TBM7 PLT CONCERNED WITH OUTPERFORMING THE FAA'S PUBLISHED CLB AND DSCNT PERFORMANCE CERTIFICATION CATEGORIES; CAUSING ADDITIONAL PLT CTLR PERFORMANCE VERIFICATION.

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I HAVE BEEN WELL AWARE SINCE I STARTED FLYING A SOCATA TBM700 PRESSURIZED TURBOPROP MORE THAN 2 YRS AGO THAT MODE C ENCODED ALT REPLIES DROP OFF AIR TFC RADAR SCREENS DURING CLBS AND DSCNTS. THIS IS BECAUSE THE 'MODEL' IN THE ATC COMPUTER DOES NOT EXPECT A CLB OR DSND AT THE RATE EASILY ACCOMPLISHED BY A TBM700. APPARENTLY THE MODEL IS BASED UPON SOCATA NON-PRESSURIZED PISTON ACFT. WHEN THE COMPUTER SEES A TARGET OUTSTRIPPING WHAT IT THINKS SHOULD BE THE PLANE'S PERFORMANCE; IT DELETES THE ALT; ASSUMING THE INFO IS ERRONEOUS. THIS OFTEN MAKES FOR ATC PROBS; DELAYS HDOFS; CAUSES UNNECESSARY LEVELOFFS; AND MAY CONTRIBUTE TO TFC CONFLICTS. OF COURSE; IT ADDS TO FREQ CONGESTION EACH TIME A CTLR AND PLT HAVE TO CONFIRM THE ALT. THIS HAPPENS FREQUENTLY; AND HAS BEEN NOTED BY A NUMBER OF TBM700 OPERATORS. I CONSIDER THIS A SAFETY HAZARD. UNFORTUNATELY; THE ATC HANDBOOK AND ATC COMPUTER SIMULATION OF PERFORMANCE ARE OFTEN IN ERROR; FOR MANY ACFT; AND PERHAPS THIS IS THE BASIS OF THE COMPUTER MODELS. THE TBM700 IS LISTED AS HAVING A 1700 FPM CLB AND A 1500 FPM DSCNT IN THE AIR TFC CTL HANDBOOK. THIS IS LESS THAN A TBM700 TYPICALLY CLBS AND DSNDS; AND IS MUCH LESS THAN MAX PERFORMANCE. BECAUSE ATC DOES NOT UNDERSTAND WE ARE A TURBOPROP; AND CAN DSND AT 3000 FPM WITHOUT DIFFICULTY; I AM CLRED TO DSND BELOW 10000 FT SOMETIMES 100+ MI SHORT OF DESTS IN NEW JERSEY; MIAMI; ORLANDO; RALEIGH; ETC. ATC SEEMS NOT TO REALIZE HOW MUCH MORE FUEL I AM EXPENDING WITH PROLONGED FLT BELOW THE FLT LEVELS. I AM ALSO UNNECESSARILY CONTRIBUTING TO LOW LEVEL CONGESTION WHEN I COULD BE KEPT ON HIGH UNTIL MUCH CLOSER TO MY DEST. CLB OUT FROM METROPOLITAN AREAS ARE ALSO OFTEN PROLONGED.