PLT OF A GRUMMAN AMERICAN CHEETAH; AA5; LOST CTL OF THE ACFT WHEN LNDG AT A NON TWR ARPT AT NIGHT IN GUSTY WIND CONDITIONS RESULTING IN GOING OFF THE END OF THE RWY INTO AN ALFALFA FIELD. THERE WAS NO DAMAGE TO THE ACFT AND ONLY MINOR DAMAGE TO THE CROP WHERE THE PROP CUT A SWATH THROUGH THE ALFALFA. THE RPTR TAXIED BACK TO THE APCH END OF THE RWY AND DEPARTED WITHOUT FURTHER INCIDENT.

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I ATTEMPTED TO LAND ON RWY 17 AT NIGHT IN A GUSTY XWIND. THE NEAREST WX OBSERVATION STATION; ABE; APPROX 12 NM E; SAID 9 KTS; BUT IT WAS MUCH STRONGER; POSSIBLY DUE TO AN APCHING COLD FRONT TO THE W. BECAUSE OF THE TURB; I KEPT MY APCH SPD FAST; 90 MPH (MY AIRSPD READS IN MPH; NOT KTS). BECAUSE THE APCH TO RWY 17 IS OVER BUILDINGS AND PWR LINES I MADE A HIGH APCH. THE COMBINATION OF THESE; WHEN FLOWN IN AN AA5; WITH ITS SMALL FLAPS AND TENDENCY TO FLOAT; IS A RECIPE FOR DISASTER AND I SHOULD HAVE KNOWN BETTER; WITH 600 HRS IN TYPE. I OVERRAN THE RWY ON ROLLOUT; GOING 75 FT INTO AN ALFALFA FIELD. CONTRIBUTING FACTORS TO MY POOR JUDGEMENT: RWY 17/35'S LIGHTS ARE 230 FT APART DUE TO THE WIDE GRASS ON EITHER SIDE OF THE 50 FT PAVED RWY. THE GRASS IS TYPICALLY USED FOR GLIDER OPS. THIS MEANS NIGHT LNDGS ARE DONE BY AIMING FOR THE CTR OF A 230 FT BY 2500 FT RECTANGLE; WHICH IS AN UNUSUAL APPEARANCE COMPARED TO MOST RWYS. I WAS POSSIBLY FATIGUED BY A FULL DAY AT WORK AND HUNGRY -- I WAS LNDG THERE TO GET SOMETHING TO EAT. WHILE I HAD LANDED AT N31 SEVERAL TIMES BEFORE; IT HAD ALWAYS BEEN USING RWY 35; WHICH HAS AN UNOBSTRUCTED APCH. I HAVE A HABIT OF MAKING FAST APCHS UNDER ANY CONDITION; USUALLY NOT A PROB; AND SOMETIMES HELPFUL WITH TFC FLOW; AT THE LARGER ARPTS I FREQUENTLY USE. BUT THIS HAS LEFT ME UNFAMILIAR AND UNCOMFORTABLE IN LOW SPD OPS. MY BFR IS DUE SOON; I WILL CONCENTRATE ON THESE ERRORS. THERE WAS NO DAMAGE TO THE ACFT OR PROPERTY; NOT COUNTING THE SWATH CUT BY THE PROP IN THE ALFALFA; THERE IS ONLY 5 INCHES OF PROP CLRNC. I TAXIED BACK TO THE APCH END OF RWY 17 AND DEPARTED WITHOUT INCIDENT.