 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Captain of a B757 lost control of the aircraft's ability to hold FL410 due to windshear resulting in losing altitude and requesting a lower altitude from ARTCC after regaining aircraft control at a lower altitude.
| Attributes | |
| ACN | 472449 |
| Time | |
| Date | 200005 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| State Reference | CA |
| Altitude | msl bound lower : 37000 msl bound upper : 41000 |
| Environment | |
| Flight Conditions | VMC |
| Weather Elements | Windshear |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zoa.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : multi engine pilot : instrument pilot : flight engineer |
| Experience | flight time last 90 days : 180 flight time total : 18500 flight time type : 10000 |
| ASRS Report | 472449 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : atp |
| Experience | flight time last 90 days : 240 flight time total : 11500 flight time type : 3700 |
| ASRS Report | 472453 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter other other anomaly |
| Independent Detector | aircraft equipment other aircraft equipment : airspeed + altimeter other flight crewa other flight crewb |
| Resolutory Action | controller : issued new clearance flight crew : exited adverse environment flight crew : regained aircraft control |
| Consequence | Other |
| Supplementary | |
| Problem Areas | Weather Environmental Factor Flight Crew Human Performance |
| Primary Problem | Weather |
Narrative:
While cruising east at FL410 and .80 mach, wind component changed from 115 KT tailwind to 30 KT headwind. Despite captain's throttle action, overspd warnings occurred at .845 mach. Wind then reversed to 95 KT tailwind. Speed decreased to .70 mach despite full power. Since minimum buffet speed was .73 mach at weight of 171000 pounds, captain disconnected autoplt and began a full power descent while copilot requested immediate lower altitude. Aircraft descended approximately 300 ft before clearance received, then continued descent to FL370 with clearance. No stall shakers or warnings occurred. Aircraft proceeded to destination without further incident. Crew and passenger largely unaware of procedure. I would do the same actions again. It is always necessary to monitor the aircraft and keep it flying, as a first priority.
Original NASA ASRS Text
Title: CAPT OF A B757 LOST CTL OF THE ACFT'S ABILITY TO HOLD FL410 DUE TO WINDSHEAR RESULTING IN LOSING ALT AND REQUESTING A LOWER ALT FROM ARTCC AFTER REGAINING ACFT CTL AT A LOWER ALT.
Narrative: WHILE CRUISING E AT FL410 AND .80 MACH, WIND COMPONENT CHANGED FROM 115 KT TAILWIND TO 30 KT HEADWIND. DESPITE CAPT'S THROTTLE ACTION, OVERSPD WARNINGS OCCURRED AT .845 MACH. WIND THEN REVERSED TO 95 KT TAILWIND. SPD DECREASED TO .70 MACH DESPITE FULL PWR. SINCE MINIMUM BUFFET SPD WAS .73 MACH AT WT OF 171000 LBS, CAPT DISCONNECTED AUTOPLT AND BEGAN A FULL PWR DSCNT WHILE COPLT REQUESTED IMMEDIATE LOWER ALT. ACFT DSNDED APPROX 300 FT BEFORE CLRNC RECEIVED, THEN CONTINUED DSCNT TO FL370 WITH CLRNC. NO STALL SHAKERS OR WARNINGS OCCURRED. ACFT PROCEEDED TO DEST WITHOUT FURTHER INCIDENT. CREW AND PAX LARGELY UNAWARE OF PROC. I WOULD DO THE SAME ACTIONS AGAIN. IT IS ALWAYS NECESSARY TO MONITOR THE ACFT AND KEEP IT FLYING, AS A FIRST PRIORITY.
Data retrieved from NASA's ASRS site as of July 2007 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.