A GULFSTREAM 111 WAS DISPATCHED WITH AN INCORRECT FUEL QUANTITY TEST CABLE INSTALLED THAT ALLOWED BOTH FUEL QUANTITY INDICATORS TO READ 5000 LBS HIGHER IN EACH TANK.

Narrative

PRIOR TO DEP WE; THE FLC; WERE INFORMED BY COMPANY MAINT PERSONNEL THAT THEY HAD INSTALLED A SPECIAL CABLE BTWN THE FUEL PROBES AND INDICATORS IN AN EFFORT TO TROUBLESHOOT A FUEL QUANTITY INDICATION PROB THAT WE HAD BEEN EXPERIENCING. WE FUELED OUR ACFT AT DET FOR A FLT TO MMU AND DEPARTED AT APPROX XA45. WHILE IN CRUISE FLT AT FL370 THE LOW FUEL ANNUNCIATOR FOR THE R ENG ILLUMINATED. WE STILL HAD AN INDICATION OF APPROX 6000 LBS OF FUEL LEFT IN EACH TANK. WHILE OUR INITIAL REACTION WAS THAT THIS WAS A FALSE INDICATION; WE CONFERRED AND DECIDED THAT THE SAFEST COURSE OF ACTION WAS TO LAND ASAP. WE NOTIFIED ZOB OF THE POTENTIAL PROB AND LANDED AT ELM. THE LOW FUEL INDICATOR WENT ON AND OFF AND THEN STAYED ON AS WE ENTERED THE PATTERN TO LAND. WE ADDED ADDITIONAL FUEL; CALLED OUR MAINT DEPT TO DISCUSS THE SIT; AND SINCE THE LOW FUEL LIGHT WAS OUT AND NO OTHER PROB WAS INDICATED WE COMPLETED THE MISSION WITHOUT FURTHER INCIDENT. IN FACT; AFTER OUR RETURN TO HOME BASE IT WAS DISCOVERED THAT THE INSTALLED SPECIAL CABLE WAS THE WRONG ONE AND CAUSED OUR FUEL GAUGES TO READ 5000 LBS HIGH ON EACH TANK. THEREFORE; WE REALLY DID HAVE A LOW FUEL SIT. I BELIEVE 3 THINGS CONSPIRED TO CAUSE THIS PROB: 1) THE CABLE CAME FROM THE GULFSTREAM FACTORY WITH NEXT TO NO DIRECTIONS ON ITS USE AND THE RAMIFICATIONS OF ITS USE. 2) OUR MAINT PEOPLE DID AN INADEQUATE JOB OF FAMILIARIZING THEMSELVES WITH THE PRODUCT AND DID NOT PROPERLY CHK THE FUEL SYS AND ALL ITS INDICATIONS AFTER CABLE INSTALLATION. 3) WE; THE PLTS; SHOULD HAVE TAKEN A MORE CRITICAL LOOK AT THE SIT CONSIDERING THE CRITICAL NATURE OF THIS ACFT SYS. ALL PARTIES CONCERNED NEEDED TO PAY ATTN TO THE DETAILS AND COMMUNICATE MORE EFFECTIVELY.