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Aviation Wind Shear

byBob Jackson, MICSeattle CWSU

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Introduction• Pilots do not always understand

how the NWS uses particular terms, and when a term can/cannot be used in the preparation of forecasts.

• This presentation will show common mis-understandings of ‘WS’ terminology and applications.

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Main Goals:

• Help forecasters realize short-comings in terminology of Wind-shear

• Improve awareness and understanding of proper application of Wind Shear in TAFs

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This Presentation Discusses:

• How the pilots perceive WS• How many meteorologists perceive

WS

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How Pilots perceive WS• “Forecasters tend to believe that pilots

know more about weather than they actually do.” (R. Jackson)

• Two Studies by R. Jackson demonstrate pilot’s lack of knowledge of Wind Shear:– “Low-Level Wind Shear Terminology”– “A Comparative Study of Pilot’s

Understanding of Low-Level Wind Shear Terminology”

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“Low-Level Wind Shear Terminology”

• Survey taken by Certified Flight Instructors in Washington State in 1991.

• Presented at the “Fourth International Conference on Aviation Weather Systems” June 24-28 1991, in Paris, France

• Printed in Post-Print Proceedings Volume, pp13-15 by AMS and French Met. Society.

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“Low-Level Wind Shear Terminology”

• It was suggested that pilots in Washington may not be as aware of WS terminology because of less convective activity than in other states,

• So a second survey was taken in Texas.

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“A Comparative Study of Pilot’s

Understanding of Low-Level Wind Shear

Terminology”• Results of same survey taken by

Certified Flight Instructors in Texas, July 1991.

• The results of both states were very similar.

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“A Comparative Study of Pilot’s

understanding of Low-Level Wind Shear

Terminology”• Delivered to AMS/NWS Aviation Weather

Conference, Kansas City, Dec 1991, and printed in post-print volume.

• Meteorologists at the conference also took survey.

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The Survey

• Participants were asked not to guess…”If you don’t know, please indicate in appropriate space.”

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How WS is Perceived

Question 1• Is there a difference between ‘WS’

and ‘Micro-burst’?

X

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Difference between WS & Micro-burst?

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How WS is Perceived

Question 2• “You are on approach and are told

that there is a LLWA in effect.• Would you expect micro-burst

activity in the area?X

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Does LLWA Indicate Micro-burst?

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How WS is Perceived

Question 3• If you see WS mentioned in the

TAF, • Would you expect Micro-burst

activity in the area?X

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Does WS = Micro-burst?

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How WS is Perceived

Question 4• Does ‘WS’ in the TAF and ‘LLWA’

given by tower mean the same thing?

X

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Does ‘WS’ = ‘LLWA’?

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How WS is Perceived

Question 5• Is the recovery procedure the

same for WS as it is for the micro-burst?

X

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Recovery Procedures

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How WS is Perceived

Question 6• If micro-burst is expected to occur

in terminal area, • How would it be indicated in the

TAF?– A. WS– B. +TRW VRB50G55– C. Don’t know / Unsure

X

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Micro-burst in TAF?

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How WS is Perceived

Question 7• Is turbulence always experienced

when encountering a micro-burst?

X

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Does Micro-burst = Turbulence?

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How WS is Perceived Discussion - 1

• The majority knew WS and Micro-burst were different (Question 1)

• Less than 1/3 of the pilots knew recovery procedure was different for each phenomenon

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How WS is Perceived Discussion - 2

• Only 2% of Pilots and• Only 14% of the Meteorologists • Answered all of the questions

correctly.

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How WS is Perceived Discussion - 3

• Nearly 80% of pilots did not know how micro-bursts are identified in TAFs,

• Nearly 60% of responding “aviation experts” didn’t know.

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How WS is Perceived Discussion - 4

• Only 1/2 of the meteorologists knew that the term “WS” in a TAF Does not mean that Micro-bursts are expected.

• Less than 1/4 of the Pilots knew.

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How WS is Perceived Discussion - 5

• 13% of Pilots and • 5% of the Meteorologists• answered all questions wrong, or

didn’t know.

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How WS is Perceived Discussion - 6

• If a 70% score was needed for a passing grade,

• 90% of the pilots would have failed.

• 42% of the meteorologists would have failed. – (Not all of the meteorologists were

forecasters.)

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Why the Confusion?• Most training materials do not

differentiate between Convective and Mechanical WS.

• The term ‘Wind shear’ has been used interchangeably with Micro-bursts by:– FAA - in training and investigations– NCAR - training materials– NTSB - in accident investigations– MEDIA - reporting aircraft accidents

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Why the Confusion?

• As an example, “The Probable Cause - Wind Shear” , NCAR, 1884– By NCAR for the FAA

• Training Video “Geared toward alerting pilots to Wind-Shear…”

• Actually discussed an aircraft accident involving Micro-burst.

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Why the Confusion?

• Described as: “The Wind Shear Factor” , NCAR, 1886– By NCAR for the FAA

• “Training Video geared toward pilots and traffic controllers to Wind-Shear…”

• Discussed Micro-bursts.

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Why the Confusion?• An example of an FAA training material

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Why the Confusion?

• A system designed to detect Micro-bursts is called

• The “Low Level Wind Shear Alert system” (LLWAS)

• When a Micro-burst is detected, then– A Low Level Wind Shear Alert (LLWA)

is issued, warning of a Micro-burst.

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In Closing

• Most pilots and many forecasters do not fully understand the ‘WS’ and Micro-burst elements that can be included in TAFs.

• Do You?

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The End

Of Part One