A G-IV PLT NOTES THE HAZARDS OF ACCEPTING MARSHALING FROM AN UNKNOWN SOURCE AFTER BEING GUIDED TOO CLOSE TO THE RAMP EDGE THAT WOULD NOT SUPPORT THE ACFT AT A CONGESTED UNCTLED ARPT.

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THE ARPT WAS UNCTLED WITH ONLY A UNICOM. WE LANDED TO THE SE AND EXITED AT THE END OF THE RWY. AS WE TAXIED BACK NWBOUND; ON THE PARALLEL TXWY; THE FBO REQUESTED US TO ENTER THE CENTRAL RAMP AREA VIA PERPENDICULAR TXWY AND PARK 'TO THE L OF THE WINDSOCK.' AS I APCHED THE L TURN ONTO THE SHORT TXWY LEADING TO THE RAMP; I WAS STARTING TO ASSESS WHERE TO PARK THE ACFT. I THEN MADE THE TURN ONTO THE TXWY AND CONTINUED TO ASSESS THE RAMP SIT. THE WINDSOCK WAS NOT ON MY R. SINCE THERE HAD BEEN NOTHING IN THE XMISSION FROM THE FBO TO INDICATE THAT A PARKING MARSHAL WOULD PARK US; I WAS CONSIDERING WHERE TO SELF-PARK (WITHOUT A MARSHAL'S ASSISTANCE). BEING A BEACH RESORT AREA THE RAMP WAS VERY CROWDED WITH LIGHT ACFT; TWIN TURBOPROPS AND SMALLER JETS. AS I TAXIED ONTO THE RAMP; THE AREA TO MY L HAD NO AVAILABLE PARKING SPACES. AHEAD; THE TXWY (WHICH RAN UP THE CTR OF THE RAMP) MADE A R 90 DEG TURN AND CONTINUED THE LENGTH OF THE RAMP. ABOUT 170 FT AFTER THE TURN; IT REACHED AN AREA WITH TXWY EDGE MARKINGS AND WHERE ACFT WERE PARKED ON BOTH SIDES OF THE TXWY; FACING THE CTRLINE. THE TXWY IN THAT AREA WAS ABOUT 70 FT WIDE. AS WE TAXIED ONTO THE RAMP; THERE WAS A HANGAR ON THE OPPOSITE (W) SIDE OF THE RAMP. I HAD DETERMINED THAT IF I WERE TO SELF-PARK; I WOULD SIDESTEP SLIGHTLY TO THE R AND PARK IN THE MIDDLE OF THE RAMP; AWAY FROM RAMP EDGES AND THE HANGAR; AND IN SUCH A POS AS TO NOT SUBSTANTIALLY AFFECT ANY PARKED ACFT OR HANGAR WITH MY PROX OR JET EXHAUST. THE RAMP; AS APCHED FROM THE TXWY; WAS INITIALLY 120 FT DEEP -- 60 FT ON EACH SIDE OF THE CTRLINE. THE ACFT IS 88 FT LONG AND HAS A 78 FT WING SPAN; SO MANEUVERING ROOM WAS SUFFICIENT BUT NOT OVERLY ABUNDANT. MY PLAN WAS TO PARK IN THE MIDDLE OF THE RAMP; ACROSS THE TXWY; FOR THE 10-15 MINS OR SO WE WOULD BE THERE. AT SOME POINT; WHILE ON THE TXWY ENTERING THE RAMP AREA; I SAW 2 LINE MEN STANDING CLOSE TO THE EDGE OF THE RAMP ON MY FAR R. ONE WAS HOLDING A CHOCK IN EACH HAND AS TAXI WANDS. HE WAS HOLDING THEM HORIZLY; STRAIGHT OUT IN FRONT OF HIMSELF; INDICATING HE WOULD MARSHAL US AND HE WANTED US TO TURN TOWARD HIM AND PARALLEL THE EDGE OF THE RAMP. HE WAS STANDING CLOSE TO THE WINGTIP OF A PARKED ACFT -- THE LAST IN THE ROW PARKED TO THE R OF THE TXWY. HE WAS LOCATED ON THE RAMP ABOUT 15-20 FT FROM ITS R EDGE. HIS LOCATION AND THE DIRECTION HE WAS FACING INDICATED SEVERAL THINGS