INSTRUCTOR WITH STUDENT PLT ON XCOUNTRY FLT IN C152 HAVE STRONG WINDS WX AND DO NOT MONITOR FUEL VERY WELL. THEY LAND WITH ONE HALF HR FUEL LEFT INSTEAD OF THE REQUIRED 45 MINS FOR NIGHT FLT.

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XCOUNTRY CDW DIRECT BID DIRECT CDW. TOTAL DURATION OF FLT 3 HRS 25 MINS. REMAINING FUEL WAS 3 GALS WHICH IS 0.5 HRS FLT TIME. FUEL NIGHT REQUIREMENT IS 45 MINS. DUE TO THE GOOD FLT TIME ON THE FIRST LEG AND THE WINDS WERE NOT RPTED TOO STRONG (FROM THE SW); I DECIDED NOT TO STOP ON THE WAY BACK. I AND MY STUDENT CALCULATED THE LAST LEG WITH 1 HR 45 MINS; WHICH LEAVES US AT LEAST 45 MINS REMAINING FUEL. OVER EAST LONG ISLAND WE ENCOUNTERED A LOW OVCST LAYER. I CALLED BRIDGEPORT FSS AND ASKED FOR A STANDARD WX BRIEFING FOR MY RTE. AT THIS TIME I WAS CIRCLING; I DIDN'T WANT TO FLY OVER THIS LAYER. THE FSS SAID; THEY DON'T KNOW ABOUT IT AND CALDWELL RPTS 060 BKN. THE BRIEFER DID NOT SEE ANY REASON WHY WE SHOULD NOT PROCEED. SO WE DECIDED TO GO ON AND LAND IN CDW. I CHKED THE FUEL GAUGES; WHICH SHOWED HALF FULL; AND WE STAYED S OF THE OVCST LAYER TO ASSURE WE DON'T LOSE CONTACT WITH THE GND. N OF MC ARTHUR ARPT; WE ENCOUNTERED GOOD WX CONDITIONS AND THE FUEL GAUGES SHOWED; L JUST BELOW HALF FULL; AND R HALF FULL. THEN WE STARTED TO DSND FROM 4500 FT TO 1500 FT AND PROCEED TO THE ALPINE TWR AND DIRECT CDW. LANDED IN CDW WE REALIZED OUR CALCULATION WAS WRONG. WE RELIED ON THE FUEL GAUGES WITHOUT CONSIDERING THE TIME LOSS; WHEN WE CIRCLED IN FRONT OF THE OVCST CLOUDS. WE ALSO DIVERTED TO THE S; AND DIDN'T GET CLRNC INTO CLASS B. ALSO THE WINDS ALOFT WERE STRONGER THAN WE THOUGHT; BUT WE DID NOT CONSIDER IT; WHICH WAS POOR JUDGEMENT.