12/2/21
AIM
c. Pilot Actions When Encountering Weather
(e.g., Severe Turbulence or MWA)
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
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6
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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
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“Yankee 123, FL 310, unable RVSM due severe
turbulence.”
“Yankee 123, fly heading 290; traffic twelve o’clock,
10 miles, opposite direction; eastbound MD
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80 at
FL 320” (or the controller may issue a vector to the
MD
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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
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“Yankee 123, FL 310, unable RVSM due mountain wave.”
“Yankee 123, fly heading 290; traffic twelve o’clock,
10 miles, opposite direction; eastbound MD
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80 at
FL 320” (or the controller may issue a vector to the
MD
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80 traffic to avoid Yankee 123).
4. FL Change or Re
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route.
To leave airspace
where MWA or severe turbulence is being
encountered, the pilot may request a FL change
and/or re
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route, if necessary.
4
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6
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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
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30 miles after passing
1,000 feet below opposite
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direction traffic.
(c)
Approximately 10
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30 miles behind and
1,000 feet below same
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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
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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.
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6
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8. Pilot/Controller Phraseology
TBL 4
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6
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1 shows standard phraseology that pilots
and controllers will use to communicate in DRVSM
operations.
Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the
4
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6
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5
Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR