Narrative:

My safety suggestion is that limitations be placed in all flight handbooks or manuals prohibiting flight maneuvers with yaw damper applied without autoplt operation. On aug/wed/91, while on a proficiency flight with mr. X in the pilot's seat of the turbo small transport, I requested him to demonstrate a stall straight ahead. He slowed the aircraft to full flap speed 130 KTS and applied 100 percent flaps with a power setting of 400 pounds per engine. He then began to pitch the aircraft upward and when the airspeed began to bleed off applied increasing power and pitch until maximum power 1315 pounds was attained. The airspeed fell below 60 KTS upon which time I was going to pitch the nose over to prevent a stall in such a steep attitude. Before I could react, the aircraft pitched forward and the left wing began to fall. Mr. X then applied full right aileron and the aircraft started turning left. After about 1/3 of a revolution, mr. X retarded the throttles to idle and immediately feathered both propellers leaving no option for power manipulation. He yelled at me to disconnect the yaw damper which I could not reach since the disconnect button was on his yoke. The rotation tightened up on the second turn, and slowed on the third turn to a recovery on the entry heading at the end of 3 full turns. The airspeed indicated 90 KTS on recovery from rotation nose down so I pushed forward to attain 120 KTS, instructing mr. X to unfeather the propellers and bring up the power. We retracted the flaps and then the landing gear, returning to level flight. All instruments remained erect except for the flight director showing about 5 degrees up and 5 degrees right bank in level flight. The G loading on pull out I estimate to be less than 1 1/2 GS. Also the flight director was slow to erect prior to departure on flight. Supplemental information from acn 186843: the great falls ATCT asked if we could take an FAA ATCT controller as a passenger with us and we agreed. The chkplt then requested a stall and stall recovery. I assumed that the first stall being requested was an approach to landing stall. When the stall warning horn activated, I started to initiate a normal stall recovery by lowering the nose and advancing the power levers. I asked the chkplt if that was ok? He said he would like to see or feel the onset of the stall, ie, the initial buffet or burble. I said ok and retarded the power levers to the previously set 600-700 pounds of torque, reestablished the 10 percent nose up pitch, and allowed the airspeed to bleed off. Somewhere between 60-70 KTS of airspeed, and with no advance warning (ie, no prebuffet or burble) the airplane abruptly and rapidly rolled to the left and into a left turning spin. At this point, immediate standard spin recovery procedures were started, ie, power levers to idle, nose down, yaw damper off, full right rudder. After approximately 1 1/2 turns, the rate of turn did not appear to be slowing down. I then feathered both propellers and the rate of turn immediately started slowing down and stopped after the completion of 1 1/2 additional turns. The altitude loss was estimated at 1500 ft.

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Original NASA ASRS Text

Title: FAA FLC CHK ACFT WITH 2 CHK AIRMEN ON BOARD IN POSSIBLE VIOLATION OF FAR 91 PT 13 AND 91 PT 301. AS ACFT GETS INTO SPIN DURING PLT CERTIFICATION FLT.

