AIM 8/15/19  gained since 1997 has shown that such encounters in RVSM airspace are generally moderate or less in magnitude. 1. Weather Encounters Inducing Altitude Deviations of Approximately 200 feet. When the pilot experiences weather induced altitude deviations of approximately 200 feet, the pilot will contact ATC and state “Unable RVSM Due (state reason)” (e.g., turbulence, mountain wave). See contingency actions in paragraph 4 − 6 − 9. b. Prior to DRVSM implementation, the FAA established provisions for pilots to report wake turbulence events in RVSM airspace using the NASA Aviation Safety Reporting System (ASRS). A “Safety Reporting” section established on the FAA RVSM Documentation web page provides contacts, forms, and reporting procedures. c. To date, wake turbulence has not been reported as a significant factor in DRVSM operations. European authorities also found that reports of wake turbulence encounters did not increase significantly after RVSM implementation (eight versus seven reports in a ten − month period). In addition, they found that reported wake turbulence was generally similar to moderate clear air turbulence. 2. Severe Turbulence (including that associ- ated with MWA). When pilots encounter severe turbulence, they should contact ATC and report the situation. Until the pilot reports clear of severe turbulence, the controller will apply merging target vectors to one or both passing aircraft to prevent their targets from merging: “Yankee 123, FL 310, unable RVSM due severe turbulence.” d. Pilot Action to Mitigate Wake Turbulence Encounters “Yankee 123, fly heading 290; traffic twelve o’clock, 10 miles, opposite direction; eastbound MD − 80 at FL 320” (or the controller may issue a vector to the MD − 80 traffic to avoid Yankee 123). 3. MWA. When pilots encounter MWA, they should contact ATC and report the magnitude and location of the wave activity. When a controller makes a merging targets traffic call, the pilot may request a vector to avoid flying directly over or under the traffic. In situations where the pilot is experiencing altitude deviations of 200 feet or greater, the pilot will request a vector to avoid traffic. Until the pilot reports clear of MWA, the controller will apply merging target vectors to one or both passing aircraft to prevent their targets from merging: 1. Pilots should be alert for wake turbulence when operating: EXAMPLE − (a) In the vicinity of aircraft climbing or descending through their altitude. (b) Approximately 10 − 30 miles after passing 1,000 feet below opposite − direction traffic. (c) Approximately 10 − 30 miles behind and 1,000 feet below same − direction traffic. 2. Pilots encountering or anticipating wake turbulence in DRVSM airspace have the option of requesting a vector, FL change, or if capable, a lateral offset. 1. Offsets of approximately a wing span upwind generally can move the aircraft out of the immediate vicinity of another aircraft’s wake vortex. 2. In domestic U.S. airspace, pilots must request clearance to fly a lateral offset. Strategic lateral offsets flown in oceanic airspace do not apply. “Yankee123, FL 310, unable RVSM due mountain wave.” “Yankee 123, fly heading 290; traffic twelve o’clock, 10 miles, opposite direction; eastbound MD − 80 at FL 320” (or the controller may issue a vector to the MD − 80 traffic to avoid Yankee 123). 4. FL Change or Re − route. To leave airspace where MWA or severe turbulence is being encountered, the pilot may request a FL change and/or re − route, if necessary. TBL 4 − 6 − 1 shows standard phraseology that pilots and controllers will use to communicate in DRVSM operations. a. Pilots should be aware of the potential for wake turbulence encounters in RVSM airspace. Experience NOTE − 4 − 6 − 8. Pilot/Controller Phraseology 4 − 6 − 7. Guidance on Wake Turbulence EXAMPLE − 4 − 6 − 5 Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR