3.4 Flights at RVSM Levels Prior to Entering RVSM Airspace 3.4.1 Before entering RVSM Airspace, the pilot should review the status of required equipment. The following altimetry equipment should be operating normally a) two primary altitude measurement systems bone Assigned Altitude Deviation (AAD); and cone altitude-alerting device. 3.4.2 In the event that any of the required equipment fails prior to an aircraft entering RVSM Airspace, the pilot should request a clearance so as to avoid flight in this airspace.