A PLT RPTS THE ONBOARD COMPUTER CALCULATES XWIND COMPONENT FROM RWY NUMBER NOT RWY HDG POTENTIALLY CAUSING OUT OF LIMIT LNDGS.

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THIS COULD BE A SERIOUS ISSUE. I BELIEVE THERE IS A PROB WITH OUR OPC WHEN IT CALCULATES XWIND AND TAILWIND DATA FOR TKOFS AND LNDGS. THIS PROB OCCURS DUE TO THE FACT IT CALCULATES WIND COMPONENTS FROM THE RWY NUMBER AND NOT THE RWY HDG. IN MOST CASES THESE ARE ABOUT THE SAME AND IT WOULDN'T PRESENT A PROB. BUT CONSIDER THE FOLLOWING EXAMPLE WITH ACTUAL OPC OUTPUT: MCO RWYS 17L/R AND 18L/R BOTH HAVE A MAGNETIC HDG OF 184 DEGS. WINDS: 080 DEGS AT 36 KTS COMPUTES TO: A 36 KT XWIND FOR RWY 17L/R? WHICH IS OUT OF LIMITS; AND A 35 KT XWIND FOR RWY 18L/R? WHICH IS OK. THESE WINDS ALSO COMPUTE VREF/VAPP SPDS AS: RWY 17L/R 131/149 RWY 18L/R 131/136. IN THIS CASE; WE ARE ADDING AN ADDITIONAL 13 KTS TO VREF FOR APCH SPDS TO ONE SET OF RWYS THAT ARE PARALLEL ANOTHER SET. THAT DOESN'T MAKE ANY SENSE AND MIGHT NOT BE THE SAFEST THING TO DO. ANOTHER EXAMPLE FOR THE SAME RWYS IN MCO: WINDS: 280 DEGS AT 36 KTS COMPUTES TO: A 12 KT TAILWIND FOR RWY 17L/R; WHICH IS OUT OF LIMITS; AND A 6 KT TAILWIND FOR RWY 18L/R; WHICH IS OK. AGAIN; PARALLEL RWYS AND ONE IS OUT OF LIMITS AND ONE IS NOT. I DON'T THINK THE ORLANDO TWR CTLRS WOULD UNDERSTAND WHY WE CAN LAND ON THE W COMPLEX RWYS AND NOT THE E COMPLEX RWYS. THIS EXAMPLE COULD ALSO OCCUR IN DTW (WHICH IS WHERE I SAW IT THIS LAST TRIP). IT IS MUCH MORE PRONOUNCED IN MCO DUE TO THE FACT THAT RWYS 17L/R ARE 14 DEGS OFF FROM THE ACTUAL HDG. BECAUSE OF THIS ANOMALY; THE OPC COULD BE TELLING CREWS IT IS ACCEPTABLE TO LAND AND TAKE OFF WHEN THEY ARE REALLY NOT ALLOWED TO DUE TO FOM LIMITATIONS. OR; CREWS MAY BE DIVERTING DUE TO WINDS BEING OUT OF LIMITS WHEN THEY COULD ACTUALLY LAND. NEITHER CASE WOULD BE GOOD. RECOMMENDATION: I BELIEVE WE NEED TO CHANGE THE OPC TO CALCULATE WIND COMPONENTS FROM THE ACTUAL RWY HDG AND NOT THE RWY 'NUMBER/NAME.'