Narrative: MY SAFETY SUGGESTION IS THAT LIMITATIONS BE PLACED IN ALL FLT HANDBOOKS OR MANUALS PROHIBITING FLT MANEUVERS WITH YAW DAMPER APPLIED WITHOUT AUTOPLT OP. ON AUG/WED/91, WHILE ON A PROFICIENCY FLT WITH MR. X IN THE PLT'S SEAT OF THE TURBO SMT, I REQUESTED HIM TO DEMONSTRATE A STALL STRAIGHT AHEAD. HE SLOWED THE ACFT TO FULL FLAP SPD 130 KTS AND APPLIED 100 PERCENT FLAPS WITH A PWR SETTING OF 400 POUNDS PER ENG. HE THEN BEGAN TO PITCH THE ACFT UPWARD AND WHEN THE AIRSPD BEGAN TO BLEED OFF APPLIED INCREASING PWR AND PITCH UNTIL MAX PWR 1315 POUNDS WAS ATTAINED. THE AIRSPD FELL BELOW 60 KTS UPON WHICH TIME I WAS GOING TO PITCH THE NOSE OVER TO PREVENT A STALL IN SUCH A STEEP ATTITUDE. BEFORE I COULD REACT, THE ACFT PITCHED FORWARD AND THE L WING BEGAN TO FALL. MR. X THEN APPLIED FULL R AILERON AND THE ACFT STARTED TURNING L. AFTER ABOUT 1/3 OF A REVOLUTION, MR. X RETARDED THE THROTTLES TO IDLE AND IMMEDIATELY FEATHERED BOTH PROPS LEAVING NO OPTION FOR PWR MANIPULATION. HE YELLED AT ME TO DISCONNECT THE YAW DAMPER WHICH I COULD NOT REACH SINCE THE DISCONNECT BUTTON WAS ON HIS YOKE. THE ROTATION TIGHTENED UP ON THE SECOND TURN, AND SLOWED ON THE THIRD TURN TO A RECOVERY ON THE ENTRY HDG AT THE END OF 3 FULL TURNS. THE AIRSPD INDICATED 90 KTS ON RECOVERY FROM ROTATION NOSE DOWN SO I PUSHED FORWARD TO ATTAIN 120 KTS, INSTRUCTING MR. X TO UNFEATHER THE PROPS AND BRING UP THE PWR. WE RETRACTED THE FLAPS AND THEN THE LNDG GEAR, RETURNING TO LEVEL FLT. ALL INSTS REMAINED ERECT EXCEPT FOR THE FLT DIRECTOR SHOWING ABOUT 5 DEGS UP AND 5 DEGS R BANK IN LEVEL FLT. THE G LOADING ON PULL OUT I ESTIMATE TO BE LESS THAN 1 1/2 GS. ALSO THE FLT DIRECTOR WAS SLOW TO ERECT PRIOR TO DEP ON FLT. SUPPLEMENTAL INFO FROM ACN 186843: THE GREAT FALLS ATCT ASKED IF WE COULD TAKE AN FAA ATCT CTLR AS A PAX WITH US AND WE AGREED. THE CHKPLT THEN REQUESTED A STALL AND STALL RECOVERY. I ASSUMED THAT THE FIRST STALL BEING REQUESTED WAS AN APCH TO LNDG STALL. WHEN THE STALL WARNING HORN ACTIVATED, I STARTED TO INITIATE A NORMAL STALL RECOVERY BY LOWERING THE NOSE AND ADVANCING THE PWR LEVERS. I ASKED THE CHKPLT IF THAT WAS OK? HE SAID HE WOULD LIKE TO SEE OR FEEL THE ONSET OF THE STALL, IE, THE INITIAL BUFFET OR BURBLE. I SAID OK AND RETARDED THE PWR LEVERS TO THE PREVIOUSLY SET 600-700 POUNDS OF TORQUE, REESTABLISHED THE 10 PERCENT NOSE UP PITCH, AND ALLOWED THE AIRSPD TO BLEED OFF. SOMEWHERE BTWN 60-70 KTS OF AIRSPD, AND WITH NO ADVANCE WARNING (IE, NO PREBUFFET OR BURBLE) THE AIRPLANE ABRUPTLY AND RAPIDLY ROLLED TO THE L AND INTO A L TURNING SPIN. AT THIS POINT, IMMEDIATE STANDARD SPIN RECOVERY PROCS WERE STARTED, IE, PWR LEVERS TO IDLE, NOSE DOWN, YAW DAMPER OFF, FULL R RUDDER. AFTER APPROX 1 1/2 TURNS, THE RATE OF TURN DID NOT APPEAR TO BE SLOWING DOWN. I THEN FEATHERED BOTH PROPS AND THE RATE OF TURN IMMEDIATELY STARTED SLOWING DOWN AND STOPPED AFTER THE COMPLETION OF 1 1/2 ADDITIONAL TURNS. THE ALT LOSS WAS ESTIMATED AT 1500 FT.

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.