Fuel System Icing Inhibitor
Encyclopedia
Fuel system icing inhibitor (FSII) is an additive to aviation fuel
s that prevents the formation of ice in fuel lines. FSII is sometimes referred to by the registered, genericized trademark
Prist. Jet fuel can contain a small amount of dissolved water
that does not appear in particulate form. As an aircraft gains altitude, the temperature drops and Jet fuel's capacity to hold water is diminished. Particulate water can separate out and could become a serious problem if it freezes in fuel lines or filters, blocking the flow of fuel and shutting down an engine
.
. http://www.csdinc.org/prist/faq2.html
FSII retards the growth of microorganisms eventually present in the fuel, mostly Cladosporium resinae fungi and Pseudomonas aeruginosa
bacteria, known as "hydrocarbon utilizing microorganisms" or "HUM bugs", which live in the water-fuel interface of the water droplets, form dark, gel-like mats, and cause microbial corrosion
to plastic and rubber parts.
EGMME had been certified as a pesticide
by the EPA, but as the requirement changes raised the certification costs, DEGMME has no official pesticide certification. DEGMME is a potent solvent
, and at high concentrations can damage fuel bladders and filters. Long-term storage of FSII-fuel mixtures is therefore not recommended.
Anhydrous isopropyl alcohol
is sometimes used as an alternative.
as it is pumped into the aircraft. The mixture of FSII must be between 0.10% and 0.15% by volume for the additive to work correctly, and the FSII must be distributed evenly throughout the fuel. Simply adding FSII after the fuel has been pumped is therefore not sufficient. As aircraft climbs after takeoff, the temperature drops, and any dissolved water will separate out from the fuel. FSII dissolves itself in particulate water preferentially over the jet fuel, where it then serves to depress the freezing point
of water to -43°C. Since the freezing point of jet fuel itself is usually in this region, the formation of ice is now a minimal concern.
Large aircraft do not require FSII as they are usually equipped with electric fuel line heaters that keep the fuel at an appropriate temperature to prevent icing. However, if the fuel heaters are inoperable, the aircraft may be still be declared fit to fly, if FSII is added to the fuel.
allow FSII injection to be turned on or off so that one fuel truck can service planes that do require FSII as well as planes that don't. Line crew, however, must be able to deliver FSII when it is needed.
Such necessity was illustrated when a Flight Options Beechjet
experienced a double flameout
over the Gulf of Mexico
in July 2004. The crew was able to glide to a lower altitude and restart the engines, and the aircraft landed safely. The FAA
investigators found no mechanical problems with the engines, but when fuel samples were taken, FSII concentration was only 0.02%. Either the FSII injector in the refueler was not working at the FBO where the aircraft had received fuel, or the line staff failed to turn it on.
Aviation fuel
Aviation fuel is a specialized type of petroleum-based fuel used to power aircraft. It is generally of a higher quality than fuels used in less critical applications, such as heating or road transport, and often contains additives to reduce the risk of icing or explosion due to high temperatures,...
s that prevents the formation of ice in fuel lines. FSII is sometimes referred to by the registered, genericized trademark
Genericized trademark
A genericized trademark is a trademark or brand name that has become the colloquial or generic description for, or synonymous with, a general class of product or service, rather than as an indicator of source or affiliation as intended by the trademark's holder...
Prist. Jet fuel can contain a small amount of dissolved water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
that does not appear in particulate form. As an aircraft gains altitude, the temperature drops and Jet fuel's capacity to hold water is diminished. Particulate water can separate out and could become a serious problem if it freezes in fuel lines or filters, blocking the flow of fuel and shutting down an engine
Engine
An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...
.
Chemical composition
Chemically, FSII is an almost pure (99.9%) ethylene glycol monomethyl ether (EGMME, 2-methoxy ethanol, APISOLVE 76, CAS number ), or glycol monomethyl ether since 1994 diethylene (DEGMME, 2- (2-methoxy ethoxy) ethanol, APITOL 120, methyl carbitol, CAS number ). http://www.advancepetro.com/fsii.htm Prior to 1994, Prist was regulated under the MIL-I-27686E standard, which specified use of EGMME, but subsequently came under the MIL-DTL-85470B, with use of less hazardous DEGMME with higher flash pointFlash point
The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source...
