2006.13 Vehicle and equipment restrictions.
FC § 2006.13
During aircraft-fueling operations, only aircraft-fueling vehicles or other equipment actively involved in the fueling operation are allowed within 50 feet (15 240 mm) of the aircraft being fueled. Other aircraft-fueling vehicles or equipment are prohibited in this area until the fueling operation is complete. Exception: Aircraft-fueling operations utilizing single-point refueling with a sealed, mechanically locked fuel line connection and the fuel is not a flammable liquid.
