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AIM

10/12/17

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

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.

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:

EXAMPLE−

“Yankee 123, FL 310, unable RVSM due severe

turbulence.”

 

“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:

EXAMPLE−

“Yankee 123, 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.

4−6−7. Guidance on Wake Turbulence

a. Pilots should be aware of the potential for wake

turbulence encounters in RVSM airspace. Experience

gained since 1997 has shown that such encounters in

RVSM airspace are generally moderate or less in

magnitude.

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.

d. Pilot Action to Mitigate Wake Turbulence

Encounters

1. Pilots should be alert for wake turbulence

when operating:

(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.

NOTE−

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.

4−6−8. Pilot/Controller Phraseology

TBL 4−6−1 shows standard phraseology that pilots

and controllers will use to communicate in DRVSM

operations.