912051710
Just last year I watched my husband catch a strong crosswind on a snowy, icy surface. As he spun madly the snow fountained and my heart almost stopped before he did. He handled it beautifully, but I do not recommend the experience to anyone. Check out those Snotams!