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A B727 in cruise flight has to lose 300 ft of altitude from FL370 to maintain airspeed near the tops of thunderstorm activity.
| Attributes | |
| ACN | 428133 |
| Time | |
| Date | 199902 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | navaid : atl.vortac |
| State Reference | GA |
| Altitude | msl bound lower : 36700 msl bound upper : 37000 |
| Environment | |
| Flight Conditions | VMC |
| Weather Elements | Turbulence Thunderstorm |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : ztl.artcc tower : sat.tower |
| Operator | common carrier : air carrier |
| Make Model Name | B727 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other vortac |
| Flight Phase | cruise : level |
| Route In Use | enroute airway : ns.airway |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| ASRS Report | 428133 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : multi engine pilot : instrument pilot : commercial |
| Events | |
| Anomaly | aircraft equipment problem : critical altitude deviation : excursion from assigned altitude conflict : airborne less severe inflight encounter : weather non adherence : clearance other anomaly other anomaly |
| Independent Detector | atc equipment other atc equipment : mode c other controllera other flight crewa other flight crewb other other : 3 |
| Resolutory Action | controller : separated traffic controller : issued new clearance flight crew : exited adverse environment flight crew : regained aircraft control flight crew : returned to original clearance |
| Supplementary | |
| Problem Areas | Airspace Structure Environmental Factor Weather Aircraft |
| Primary Problem | Weather |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Location: 30 mi west atl VOR. I was PF. Aircraft gross weight 150000 pounds at FL370. Performance data computers showed maximum habitable altitude of approximately FL390. Ride conditions were smooth while overflying thunderstorm conditions. Aircraft began to encounter moderate chop to light turbulence. Aircraft performance began to deteriorate with rapidly decreasing airspeed. Requested dscnts with center were denied due to traffic conflict at FL350. I had added climb power and elected to descend to FL367, converting altitude to airspeed to prevent further airspeed decay and the possible onset of low speed buffet. After 1 min at FL367, airspeed was regained and aircraft returned to FL370. Center issued vector to southeast for traffic avoidance. Flight attendants and passenger seated with seatbelt on. No TCASII alert received.
Original NASA ASRS Text
Title: A B727 IN CRUISE FLT HAS TO LOSE 300 FT OF ALT FROM FL370 TO MAINTAIN AIRSPD NEAR THE TOPS OF TSTM ACTIVITY.
Narrative: LOCATION: 30 MI W ATL VOR. I WAS PF. ACFT GROSS WT 150000 LBS AT FL370. PERFORMANCE DATA COMPUTERS SHOWED MAX HABITABLE ALT OF APPROX FL390. RIDE CONDITIONS WERE SMOOTH WHILE OVERFLYING TSTM CONDITIONS. ACFT BEGAN TO ENCOUNTER MODERATE CHOP TO LIGHT TURB. ACFT PERFORMANCE BEGAN TO DETERIORATE WITH RAPIDLY DECREASING AIRSPD. REQUESTED DSCNTS WITH CTR WERE DENIED DUE TO TFC CONFLICT AT FL350. I HAD ADDED CLB PWR AND ELECTED TO DSND TO FL367, CONVERTING ALT TO AIRSPD TO PREVENT FURTHER AIRSPD DECAY AND THE POSSIBLE ONSET OF LOW SPD BUFFET. AFTER 1 MIN AT FL367, AIRSPD WAS REGAINED AND ACFT RETURNED TO FL370. CTR ISSUED VECTOR TO SE FOR TFC AVOIDANCE. FLT ATTENDANTS AND PAX SEATED WITH SEATBELT ON. NO TCASII ALERT RECEIVED.
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.