Instructions for the completion of the snowtam format
a) When reporting on two or three runways, repeat Items C to P inclusive.
b) Items together with their indicator must be dropped completely, where no information is to be included.
c) Metric units must be used and the unit of measure- ment not reported.
d) The maximum validity of SNOWTAM is 24 hours. New SNOWTAM must be issued whenever there is a significant change in conditions. The following changes relating to runway conditions are considered
- 1) a change in the coefficient of friction of about 0.05;
- 2) changes in depth of deposit greater than the following: 20 mm for dry snow, 10 mm for wet snow, 3 mm for slush;
- 3) a change in the available length or width of a runway of 10 per cent or more;
- 4) any change in the type of deposit or extent of coverage which requires reclassification in Items F or T of the SNOWTAM;
- 5) when critical snow banks exist on one or both sides of the runway, any change in the height or distance from centre line;
- 6) any change in the conspicuity of runway lighting caused by obscuring of the lights;
- 7) any other conditions known to be significant according to experience or local circumstances.
e) The abbreviated heading “TTAAiiii CCCC MMYYGGgg (BBB)” is included to facilitate the automatic processing of SNOWTAM messages in computer data banks. The explanation of these symbols is:
TT = data designator for SNOWTAM = SW;
AA = geographical designator for States, e.g. LF = FRANCE, EG = United Kingdom (see Location Indicators (Doc 7910), Part 2, Index to Nationality Letters for Location Indicators);
iiii = SNOWTAM serial number in a four-figure group;
CCCC = four-letter location indicator of the aerodrome to which the SNOWTAM refers (see Location Indicators (Doc 7910));
MMYYGGgg = date/time of observation/measure- ment, whereby:
- MM = month, e.g. January = 01, December = 12
- YY = day of the month
- GGgg = time in hours (GG) and minutes (gg) UTC;
- (BBB) = optional group for:
Correction to SNOWTAM message previously disseminated with the same serial number = COR.
- Note. Brackets in (BBB) are used to indicate that this group is optional.
Example: Abbreviated heading of SNOWTAM No. 149 from Zurich, measurement/observation of 7 November at 0620 UTC:
- SWLS0149 LSZH 11070620
2. Item A — Aerodrome location indicator (four-letter location indicator).
3. Item B — Eight-figure date/time group — giving time of observation as month, day, hour and minute in UTC; this item must always be completed.
4. Item C — Lower runway designator number.
5. Item D — Cleared runway length in metres, if less than published length (see Item T on reporting on part of runway not cleared).
6. Item E — Cleared runway width in metres, if less than published width; if offset left or right of centre line, add “L” or “R”, as viewed from the threshold having the lower runway designation number.
7. Item F — Deposit over total runway length as explained in SNOWTAM Format. Suitable combinations of these numbers may be used to indicate varying conditions over runway segments. If more than one deposit is present on the same portion of the runway, they should be reported in sequence from the top to the bottom. Drifts, depths of deposit appreciably greater than the average values or other significant characteristics of the deposits may be reported under Item T in plain language.
- Note. Definitions for the various types of snow are given at the end of this Appendix.
8. Item G — Mean depth in millimetres deposit for each third of total runway length, or “XX” if not measurable or operationally not significant; the assessment to be made to an accuracy of 20 mm for dry snow, 10 mm for wet snow and 3 mm for slush.
9. Item H — Friction measurements on each third of the run- way and friction measuring device. Measured or calculated coefficient (two digits) or, if not available, estimated surface friction (single digit) in the order from the threshold having the lower runway designation number. Insert a code 9 when surface conditions or available friction measuring device do not permit a reliable surface friction measurement to be made. Use the following abbreviations to indicate the type of friction measuring device used:
GRT Grip tester
RFT Runway friction tester
SFH Surface friction tester (high-pressure tire)
SFL Surface friction tester (low-pressure tire)
SKH Skiddometer (high-pressure tire)
SKL Skiddometer (low-pressure tire)
TAP Tapley meter
If other equipment is used, specify in plain language.
10. Item J — Critical snowbanks. If present insert height in centimetres and distance from edge of runway in metres, followed by left (“L”) or right (“R”) side or both sides (“LR”), as viewed from the threshold having the lower runway designation number.
11. Item K — If runway lights are obscured, insert “YES” followed by “L”, “R” or both “LR”, as viewed from the threshold having the lower runway designation number.
12. Item L — When further clearance will be undertaken, enter length and width of runway or “TOTAL” if runway will be cleared to full dimensions.
13. Item M — Enter the anticipated time of completion in UTC.
14. Item N — The code for Item F may be used to describe taxiway conditions; enter “NO” if no taxiways serving the associated runway are available.
15. Item P — If applicable, enter “YES” followed by the lateral distance in metres.
16. Item R — The code for Item F may be used to describe apron conditions; enter “NO” if the apron is unusable.
17. Item S — Enter the anticipated time of next observation/measurement in UTC.
18. Item T — Describe in plain language any operationally significant information but always report on length of uncleared runway (Item D) and extent of runway contamination (Item F) for each third of the runway (if appropriate) in accordance with the following scale:
Runway contamination — 10% — if less than 10% of runway contaminated
Runway contamination — 25% — if 11–25% of runway contaminated
Runway contamination — 50% — if 26–50% of runway contaminated
Runway contamination — 100% — if 51–100% of runway contaminated.
EXAMPLE OF COMPLETED SNOWTAM FORMAT
GG EHAMZQZX EDDFZQZX EKCHZQZX 070645 LSZHYNYX
SWLS0149 LSZH 11070620
A) LSZH B) 11070620
C) 02 D) …P)
C) 09 D) …P)
C) 12 D) …P)
R) NO S)11070920 T) DEICING
Definitions of the various types of snow
Slush. Water-saturated snow which with a heel-and-toe slap- down motion against the ground will be displaced with a splatter; specific gravity: 0.5 up to 0.8.
- Note. Combinations of ice, snow and/or standing water may, especially when rain, rain and snow, or snow is falling, produce substances with specific gravities in excess of 0.8. These substances, due to their high water/ice content, will have a transparent rather than a cloudy appearance and, at the higher specific gravities, will be readily distinguishable from slush.
Snow (on the ground).
a) Dry snow. Snow which can be blown if loose or, if compacted by hand, will fall apart again upon release; specific gravity: up to but not including 0.35.
b) Wet snow. Snow which, if compacted by hand, will stick together and tend to or form a snowball; specific gravity: 0.35 up to but not including 0.5.
c) Compacted snow. Snow which has been compressed into a solid mass that resists further compression and will hold together or break up into lumps if picked up; specific gravity: 0.5 and over.
Source: ICAO Annex 15
Adverse Runway Condition