Narrative:

I was late for a trip, and I planned my trip with some haste. I carefully weighed all passenger and cargo. I calculated my takeoff weight to be 10 pounds below the maximum takeoff weight for the aircraft. I arrived at the airport a little later than scheduled. I preflted the airplane very carefully. Both fuel tanks were full. I carefully finished all preflight duties and was cleared for takeoff on runway 2L. I climbed out at 70-75 KIAS. This was close to vy for the airplane. I noticed that the rate of climb was not normal, so I asked the tower to land. The tower cleared me to land on runway 16. I entered the traffic pattern and made a routine landing. I taxied to the ramp and suspected that I must be slightly overweight. I tried to off load some fuel, but this was going to take some time. I then discharged some passenger. I discharged them because I wanted to be darned certain that I was operating the aircraft safely and that the airplane was not overweight. I then proceeded with the flight to my destination, and it was made without incident. Later than evening, I checked my weight calculations, and I discovered that I had made a mathematical error. I was off by 100 pounds. 2 days later, I learned that the aircraft's fuel tanks were the extended range type. This meant that I had not included an additional 60 pounds (10 gallons) in my calculations. After analyzing this information, I concluded that I was actually 150 pounds over weight. Had I known this, I never would have taken off. I was completely unaware of my mistake, and I believed that I was in complete compliance with the FARS. In my haste to prepare for the flight, I made the weight calculation mistake. However, I immediately took remedial action by landing as soon as practical and unloading some of the aircraft's weight. I would recommend that there be a requirement for aircraft with extended range tanks. The FAA should require that a placard be placed on the instrument panel stating that the aircraft has extended range tanks and the total capacity of usable fuel of those tanks.

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Original NASA ASRS Text

Title: PLT OF AN SMA SEL ACFT INADVERTENTLY TOOK OFF OVER GROSS WT DUE TO A MISCALCULATION AND MORE FUEL WT THAN PLANNED.

Narrative: I WAS LATE FOR A TRIP, AND I PLANNED MY TRIP WITH SOME HASTE. I CAREFULLY WEIGHED ALL PAX AND CARGO. I CALCULATED MY TKOF WT TO BE 10 LBS BELOW THE MAX TKOF WT FOR THE ACFT. I ARRIVED AT THE ARPT A LITTLE LATER THAN SCHEDULED. I PREFLTED THE AIRPLANE VERY CAREFULLY. BOTH FUEL TANKS WERE FULL. I CAREFULLY FINISHED ALL PREFLT DUTIES AND WAS CLRED FOR TKOF ON RWY 2L. I CLBED OUT AT 70-75 KIAS. THIS WAS CLOSE TO VY FOR THE AIRPLANE. I NOTICED THAT THE RATE OF CLB WAS NOT NORMAL, SO I ASKED THE TWR TO LAND. THE TWR CLRED ME TO LAND ON RWY 16. I ENTERED THE TFC PATTERN AND MADE A ROUTINE LNDG. I TAXIED TO THE RAMP AND SUSPECTED THAT I MUST BE SLIGHTLY OVERWT. I TRIED TO OFF LOAD SOME FUEL, BUT THIS WAS GOING TO TAKE SOME TIME. I THEN DISCHARGED SOME PAX. I DISCHARGED THEM BECAUSE I WANTED TO BE DARNED CERTAIN THAT I WAS OPERATING THE ACFT SAFELY AND THAT THE AIRPLANE WAS NOT OVERWT. I THEN PROCEEDED WITH THE FLT TO MY DEST, AND IT WAS MADE WITHOUT INCIDENT. LATER THAN EVENING, I CHKED MY WT CALCULATIONS, AND I DISCOVERED THAT I HAD MADE A MATHEMATICAL ERROR. I WAS OFF BY 100 LBS. 2 DAYS LATER, I LEARNED THAT THE ACFT'S FUEL TANKS WERE THE EXTENDED RANGE TYPE. THIS MEANT THAT I HAD NOT INCLUDED AN ADDITIONAL 60 LBS (10 GALLONS) IN MY CALCULATIONS. AFTER ANALYZING THIS INFORMATION, I CONCLUDED THAT I WAS ACTUALLY 150 LBS OVER WT. HAD I KNOWN THIS, I NEVER WOULD HAVE TAKEN OFF. I WAS COMPLETELY UNAWARE OF MY MISTAKE, AND I BELIEVED THAT I WAS IN COMPLETE COMPLIANCE WITH THE FARS. IN MY HASTE TO PREPARE FOR THE FLT, I MADE THE WT CALCULATION MISTAKE. HOWEVER, I IMMEDIATELY TOOK REMEDIAL ACTION BY LNDG AS SOON AS PRACTICAL AND UNLOADING SOME OF THE ACFT'S WT. I WOULD RECOMMEND THAT THERE BE A REQUIREMENT FOR ACFT WITH EXTENDED RANGE TANKS. THE FAA SHOULD REQUIRE THAT A PLACARD BE PLACED ON THE INST PANEL STATING THAT THE ACFT HAS EXTENDED RANGE TANKS AND THE TOTAL CAPACITY OF USABLE FUEL OF THOSE TANKS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.