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B757-200 captain's exercise of command authority to avoid thunderstorms is disputed by ARTCC radar controller.
| Attributes | |
| ACN | 772975 |
| Time | |
| Date | 200801 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| State Reference | US |
| Altitude | msl single value : 35000 |
| Environment | |
| Weather Elements | Thunderstorm |
| Aircraft 1 | |
| Controlling Facilities | artcc : zzz.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| ASRS Report | 772975 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Events | |
| Anomaly | inflight encounter : weather non adherence : clearance other spatial deviation |
| Independent Detector | other controllera |
| Resolutory Action | flight crew : exited adverse environment flight crew : took evasive action |
| Consequence | faa : reviewed incident with flight crew |
| Supplementary | |
| Problem Areas | Weather ATC Human Performance Flight Crew Human Performance |
| Primary Problem | Weather |
Narrative:
30 mi northwest of ZZZ; FL350; captain idents line of WX tops above FL350; moving very rapidly; steep gradient in calibrated mode; scalloped edges; winds parallel at 120 KTS; pronounced radar shadow beyond. Captain decides this is an area of potentially severe turbulence. Captain asks ATC which way flts deviating. ATC advises not practical due distance required to deviate. Captain advises abc to flts left looks like best spot to traverse the line. ATC advises captain that flight would have to deviate to ZZZ to get around WX and that flight could go straight ahead; however it 'wouldn't be much fun.' captain declines further progress and requests direct abc. ATC advises 'stand by.' frequency congestion prevents further discussion. Captain checks TCAS and turns left. Intends to exercise captain's emergency authority/authorized. ATC queries flight about turn. Captain offers up captain's emergency authority/authorized. ATC declines; however; with a lecture on the dangers of turning without ATC concurrence. Captain advises that further flight would have put aircraft in harm's way. ATC offers opinion that flight was in the clear. ATC not considering radius of turn. Captain can guarantee straight ahead penetration would have been disastrous. Captain delayed initiation of turn as long as possible in a failed attempt to get an amended clearance. This turn not a matter of convenience but instead safety.
Original NASA ASRS Text
Title: B757-200 CAPT'S EXERCISE OF COMMAND AUTHORITY TO AVOID THUNDERSTORMS IS DISPUTED BY ARTCC RADAR CTLR.
Narrative: 30 MI NW OF ZZZ; FL350; CAPT IDENTS LINE OF WX TOPS ABOVE FL350; MOVING VERY RAPIDLY; STEEP GRADIENT IN CALIBRATED MODE; SCALLOPED EDGES; WINDS PARALLEL AT 120 KTS; PRONOUNCED RADAR SHADOW BEYOND. CAPT DECIDES THIS IS AN AREA OF POTENTIALLY SEVERE TURB. CAPT ASKS ATC WHICH WAY FLTS DEVIATING. ATC ADVISES NOT PRACTICAL DUE DISTANCE REQUIRED TO DEVIATE. CAPT ADVISES ABC TO FLTS LEFT LOOKS LIKE BEST SPOT TO TRAVERSE THE LINE. ATC ADVISES CAPT THAT FLT WOULD HAVE TO DEVIATE TO ZZZ TO GET AROUND WX AND THAT FLT COULD GO STRAIGHT AHEAD; HOWEVER IT 'WOULDN'T BE MUCH FUN.' CAPT DECLINES FURTHER PROGRESS AND REQUESTS DIRECT ABC. ATC ADVISES 'STAND BY.' FREQ CONGESTION PREVENTS FURTHER DISCUSSION. CAPT CHKS TCAS AND TURNS L. INTENDS TO EXERCISE CAPT'S EMER AUTH. ATC QUERIES FLT ABOUT TURN. CAPT OFFERS UP CAPT'S EMER AUTH. ATC DECLINES; HOWEVER; WITH A LECTURE ON THE DANGERS OF TURNING WITHOUT ATC CONCURRENCE. CAPT ADVISES THAT FURTHER FLT WOULD HAVE PUT ACFT IN HARM'S WAY. ATC OFFERS OPINION THAT FLT WAS IN THE CLR. ATC NOT CONSIDERING RADIUS OF TURN. CAPT CAN GUARANTEE STRAIGHT AHEAD PENETRATION WOULD HAVE BEEN DISASTROUS. CAPT DELAYED INITIATION OF TURN AS LONG AS POSSIBLE IN A FAILED ATTEMPT TO GET AN AMENDED CLRNC. THIS TURN NOT A MATTER OF CONVENIENCE BUT INSTEAD SAFETY.
Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.