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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Flight crew of a B757 descended below assigned when the aircraft started a high altitude stall during level flight at FL410. Upon executing the high altitude stall recovery, they were able to maintain FL370 to which they were reclred.
| Attributes | |
| ACN | 461086 |
| Time | |
| Date | 200001 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : mhtg.artcc |
| State Reference | FO |
| Altitude | msl bound lower : 37000 msl bound upper : 41000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : mhtg.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B757 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Route In Use | enroute : other oceanic |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 240 flight time total : 20000 flight time type : 1100 |
| ASRS Report | 461086 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial pilot : multi engine |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude inflight encounter other non adherence : clearance other anomaly |
| Resolutory Action | controller : issued new clearance flight crew : regained aircraft control other |
| Consequence | Other |
| Supplementary | |
| Problem Areas | Environmental Factor Aircraft |
| Primary Problem | Aircraft |
Narrative:
We had been cruising at FL410 for approximately 30 mins in day, smooth, unlimited visibility WX. Winds from west at 66 KTS. Over international waters. Mach .793 during first 15 mins. Diligently watched how airplane was performing (near maximum cruise altitude). Got into conversation with first officer, occasionally observing instruments but not overly concerned about our status, since we were in a straight and level, clear, smooth environment. Felt a shudder and both of us observed airspeed at approximately 185 KTS, level, with engines producing maximum cruise power. Disconnected autoplt, autothrottles, applied full power, and began slow descent (high altitude stall recovery procedure. At FL408, first officer asked and received clearance to FL350 from center. By FL375, aircraft back on cruise speed and requested FL370 as new cruise altitude. No emergency declared. Aircraft typically is +/-15 KTS off airspeed in normal conditions. I have approximately 300 hours PIC with previous 800-1000 hours first officer time over 10 yrs. First officer has 3 yrs in type. I didn't feel I would have done anything differently at cruise. I can only figure that a gradual temperature increase must have occurred when airspeed was 5 KTS slow and aircraft slowly went to maximum cruise with airspeed continuing to decrease with neither of us noting a serious condition building.
Original NASA ASRS Text
Title: FLC OF A B757 DSNDED BELOW ASSIGNED WHEN THE ACFT STARTED A HIGH ALT STALL DURING LEVEL FLT AT FL410. UPON EXECUTING THE HIGH ALT STALL RECOVERY, THEY WERE ABLE TO MAINTAIN FL370 TO WHICH THEY WERE RECLRED.
Narrative: WE HAD BEEN CRUISING AT FL410 FOR APPROX 30 MINS IN DAY, SMOOTH, UNLIMITED VISIBILITY WX. WINDS FROM W AT 66 KTS. OVER INTL WATERS. MACH .793 DURING FIRST 15 MINS. DILIGENTLY WATCHED HOW AIRPLANE WAS PERFORMING (NEAR MAX CRUISE ALT). GOT INTO CONVERSATION WITH FO, OCCASIONALLY OBSERVING INSTS BUT NOT OVERLY CONCERNED ABOUT OUR STATUS, SINCE WE WERE IN A STRAIGHT AND LEVEL, CLR, SMOOTH ENVIRONMENT. FELT A SHUDDER AND BOTH OF US OBSERVED AIRSPD AT APPROX 185 KTS, LEVEL, WITH ENGS PRODUCING MAX CRUISE PWR. DISCONNECTED AUTOPLT, AUTOTHROTTLES, APPLIED FULL PWR, AND BEGAN SLOW DSCNT (HIGH ALT STALL RECOVERY PROC. AT FL408, FO ASKED AND RECEIVED CLRNC TO FL350 FROM CTR. BY FL375, ACFT BACK ON CRUISE SPD AND REQUESTED FL370 AS NEW CRUISE ALT. NO EMER DECLARED. ACFT TYPICALLY IS +/-15 KTS OFF AIRSPD IN NORMAL CONDITIONS. I HAVE APPROX 300 HRS PIC WITH PREVIOUS 800-1000 HRS FO TIME OVER 10 YRS. FO HAS 3 YRS IN TYPE. I DIDN'T FEEL I WOULD HAVE DONE ANYTHING DIFFERENTLY AT CRUISE. I CAN ONLY FIGURE THAT A GRADUAL TEMP INCREASE MUST HAVE OCCURRED WHEN AIRSPD WAS 5 KTS SLOW AND ACFT SLOWLY WENT TO MAX CRUISE WITH AIRSPD CONTINUING TO DECREASE WITH NEITHER OF US NOTING A SERIOUS CONDITION BUILDING.
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.