TO ME. THE FIRST WAS THE GENERAL AREA THAT HE WANTED US TO PARK -- FAR OVER TO OUR R AND CLOSE TO THE EDGE OF THE RAMP. THIS WAS NOT A MARKED PARKING AREA FOR A LARGER ACFT AND IS NOT WHERE I WOULD HAVE PREFERRED TO PARK. HIS POS FURTHER INDICATED THAT HE WANTED US TO PARK AS CLR OF THE TXWY AS POSSIBLE AND; BY EXTENSION; THAT HE WAS CONCERNED ABOUT KEEPING THE TXWY UNBLOCKED. IF THIS WERE NOT A CONCERN; THERE WOULD BE NO JUSTIFICATION FOR HIS POS AT AN EXTREMITY OF THE OPEN RAMP. LASTLY; IT INDICATED WE WERE TO TURN TO TAXI TOWARD HIM. BECAUSE THERE WAS A MARSHAL PRESENT TO GUIDE ME; I STARTED TO COMPLY WITH HIS GUIDANCE. WHILE ASSESSING THIS NEW PARKING LOCATION; I KNEW THAT MY ABILITY TO KEEP THE ACFT CLR OF THE TXWY WAS LIMITED BECAUSE OF OUR ACFT'S RELATIVE SIZE AND TURNING ABILITY. I FELT THAT POSITIONING THE ACFT IN THIS LOCATION WAS NOT UNSAFE PRIMARILY BECAUSE OF THE MARSHAL'S PRESENCE AND GUIDANCE. IN MY EXPERIENCE; IT IS NOT UNCOMMON FOR A MARSHAL TO FAIL TO INDICATE HIS FINAL INTENTIONS TO THE ACFT CREW. OFTEN THE MARSHAL WILL SIGNAL THE ACFT TO TAXI TOWARD HIM ONLY TO DIRECT A TURN AT THE LAST MIN. PROGRESSIVE GUIDANCE CAN OCCASIONALLY SURPRISE A CREW WHO WAS ANTICIPATING A DIFFERENT PARKING LOCATION OR ORIENTATION. THIS MARSHAL GAVE NO INDICATION OF HIS FINAL INTENTIONS; ONLY HOLDING THE CHOCKS OUT TO INDICATE WHERE TO POS THE ACFT AND TO TAXI TOWARD HIM. IN CONSIDERING HIS DIRECTIONS; I EXPECTED WE COULD ANTICIPATE 1 OF 2 POSSIBLE FINAL PARKING SCENARIOS -- EITHER HE WOULD PARK US PARALLEL TO ALL OTHER PARKED ACFT OR HE WOULD PARK US PERPENDICULAR TO THEM. I WAS TRYING TO ENSURE THAT REGARDLESS OF SCENARIO; I WOULD BE IN A POS TO BE ABLE TO COMPLY. ALL OTHER ACFT ON THE RAMP WERE PARKED IN PARALLEL. FOR US TO ALIGN THE ACFT IN THIS DIRECTION; WHILE MINIMIZING OUR IMPACT ON THE TXWY; WOULD REQUIRE US TO START A L TURN FROM CLOSE TO THE R EDGE OF THE RAMP AND; USING MAX NOSEWHEEL STEERING DEFLECTION AND OUR MOMENTUM; TO MAKE A MINIMUM RADIUS TURN TO THE L. EVEN THEN; THE NOSE OF THE ACFT WOULD END UP VERY CLOSE TO THE CTRLINE OF THE TXWY; LEAVING THE TXWY HALF BLOCKED. IF WE PARKED PERPENDICULAR TO ALL OTHER ACFT; WHICH I FELT WAS LESS LIKELY; THERE MIGHT BE SLIGHTLY MORE ROOM RELATIVE TO THE TXWY; BUT DEPARTING THE PARKING SPACE WOULD REQUIRE US TO MAKE A FULL 180 DEG TURN FROM A STANDING START. WITH OUR R MAIN GEAR AT THE VERY EDGE OF THE RAMP; OUR WINGTIP WOULD STILL BE IN PROX TO THE CTRLINE OF THE TXWY. THIS WOULD ALMOST CERTAINLY HAVE REQUIRED US TO ADVANCE PWR FOR THE TURN; IN CLOSE PROX TO NUMEROUS LIGHT ACFT THAT WOULD BE IN LINE WITH