Katerina Swanson
Jet fuel is a type of aviation fuel used in aircraft powered by gas-turbine engines. It is typically straw-coloured or colourless and is composed of a variety of hydrocarbons. Jet fuel is susceptible to water contamination, which can cause issues during flight as the water droplets can freeze and block fuel inlet pipes. The acceptable limit of water contamination in jet fuel is considered to be 30 parts per million (ppm). This limit is set to prevent potential issues caused by water freezing in fuel lines and blocking fuel inlet pipes. While complete removal of water from jet fuel is impractical, measures such as fuel heaters are employed to prevent water freezing.
Characteristics and Values of Water in Jet Fuel
| Characteristics | Values |
|---|---|
| Maximum water contamination | 30ppm |
| Fuel check methods | ATA 103, EI 1530, GOST 10227 (Russia) |
| Water detection methods | Water-sensitive filter pad, visual check, ASTM standard D3948 test |
| Water in jet fuel exhaust | 1.23 kg water per kg of kerosene fuel |
| Water in jet fuel exhaust (gasoline) | 1.17 kg water per kg of fuel |
| Water in jet fuel exhaust (other estimates) | 1/4oz of water per pound of fuel, 1:50 ratio by volume |
| Water in jet fuel exhaust (747 plane) | 20lbs of water per second |
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What You'll Learn
Water contamination in jet fuel
Additionally, water provides an ideal environment for microbial growth, which is one of the leading causes of engine shutdowns, engine failures, and fuel filter plugging. Microorganisms, such as bacteria, yeasts, and fungi, can form solid debris that clogs fuel filters and produce acidic by-products that accelerate metal corrosion. The accumulation of water in jet fuel can also affect the fuel's performance and increase maintenance costs.
To address water contamination, the aviation industry has implemented various detection methods and standards. Visual inspections can identify high concentrations of water, as the fuel's appearance may become hazy. The water tablet test is a commonly used method for detecting water in jet fuel. Additionally, the industry has set standards for acceptable levels of water contamination, with 30 ppm (parts per million) considered the maximum allowable limit for commercial jet fuel.
To mitigate the risks associated with water contamination, fuel heaters are used on commercial aircraft to prevent water in the fuel from freezing. Biocides, such as Biobor JF, are also employed to eradicate microbial growth and maintain sterile fuel systems. Regular use of biocides at maintenance dosages is crucial for effective prevention and maintenance.
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Jet fuel testing methods
Water is a common contaminant in jet fuel, and even small quantities can lead to rust, corrosion, and engine malfunction. Water contamination in jet fuel can be detected in several ways, and it is important to do so to avoid costly consequences.
Water Tablet Test
The water tablet test is the most common method for detecting water in jet fuel. It indicates whether the water in the fuel is above or below 30 ppm, the maximum allowed limit.
CFU, ATP, and Immunoassay Antibody Tests
These tests are used to detect microbial contamination in jet fuel. The CFU method requires sending fuel off-site for testing, which can take up to 10 days. ATP tests require a laboratory and special equipment, while immunoassay antibody tests can be done on-site with little training and provide results in 10-15 minutes.
CASRI Water Detector Capsules
These capsules can be used to rapidly and sensitively indicate the presence of free water in jet fuels at handling temperature. They are available in different types, dimensions, grips, and materials, such as aluminium and copper.
Visual Inspection
A simple visual inspection of jet fuel can also help detect water contamination. The fuel should be checked against a white backdrop and illuminated from the side to easily detect its colour and any debris or contaminants. Water in the fuel may appear as ice crystals that slowly precipitate to the bottom of the sample.
Touch Test
By pouring a small amount of fuel onto your finger, you can detect water contamination. Avgas evaporates quickly and leaves a cool feeling, while water evaporates more slowly and leaves an oily residue.
Odour
Odour can also be an indicator of water contamination in jet fuel. Jet fuel has a distinct kerosene smell, while water may carry a slight avgas odour if it has been in contact with avgas.
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Jet fuel and water vapour
Jet fuel, or aviation turbine fuel (ATF), is a type of aviation fuel designed for aircraft powered by gas-turbine engines. It is typically straw-coloured or colourless. Jet A and Jet A-1 are the most commonly used jet fuels for commercial aviation. Jet B is another type of jet fuel that is used for its enhanced performance in cold weather.
Water is a common contaminant in jet fuel. During flight, the temperature of the fuel tanks decreases due to low temperatures in the upper atmosphere, causing the precipitation of dissolved water from the fuel. As water is denser than fuel, it drops to the bottom of the tank and can form droplets that may freeze, resulting in blocked fuel inlet pipes. The British Airways Flight 38 accident was caused by this phenomenon.
