AIM
4/3/14
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
(FAA Order JO 7110.65, paragraph 2−1−2, Duty
Priority, states that the controller’s first priority is to
separate aircraft and issue safety alerts).
(c)
Explanation of the term “traffic permit-
ting.” The contingency actions for MWA and severe
turbulence detailed in paragraph 4−6−9, Contingency
Actions: Weather Encounters and Aircraft System
Failures, state that the controller will “vector aircraft
to avoid merging targets with traffic at adjacent flight
levels, traffic permitting.” The term “traffic permit-
ting” is not intended to imply that merging target
procedures are not a priority duty. The term is
intended to recognize that, as stated in FAA
Order JO 7110.65, paragraph 2−1−2, Duty Priority,
there are circumstances when the controller is
required to perform more than one action and must
“exercise their best judgment based on the facts and
circumstances known to them” to prioritize their
actions. Further direction given is: “That action
which is most critical from a safety standpoint is
performed first.”
5. TCAS Sensitivity.
For both MWA and
severe turbulence encounters in RVSM airspace, an
additional concern is the sensitivity of collision
avoidance systems when one or both aircraft
operating in close proximity receive TCAS adviso-
ries in response to disruptions in altitude hold
capability.
b. Pre
−flight tools. Sources of observed and
forecast information that can help the pilot ascertain
the possibility of MWA or severe turbulence are:
Forecast Winds and Temperatures Aloft (FD), Area
Forecast (FA), SIGMETs and PIREPs.
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
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 webpage 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