While crossing a large mountain range, you encounter moderate turbulence. Is there an obligation to report this?
No, pilots are not obliged to report on weather conditions. However, if the conditions could affect the safety of other aircraft the pilot can decide to provide a report via voice communication.
If an air-ground data link is available, a special aircraft observation must be reported. If only voice communication is available no report should be made, to avoid frequency congestion.
Yes, a special aircraft observation shall be made by air-ground datalink. Where air-ground data link is not available it shall be reported via voice communication.
No. Reporting is obligatory in case of severe turbulence, or in case of severe mountain wave associated with moderate turbulence.
ICAO Doc 4444
4.12 REPORTING OF OPERATIONAL AND METEOROLOGICAL INFORMATION
4.12.3 Contents of special air-reports
126.96.36.199 Special air-reports shall be made by all aircraft whenever the following conditions are encountered or observed:
a) moderate or severe turbulence; or
b) moderate or severe icing; or
c) severe mountain wave; or
d) thunderstorms, without hail that are obscured, embedded, widespread or in squall lines; or
e) thunderstorms, with hail that are obscured, embedded, widespread or in squall lines; or
f) heavy duststorm or heavy sandstorm; or
g) volcanic ash cloud; or
h) pre-eruption volcanic activity or a volcanic eruption.
Note.— Pre-eruption volcanic activity in this context means unusual and/or increasing volcanic activity which could presage a volcanic eruption. In addition, in the case of transonic and supersonic flight:
i) moderate turbulence; or
j) hail; or
k) cumulonimbus clouds.
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