As part of an effort to develop technical information on the electrical charging characteristics of aircraft fuels and ground filtration equipment, the Coordinating Research Council (CRC) conducted an extensive study using the filtration equipment of the pipeline supplying J F. Kennedy Airport, New York. Relative charging tendencies of 10 different types and makes of coalescer and separator elements were obtained on the jet fuels being pumped to the airport. Fuel effects were eliminated as far as possible by simultaneously monitoring a “test” filter-separator and a “control” filter-separator, mounted in parallel. Over a 3-1/2 month period, 199 fuel batches totaling 154.2 million gallons were filtered and monitored. The results showed fuel characteristics to have the major effect on filter charging characteristics, as batch-to-batch variations were greater than differences between filters on an absolute basis. However, simultaneous side-by-side tests showed teflon-coated screen type separators to charge less than pleated paper separators. No relationships were found between charging rates and fuel properties, such as rest conductivity and fuel cleanliness.