Ok. To redefine my question. What has to happen, so that UNABLE RVSM DUE TURBULENCE is announced? ICAO Doc 4444 says it has to be reported when: ...affects the capability of an aircraft to maintain height-keeping requirements for RVSM. (12.3.1.12 REDUCED VERTICAL SEPARATION MINIMUM (RVSM) OPERATIONS). Height-keeping requirement is ±200ft from the FL, so if you lose 2500ft in few seconds you do not meet the requirement. Or you do?