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SNOWTAM

 
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K.Haroon
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Joined: 11 Dec 2005
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PostPosted: Sat Mar 30, 2013 11:45 am    Post subject: SNOWTAM Reply with quote

SNOWTAM

A SNOWTAM or SNOTAM, is part of the NOTAM system originating from AIS (Aeronautical Information Service) and not from the Met Authority.

It is a detailed statement of snow conditions at an airfield, including information on aprons, taxiways, snow banks, times of clearance, runway braking action and so on.

The essential parts of a SNOWTAM, including runway braking action, will be added to the METAR or SPECI as an eight figure group if snow or other runway contamination is present.


SNOTAM DECODES

Runway Designator - First and Second Digits

27 (Runway 27) - magnetic heading for single runways or left hand parallel runways

77 (Runway 27 right) - heading plus 50 to indicate right hand parallel runways

88 All Runways

99 Repeat of last message, no new information


Runway Contamination Type - Third Digit

0 Clear and dry

1 Damp

2 Wet or water patches

3 Rime or frost covered

4 Dry snow

5 Wet snow

6 Slush

7 Ice

8 Compacted snow

9 Frozen ruts or ridges

/ Type of contamination not reported


Extent of Contamination - Fourth Digit

1 10% contaminated

2 11% to 25% contaminated

5 26% to 50% contaminated

9 51% to 100% contaminated

/ extent of runway contamination not reported


Depth of Deposit - Fifth and Sixth Digits

00 Less than 1mm

01-90 Whole mm's depth

91 Not used

92 10cm

93 15cm

94 20cm

95 25cm

96 30cm

97 35cm

98 40cm or more

99 Runway(s) non-operational, but depth not reported

// Depth not significant or not reported


Friction Coefficient - Seventh and Eighth Digits

25 Friction coefficient measured as 0.25

26 Friction coefficient measured as 0.26

27 Friction coefficient measured as 0.27

28 Friction coefficient measured as 0.28

29 Friction coefficient measured as 0.29

etc ...

Braking coefficients can be related to verbal descriptions of Braking Action:

0.40 and higher = Good

0.39 - 0.36 = Medium to Good

0.35 - 0.30 = Medium

0.29 - 0.26 = Medium to Poor

0.25 and below = Poor
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