FO OF AN MDT TURBOPROP MISCALCULATED THE FUEL LOAD FROM THE TANK DIPPING RESULTING IN LESS FUEL ON BOARD THAN ORDERED BY THE CAPT.

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MY COPLT HAD OUR MECHS DIP THE R FUEL TANK TO DETERMINE THE QUANTITY OF FUEL ON THAT TANK BECAUSE THAT TANK HAD AN INOP FUEL GAUGE. HE HAD LEARNED THE FUEL CONVERSION JUST A DAY EARLIER FOR IMPERIAL GALLONS TO UNITED STATES GALLONS. HE APPLIED THAT CORRECTLY FOR A FUEL ORDER THAT PREVIOUS DAY FOR A FLT FROM TORONTO; ONTARIO; CANADA TO IND; IN; USA. OUR MECHS WORKED ON THE FUEL TANK THAT DAY; BUT WERE UNABLE TO FIX THE GAUGE. MY COPLT; ACCORDING TO MEL PROCS; HAD THE MECH DIP THE TANK DURING PREFLT FOR THIS FLT AND FOUND 190 IMPERIAL GALLONS. I DID NOT RECEIVE THE IMPERIAL GALLONS FIGURE; JUST THE COPLT'S CONVERTED AMOUNT. HE SAID WE HAD 2400 LBS. THAT INFO WAS RADIOED TO MY LOCATION IN THE FLT PLANNING ROOM. I ORDERED 600 LBS OF FUEL TO BRING THAT SIDE TO THE 3000 LBS LEVEL OF THE OTHER SIDE. UNFORTUNATELY THE FO'S CONVERSION WAS INCORRECT AND INCOMPLETE. HE MULTIPLIED 190 BY 1.25 FOR UNITED STATES GALLONS BUT FOR SOME REASON HE DROPPED THE DECIMAL AND STOPPED AT GALLONS; CALLING THEM LBS. WHEN I GOT TO THE ACFT; THE MECHS WERE DIPPING THE TANK AGAIN TO VERIFY THE FINISHED LEVEL. JUST AS THE MECH WAS RPTING THE DIPPED AMOUNT TO ME; THE FO LOUDLY AND PROUDLY EXCLAIMED; 'THAT'S RIGHT; THAT'S WHAT WE'RE SUPPOSED TO HAVE!' I ASKED HIM; 'ARE YOU SURE?' HE SAID; 'YES.' HIS CONFIDENCE GAVE ME CONFIDENCE AND THAT WAS MY MISTAKE. I NORMALLY; AND WILL ASSUREDLY IN THE FUTURE; HAVE BOTH TANKS DIPPED UNDER ABNORMAL CONDITIONS; IE; AN INOP FUEL GAUGE. WE DIDN'T FIND OUT THAT WE HAD ACTUALLY LEFT OUR DEST WITH APPROX 821 LBS LESS FUEL IN THE R TANK THAN WHAT I HAD DESIRED; UNTIL THE MECH AT OUR DEST INFORMED ME THE LEVELS HE FOUND. MY PREFLT FIGURES ARE GENEROUS WHEN CALCULATING MINIMUM FUEL FOR FLT. IT JUST SO HAPPENS THAT THE ACTUAL AMOUNT OF FUEL ON BOARD COVERED BOTH UNITED STATES; INTL; AND COMPANY MINIMUM FUEL REQUIREMENTS. WE WERE WITHIN THE IMBAL LIMITS OF THE ACFT. THE SIT JUST WASN'T RIGHT. I BELIEVE THAT MY CREW MEMBERS ARE A VITAL PART OF MY CREW AND THE FLTS THEY FLY WITH ME. I ALSO BELIEVE I NEED TO TRUST THEM AT THEIR DUTIES. BUT NOW I'VE LEARNED THAT IT IS ESPECIALLY IMPORTANT TO CHK THEIR WORK WHEN ABNORMAL SITS ARE AT HAND. SINCE SAFETY OF FLT IS A CONCERN; IT SHOULD BE STANDARD TO HAVE FUEL DIP STICKS READ THE SAME MEASURE. PRESENTLY; WE HAVE 3 DIFFERENT MODELS OF THE SAME ACFT AND 3 DIFFERENT MEASURES FOR MANUALLY CHKING THE FUEL. THOSE MEASURES INCLUDE: LITERS; GALLONS AND IMPERIAL GALLONS.