THE JET EXHAUST DURING THE TURN. IN EITHER SCENARIO; THE ACFT WOULD PARTIALLY BLOCK THE TXWY TO A DEG DETERMINED BY ITS STARTING POS RELATIVE TO THE RAMP EDGE. I WOULD NOT HAVE CONSIDERED MANEUVERING CLOSE TO THE RAMP EDGE BEFORE I WAS REQUESTED TO DO SO BY THE MARSHAL AND ONLY HIS PRESENCE AND GUIDANCE MADE ME FEEL COMFORTABLE WITH THE MANEUVER BECAUSE HE COULD SEE MY LNDG GEAR AND I COULD NOT. RESPONDING TO THE MARSHAL'S INSTRUCTIONS; I STARTED THE TURN ONTO THE RAMP AND BEGAN TO ALIGN THE ACFT AS DIRECTED NEAR THE EDGE OF THE RAMP. THIS REQUIRED ME; FROM THE PERSPECTIVE OF THE PLT POS; TO TAXI WELL PAST THE EDGE OF THE RAMP AND THEN TURN BACK TO THE R. AS I PASSED THE 1/2 WAY POINT IN THE TURN; I BEGAN TO FOCUS MY ATTN ON THE MARSHAL FOR HIS CONTINUED GUIDANCE. HIS HAND SIGNALS REMAINED CONSTANT THROUGHOUT OUR TURN. JUST AS THE ACFT APPEARED TO STRAIGHTEN OUT PARALLEL TO THE EDGE; IT SUDDENLY LURCHED AS THE R WING DROPPED ABOUT 10 DEGS. ONLY AT THIS POINT DID HE CHANGE HIS HAND SIGNALS. HE HELD UP THE CHOCKS IN THE FORM OF AN 'X;' THE SIGNAL FOR EMER STOP. HE THEN DISAPPEARED FROM VIEW AND I RECEIVED NO FURTHER ASSISTANCE FROM HIM. COINCIDENTAL TO THE ACFT BREAKING THROUGH AND STOPPING; THE PLT IN THE R SEAT MADE A COMMENT THAT INDICATED HE FELT THE MARSHAL WAS ALLOWING US TO GET TOO CLOSE TO THE EDGE OF THE RAMP. I DON'T BELIEVE HE HAD EVEN FINISHED HIS SENTENCE BEFORE THE RAMP GAVE WAY. WE SECURED THE ENGS; DETERMINED THERE WAS NO EMER AND THE OTHER PLT EXITED THROUGH THE BAGGAGE DOOR TO MAKE ARRANGEMENTS TO DEPLANE PAX. INSPECTION OF THE R MAIN LNDG GEAR INDICATED THAT THE OUTBOARD TIRE HAD DEPARTED THE EDGE OF THE RAMP. THE PAVEMENT UNDER THE INBOARD TIRE THEN COLLAPSED; FORCING THE LNDG GEAR TO LURCH SIDEWAYS UNTIL THE INBOARD TIRE WAS OFF THE PAVEMENT AND HAD SUNK INTO SAND TO A POINT JUST BELOW THE AXLE. THE R WINGTIP WAS ABOUT 1 FT OFF THE GND. THE NOSEWHEEL WAS IN A L TURN. SUBSEQUENT CONVERSATION WITH THE ARPT MGR INDICATED THAT HIS VIEW WAS THAT THE LINE MAN WAS NOT A MARSHAL AND; IN FACT; EVEN HAD HIS HANDS IN HIS POCKETS DURING THE INCIDENT. WE SAW VARIOUS PERSONNEL MARSHALING ALMOST EVERY OTHER ACFT ON THE CROWDED RAMP THROUGHOUT THE REST OF THE WKEND. I BELIEVE THIS WAS A COMPLETELY AVOIDABLE INCIDENT. I DO NOT BELIEVE IT WOULD HAVE OCCURRED IF WE WERE NOT IN THE AREA IN WHICH IT OCCURRED. THE ONLY REASON WE WERE IN THAT LOCATION WAS THAT WE WERE DIRECTED TO THAT LOCATION BY THE MARSHAL. THIS TYPE OF INCIDENT HIGHLIGHTS THE TOUGH POS THAT A PLT IS PUT INTO RELATIVE TO HIS RESPONSIBILITY WHEN TAXIING WITH A MARSHAL PRESENT. THERE IS NO DIRECTION