ROTARY WINGED TFC WITH TRAINING IN PROGRESS SUFFERS DAMAGE TO FIXED GEAR IN LNDG PROC ROLLOUT.

Narrative

DURING AN INSTRUCTIONAL FLT; MY FLT INSTRUCTOR WAS OBSERVING FROM GND MAINTAINING 2-WAY RADIO CONTACT TO ME. I WAS BEING INSTRUCTED ON THE PERFORMANCE OF FULL AUTOROTATIONS TO THE GND IN PREPARATION FOR MY CERTIFIED FLT INSTRUCTOR PRACTICAL TEST WHICH REQUIRES TOUCHDOWN AUTOROTATIONS ACCORDING TO THE FAA FSDO PORTLAND; ME. AFTER PERFORMING 3 AUTOROTATIONS TO A PWR RECOVERY; THE FOURTH AUTOROTATION WAS A FULL ONE TO THE GND AT THE CTR OF THE ARPT GRASS AREA AS REQUESTED BY MY INSTRUCTOR. THIS FULL AUTOROTATION LANDED WITHOUT INCIDENT. MY FIFTH AUTOROTATION WAS TO A PWR RECOVERY. THE SIXTH AUTOROTATION; I WAS HDG 190 DEGS INTO A LIGHT WIND FROM 1000 FT MSL WHEN I INITIATED MY AUTOROTATION. AT 65 KTS; AIRSPD; WITH A DSCNT RATE OF 1500 FPM; AND ROTOR RPM AT THE TOP OF THE GREEN; AND THROTTLE IN THE DETENT POS WITH FULL DOWN COLLECTIVE AND R PEDAL; I PERFORMED MY FLARE FOR A FULL AUTOROTATION TO THE GND AREA TO THE L OF THE TAXIWAY AS REQUESTED BY MY INSTRUCTOR. MY APCH TO TOUCHDOWN AFTER THE FLARE WAS WITH LEVEL SKIDS AND FORWARD AIRSPD AS I WAS INSTRUCTED. UPON CONTACT WITH THE SURFACE; CUSHIONING THE LNDG WITH COLLECTIVE; I SLID STRAIGHT FORWARD FOR APPROX 26 FT ON THE GND. DURING THE GND SLIDE; THE EARTH STARTED TO GIVE WAY TO THE WT OF THE HELI WITH THE SKIDS DIGGING DEEPER INTO THE EARTH UNTIL THE HELI CAME TO AN ABRUPT HALT PITCHING THE ACFT FORWARD ONTO THE FRONT OF THE SKIDS; ENDING WITH THE REAR PORTION OF THE SKIDS FALLING BACK TO THE GND. THE GND SLIDE WAS STRAIGHT WITH THE TRACKS 76 INCHES APART; THE NORMAL WIDTH OF THE SKIDS ON THIS MODEL. THINKING THAT THE GND HAD JUST GIVEN AN ABRUPT STOP TO THE HELI; WITHOUT DAMAGE; I LIFTED OFF AND FLEW BACK TO THE HANGAR TO DISCUSS THE AUTOROTATION WITH INSTRUCTOR. UPON TOUCHDOWN; I DISCOVERED WRINKLED ACFT SKIN BY THE L DOOR; AND A BENT STRUT THAT APPEARED TO BE LNDG GEAR FAILURE AS DETERMINED BY MY INSTRUCTOR. APPROX 30 MINS LATER; UPON EXAMINATION OF THE TOUCHDOWN AREA; THE GND WAS FOUND TO BE EXTREMELY SOFT; MARSH-LIKE TYPE SOIL UNDER A TOP CRUST THAT WAS EASILY DISPLACED BY THE WT OF THE HELI. THIS IRREGULAR SOIL CONDITION WAS INDISCERNIBLE FROM THE AIR. I SPOKE WITH THE HELI FACTORY ABOUT FACTORY-RECOMMENDED PROCS FOR FULL AUTOROTATIVE LNDGS TO THE GND. IT WAS HIGHLY RECOMMENDED BY A FACTORY TECHNICAL REPRESENTATIVE THAT LNDGS SHOULD BE DOWN TO AN ASPHALT HARD SURFACE RWY AS THE SOFT GND HAS A VERY HIGH FRICTION COEFFICIENT THAT CAN CAUSE ACFT DAMAGE OR ROLLOVERS DUE TO SUDDEN STOPPAGE OF THE ACFT'S FORWARD MOTION. ADDITIONALLY; THE INSTRUCTOR WAS NOT IN THE ACFT AS HE WANTED TO SEE IF AUTOROTATIONS COULD BE PERFORMED EASIER WITHOUT THE WT OF ANOTHER PERSON IN THE ACFT. I DID REQUEST THAT MY FLT INSTRUCTOR REMAIN IN THE HELI DURING THE AUTOROTATIONS; BUT THE INSTRUCTOR FELT THAT MORE PAX WT WITH THE LIGHT WINDS THAT DAY WOULD MAKE THE AUTOROTATIONS MORE DIFFICULT TO DO. THE AUTOROTATIONS WERE PERFORMED AT REMOTE LOCATIONS ON THE ARPT PROPERTY AWAY FROM PEOPLE; BUILDINGS; OR OTHER ACFT; WHERE PREVIOUS LESSONS ON VARIOUS FLT MANEUVERS HAD BEEN CONDUCTED. 1 SITUATION THAT MAY HAVE CONTRIBUTED TO THE ACCIDENT WAS AFTER LIFTOFF; I NOTICED THAT THE FOAM GRIP WAS LOOSE IN THE THROTTLE; SPINNING INDEPENDENTLY OF THE THROTTLE WHEN HELD IN THE DETENT POS. I IMMEDIATELY BROUGHT THE HELI BACK TO HAVE THIS CORRECTED. DURING THE REST OF THE FLT; IT APPEARED TO BE FIXED; HOWEVER; UPON INSPECTING THE THROTTLE AFTER THE ACCIDENT; I FOUND THE FOAM GRIP LOOSE; MOVING INDEPENDENTLY OF THE THROTTLE WHEN HELD IN THE DETENT POS. THIS INDEPENDENT THROTTLE MOVEMENT MAY HAVE CAUSED THE ENG TO COME ON; PITCHING THE ACFT FORWARD.