. http://www.csdinc.org/prist/faq2.html
FSII retards the growth of microorganisms eventually present in the fuel, mostly Cladosporium resinae fungi and Pseudomonas aeruginosa
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...
bacteria, known as "hydrocarbon utilizing microorganisms" or "HUM bugs", which live in the water-fuel interface of the water droplets, form dark, gel-like mats, and cause microbial corrosion
Microbial corrosion
Microbial corrosion, also called bacterial corrosion, bio-corrosion, microbiologically-influenced corrosion, or microbially-induced corrosion , is corrosion caused or promoted by microorganisms, usually chemoautotrophs...
to plastic and rubber parts.
EGMME had been certified as a pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
by the EPA, but as the requirement changes raised the certification costs, DEGMME has no official pesticide certification. DEGMME is a potent solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
, and at high concentrations can damage fuel bladders and filters. Long-term storage of FSII-fuel mixtures is therefore not recommended.
Anhydrous isopropyl alcohol
Isopropyl alcohol
Isopropyl alcohol is a common name for a chemical compound with the molecular formula C3H8O. It is a colorless, flammable chemical compound with a strong odor...
is sometimes used as an alternative.
Purpose
FSII is an agent that is mixed with jet fuelJet fuel
Jet fuel is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is clear to straw-colored in appearance. The most commonly used fuels for commercial aviation are Jet A and Jet A-1 which are produced to a standardized international specification...
as it is pumped into the aircraft. The mixture of FSII must be between 0.10% and 0.15% by volume for the additive to work correctly, and the FSII must be distributed evenly throughout the fuel. Simply adding FSII after the fuel has been pumped is therefore not sufficient. As aircraft climbs after takeoff, the temperature drops, and any dissolved water will separate out from the fuel. FSII dissolves itself in particulate water preferentially over the jet fuel, where it then serves to depress the freezing point
Freezing Point
Freezing Point is a news journal in the People's Republic of China which has been the subject of controversy over its criticism of Communist Party officials and the sympathetic ear it lent to a Chinese historian who had criticized official history textbooks...
of water to -43°C. Since the freezing point of jet fuel itself is usually in this region, the formation of ice is now a minimal concern.
Large aircraft do not require FSII as they are usually equipped with electric fuel line heaters that keep the fuel at an appropriate temperature to prevent icing. However, if the fuel heaters are inoperable, the aircraft may be still be declared fit to fly, if FSII is added to the fuel.
Storage and dispensing
It is extremely important to store FSII properly. Drums containing FSII must be kept clean and dry, since the additive is hygroscopic and can absorb water directly from moisture in the air. Since some brands of FSII are highly toxic, a crew member must wear gloves when handling it undiluted. Many FBOsFixed base operator
A Fixed-base operator or commonly abbreviated FBO is a term developed in the United States after the passage of the Air Commerce Act of 1926...
allow FSII injection to be turned on or off so that one fuel truck can service planes that do require FSII as well as planes that don't. Line crew, however, must be able to deliver FSII when it is needed.
Such necessity was illustrated when a Flight Options Beechjet
Raytheon Hawker 400XP
|-See also:-References:*Field, Hugh and Hurst, Mike. "". Flight International, 30 September 1978, pp. 1261–1266.*Taylor, John W.R. . Jane's All The World's Aircraft 1988-89. Coulsdon, UK: Jane's Defence Data, 1988. ISBN 0 7106-0867-5....
experienced a double flameout
Flameout
A flameout refers to the failure of a jet engine caused by the extinction of the flame in the combustion chamber. It can be caused by a number of factors, including fuel exhaustion; compressor stall; insufficient oxygen supply; foreign object damage ; severe inclement weather; and mechanical...
over the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
in July 2004. The crew was able to glide to a lower altitude and restart the engines, and the aircraft landed safely. The FAA
Federal Aviation Administration
The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
investigators found no mechanical problems with the engines, but when fuel samples were taken, FSII concentration was only 0.02%. Either the FSII injector in the refueler was not working at the FBO where the aircraft had received fuel, or the line staff failed to turn it on.