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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Upon leveling at 41000 ft aircraft was too heavy to obtain cruise speed. A lower altitude was requested and received. During the descent, a high sink rate ensued, causing an altitude overshoot.
| Attributes | |
| ACN | 489422 |
| Time | |
| Date | 200010 |
| Day | Mon |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : zkc.artcc |
| State Reference | KS |
| Altitude | msl bound lower : 36.500 msl bound upper : 41000 |
| Environment | |
| Flight Conditions | IMC |
| Weather Elements | Turbulence |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zkc.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other Other |
| Flight Phase | cruise : enroute altitude change |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : multi engine pilot : flight engineer pilot : commercial pilot : cfi pilot : atp |
| Experience | flight time last 90 days : 165 flight time total : 19800 flight time type : 2630 |
| ASRS Report | 489422 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : multi engine pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 7500 flight time type : 150 |
| ASRS Report | 489624 |
| Events | |
| Anomaly | altitude deviation : overshoot inflight encounter : turbulence non adherence : clearance non adherence : company policies |
| Independent Detector | other flight crewa |
| Resolutory Action | controller : issued new clearance other |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Weather |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
We were cruising at FL370, cleared 'direct rmg' (rome, GA, VOR) and had just passed abeam publication (pueblo, co) VOR. The 'light chop' ride was beginning to get worse and we were handed off to ZKC. A flight on frequency reported a good ride at FL410 and we requested FL410, which was close to our altitude limit at current weight. ZKC cleared us to FL410 and I initiated a climb in 'VNAV.' climbing through FL390 the turbulence was causing the autoplt to 'hunt' the speed, decreasing the climb rate. I changed the autoplt mode to 'vertical speed/speed' mode. I decreased the vertical speed command from 1000 FPM to 200 FPM approaching FL410. The speed had decreased to less than 220 KIAS. At FL410 the airplane did not accelerate even though climb/maximum control thrust was selected. Shortly thereafter the speed began to decay. I advanced the thrust levers, but the eec's held the thrust to 'climb.' I told the first officer that we could not remain at FL410 and he requested a lower altitude from ATC. The speed continued to decay below 200 KIAS and the 'fast/slow' pointer reverted to 'alpha' mode. ATC said '4 mins' for a lower altitude. About then we began to get low speed buffet. The first officer requested an 'immediate' descent and responded to the ATC request for reason for 'immediate' with 'we cannot maintain FL410 with this turbulence' and ATC cleared us to FL370 'in 2 mins or less.' I disconnected the autoplt and began the descent. The descent exceeded 6000 FPM as we accelerated. I engaged flight director in 'flight change' mode going through FL380, I underestimated the altitude required to level off at that high rate of descent and the descent was stopped at 36500 ft. I immediately recovered back to FL370. ATC made no comment about altitude. I believe the speed decay was due to a 'mountain wave' type flow from either the rockies or local convective WX.
Original NASA ASRS Text
Title: UPON LEVELING AT 41000 FT ACFT WAS TOO HVY TO OBTAIN CRUISE SPD. A LOWER ALT WAS REQUESTED AND RECEIVED. DURING THE DSCNT, A HIGH SINK RATE ENSUED, CAUSING AN ALT OVERSHOOT.
Narrative: WE WERE CRUISING AT FL370, CLRED 'DIRECT RMG' (ROME, GA, VOR) AND HAD JUST PASSED ABEAM PUB (PUEBLO, CO) VOR. THE 'LIGHT CHOP' RIDE WAS BEGINNING TO GET WORSE AND WE WERE HANDED OFF TO ZKC. A FLT ON FREQ RPTED A GOOD RIDE AT FL410 AND WE REQUESTED FL410, WHICH WAS CLOSE TO OUR ALT LIMIT AT CURRENT WT. ZKC CLRED US TO FL410 AND I INITIATED A CLB IN 'VNAV.' CLBING THROUGH FL390 THE TURB WAS CAUSING THE AUTOPLT TO 'HUNT' THE SPD, DECREASING THE CLB RATE. I CHANGED THE AUTOPLT MODE TO 'VERT SPD/SPD' MODE. I DECREASED THE VERT SPD COMMAND FROM 1000 FPM TO 200 FPM APCHING FL410. THE SPD HAD DECREASED TO LESS THAN 220 KIAS. AT FL410 THE AIRPLANE DID NOT ACCELERATE EVEN THOUGH CLB/MAX CTL THRUST WAS SELECTED. SHORTLY THEREAFTER THE SPD BEGAN TO DECAY. I ADVANCED THE THRUST LEVERS, BUT THE EEC'S HELD THE THRUST TO 'CLB.' I TOLD THE FO THAT WE COULD NOT REMAIN AT FL410 AND HE REQUESTED A LOWER ALT FROM ATC. THE SPD CONTINUED TO DECAY BELOW 200 KIAS AND THE 'FAST/SLOW' POINTER REVERTED TO 'ALPHA' MODE. ATC SAID '4 MINS' FOR A LOWER ALT. ABOUT THEN WE BEGAN TO GET LOW SPD BUFFET. THE FO REQUESTED AN 'IMMEDIATE' DSCNT AND RESPONDED TO THE ATC REQUEST FOR REASON FOR 'IMMEDIATE' WITH 'WE CANNOT MAINTAIN FL410 WITH THIS TURB' AND ATC CLRED US TO FL370 'IN 2 MINS OR LESS.' I DISCONNECTED THE AUTOPLT AND BEGAN THE DSCNT. THE DSCNT EXCEEDED 6000 FPM AS WE ACCELERATED. I ENGAGED FLT DIRECTOR IN 'FLT CHANGE' MODE GOING THROUGH FL380, I UNDERESTIMATED THE ALT REQUIRED TO LEVEL OFF AT THAT HIGH RATE OF DSCNT AND THE DSCNT WAS STOPPED AT 36500 FT. I IMMEDIATELY RECOVERED BACK TO FL370. ATC MADE NO COMMENT ABOUT ALT. I BELIEVE THE SPD DECAY WAS DUE TO A 'MOUNTAIN WAVE' TYPE FLOW FROM EITHER THE ROCKIES OR LCL CONVECTIVE WX.
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.