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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Medium large transport enters low speed buffet as it reaches cruise altitude and must descend without a clearance.
| Attributes | |
| ACN | 198629 |
| Time | |
| Date | 199201 |
| Day | Wed |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : oma |
| State Reference | NE |
| Altitude | msl bound lower : 33000 msl bound upper : 35000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zmp |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | climbout : intermediate altitude descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : cfi |
| Experience | flight time last 90 days : 150 flight time total : 13500 flight time type : 5000 |
| ASRS Report | 198629 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude |
| Independent Detector | other flight crewa |
| Resolutory Action | controller : issued new clearance |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Normal climb to 35000 ft with last 1000 ft at 500 FPM. Speed fell about 10 KTS below optimum climb (.72) during last 500 ft of climb. After level off speed continued to fall off at about 2 KTS per second to slight buffet at 215 KTS. I disconnected the autoplt and had to descend at about 500 FPM to keep the aircraft out of low speed buffet. We had verified correct climb power and checked maximum continuous power (only .01 higher than climb) and requested immediate descent from ATC when airspeed did not accelerate at level off. ATC gave us a block altitude of 330 to 350 as we descended out of 34600. No conflict occurred. I had been careful to check our computer flight plan to show an initial climb to 350 was ok. We showed to be 2000 pounds lighter than planned on our weight data. Also our buffet chart showed we had 1.3 protection at 115000 and we weighed 108000. Also the actual temperature agreed with the flight plan. I requested a load check and was advised we were loaded nose heavy (within 1/2 unit of forward limit) but legal. My request for a bag count was refused by the company. I can only assume we weighed more than advertised.
Original NASA ASRS Text
Title: MLG ENTERS LOW SPD BUFFET AS IT REACHES CRUISE ALT AND MUST DSND WITHOUT A CLRNC.
Narrative: NORMAL CLB TO 35000 FT WITH LAST 1000 FT AT 500 FPM. SPD FELL ABOUT 10 KTS BELOW OPTIMUM CLB (.72) DURING LAST 500 FT OF CLB. AFTER LEVEL OFF SPD CONTINUED TO FALL OFF AT ABOUT 2 KTS PER SECOND TO SLIGHT BUFFET AT 215 KTS. I DISCONNECTED THE AUTOPLT AND HAD TO DSND AT ABOUT 500 FPM TO KEEP THE ACFT OUT OF LOW SPD BUFFET. WE HAD VERIFIED CORRECT CLB PWR AND CHKED MAX CONTINUOUS PWR (ONLY .01 HIGHER THAN CLB) AND REQUESTED IMMEDIATE DSCNT FROM ATC WHEN AIRSPD DID NOT ACCELERATE AT LEVEL OFF. ATC GAVE US A BLOCK ALT OF 330 TO 350 AS WE DSNDED OUT OF 34600. NO CONFLICT OCCURRED. I HAD BEEN CAREFUL TO CHK OUR COMPUTER FLT PLAN TO SHOW AN INITIAL CLB TO 350 WAS OK. WE SHOWED TO BE 2000 POUNDS LIGHTER THAN PLANNED ON OUR WT DATA. ALSO OUR BUFFET CHART SHOWED WE HAD 1.3 PROTECTION AT 115000 AND WE WEIGHED 108000. ALSO THE ACTUAL TEMP AGREED WITH THE FLT PLAN. I REQUESTED A LOAD CHK AND WAS ADVISED WE WERE LOADED NOSE HVY (WITHIN 1/2 UNIT OF FORWARD LIMIT) BUT LEGAL. MY REQUEST FOR A BAG COUNT WAS REFUSED BY THE COMPANY. I CAN ONLY ASSUME WE WEIGHED MORE THAN ADVERTISED.
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.