Narrative:

While on the FNKS6 arrival to dca we were told to hold at doccs intersection at 16000 ft. We were experiencing moderate turbulence as we entered holding. Autoplt was on with +/-800 ft on the ivsi and with altitude changes of +/-100 ft. Suddenly we received a nose up out of trim warning on the multi function display unit, but the autoplt corrected by lowering the nose. Then suddenly we entered a severe downdraft. The autoplt could not handle the turbulence and the aircraft kept descending. At 15710 ft I had the autoplt disconnected and we climbed back to 16000 ft. We told center about the turbulence and he said that there was no conflict. Several aircraft in the holding pattern were reporting the turbulence, but center had nowhere else to send us, so we had to continue to hold in the turbulence. Supplemental information from acn 331004: during our first turn in holding, while in 25 degrees of bank, we encountered a large up- and downdraft and the altitude alert went off. The autoplt did not kick itself off and was trying to return the aircraft to 16000 ft. At that time ZDC called and asked us to check our altitude. Later we asked if there had been a conflict. Center said there was no conflict, but had noted us 400 ft low. Lessons learned: even with the autoflt system engaged and close monitoring by the flight crew, severe conditions can alter aircraft position surprisingly fast.

Google
 

Original NASA ASRS Text

Title: WHILE HOLDING ON AN ARR RTE, AN FK10 FLC EXPERIENCED TURB THAT DISPLACED THE ACFT BTWN 300 AND 400 FT FROM ASSIGNED ALT. THE AUTOPLT WAS DISCONNECTED AND THE FLC RETURNED TO THE ORIGINAL CLRNC ALT.

Narrative: WHILE ON THE FNKS6 ARR TO DCA WE WERE TOLD TO HOLD AT DOCCS INTXN AT 16000 FT. WE WERE EXPERIENCING MODERATE TURB AS WE ENTERED HOLDING. AUTOPLT WAS ON WITH +/-800 FT ON THE IVSI AND WITH ALT CHANGES OF +/-100 FT. SUDDENLY WE RECEIVED A NOSE UP OUT OF TRIM WARNING ON THE MULTI FUNCTION DISPLAY UNIT, BUT THE AUTOPLT CORRECTED BY LOWERING THE NOSE. THEN SUDDENLY WE ENTERED A SEVERE DOWNDRAFT. THE AUTOPLT COULD NOT HANDLE THE TURB AND THE ACFT KEPT DSNDING. AT 15710 FT I HAD THE AUTOPLT DISCONNECTED AND WE CLBED BACK TO 16000 FT. WE TOLD CTR ABOUT THE TURB AND HE SAID THAT THERE WAS NO CONFLICT. SEVERAL ACFT IN THE HOLDING PATTERN WERE RPTING THE TURB, BUT CTR HAD NOWHERE ELSE TO SEND US, SO WE HAD TO CONTINUE TO HOLD IN THE TURB. SUPPLEMENTAL INFO FROM ACN 331004: DURING OUR FIRST TURN IN HOLDING, WHILE IN 25 DEGS OF BANK, WE ENCOUNTERED A LARGE UP- AND DOWNDRAFT AND THE ALT ALERT WENT OFF. THE AUTOPLT DID NOT KICK ITSELF OFF AND WAS TRYING TO RETURN THE ACFT TO 16000 FT. AT THAT TIME ZDC CALLED AND ASKED US TO CHK OUR ALT. LATER WE ASKED IF THERE HAD BEEN A CONFLICT. CTR SAID THERE WAS NO CONFLICT, BUT HAD NOTED US 400 FT LOW. LESSONS LEARNED: EVEN WITH THE AUTOFLT SYS ENGAGED AND CLOSE MONITORING BY THE FLC, SEVERE CONDITIONS CAN ALTER ACFT POS SURPRISINGLY FAST.

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.