Narrative:

Medium large transport was level at FL350 close to syr VOR. ATC gave us a 30 degree right turn for spacing into dtw. Halfway through the turn the aircraft started a very rapid 2000 FPM descent with the autoplt on. When the autoplt was disconnected there was a lot of nose down trim which slowed recovery from the rapid descent. 1000 ft was lost. ATC was notified. A normal climb was started back to FL350. Everything seemed normal until a left turn back on course was issued by ATC. Approximately 1/2 through the turn, a descent was started again. This time recovery was made at a 400 ft loss. ATC was notified. Autoplt was not used for turns rest of the flight. Maintenance was notified of problem. ATC said there were no conflicts and requested that we not use the autoplt after the second descent. Rest of the flight was normal.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION DURING RADAR VECTORING.

Narrative: MLG WAS LEVEL AT FL350 CLOSE TO SYR VOR. ATC GAVE US A 30 DEG R TURN FOR SPACING INTO DTW. HALFWAY THROUGH THE TURN THE ACFT STARTED A VERY RAPID 2000 FPM DSCNT WITH THE AUTOPLT ON. WHEN THE AUTOPLT WAS DISCONNECTED THERE WAS A LOT OF NOSE DOWN TRIM WHICH SLOWED RECOVERY FROM THE RAPID DSCNT. 1000 FT WAS LOST. ATC WAS NOTIFIED. A NORMAL CLB WAS STARTED BACK TO FL350. EVERYTHING SEEMED NORMAL UNTIL A L TURN BACK ON COURSE WAS ISSUED BY ATC. APPROX 1/2 THROUGH THE TURN, A DSCNT WAS STARTED AGAIN. THIS TIME RECOVERY WAS MADE AT A 400 FT LOSS. ATC WAS NOTIFIED. AUTOPLT WAS NOT USED FOR TURNS REST OF THE FLT. MAINT WAS NOTIFIED OF PROB. ATC SAID THERE WERE NO CONFLICTS AND REQUESTED THAT WE NOT USE THE AUTOPLT AFTER THE SECOND DSCNT. REST OF THE FLT WAS NORMAL.

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.