Fuel System Independence Fuel System Lightning Protection 14-2 Figure 14-2.  Lightning streamering at the wingtips of a jet fighter. Figure 14-1.  Aircraft fuel systems must deliver fuel during any  maneuver for which the aircraft is certified. Each fuel system for a turbine engine powered airplane  must meet applicable fuel venting requirements. 14 CFR  part 34 outlines requirements that fall under the jurisdiction  of the Environmental Protection Agency (EPA). A turbine  engine fuel system must be capable of sustained operation  Each fuel system must be constructed and arranged to ensure  fuel flow at a rate and pressure established for proper engine  and auxiliary power unit (APU) functioning under each likely  operating condition. This includes any maneuver for which  certification is requested and during which the engine or  APU may be in operation.  [Figure 14-1]  Each fuel system  must be arranged so that no fuel pump can draw fuel from  more than one tank at a time. There must also be a means to  prevent the introduction of air into the system. Title 14 of the CFR, part 23, Normal, Utility, Acrobatic,  and Commuter Category Airplanes, section 23.2430, Fuel  Systems, is summarized below. Airworthiness standards  specified for air carrier and helicopter certification are  similar. Although the technician is rarely involved with  designing fuel systems, a review of these criteria gives insight  into how an aircraft fuel system operates.  The fuel system must be designed and arranged to prevent  the ignition of the fuel within the system by direct lightning  strikes or swept lightning strokes to areas where such  occurrences are highly probable, or by corona or streamering  at fuel vent outlets. A corona is a luminous discharge  that occurs as a result of an electrical potential difference  between the aircraft and the surrounding area. Streamering  is a branch-like ionized path that occurs in the presence of a  direct stroke or under conditions when lightning strikes are  imminent.  [Figure 14-2]  Additional information is found in 14 CFR part 33. It  addresses airworthiness standards for engines and pertains  mainly to engine fuel filter and intake requirements. Each fuel system must be designed and arranged to provide  independence between multiple fuel storage and supply  systems so that failure of any one component in one system  will not result in loss of fuel storage or supply of another  system. throughout its flow and pressure range even though the fuel  has some water in it. The standard is that the engine continues  to run using fuel initially saturated with water at 80 °F having  0.75 cubic centimeters (cm) of free water per gallon added  to it and then cooled to the most critical condition for icing  likely to be encountered in operation. Each Federal Aviation Administration (FAA) certified aircraft  is designed and constructed under regulations applicable to  that type of aircraft. The certification airworthiness standards  are found in 14 CFR as follows:  14 Part 23—Normal, Utility, Acrobatic, and Commuter Category Airplanes 14 Part 25—Transport Category Airplanes 14 Part 27—Normal Category Rotorcraft 14 Part 29—Transport Category Rotorcraft 14 Part 31—Manned Free Balloons