During refueling or defueling, tank vehicles shall be so placed as to be readily removable in event of fire so as to permit direct driving away from the loading or fueling position. Not more than one refueler shall be positioned to refuel each wing of an aircraft and not more than two refuelers shall be positioned to serve the same aircraft. When high capacity aircraft are refueled additional refuelers shall not be parked or positioned within 100 feet from the aircraft served and then only in areas approved by the manager.