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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Air carrier medium large transport encountered turbulence after climb to optimum altitude. PIC perceived a low speed buffet and started descent before being cleared by ZDC.
| Attributes | |
| ACN | 130125 |
| Time | |
| Date | 198912 |
| Day | Sun |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : chs |
| State Reference | SC |
| Altitude | msl bound lower : 36600 msl bound upper : 37000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdc |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | cruise other |
| Route In Use | enroute airway : j165 |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 125 flight time total : 6700 flight time type : 350 |
| ASRS Report | 130125 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance |
| 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:
While cruising at FL330, I experienced light chop (continuous) and thought about going up to FL370 for a smoother ride. I checked the performance data which showed that operation at FL370 was in a narrow range between low and high speed buffet for our gross weight at G loads of 1.25 (37 degree bank angle). Since I did not anticipate such G loads or bank angles, I elected to ask for clearance to FL370, which I received. Just as I leveled off at FL370, I encountered turbulence (moderate) which I perceived put us in the low speed buffet. I had no choice but to lower the nose to avoid possibly getting into a stall, while simultaneously requesting lower. We received clearance immediately to FL330, but not actually before I was already 400' below assigned altitude of FL370. From now on I will give myself more margin for error when deciding whether or not to operate in an authorized, but marginal area of the aerodynamic envelope.
Original NASA ASRS Text
Title: ACR MLG ENCOUNTERED TURBULENCE AFTER CLIMB TO OPTIMUM ALT. PIC PERCEIVED A LOW SPEED BUFFET AND STARTED DESCENT BEFORE BEING CLEARED BY ZDC.
Narrative: WHILE CRUISING AT FL330, I EXPERIENCED LIGHT CHOP (CONTINUOUS) AND THOUGHT ABOUT GOING UP TO FL370 FOR A SMOOTHER RIDE. I CHECKED THE PERFORMANCE DATA WHICH SHOWED THAT OPERATION AT FL370 WAS IN A NARROW RANGE BETWEEN LOW AND HIGH SPEED BUFFET FOR OUR GROSS WEIGHT AT G LOADS OF 1.25 (37 DEG BANK ANGLE). SINCE I DID NOT ANTICIPATE SUCH G LOADS OR BANK ANGLES, I ELECTED TO ASK FOR CLRNC TO FL370, WHICH I RECEIVED. JUST AS I LEVELED OFF AT FL370, I ENCOUNTERED TURBULENCE (MODERATE) WHICH I PERCEIVED PUT US IN THE LOW SPEED BUFFET. I HAD NO CHOICE BUT TO LOWER THE NOSE TO AVOID POSSIBLY GETTING INTO A STALL, WHILE SIMULTANEOUSLY REQUESTING LOWER. WE RECEIVED CLRNC IMMEDIATELY TO FL330, BUT NOT ACTUALLY BEFORE I WAS ALREADY 400' BELOW ASSIGNED ALT OF FL370. FROM NOW ON I WILL GIVE MYSELF MORE MARGIN FOR ERROR WHEN DECIDING WHETHER OR NOT TO OPERATE IN AN AUTHORIZED, BUT MARGINAL AREA OF THE AERODYNAMIC ENVELOPE.
Data retrieved from NASA's ASRS site as of August 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.