Narrative:

At approximately XA30Z on aug/xa/00, our flight encountered an area of unforecasted extreme turbulence. The area was encountered while descending through FL210 over orley intersection located on the sweed 4 arrival into the cincinnati area, with clearance to cross tiggr intersection at 11000 ft MSL. Flight conditions were IMC with continuous light chop. WX radar was operating and displayed no returns. The tilt and gain settings were set properly for the conditions. Due to advisories from ZID of possible moderate turbulence, we had elected to activate the continuous ignition. The onset of the turbulence was rapid and immediate. The PF (captain) immediately retarded the throttles to idle thrust and disengaged the autoplt. He was able to prevent the plane from rolling to an inverted attitude, but the descent rate or an altitude was impossible to maintain. The aircraft began climbing at a moderate rate. About 5-10 seconds into the encounter, we received simultaneous left and right engine oil pressure warning messages. I shifted my focus to the engine instrument and noticed that the engines were maintaining idle thrust. No other abnormal engine indications were present. We escaped the area of extreme turbulence and readily notified ATC. No passenger or flight attendants were on board, as this was a ferry flight. The captain and myself had 5-POINT restraints secured. There was no way to predict or avoid the stated conditions. Both crew members had been on duty since AM15Z and had minimal sleep. Nothing could have been done differently to improve the situation. Company maintenance was notified and a chief pilot was consulted.

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Original NASA ASRS Text

Title: CL65 CREW ENCOUNTERED SEVERE TURB IN ZID CLASS A AIRSPACE.

Narrative: AT APPROX XA30Z ON AUG/XA/00, OUR FLT ENCOUNTERED AN AREA OF UNFORECASTED EXTREME TURB. THE AREA WAS ENCOUNTERED WHILE DSNDING THROUGH FL210 OVER ORLEY INTXN LOCATED ON THE SWEED 4 ARR INTO THE CINCINNATI AREA, WITH CLRNC TO CROSS TIGGR INTXN AT 11000 FT MSL. FLT CONDITIONS WERE IMC WITH CONTINUOUS LIGHT CHOP. WX RADAR WAS OPERATING AND DISPLAYED NO RETURNS. THE TILT AND GAIN SETTINGS WERE SET PROPERLY FOR THE CONDITIONS. DUE TO ADVISORIES FROM ZID OF POSSIBLE MODERATE TURB, WE HAD ELECTED TO ACTIVATE THE CONTINUOUS IGNITION. THE ONSET OF THE TURB WAS RAPID AND IMMEDIATE. THE PF (CAPT) IMMEDIATELY RETARDED THE THROTTLES TO IDLE THRUST AND DISENGAGED THE AUTOPLT. HE WAS ABLE TO PREVENT THE PLANE FROM ROLLING TO AN INVERTED ATTITUDE, BUT THE DSCNT RATE OR AN ALT WAS IMPOSSIBLE TO MAINTAIN. THE ACFT BEGAN CLBING AT A MODERATE RATE. ABOUT 5-10 SECONDS INTO THE ENCOUNTER, WE RECEIVED SIMULTANEOUS L AND R ENG OIL PRESSURE WARNING MESSAGES. I SHIFTED MY FOCUS TO THE ENG INST AND NOTICED THAT THE ENGS WERE MAINTAINING IDLE THRUST. NO OTHER ABNORMAL ENG INDICATIONS WERE PRESENT. WE ESCAPED THE AREA OF EXTREME TURB AND READILY NOTIFIED ATC. NO PAX OR FLT ATTENDANTS WERE ON BOARD, AS THIS WAS A FERRY FLT. THE CAPT AND MYSELF HAD 5-POINT RESTRAINTS SECURED. THERE WAS NO WAY TO PREDICT OR AVOID THE STATED CONDITIONS. BOTH CREW MEMBERS HAD BEEN ON DUTY SINCE AM15Z AND HAD MINIMAL SLEEP. NOTHING COULD HAVE BEEN DONE DIFFERENTLY TO IMPROVE THE SIT. COMPANY MAINT WAS NOTIFIED AND A CHIEF PLT WAS CONSULTED.

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.