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Safety Recommendation Details

Safety Recommendation A-84-108
Details
Synopsis: ON NOVEMBER 24, 1983, AIR CANADA FLIGHT 965, AN L-1011 EN ROUTE FROM PORT OF SPAIN, TRINIDAD, TO TORONTO, CANADA, ENCOUNTERED CLEAR AIR TURBULENCE APPROXIMATELY 70 MILES SOUTH OF THE WILMINGTON, NORTH CAROLINA VOR. THREE PASSENGERS AND 1 FLIGHT ATTENDANT WERE SERIOUSLY INJURED. ON APRIL 3, 1981, UNITED AIRLINES FLIGHT 12, A DC-10 EN ROUTE FROM LOS ANGELES, CALIFORNIA, TO NEWARK, NEW JERSEY, ENCOUNTERED SEVERE CLEAR AIR TURBULENCE IN THE VICINITY OF HANNIBAL, MISSOURI. TWENTY PASSENGERS AND 9 CREWMEMBERS WERE INJURED. IN BOTH OF THESE ACCIDENTS THE SAFETY BOARD'S INVESTIGATION DISCLOSED THAT THE AIRCRAFT INVOLVED WERE IN CLEAR AIR OR CIRRUS CLOUDS ABOVE AND DOWNWIND OF THUNDER STORM ACTIVITY. IT APPEARS FROM THE STATEMENTS OF BOTH FLIGHTCREWS THAT IN VIEW OF THE INFORMATION DISPLAYED ON THEIR AIRBORNE RADAR THEY BELIEVED THEY WERE SUFFICIENTLY CLEAR OF THE THUNDERSTORMS TO HAVE AVERTED CONVECTIVE TURBULENCE. WE BELIEVE THAT THERE IS SUFFICIENT EVIDENCE TO CLASSIFY THE COMBINATION OF THUNDERSTORM ACTIVITY AND STRONG WINDS ALOFT AS A MECHANISM WHICH CAN GENERATE SIGNIFICANT TURBULENCE OVER A VOLUME OF THE ATMOSPHERE FROM ABOUT THE SAME LEVEL AS THE TOPS OF THE THUNDERSTORMS UP TO THE TROPOPAUSE AND DOWNWIND FOR SOME UNKNOWN DISTANCE. THIS IS A VOLUME OF POTENTIAL TURBULENCE THAT IS CONSIDER ABLY LARGER THAN PILOTS NORMALLY EXPECT TO BE ASSOCIATED WITH THUNDERSTORMS. IT IS OUR OPINION THAT ACTION SHOULD BE TAKEN TO WARN PILOTS OF THIS POTENTIAL HAZARD WHEN IT EXISTS.
Recommendation: THE NTSB RECOMMENDS THAT THE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION: ADVISE ITS WEATHER FORECASTERS TO BE ALERT FOR SITUATIONS WHERE THERE IS A JET STREAM OR STRONG UPPER LEVEL WINDS IN ASSOCIATION WITH LINES OF DEVELOPING OR DEVELOPED THUNDERSTORMS WHICH MAY PRODUCE AN AREA OF SEVERE CLEAR AIR TURBULENCE, AND TO ISSUE APPROPRIATE WARNINGS OF THIS POTENTIAL TURBULENCE TO PILOTS THROUGH AREA FORECASTS, SIGMETS OR OTHER APPROPRIATE MEANS OF COMMUNICATION.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Action
Mode: Aviation
Location: CHARLESTON, SC, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA84AA008
Accident Reports: Air Canada Flight 965, Lockheed L-1011, C-FTNJ
Report #: AAR-84-13
Accident Date: 11/24/1983
Issue Date: 10/1/1984
Date Closed: 3/18/2002
Addressee(s) and Addressee Status: United States Department of Commerce, National Oceanic and Atmospheric Administration (Closed - Acceptable Action)
Keyword(s): Weather, Turbulence

Safety Recommendation History
From: NTSB
To: United States Department of Commerce, National Oceanic and Atmospheric Administration
Date: 3/18/2002
Response: Safety Recommendation A-84-108 closed by memorandum approved by the Board on 18 March 2002. In the last 16 years, significant research by NOAA and the Air Force has greatly improved the ability to forecast clear air turbulence, especially in conjunction with pilot reports made by airline pilots flying near thunderstorms. NOAA now issues much more thorough area forecasts and significant meteorological information (SIGMET) that contain clear air turbulence predictions. Safety Recommendation A-84-108 is classified "Closed-Acceptable Action."

