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何况调查显示左右两个主油箱油料均符合国际通用标准,,,
Tests for the presence of water in the fuel
It was not possible to establish the condition of the fuel in the centre tank at the time of the accident as it had subsequently been grossly contaminated with fire fighting foam and water applied by the fire crews immediately following the accident.
A requirement in the fuel specification is that the fuel should be visually inspected to ensure that it is clear, bright and free of water and sediment. In addition to the appearance test, the Karl Fischer test, which uses a chemical method to establish the total amount of water (dissolved and entrained) in the fuel, was carried out on fuel samples taken from the left main tank sump, the APU fuel line and the right engine variable stator vanes.
With the exception of the samples taken from the engine fuel filters and housings, all the samples that were tested passed the appearance tests. The samples from the engine fuel filters and housings contained a small number of very small droplets of water. These droplets could have resulted from the ingress of fire fighting media through damaged engine components, or might have been free water, which naturally settles in these areas.
The Karl Fischer tests indicated that the total amount of water in the samples, dissolved and entrained, was below 40 ppm, which is a very low level.
During the inspection of G8209;YMMM approximately 0.25 and 0.1 ltr of free water was recovered from the left and right main fuel tanks respectively, from areas where it could not migrate to the tank sumps. It is normal for free water to collect in large aircraft fuel tanks, and this quantity was considered to be relatively low for a Boeing 777.
Ref: http://www.aaib.gov.uk/sites/aaib/cms_resources/G-YMMM%20Interim%20Report.pdf |
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