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Training Desk Notes (5/6): Preparations Prior to Weighing

January 5, 2021

An aircraft must be in its basic/empty weight configuration prior to a weight and center of gravity check to ensure the most accurate data possible. Proper preparation includes removing all extra items from the aircraft, such as ice chests, magazines, water bottles, and toolboxes.  If the manufacturer of the aircraft provides a list of empty weight items – follow it as best you can for accuracy and consistency. If possible, any items that are missing from your aircraft should be installed. For example, if there is a radio control head or receiver/transmitter that is in the shop being fixed, find out the weight and arm of that item so you can add the weight and moment to your scale weights.  This can be done mathematically, or via tools provided in software, such as Intercomp’s ACWeigh™, to automate and simplify the weighing process and documentation.

Regarding fuel; defuel the aircraft following your manufacturer’s instructions to its trapped fuel condition. Once in the trapped fuel condition, there is less than the unusable fuel condition (part of the basic/empty weight), so there is a need to add the weight and moment of the missing fuel to your scales weight and moment. Unusable fuel is part of the empty/basic weight but is not easily achieved while defueling. One cannot realistically ask a pilot to fly until the engines are starved for fuel (unusable fuel condition) and then land.  A defuel which was done incorrectly will make a big difference from our achieved weight and CG vs. our calculated weight and CG. 

Equipment used in hangars in close proximity to aircraft have increased safety standards to prevent the possibility of fire and explosions. This requirement can be met with the proper certified equipment, such as Intercomp’s intrinsically safe certified platform scales, which meet the international safety requirements for use in hangars with fuel present. Since the aircraft will probably not be weighed again until the next big modification or complete paint, using the correct equipment and procedures to prepare and weight the aircraft will maintain as much safety and accuracy as possible.

Learn more about Weight & Balance Training.

 
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