From: NTSB
To: United States Department of Commerce, National Oceanic and Atmospheric Administration
Date: 9/22/1986
Response: A-84-108 WAS CLOSED 7/22/85 & REOPENED 9/22/86 SEE LETTER.

From: United States Department of Commerce, National Oceanic and Atmospheric Administration
To: NTSB
Date: 2/5/1986
Response: IN SUBSEQUENT CORRESPONDENCE REGARDING THIS MATTER, WE INDICATED THAT THE NATIONAL WEATHER SERVICE FORECASTERS ARE AWARE OF THE ATMOSPHERIC RELATIONSHIPS DESCRIBED IN THE RECOMMENDATION AND THAT THESE ARE USED WHEN APPROPRIATE. HOWEVER, DUE TO LIMITED RESEARCH AND OUR EXPERIENCES FROM THE OPERATIONAL STANDPOINT, I BELIEVE THAT THE CURRENT PRACTICES EMPLOYED BY THE NWS ARE WITHIN A REALISTIC STATE OF THE ART. MOREOVER, I BELIEVE THAT THE METEOROLOGICAL COMMUNITY'S CURRENT ABILITY TO FORECAST TURBULENCE AT SOME DISTANCE DOWNWIND FROM A THUNDERSTORM IS ANALOGOUS TO OUR CURRENT SKILL IN PINPOINTING THUNDERSTORMS THAT SPAWN MICROBURST ACTIVITY. THUS, THE CURRENT NWS OPERATIONS IN CONJUNCTION WITH EDUCATIONAL INFORMATION AVAILABLE TO PILOTS REPRESENT THE BEST ACHIEVABLE EFFORT TO ENSURE OPERATIONAL AIR SAFETY AT THIS TIME. THE INVESTIGATION OF THE TWO INCIDENTS BY SCIENTISTS FROM THE UNIVERSITY OF ARIZONA AND NASA'S AMES RESEARCH CENTER AND THE RESEARCH NOW BEING CONDUCTED AT SAN JOSE STATE UNIVERSITY IN CONJUNCTION WITH THE USAF SHOULD YIELD GUIDELINES FOR MORE APPROPRIATE FORECAST TECHNIQUES IN THE NOT TOO DISTANT FUTURE.

From: NTSB
To: United States Department of Commerce, National Oceanic and Atmospheric Administration
Date: 7/22/1985
Response:

From: United States Department of Commerce, National Oceanic and Atmospheric Administration
To: NTSB
Date: 3/20/1985
Response: NOAA LTR: ALTHOUGH WE WERE ALREADY AWARE OF THIS ATMOSPHERIC RELATIONSHIP AND APPLY IT AS WE THINK APPROPRIATE, I HAVE HAD THE FORECASTERS REVIEW THE PERTINENT DOCUMENTS TO REINFORCE THE CONCEPTS. IN VIEW OF THE ABOVE IT IS OUR CONSIDERED OPINION THAT OUR CURRENT OPERATIONAL PRACTICES ADDRESS THE PROBLEM WITHIN THE CONTEXT OF A REALISTIC FORECASTING EFFORT.

From: NTSB
To: United States Department of Commerce, National Oceanic and Atmospheric Administration
Date: 2/19/1985
Response:

From: United States Department of Commerce, National Oceanic and Atmospheric Administration
To: NTSB
Date: 11/7/1984
Response: NOAA LETTER: SAFETY RECOMMENDATION A-84-108 HAS BEEN FORWARDED TO OUR NATIONAL AVIATION WEATHER ADVISORY UNIT (NAWAU) AT KANSAS CITY, MISSOURI, FOR REVIEW, AND TO REITERATE THE THEORETICAL ATMOSPHERIC RELATIONSHIP -- A THEORY WHICH THE NAWAU STAFF IS ALREADY AWARE OF AND APPLIES WHEN APPROPRIATE.