disappears at the bottom, air is present. If the cloud disappears at the top, water is present. If the cloud does not begin clearing in a few minutes, it is due to entrained water or very fine particulate matter. Do NOT use any fuel containing a cloud that does not disappear in a few minutes after it is drawn or use a fuel containing any visible water to fuel an aircraft. 3. The third check should be for sediment. Swirl the sample so a vortex is formed. All sediment that has settled accumulates on the bottom of the bottle directly beneath the vortex. At the most, the total sediment should be only a point or spot of silt. In a quart sample, the sediment should be no more than a slight smudge if picked up on a fingertip. Coarse contamination can be detected visually. Sediment in the fuel is visible when the particles are 40 microns or larger. Groups of particles less than 5 microns in size may be seen in the fuel when viewed at a right angle to a strong light. When a fuel sample is being inspected, it should be swirled and allowed to settle for a few moments. The coarse particles settle to the bottom center of the bottle and collect in a group. Any sediment that can be seen is too much for aircraft use. The AEL Free Water Detector should be used to determine the presence of free water above the allow- able limit (for aircraft) of 5 ppm. Free water at this level of contamination mayor may not be visible to the naked eye. Fuel that is contaminated by commingling with another petroleum product is hard to detect visually. In gasoline, if the percentage of the other petroleum is fairly high, there may be a color change. JP-5 contami- nated by JP-4, or vice versa, can be detected by a test for flash point and a laboratory test for distillation. Results If any contamination is discovered during the vis- ual inspection procedure, stop the fueling operation immediately and notify the pilot of the aircraft, the fuels officer, or other designated person in charge as to the condition of the fuel. Action A contaminated sample should be suitably tagged and retained until it is determined that a laboratory analysis of the sample is not required. When any contamination is found, another sample should be taken, preferably in a new sample container. Take care to ensure that the container is thoroughly clean before drawing the sample. Once contamination is found and the system placed out of use, a check must be mad for the source and cause of the contamination and the cause corrected before the system is placed in use again. The type of contamination discovered usually gives a clue to the source and cause. Some of these indications are as follows: 1. Mixed or commingled fuels—The valve or blank flange is open between two different systems or there is a leak through a bulkhead where two tanks containing different fuels are adjacent. 2. Water—The filter/separator elements are rup- tured or contaminated. Large amounts of water also indicate that the filter/separator float control valve was not operating and water stripping operations for the service tanks were inadequately performed. 3. Sediment and microbiological growth—The fil- ter/separator elements are ruptured or contaminated. Large amounts of sediment or microbiological growth also would indicate that the storage tanks and service tanks need cleaning. CONTAMINATED FUEL DETECTING EQUIPMENT The equipment used in the lab is portable but only to the extent that it may be earned from one area to another. You cannot carry it around with you for daily use. It is better to describe it as movable even though PMS electrical safety checks require it to be listed as portable equipment. A good fuels lab has the following facilities: good ventilation, hot and cold water to wash bottles, and a bottle drying rack. Bottle drying racks can be bought commercially, but most are constructed locally. See figure 3-4. The combined contaminated fuel detector (CCFD) is a single unit that contains both the AEL Mk I and AEL Mk III. Many stations and ships have both the CCFD and the single units. The AEL Mk II is the same as the Mk I except it has a carrying handle, The AEL Mk I and Mk II are used to measure water contamination, and the AEL Mk III is used for sediment detection. The closed cup flash-point tester is used to determine the flash point of jet fuels. The flash-point tester is not to be used to test gasoline products. The refractometer indicates the amount of 3-14