# Commission Implementing Regulation (EU) No 923/2012 of 26 September 2012 laying down the common rules of the air and operational provisions regarding services and procedures in air navigation and amending Implementing Regulation (EU) No 1035/2011 and Regulations (EC) No 1265/2007, (EC) No 1794/2006, (EC) No 730/2006, (EC) No 1033/2006 and (EU) No 255/2010 (Text with EEA relevance), Division (a): Special observations shall be made and reported by all aircraft whenever the following conditions are encountered or observed:

Extent: E+W+S+N.I.

(1)moderate or severe turbulence; or
(2)moderate or severe icing; or
(3)severe mountain wave; or
(4)thunderstorms, without hail, that are obscured, embedded, widespread or in squall lines; or
(5)thunderstorms, with hail, that are obscured, embedded, widespread or in squall lines; or
(6)heavy dust storm or heavy sandstorm; or
(7)volcanic ash cloud; or
(8)pre-eruption volcanic activity or a volcanic eruption ; or
(9)the runway braking action encountered is not as good as reported

---
Source: https://www.legislation.gov.uk/eur/2012/923/annex/section/12/division/SERA.12005/division/a (the official version)
Page: https://openlegislation.uk/eu-regulation-2012-923/annex/section-12/division-SERA.12005/division-a
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.