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Safety Recommendation Details

Safety Recommendation A-80-139
Details
Synopsis: ON JUNE 12, 1980, AN AIR WISCONSIN, INC., SWEARINGEN SA-226 METRO CRASHED NEAR VALLEY, NEBRASKA, KILLING 13 PERSONS AND SERIOUSLY INJURING 2 OTHERS. THE AIRCRAFT ENCOUNTERED AN AREA OF SEVERE THUNDERSTORMS WHILE AT AN ALTITUDE OF LESS THAN 6,000 FT AND EXPERIENCED A SIMULTANEOUS LOSS OF POWER TO BOTH ENGINES BECAUSE OF MASSIVE WATER INGESTION. DURING ITS INVESTIGATION OF THE ACCIDENT, THE NATIONAL TRANSPORTATION SAFETY BOARD DETERMINED THAT THE NATIONAL WEATHER SERVICE METEOROLOGISTS AT THE MINNEAPOLIS CENTER WEATHER SERVICE UNIT WERE AWARE OF THE THUNDERSTORMS WHICH HAD DEVELOPED IN THE VICINITY OF THE ACCIDENT SITE AND HAD BRIEFED SUPERVISORY AIR TRAFFIC CONTROL PERSONNEL ON THE LOCATION AND SEVERITY OF THE STORM CELLS. IN ADDITION, THE METEOROLOGISTS WERE AWARE OF CONVECTIVE SIGMET'S WHICH FORECAST THE SEVERE THUNDERSTORM ACTIVITY. BOTH METEOROLOGISTS TESTIFIED AT THE PUBLIC HEARING THAT THEY BELIEVED THAT THE CONVECTIVE SIGMET'S WHICH WERE IN EFFECT DESCRIBED ADEQUATELY THE EXISTING METEOROLOGICAL CONDITIONS. THEREFORE, NO CENTER WEATHER ADVISORIES WERE ISSUED TO SUPPLEMENT THE EXISTING CONVECTIVE SIGMET'S.
Recommendation: THE NTSB RECOMMENDS THAT THE NATIONAL WEATHER SERVICE: DEVELOP SPECIFIC CRITERIA FOR CENTER WEATHER SERVICE UNITS WHICH WOULD GOVERN THE ISSUANCE OF CENTER WEATHER ADVISORIES TO UPDATE OR SUPPLEMENT CONVECTIVE SIGMET'S.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Alternate Action
Mode: Aviation
Location: Valley, NE, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA80AA019
Accident Reports: Air Wisconsin, Inc., Swearingen A-226 Metro, N650S
Report #: AAR-80-15
Accident Date: 6/12/1980
Issue Date: 1/5/1981
Date Closed: 4/12/1982
Addressee(s) and Addressee Status: United States Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service (Closed--No Longer Applicable)
Keyword(s): Air Traffic Control, Weather, Weather Equipment/Products/Reports

Safety Recommendation History
From: NTSB
To: United States Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service
Date: 4/12/1982
Response:

From: United States Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service
To: NTSB
Date: 12/3/1981
Response: NWS LTR: OUR FEBRUARY 27, 1981, RESPONSE INDICATED THAT THE CIRCUMSTANCES UNDER WHICH THE CENTER WEATHER SERVICE UNIT (CWSU) METEOROLOGIST ISSUES A CENTER WEATHER ADVISORY (CWA) WERE ADEQUATELY DISCUSSED WITHIN THE APPROPRIATE WEATHER SERVICE OPERATIONS MANUALS (WSOM'S). THE GUIDELINES FOUND WITHIN WSOM CHAPTER D-25, IN CONSONANCE WITH WSOM CHAPTER D-22, DEFINE THE OPERATIONAL PROCEDURES AND CRITERIA RELEVANT TO THE ISSUANCE OF A CWA. AT THE SAME TIME, THEY ALLOW THE METEOROLOGIST MAXIMUM FLEXIBILITY AND LATITUDE OF JUDGEMENT IN CONSIDERATION OF THE NATURE OF THE WEATHER PHENOMENON, THE STATE OF THE ART, LIMITATIONS OF EQUIPMENT OF COMMUNICATIONS, AND OTHER VARIABLE CIRCUMSTANCES. THE NWS HAS BEEN WORKING CLOSELY WITH THE FAA ON THE CWSU PROGRAM SINCE ITS INCEPTION IN LATE 1977 TO PROVIDE THE GREATEST OPERATIONAL BENEFITS TO THE ARTCC. THIS CLOSE WORKING RELATIONSHIP CONTINUES. WSOM CHAPTER D-25, "SUPPORT TO AIR TRAFFIC FACILITIES," IS UNDER REVIEW FOR THE PURPOSE OF IDENTIFYING ANY INSTRUCTIONS RELEVANT TO THE OPERATIONS AND RESPONSIBILITIES OF THE CWSU WHICH MAY NEED CLARIFICA TION. IN CONCLUSION, WE FEEL THAT THE JUDGEMENT EXERCISED BY CWSU METEOROLOGISTS, GIVEN THE CIRCUMSTANCES AT THE MINNEAPOLIS ARTC CENTER ON JUNE 12, 1980, WAS PRUDENT AND CORRECT AND THAT THE CWSU METEOROLOGIST'S ABILITY TO EFFEC TIVELY IMPROVE ON WEATHER INFORMATION ALREADY AVAILABLE WAS NOT SUFFICIENT TO WARRANT HIS INTERVENTION. WE RECOGNIZE THE ADVISABILITY OF PERIODIC REVIEW OF OPERATIONAL GUIDE LINES, ESPECIALLY THOSE COVERING NEW ENDEAVORS, AND WILL COMPLETE SUCH A REVIEW OF THOSE PERTINENT TO THIS RECOMMENDATION IN THE NEAR FUTURE.

From: NTSB
To: United States Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service
Date: 7/1/1981
Response:

From: United States Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service
To: NTSB
Date: 2/27/1981
Response: NATIONAL WEATHER SERVICE LTR: WE FEEL THAT THE PRESENT CRITERIA FOR THE ISSUANCE OF CENTER WEATHER ADVISORIES (CWA'S) ARE SATISFACTORY. THE WEATHER SERVICE OPERATIONS MANUAL (WSOM) CHAPTER D-25, "SUPPORT TO AIR TRAFFIC FACILITIES," DESCRIBES THREE CIRCUMSTANCES IN WHICH A CWSU METEOROLOGIST WILL ISSUE A CWA.