SUMMARY OF CHARACTERISTICS OF FUELS In summary, it is important that you remember the following characteristics of fuels: —From the standpoint of fire, explosion, and health, gasolines, JP-4, and JP-8 are extremely hazard- ous and must be handled with equal caution. JP-5 jet fuel is safer, with respect to possible explosions and poisoning. However, the potential hazards of fire from fuel-soaked rags and waste and of skin blistering from soaked clothing must not be ignored. —Jet engine fuels and gasolines are designed for entirely different types of engines. Therefore, the proper fuel must be used for each type of engine. QUALITY SURVEILLANCE LEARNING OBJECTIVES: Describe the prob- lems caused by fuel contamination. State the types and limits of fuel contaminants. Describe the equipment used and explain the correct operating procedures in testing for fuel con- tamination. The major objective of fuel-handling personnel is to deliver fuel to aircraft, clean and free of water. The complex fuel systems of modem aircraft do not func- tion properly if the fuel is contaminated with dirt, rust, water, or other foreign matter. Even very small quan- tities of dirt or solid matter can plug or restrict fuel metering orifices and accelerate the clogging of fuel filters. Very small quantities of water are also harmful since ice may form in aircraft tanks at high altitudes. Ice affects orifices, controls, and filters like dirt. The complete stoppage of fuel flow by ice or dirt causes engine failure, and partial stoppage causes poor engine performance. PROBLEMS CAUSED BY FUEL CONTAMINATION Contaminated fuel has caused aircraft accidents with a tragic loss of life, loss of valuable aircraft, and the grounding of entire squadrons. This means that clean fuel is a LIFE-OR-DEATH matter with aviation personnel. The lesson has been learned the hard way by too many, and with fatal results. The time to be- come fuel conscious is NOW. ENGINE FAILURES Besides being deadly, contaminants can be sneaky. A certain type of emulsion resulting from the presence of water and rust particles can stick to the sides of an aircraft’s fuel cells and not be noticed. You can even drain out a sample of fuel and find no evidence of this deposit. It can continue to build up and part of it may wash off and pass through a strainer into a fuel control. There can be only one result, reduced power and, fi- nally, engine failure. Foreign particles so small they cannot be seen with the naked eye can cause damage in a jet engine. The fuel control of a jet engine is a masterpiece of engi- neering and craftsmanship. It automatically regulates fuel flow to compensate for changes in altitude and speed. It makes practical the piloting by human beings of incredibly powerful jet aircraft. But doing these things requires that the fuel control have precisely fitted meters and valves. The moving parts within some of these meters and valves have clearances of less than 0.005 of an inch. Particles of foreign matter only slightly larger than this clearance can jam the valve or prevent it from seating properly. Particles slightly smaller can stick and build up, or wedge between the parts. Thus, we must remove particles so small they can be seen only with a microscope. UNNECESSARY REPAIR WORK Fuel carrying water or dirt can cause a great deal of extra maintenance work. For example, in atypical Navy engine overhaul shop it became necessary at one time to completely disassemble every jet engine fuel control that came into the shop because of the chance of internal damage. Ordinarily, the controls that had been in use less than half of their overhaul time could have simply been bench-checked to verify their performance and then returned for use on the engine. However, experi- ence showed that more than 50 percent of the fuel controls overhauled had failed because of internal cor- rosion. The cause was water in the fuel. Such extra repair work is not confined to jet engines. Water in the fuel also can cause erroneous readings on the aircraft’s fuel quantity gages, which can be exceedingly danger- ous in flight. DELAYED FLIGHTS In addition to causing engine failures, fuel contami- nation can mean serious delays in flight operations. Normal procedure requires that all aircraft fueled from a source where contamination is discovered be checked. 3-5