Page 33 - Volume 12 Number 1

deposits will flow through the aircraft fuel system and may accumulate on filters, fuel metering components, other fuel system components, or engine fuel nozzles. The deposits may also settle in the fuel tanks or other areas of the aircraft fuel system where they may potentially become dislodged over time and accumulate downstream in the fuel system as described. Several of the identified airplanes have already experienced clogged fuel filters and fuel nozzle deposits that lead to service difficulties and unplanned diversions.
The crystalline deposits are not soluble in fuel, so they cannot be removed by flushing the airplane fuel system with jet fuel. The deposits are soluble in methanol and other polar solvents, but use of these chemicals may have adverse consequences on airplanes and engine fuel system materials. Consequently, OEMs should be contacted to develop inspection techniques and corrective maintenance actions appropriate for each specific aircraft model type.
Jet fuel that has been contaminated with DEF no longer meets the aviation fuel operating limitations of airplanes certificated to operate on Jet A fuel, and therefore cannot be used on those airplanes. Jet fuel that has been removed from airplanes listed should be downgraded to other non–aviation fuel grades and not used on airplanes in the future.
The FAA is monitoring the situation to determine if additional action is required. We are requesting that any service difficulties and maintenance and inspection findings on the aircraft identified be reported to us in support of this effort.
Recommendations
The FAA recommends the following:
1. Owners or operators of airplanes identified contact their airplane, engine, and APU OEMs to determine the appropriate inspections and maintenance actions to remove urea-based crystalline deposits from the fuel system. This may include the removal and replacement of fuel system parts or components affected by exposure to these deposits.
2. Owners or operators of airplanes identified report to the FAA any service difficulties (including fuel filter bypass and clogging incidents), fuel system repairs, and fuel system inspection results related to the presence of these urea-based crystalline deposits.
3. Jet fuel suspected of being contaminated with DEF that has been removed from the airplanes listed be downgraded to other non-aviation fuel grades, and not be used on airplanes.
Paperwork Reduction Act Burden Statement: A
federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to a penalty for failure to comply with a
JANUARY 2018
collection of information subject to the requirements of the Paperwork Reduction Act unless that collec- tion of information displays a currently valid OMB Control Number. The OMB Control Number for this information collection is 2120-0731. Public reporting for this collection of information is estimated to be approximately five minutes per response, including the time for reviewing instructions, searching exist- ing data sources, gathering and maintaining the data needed, completing and reviewing the collection of information. All responses to this collection of infor- mation are voluntary. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to the FAA at: 800 Independence Ave. SW, Washington, DC 20591, Attn: Information Collection Clearance Officer, ASP-110.
For Further Information Contact
Mark Rumizen, Senior Technical Specialist, FAA, 12 New England Executive Park, Burlington, MA 01803; phone: (781) 238-7113; mobile: (781) 402-4609; fax: (781) 238-7199; email: mark.rumizen@faa.gov.
The above information is abbreviated for space purposes. For the entire communication,
go to www.txtavsupport.com.
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