4/20/23 

AIM 

(c) 

Inflight MWA Indicators (Including Turbulence). Indicators that the aircraft is being subjected to 

MWA are: 

(1) 

Altitude excursions and/or airspeed fluctuations with or without associated turbulence. 

(2) 

Pitch and trim changes required to maintain altitude with accompanying airspeed fluctuations. 

(3) 

Light to severe turbulence depending on the magnitude of the MWA. 

4.  Priority for Controller Application of Merging Target Procedures 

(a)  Explanation of Merging Target Procedures. 

As described in subparagraph c3 below, ATC will use 

“merging target procedures” to mitigate the effects of both severe turbulence and MWA. The procedures in 

subparagraph c3 have been adapted from existing procedures published in FAA Order JO 7110.65, Air Traffic 

Control, paragraph 5

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4, Merging Target Procedures. Paragraph 5

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4 calls for en route controllers to advise 

pilots of potential traffic that they perceive may fly directly above or below his/her aircraft at minimum vertical 

separation. In response, pilots are given the option of requesting a radar vector to ensure their radar target will 

not merge or overlap with the traffic’s radar target. 

(b) 

The provision of “merging target procedures” to mitigate the effects of severe turbulence and/or 

MWA is not optional for the controller, but rather is a priority responsibility. Pilot requests for vectors for traffic 

avoidance when encountering MWA or pilot reports of “Unable RVSM due turbulence or MWA” are considered 

first priority aircraft separation and sequencing responsibilities. (FAA Order JO 7110.65, paragraph 2

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2, Duty 

Priority, states that the controller’s first priority is to separate aircraft and issue safety alerts). 

(c) 

Explanation of the term “traffic permitting.”  The contingency actions for MWA and severe 

turbulence detailed in paragraph 4

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9, Contingency Actions: Weather Encounters and Aircraft System Failures 

that Occur After Entry into RVSM Airspace, state that the controller will “vector aircraft to avoid merging targets 

with traffic at adjacent flight levels, traffic permitting.” The term “traffic permitting” 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

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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 advisories in response to disruptions in altitude hold capability. 

b.  Pre

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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), 

Graphical Turbulence Guidance (GTG), 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 actions in paragraph 

4

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9. 

2.  Severe Turbulence (including that associated 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). 

Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the 

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Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR