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A B737-300 encounters severe clear air turbulence in its climb to FL270. The autoplt reverts to control wheel steering and the aircraft overshot assigned altitude.
| Attributes | |
| ACN | 391024 |
| Time | |
| Date | 199801 |
| Day | Thu |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : ood |
| State Reference | NJ |
| Altitude | msl bound lower : 26200 msl bound upper : 27900 |
| Environment | |
| Flight Conditions | IMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdc |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | climbout : intermediate altitude |
| Route In Use | departure other departure sid : sid |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : commercial pilot : instrument pilot : atp |
| Experience | flight time last 90 days : 152 flight time total : 18000 flight time type : 1500 |
| ASRS Report | 391024 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 15000 flight time type : 8000 |
| ASRS Report | 391148 |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : overshoot inflight encounter other non adherence : clearance other anomaly |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem flight crew : declared emergency flight crew : regained aircraft control other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Weather |
| Air Traffic Incident | other |
Narrative:
On climb out of bwi, on the swann two departure, we encountered moderate to severe turbulence at approximately 26500-27000 ft. Our leveloff altitude was FL270. The autoplt was engaged. Initially the autoplt attempted to level at FL270 but the turbulence thrust us into a vertical climb and rolled the aircraft from left to right and back. The autoplt disconnected and reverted to control wheel steering. Our bank angle reached 30-40 degrees each side of level. The turbulence lasted approximately 15 seconds. We immediately notified ATC of the turbulence and descended to FL270. No injuries were sustained in the cabin. The turbulence wasn't violent but just rolled the aircraft from side to side even though we had full aileron deflection in the opposite direction. No conflict was noted with ATC traffic and the flight proceeded to pvd without further problems. Normal approach and landing at pvd. There was no indication of WX on our radar and no reports of turbulence from ATC. Supplemental information from acn 391148: the autoplt was unable to maintain heading and altitude and reverted to control wheel steering at about 26500 ft. The sudden upsurge was too great for the autoplt to capture FL270. We regained control of aircraft at 27900 ft and descended back to FL270.
Original NASA ASRS Text
Title: A B737-300 ENCOUNTERS SEVERE CLR AIR TURB IN ITS CLB TO FL270. THE AUTOPLT REVERTS TO CTL WHEEL STEERING AND THE ACFT OVERSHOT ASSIGNED ALT.
Narrative: ON CLB OUT OF BWI, ON THE SWANN TWO DEP, WE ENCOUNTERED MODERATE TO SEVERE TURB AT APPROX 26500-27000 FT. OUR LEVELOFF ALT WAS FL270. THE AUTOPLT WAS ENGAGED. INITIALLY THE AUTOPLT ATTEMPTED TO LEVEL AT FL270 BUT THE TURB THRUST US INTO A VERT CLB AND ROLLED THE ACFT FROM L TO R AND BACK. THE AUTOPLT DISCONNECTED AND REVERTED TO CTL WHEEL STEERING. OUR BANK ANGLE REACHED 30-40 DEGS EACH SIDE OF LEVEL. THE TURB LASTED APPROX 15 SECONDS. WE IMMEDIATELY NOTIFIED ATC OF THE TURB AND DSNDED TO FL270. NO INJURIES WERE SUSTAINED IN THE CABIN. THE TURB WASN'T VIOLENT BUT JUST ROLLED THE ACFT FROM SIDE TO SIDE EVEN THOUGH WE HAD FULL AILERON DEFLECTION IN THE OPPOSITE DIRECTION. NO CONFLICT WAS NOTED WITH ATC TFC AND THE FLT PROCEEDED TO PVD WITHOUT FURTHER PROBS. NORMAL APCH AND LNDG AT PVD. THERE WAS NO INDICATION OF WX ON OUR RADAR AND NO RPTS OF TURB FROM ATC. SUPPLEMENTAL INFO FROM ACN 391148: THE AUTOPLT WAS UNABLE TO MAINTAIN HEADING AND ALT AND REVERTED TO CTL WHEEL STEERING AT ABOUT 26500 FT. THE SUDDEN UPSURGE WAS TOO GREAT FOR THE AUTOPLT TO CAPTURE FL270. WE REGAINED CTL OF ACFT AT 27900 FT AND DSNDED BACK TO FL270.
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.