Narrative:

On feb/xd/01 I met the owner of a helicopter (an MD500-east). I met the owner at xyz airport where the sales agent delivered the helicopter within the preceding 1 hour. The new owner was anxious to fly his new helicopter, however, he is a student pilot and requested my assistance as a CFI with many hours experience in MD500 series helicopters. (My last flight in an MD500 series helicopter was within the preceding 10 days and the flight included emergency procedures and full down autorotations at ZZZ.) I took the time to preflight the aircraft. The aircraft appeared well worn but airworthy. Since it just flew in from chino to xyz, I felt comfortable that it as airworthy. The pervious pilot signed off the daily preflight inspection so I used the hfm and completed a walkaround inspection. The owner was asked to situation in the copilot position and the owner's cpr pilot was offered a seat in the left rear position, which he accepted. I had the owner read off the before start checklist from the hfm while I operated the system and started the helicopter. All system were checked and clearance was received from the xyz tower for an easterly departure. I flew the aircraft to the general area of wyz and upon feeling comfortable with the helicopter, I gave the controls to the new owner. The new owner has experience flying H269 and bell 402 helicopters so I simply monitored his actions while guarding the controls. The owner made a nonstandard approach to xyz airport intending to land on a parallel taxiway. On short approach, the owner informed me that he could not trim the cyclic and that it was becoming difficult. I informed the owner that I had the controls and I felt a runaway right/lateral cyclic trim failure. I felt the strong flight pressures from the cyclic and used my right leg and forearm to brace my cyclic hand while I made the approach to a hover and final set-down. I rolled the turbine to flight idle as the owner informed me that his trim switch appeared stuck in the in, right trim position. I observed the switch and it appeared stuck. The owner moved the switch around and it re-centered. At that point, I checked my trim -- right, left, fore and aft. While checking the aft trim, it appeared that the cyclic was traveling back which indicated a hydraulic failure of the 1-WAY lock system. I checked the rear trim again, just in case I was putting aft pressure on the cyclic, and again it went backward. I decided to run the engine at flight speed and check the trims. Upon picking the helicopter up into a hover, I used the trim system and noted that it appeared to be operational with the exception of the one-way lock. The owner was told not to touch his trim switch to avoid another runaway situation. At that point I allowed the owner to hover around the txwys at the airport. Occasionally, I would demonstrate another maneuver while hovering and I would test the trim motors to ensure that they were working properly. After approximately 5-6 mins of hover work, we decided to fly back to xyz airport. The owner had control of the aircraft and I informed him that I would make all trim adjustments from my cyclic. On a westerly departure from yyz airport at approximately 400 ft AGL, the owner informed me that the cyclic trim was 