Narrative:

Our company uses a standard manifest form for calculation of weight and balance. We use a handheld scientific calculator which has been programmed to do the calculations. As data is entered (temperature, pressure altitude, fuel, etc) the program prompts the user to enter the next piece of data. On this date, the calculator battery appeared to be dead, and the calculator did not work. Operations had no extra calculators or batteries, so I proceeded to prepare the manifest using a regular calculator, and looking up moments in the P.O.H. It had been quite a while since I had done one of our manifests manually. I completed the manifest in mke, and also did manual manifests in fnt for our leg to lan, and in lan for our leg to mke. While I was uncomfortable doing the calculations manually, the numbers seemed reasonable, based upon my experience, for the loads we had on board. That evening I worked through the manifests again to verify their accuracy. I found that they were not correct, as I had mixed moments and center of gravity in the calculation. None of my flts were out of the approved center of gravity range, but they could have been since I had done the calculations wrong. Contributing factors/areas for improvement: I, as PIC, need to make sure I am up to date on doing manifests manually. Our manifest forms (see copy attached), has the aircraft center of gravity in the moment column, resulting in the potential for mixing center of gravity and moments. The P.O.H., and our manifest, use differing moments (straight moment, moment/100, moment/1000, etc). It should be very clear (i.e., marked) on a manifest what moment is being used. It should actually say 'arm/100' or 'moment/100'. I've learned my lesson and will always keep up to date on my ability to do manifests manually.

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Original NASA ASRS Text

Title: ACFT WT AND BAL COMPUTATIONS IN ERROR DUE TO HANDHELD COMPUTERS BEING INOP.

Narrative: OUR COMPANY USES A STANDARD MANIFEST FORM FOR CALCULATION OF WT AND BAL. WE USE A HANDHELD SCIENTIFIC CALCULATOR WHICH HAS BEEN PROGRAMMED TO DO THE CALCULATIONS. AS DATA IS ENTERED (TEMP, PRESSURE ALT, FUEL, ETC) THE PROGRAM PROMPTS THE USER TO ENTER THE NEXT PIECE OF DATA. ON THIS DATE, THE CALCULATOR BATTERY APPEARED TO BE DEAD, AND THE CALCULATOR DID NOT WORK. OPS HAD NO EXTRA CALCULATORS OR BATTERIES, SO I PROCEEDED TO PREPARE THE MANIFEST USING A REGULAR CALCULATOR, AND LOOKING UP MOMENTS IN THE P.O.H. IT HAD BEEN QUITE A WHILE SINCE I HAD DONE ONE OF OUR MANIFESTS MANUALLY. I COMPLETED THE MANIFEST IN MKE, AND ALSO DID MANUAL MANIFESTS IN FNT FOR OUR LEG TO LAN, AND IN LAN FOR OUR LEG TO MKE. WHILE I WAS UNCOMFORTABLE DOING THE CALCULATIONS MANUALLY, THE NUMBERS SEEMED REASONABLE, BASED UPON MY EXPERIENCE, FOR THE LOADS WE HAD ON BOARD. THAT EVENING I WORKED THROUGH THE MANIFESTS AGAIN TO VERIFY THEIR ACCURACY. I FOUND THAT THEY WERE NOT CORRECT, AS I HAD MIXED MOMENTS AND CTR OF GRAVITY IN THE CALCULATION. NONE OF MY FLTS WERE OUT OF THE APPROVED CTR OF GRAVITY RANGE, BUT THEY COULD HAVE BEEN SINCE I HAD DONE THE CALCULATIONS WRONG. CONTRIBUTING FACTORS/AREAS FOR IMPROVEMENT: I, AS PIC, NEED TO MAKE SURE I AM UP TO DATE ON DOING MANIFESTS MANUALLY. OUR MANIFEST FORMS (SEE COPY ATTACHED), HAS THE ACFT CTR OF GRAVITY IN THE MOMENT COLUMN, RESULTING IN THE POTENTIAL FOR MIXING CTR OF GRAVITY AND MOMENTS. THE P.O.H., AND OUR MANIFEST, USE DIFFERING MOMENTS (STRAIGHT MOMENT, MOMENT/100, MOMENT/1000, ETC). IT SHOULD BE VERY CLR (I.E., MARKED) ON A MANIFEST WHAT MOMENT IS BEING USED. IT SHOULD ACTUALLY SAY 'ARM/100' OR 'MOMENT/100'. I'VE LEARNED MY LESSON AND WILL ALWAYS KEEP UP TO DATE ON MY ABILITY TO DO MANIFESTS MANUALLY.

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.