IN EITHER THE FARS OR AIM THAT STATES THE RELATIVE RESPONSIBILITIES OF EITHER THE MARSHAL OR PLT WHEN A PLOT IS CTLING THE ACFT UNDER A MARSHAL'S GUIDANCE. THE UMBRELLA REG; FAR 91.3; HOLDS THE PIC RESPONSIBLE FOR EVERYTHING. THE AIM ONLY OUTLINES STANDARD MARSHALING SIGNALS; IT DOESN'T SAY MORE. THIS LEAVES THE PLT RESPONSIBLE IN A 'DAMNED IT YOU DO/DAMNED IF YOU DON'T WAY. HE BECOMES RESPONSIBLE FOR THE ACTIONS OFTHE MARSHAL IF HE ACCEPTS MARSHALLING AND RESPONSIBLE FOR ANY UNSEEN ISSUES HE CREATES OR UNSEEN HAZARDS HE ENCOUNTERS IF HE REJECTS IT. I BELIEVE THAT; IN GENERAL; MOST UNITED STATES PLTS WOULD ACT TO FOLLOW A MARSHAL'S REASONABLE DIRECTION -- WITH THE EXPECTATION THAT THE MARSHAL IS TRUSTWORTHY. OTHER COUNTRIES SPELL IT OUT AS A PLT DUTY. IN AUSTRALIA; CIVIL AVIATION ORDERS PART 20 SAYS; IN PART: '4.3 PIC'S OF AN ACFT ARE TO COMPLY WITH ALL SIGNALS SO GIVEN EXCEPT WHERE A PIC OF AN ACFT CONSIDERS THAT TO DO SO WOULD JEOPARDIZE THE SAFETY OF THE ACFT OR OF ITS PAX OR OF PERSONS OR PROPERTY ON THE GND.' IN MANY CONDITIONS; ONCE A PLT HAS REACHED THE DECISION THAT MARSHALING REQUESTS SEEM SAFE AND HAS ACCEPTED MARSHALING; HE IS NO LONGER IN A POS TO DETERMINE WHETHER THE ACFT IS IN JEOPARDY. SAFE AND EFFICIENT OP OF ALL OPS; IN MANY CASES; DEMANDS THE USE OF A MARSHAL -- BUT NEITHER THE MARSHAL NOR THE FBO HAS ANY SPECIFIED RESPONSIBILITY FOR HIS ACTIONS. IF THE PLT CANNOT ACT WITH THE ASSURANCE THAT AN INDIVIDUAL APPEARING TO ACT AS A MARSHAL IS A MARSHAL; AND IS ACTING AS A PROPERLY TRAINED; AUTHORIZED MARSHAL WHO IS TAKING RESPONSIBILITY FOR PROVIDING THE NECESSARY GUIDANCE NEEDED BY A PLT TO ENSURE THAT SAFE OP IS NOT COMPROMISED; THE PLT IS LEFT IN A POS WHERE HE CANNOT DETERMINE OR ENSURE 'SAFE OP.' IF AN ARPT; FBO; OR MARSHAL IS FREE TO DETERMINE THEIR LEVEL OF RESPONSIBILITY AFTER THE FACT; THERE IS NO VESTED INTEREST IN THE SAFE OP OF THE ACFT. THIS CAN CREATE A SIT WHERE THE INDIVIDUAL WHO CAN ENSURE THE SAFE OP HAS NO DESIGNATED RESPONSIBILITY AND THE PERSON WHO HAS DESIGNATED RESPONSIBILITY CANNOT DIRECTLY ENSURE SAFE OP. CONVERSELY; IT CAN CREATE A SIT WHERE THE MARSHAL DOES TAKE HIS RESPONSIBILITIES VERY SERIOUSLY; BUT THE PLT CAN'T OR WON'T TRUST APPROPRIATE GUIDANCE THEREBY PUTTING THE ACFT IN JEOPARDY. THIS SIT IS NOT IN THE BEST INTEREST OF SAFETY. I HAVE ATTEMPTED TO DETERMINE WHAT; IF ANYTHING; WE COULD HAVE DONE TO PREVENT THIS ACCIDENT. THERE MAY HAVE BEEN SOME THINGS; BUT IN EACH CASE THESE WOULD HAVE REQUIRED ME TO REJECT; TO SOME DEGREE; THE MARSHAL'S GUIDANCE. PRIOR TO THE INCIDENT; I DID NOT FEEL I HAD A REASON TO DO SO.