'running away.' I grabbed onto the controls and felt a runaway left cyclic. I informed the owner that I was turning back to the yyz airport and I allowed a left bank to develop for the purpose of returning. I used opposite trim from my cyclic without any response. Within a few seconds, the force was not only to the left, but also downward. The force was so strong that I had to use both hands to hold the cyclic. Within a second or two I had to use my left leg also to try and simply hold the cyclic in the slight left turn. I yelled at the owner to work the collective as we were now losing altitude. The owner told me that he couldn't let go of the cyclic. I noted that the owner and I were now both pulling on the cyclic with minimal effect. I quickly reached over to the collective with my left hand and pulled enough pitch to balloon over a line of wires and telephone poles. There was a large green field on the other side of the wires. Upon passing over the wires, I reached over and rolled off the turbine and quickly regrippedthe cyclic and tried to simply run on with the skids level. We impacted the grass in a level attitude and slid along ground. When the aircraft came to a stop, I asked the owner and his pilot to exit the helicopter. We were in the overrun area of yyz airport. Once the owner and his pilot were out of the helicopter, I moved the copilot cyclic trim switch in all directions and left it in the neutral position. I moved my trim switches and I was able to bring the cyclic back to neutral. I added power to the turbine just below the green flight position and pulled enough pitch to lighten the helicopter skids and surface taxied over to an area near the flight line. The helicopter was shut down and secured for maintenance personnel. In retrospect, I should have thoroughly inspected the helicopter to include all supporting documentation and maintenance records. Upon the initial runaway trim,, the helicopter should have been grounded until maintenance personnel could check the trim system. Further, upon discovering that the hydraulic 1-WAY lock was not functioning I should have included that information in my maintenance report and I should have never considered flying the machine. Upon the departure trim runaway situation, I was fortunate to have a student on board that had basic helicopter skills who could assist me in getting back to the ground. The forces were so great, that, by myself in the cockpit, I do not feel that I would have been able to maintain control of the helicopter. The decision was made to trailer the helicopter to wxz where abc helicopter company will inspect the helicopter system related to the emergency and determine the cause. Callback conversation with reporter revealed the following information: the reporter stated the cause of loss of cyclic trim was the right cyclic trim switch was intermittently failing closed and was replaced. The reporter said in hindsight the aircraft should never have been flown before a more thorough check of the maintenance logbook was accomplished. The reporter stated the right cyclic trim switch had been reported in previous log pages. The reporter said when the records were checked the maintenance record was deplorable. The reporter stated 500 hours of maintenance records and maintenance performed, if any, were missing. The reporter stated a manufacturer's service bulletin was issued on the cyclic trim switch advising replacement.

