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An MD80 in cruise at FL350 on autoplt made sudden jolt 1 degree nose down caused by slight extension of the aft air stair.
| Attributes | |
| ACN | 485236 |
| Time | |
| Date | 200009 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : smf.airport |
| State Reference | CA |
| Altitude | msl single value : 35000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zoa.artcc tower : sjc.tower |
| Operator | common carrier : air carrier |
| Make Model Name | MD-80 Series (DC-9-80) Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Route In Use | enroute airway : j65.airway |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 15000 flight time type : 150 |
| ASRS Report | 485236 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | other flight crewa other flight crewb |
| Consequence | other |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Aircraft |
| Primary Problem | Aircraft |
Narrative:
MD80 at FLT350 smooth air on autoplt-perpmode. Aircraft made sudden jolt approximately 1 degree nose down. No altitude deviation. About 5 second later I discontinued autoplt and a/T hand flew the aircraft the rest of the way to sea no further events. I maintained the same indicated airspeed (275 KIAS) throughout cruise and descent to avoid any use of the stabilizer trim. I only used the low speed trim while configuring for landing. We wrote up the event in the mtx log. Aircraft is currently being inspected. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was on the ground several days for trim troubleshooting until a broken air stair support bracket was discovered. The reporter said the broken bracket allowed the air stair to drop down several inches causing a trim problem.
Original NASA ASRS Text
Title: AN MD80 IN CRUISE AT FL350 ON AUTOPLT MADE SUDDEN JOLT 1 DEGREE NOSE DOWN CAUSED BY SLIGHT EXTENSION OF THE AFT AIR STAIR.
Narrative: MD80 AT FLT350 SMOOTH AIR ON AUTOPLT-PERPMODE. ACFT MADE SUDDEN JOLT APPROX 1 DEGREE NOSE DOWN. NO ALTITUDE DEVIATION. ABOUT 5 SEC LATER I DISCONTINUED AUTOPLT AND A/T HAND FLEW THE ACFT THE REST OF THE WAY TO SEA NO FURTHER EVENTS. I MAINTAINED THE SAME INDICATED AIRSPEED (275 KIAS) THROUGHOUT CRUISE AND DESCENT TO AVOID ANY USE OF THE STAB TRIM. I ONLY USED THE LOW SPEED TRIM WHILE CONFIGURING FOR LNDG. WE WROTE UP THE EVENT IN THE MTX LOG. ACFT IS CURRENTLY BEING INSPECTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS ON THE GND SEVERAL DAYS FOR TRIM TROUBLESHOOTING UNTIL A BROKEN AIR STAIR SUPPORT BRACKET WAS DISCOVERED. THE RPTR SAID THE BROKEN BRACKET ALLOWED THE AIR STAIR TO DROP DOWN SEVERAL INCHES CAUSING A TRIM PROB.
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.