To prevent issues caused by water contamination, commercial aircraft use fuel heaters to stop water in the fuel from freezing. There are also methods to detect water in jet fuel, such as a visual check for high concentrations of suspended water, which would cause the fuel to appear hazy. An industry-standard chemical test uses a water-sensitive filter pad that turns green if the fuel exceeds 30 parts per million (ppm) of free water, which is the specification limit. For military use, the accepted value is 15 ppm, while civil aviation fuel should not exceed 30 ppm.
Regarding the amount of water vapour produced by jet fuel, there is no definitive answer. One source suggests that for every pound of jet fuel burned, approximately 1/4 oz of water vapour is produced. However, another source states that the ratio of water vapour to fuel is subject to change due to variations in altitude and temperature. Additionally, other factors such as the type of fuel and the stage of flight can impact the amount of water vapour produced, with takeoff having a higher fuel burn rate than cruise.
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Jet fuel freezing
Jet fuel is a mixture of various hydrocarbons, including alkanes, naphthenes, and aromatic hydrocarbons. The most commonly used jet fuels for commercial aviation are Jet A and Jet A-1, which are produced according to international specifications. Jet B is another type of jet fuel that is used for its improved performance in cold weather. Jet fuel is defined by its performance specifications, such as freezing point and smoke point, rather than as a chemical compound due to variations in composition based on the petroleum source.
Jet fuel has a freezing point of -40°C, although it will not freeze instantly at this temperature. The time it takes for jet fuel to freeze is influenced by several factors, including the initial fuel temperature and the outside temperature. Warmer fuel will take longer to freeze, so fuel from a plane taking off from a warmer location like South Florida will take longer to freeze than fuel from a plane taking off from a colder location like Siberia. The movement of the plane also plays a role in preventing the fuel from freezing as the motion agitates the molecules.
To prevent jet fuel from freezing, aircraft employ various methods to heat the fuel. Some aircraft are designed with hydraulic lines close to the fuel to provide heat, while other models constantly pump the fuel to keep it in motion and at a higher temperature. Fuel heaters are also used on commercial aircraft to prevent water in the fuel from freezing and causing blockages. The presence of water in jet fuel is a common form of contamination, and it can freeze and block fuel inlet pipes if it is not addressed. The maximum acceptable level of water contamination in jet fuel is 30 ppm, and various methods are used to detect and mitigate this issue.
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Jet fuel combustion
Jet fuel, or aviation turbine fuel (ATF), is a type of aviation fuel designed for aircraft powered by gas-turbine engines. Jet A, Jet A-1, and Jet B are the most commonly used jet fuels in civilian aviation. Jet fuel is a mixture of various hydrocarbons, and its exact composition varies based on its petroleum source. As a result, jet fuel is defined by its performance specifications, such as freezing and smoke points, rather than as a chemical compound.
The combustion of jet fuel has been the subject of several studies due to concerns about its impact on human health and the environment. The combustion of jet fuel releases various compounds, including CO2, H2O, CO, C, NOx, particles, and organic compounds. While jet engines do not appear to emit halogenated compounds or heavy metals, they do release toxicologically relevant compounds, including carcinogens.
The health effects of jet fuel combustion products have been studied in both humans and animals. These studies have assessed the biological and health effects of exposure to jet fuel combustion products, including kerosene-based jet fuels and their performance additives. The impact of jet fuel combustion on airport workers and communities living near airports has been a particular focus, with evidence suggesting that soot nanoparticles from incomplete combustion can have cytotoxic effects and contribute to global warming.
To address the environmental and health concerns associated with jet fuel combustion, efforts have been made to reduce soot emissions. One method involves injecting N2 containing O2 at the exhaust of enclosed spray combustion to emulate aircraft soot emissions. By increasing the concentration of O2, oxidation is enhanced, and soot emissions from jet fuel combustion are nearly eliminated. Additionally, the use of blends of jet fuel with bio-based or synthetic fuels has been explored to reduce soot emissions and their impact on the environment and public health.
In summary, jet fuel combustion releases a variety of compounds, including toxic and carcinogenic substances, which have raised concerns about their impact on human health and the environment. Studies have focused on understanding the biological and health effects of exposure to jet fuel combustion products, and efforts are being made to reduce soot emissions and mitigate their negative consequences.
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Frequently asked questions
Jet fuel, or aviation turbine fuel (ATF), is a type of aviation fuel designed for aircraft powered by gas-turbine engines.
Water contamination in jet fuel can lead to issues such as fuel freezing and blockages in fuel inlet pipes.
The International Air Transport Association (IATA) has set a limit of 30 ppm (parts per million) of undissolved (free) water for Jet A and Jet A-1 fuels.
The amount of water produced depends on the type of fuel. For gasoline, it is about 1.17 kg of water per kg of fuel, while for kerosene, it is approximately 1.23 kg of water per kg of fuel. Additionally, a 747 jet may burn 20 pounds of water per second during takeoff.