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Original NASA ASRS Text

Title: AN MD500-E HELI ON A TRAINING FLT HAD THE CYCLIC CTL RUNAWAY AT 400 FT INCURRING AN EMER OFF-FIELD LNDG. CAUSED BY R CYCLIC TRIM SWITCH.

Narrative: ON FEB/XD/01 I MET THE OWNER OF A HELI (AN MD500-E). I MET THE OWNER AT XYZ ARPT WHERE THE SALES AGENT DELIVERED THE HELI WITHIN THE PRECEDING 1 HR. THE NEW OWNER WAS ANXIOUS TO FLY HIS NEW HELI, HOWEVER, HE IS A STUDENT PLT AND REQUESTED MY ASSISTANCE AS A CFI WITH MANY HRS EXPERIENCE IN MD500 SERIES HELIS. (MY LAST FLT IN AN MD500 SERIES HELI WAS WITHIN THE PRECEDING 10 DAYS AND THE FLT INCLUDED EMER PROCS AND FULL DOWN AUTOROTATIONS AT ZZZ.) I TOOK THE TIME TO PREFLT THE ACFT. THE ACFT APPEARED WELL WORN BUT AIRWORTHY. SINCE IT JUST FLEW IN FROM CHINO TO XYZ, I FELT COMFORTABLE THAT IT AS AIRWORTHY. THE PERVIOUS PLT SIGNED OFF THE DAILY PREFLT INSPECTION SO I USED THE HFM AND COMPLETED A WALKAROUND INSPECTION. THE OWNER WAS ASKED TO SIT IN THE COPLT POS AND THE OWNER'S CPR PLT WAS OFFERED A SEAT IN THE L REAR POS, WHICH HE ACCEPTED. I HAD THE OWNER READ OFF THE BEFORE START CHKLIST FROM THE HFM WHILE I OPERATED THE SYS AND STARTED THE HELI. ALL SYS WERE CHKED AND CLRNC WAS RECEIVED FROM THE XYZ TWR FOR AN EASTERLY DEP. I FLEW THE ACFT TO THE GENERAL AREA OF WYZ AND UPON FEELING COMFORTABLE WITH THE HELI, I GAVE THE CTLS TO THE NEW OWNER. THE NEW OWNER HAS EXPERIENCE FLYING H269 AND BELL 402 HELIS SO I SIMPLY MONITORED HIS ACTIONS WHILE GUARDING THE CTLS. THE OWNER MADE A NONSTANDARD APCH TO XYZ ARPT INTENDING TO LAND ON A PARALLEL TXWY. ON SHORT APCH, THE OWNER INFORMED ME THAT HE COULD NOT TRIM THE CYCLIC AND THAT IT WAS BECOMING DIFFICULT. I INFORMED THE OWNER THAT I HAD THE CTLS AND I FELT A RUNAWAY R/LATERAL CYCLIC TRIM FAILURE. I FELT THE STRONG FLT PRESSURES FROM THE CYCLIC AND USED MY R LEG AND FOREARM TO BRACE MY CYCLIC HAND WHILE I MADE THE APCH TO A HOVER AND FINAL SET-DOWN. I ROLLED THE TURBINE TO FLT IDLE AS THE OWNER INFORMED ME THAT HIS TRIM SWITCH APPEARED STUCK IN THE IN, R TRIM POS. I OBSERVED THE SWITCH AND IT APPEARED STUCK. THE OWNER MOVED THE SWITCH AROUND AND IT RE-CTRED. AT THAT POINT, I CHKED MY TRIM -- R, L, FORE AND AFT. WHILE CHKING THE AFT TRIM, IT APPEARED THAT THE CYCLIC WAS TRAVELING BACK WHICH INDICATED A HYD FAILURE OF THE 1-WAY LOCK SYS. I CHKED THE REAR TRIM AGAIN, JUST IN CASE I WAS PUTTING AFT PRESSURE ON THE CYCLIC, AND AGAIN IT WENT BACKWARD. I DECIDED TO RUN THE ENG AT FLT SPD AND CHK THE TRIMS. UPON PICKING THE HELI UP INTO A HOVER, I USED THE TRIM SYS AND NOTED THAT IT APPEARED TO BE OPERATIONAL WITH THE EXCEPTION OF THE ONE-WAY LOCK. THE OWNER WAS TOLD NOT TO TOUCH HIS TRIM SWITCH TO AVOID ANOTHER RUNAWAY SIT. AT THAT POINT I ALLOWED THE OWNER TO HOVER AROUND THE TXWYS AT THE ARPT. OCCASIONALLY, I WOULD DEMONSTRATE ANOTHER MANEUVER WHILE HOVERING AND I WOULD TEST THE TRIM MOTORS TO ENSURE THAT THEY WERE WORKING PROPERLY. AFTER APPROX 5-6 MINS OF HOVER WORK, WE DECIDED TO FLY BACK TO XYZ ARPT. THE OWNER HAD CTL OF THE ACFT AND I INFORMED HIM THAT I WOULD MAKE ALL TRIM ADJUSTMENTS FROM MY