the fuel lines to the engine(s) and may cause the engine(s) to lose power or stop operating.
(3) On aircraft having fuel tanks located in each wing, positioning of the fuel tank selector valve to the "Both On" position may not adequately drain the system because fuel will take the path of least resistance. In this case, the fuel selector valve should be positioned at each respective tank in turn, and the sump should be checked for water and drained of all water after each individual tank selection.
(4) During preflight, a generous sample of gasoline (10 ounces or more) should be drained into a transparent container from each of the fuel sumps and from the main fuel strainer or gascolator. Visually check the fuel sample for water and by the clean and bright test. Remember bright is dry. For jet fuel, the white bucket or steel bucket test 1s appropriate to check fuel for water.
Continue to drain fuel from the contaminated sump until certain the system is clear of all water. The use of quick-drain valves in the sumps and gascolators makes it easier to keep tanks free of significant quantities of water.
(5) At postflight, completely fill the fuel tanks to provide an effective method against contamination from condensation. However, this procedure may be only practical on a few types of aircrait, since the type of aircraft, length of proposed flight, number of passengers, and weight and balance limitations dictate
(6) During routine maintenance, in addition to the preflight and postflight procedures, certain precautionary or routine maintenance should be performed on an aircraft including the inspection and cleaning of fuel tank outlet finger stainers, carburetor screens (filters), and flushing of the carburetor
8. REPORTED PROBLEM AREAS AND RELATED INFORMATION.
a. Aircraft Fuel Tank Caps.
(1) Routine monitoring of the FAA service difficulty data bank revealed continuing failures of the vented fuel tank caps installed on aircraft.
(2) Reported failure causes include warpage, cracks, and obstructed vents. wenty tailures were reported as warped, broken, and leaking caps.
Aircrait have encountered problems with fuel siphoning from around the filler caps and problems with fuel cap vents.
(3) A review of data in the FAA accident/incident data system revealed that some emergency landings were made in which the fuel storage system was listed as a causal factor. In many of those emergency landings, vented fuel. caps were listed as a cause. The design of the vent opening allowed water to enter the fuel des fuel tanks. New types of vented fuel capswere designed for installation by the aircraft manufacturers to correct this problem. Information about these new design vented fuel caps can be found in the Aircraft Manufacturer's Service Bulletins.
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b. Fuel Tank Drains. Many airplanes are equipped with fuel reservoirs (separate tanks) in addition to the wing fuel tanks. On these airplanes, the fuel reservoirs, as well as the wing fuel tanks, should be checked for contamination when water or other contaminants are found in the fuel system. Refer to the appropriate owner's manual for fuel reservoir location and proper draining procedures. Additionally, manufacturers' service information can be referenced for installation of fuel tank quick drain-kits. These kits are now available for airplanes built between 1946 and 1974.
9. WATER CONTAMINATION. Normally, upon finding water contaminated fuel the procedures for removal of water outlined in this advisory circular should suffice.
Should contamination persist or any doubt exists as to water contamination, the advice is to have the aircraft fuel system inspected by a qualified person.
10. SUMMARY. The best insurance against a water-in-fuel problem, whether aviation gasoline or jet fuel, is a responsible fuel handling chain.
information and procedures outlined in this advisory circular as well as good inspection and housekeeping practices and constant vigilance should significantly reduce the possibility of an aircraft accident due to water-in-fuel contamination.
Milin here William T. Brennan Acting Director of Flight Standards Par 8