CYCLIC. ON A WESTERLY DEP FROM YYZ ARPT AT APPROX 400 FT AGL, THE OWNER INFORMED ME THAT THE CYCLIC TRIM WAS 'RUNNING AWAY.' I GRABBED ONTO THE CTLS AND FELT A RUNAWAY L CYCLIC. I INFORMED THE OWNER THAT I WAS TURNING BACK TO THE YYZ ARPT AND I ALLOWED A L BANK TO DEVELOP FOR THE PURPOSE OF RETURNING. I USED OPPOSITE TRIM FROM MY CYCLIC WITHOUT ANY RESPONSE. WITHIN A FEW SECONDS, THE FORCE WAS NOT ONLY TO THE L, BUT ALSO DOWNWARD. THE FORCE WAS SO STRONG THAT I HAD TO USE BOTH HANDS TO HOLD THE CYCLIC. WITHIN A SECOND OR TWO I HAD TO USE MY L LEG ALSO TO TRY AND SIMPLY HOLD THE CYCLIC IN THE SLIGHT L TURN. I YELLED AT THE OWNER TO WORK THE COLLECTIVE AS WE WERE NOW LOSING ALT. THE OWNER TOLD ME THAT HE COULDN'T LET GO OF THE CYCLIC. I NOTED THAT THE OWNER AND I WERE NOW BOTH PULLING ON THE CYCLIC WITH MINIMAL EFFECT. I QUICKLY REACHED OVER TO THE COLLECTIVE WITH MY L HAND AND PULLED ENOUGH PITCH TO BALLOON OVER A LINE OF WIRES AND TELEPHONE POLES. THERE WAS A LARGE GREEN FIELD ON THE OTHER SIDE OF THE WIRES. UPON PASSING OVER THE WIRES, I REACHED OVER AND ROLLED OFF THE TURBINE AND QUICKLY REGRIPPEDTHE CYCLIC AND TRIED TO SIMPLY RUN ON WITH THE SKIDS LEVEL. WE IMPACTED THE GRASS IN A LEVEL ATTITUDE AND SLID ALONG GND. WHEN THE ACFT CAME TO A STOP, I ASKED THE OWNER AND HIS PLT TO EXIT THE HELI. WE WERE IN THE OVERRUN AREA OF YYZ ARPT. ONCE THE OWNER AND HIS PLT WERE OUT OF THE HELI, I MOVED THE COPLT CYCLIC TRIM SWITCH IN ALL DIRECTIONS AND LEFT IT IN THE NEUTRAL POS. I MOVED MY TRIM SWITCHES AND I WAS ABLE TO BRING THE CYCLIC BACK TO NEUTRAL. I ADDED PWR TO THE TURBINE JUST BELOW THE GREEN FLT POS AND PULLED ENOUGH PITCH TO LIGHTEN THE HELI SKIDS AND SURFACE TAXIED OVER TO AN AREA NEAR THE FLT LINE. THE HELI WAS SHUT DOWN AND SECURED FOR MAINT PERSONNEL. IN RETROSPECT, I SHOULD HAVE THOROUGHLY INSPECTED THE HELI TO INCLUDE ALL SUPPORTING DOCUMENTATION AND MAINT RECORDS. UPON THE INITIAL RUNAWAY TRIM,, THE HELI SHOULD HAVE BEEN GNDED UNTIL MAINT PERSONNEL COULD CHK THE TRIM SYS. FURTHER, UPON DISCOVERING THAT THE HYD 1-WAY LOCK WAS NOT FUNCTIONING I SHOULD HAVE INCLUDED THAT INFO IN MY MAINT RPT AND I SHOULD HAVE NEVER CONSIDERED FLYING THE MACHINE. UPON THE DEP TRIM RUNAWAY SIT, I WAS FORTUNATE TO HAVE A STUDENT ON BOARD THAT HAD BASIC HELI SKILLS WHO COULD ASSIST ME IN GETTING BACK TO THE GND. THE FORCES WERE SO GREAT, THAT, BY MYSELF IN THE COCKPIT, I DO NOT FEEL THAT I WOULD HAVE BEEN ABLE TO MAINTAIN CTL OF THE HELI. THE DECISION WAS MADE TO TRAILER THE HELI TO WXZ WHERE ABC HELI COMPANY WILL INSPECT THE HELI SYS RELATED TO THE EMER AND DETERMINE THE CAUSE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF LOSS OF CYCLIC TRIM WAS THE R CYCLIC TRIM SWITCH WAS INTERMITTENTLY FAILING CLOSED AND WAS REPLACED. THE RPTR SAID IN HINDSIGHT THE ACFT SHOULD NEVER HAVE BEEN FLOWN BEFORE A MORE THOROUGH CHK OF THE MAINT LOGBOOK WAS ACCOMPLISHED. THE RPTR STATED THE R CYCLIC TRIM SWITCH HAD BEEN RPTED IN PREVIOUS LOG PAGES. THE RPTR SAID WHEN THE RECORDS WERE CHKED THE MAINT RECORD WAS DEPLORABLE. THE RPTR STATED 500 HRS OF MAINT RECORDS AND MAINT PERFORMED, IF ANY, WERE MISSING. THE RPTR STATED A MANUFACTURER'S SVC BULLETIN WAS ISSUED ON THE CYCLIC TRIM SWITCH ADVISING REPLACEMENT.

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.