AIRWORTHINESS INFORMATION BULLETIN
U.S. Department of Transportation
Federal Aviation Administration
March 25, 2020
This is information only. Recommendations
This Special Airworthiness Information Bulletin (SAIB) advises gas
turbine-powered aircraft and engine manufacturers, aircraft operators,
fixed-base operators (FBOs), FAA repair stations, flight standards
district offices, and other civil aviation authorities of the recent
developments regarding the use of aviation fuel biocides and adverse
engine operating conditions that have resulted from its use. The
recommendations in this bulletin provide general guidance on the use of
Kathon FP1.5 and Biobor JF biocide jet fuel additives that can be used
to supplement existing original equipment manufacturer procedures.
While the airworthiness concern is not an unsafe condition that would
warrant airworthiness directive (AD) action for every aircraft and
engine combination, under Title 14 of the Code of Federal Regulations
(14 CFR) part 39, some individual AD action may be necessary on certain
aircraft engine combinations.
FAA approved aviation fuel operating limitations may be listed in the
product’s aircraft flight manual, type certificate data sheet (TCDS),
installation manual, service instructions or manuals, or as limitations
associated with a supplemental type certificate. Many of the fuel
specifications allow for the use of a biocide to control
microbiological growth in the fuel system of the aircraft. The two most
common biocides in use today are Kathon FP1.5 and Biobor JF.
Microbiological contamination is caused by micro-organisms (bacteria,
molds, yeasts) that grow in water and feed off the hydrocarbons in the
fuel. Good housekeeping to prevent water accumulation in the fuel tanks
is the most effective means to prevent this contamination. In case
microbiological contamination is detected and needs to be treated with
biocides, all maintenance personnel, aircraft owners and operators are
expected to follow up-to-date instructions in the engine and aircraft
manufacturer’s Aircraft Maintenance Manuals (AMMs) to ensure that the
correct method and dosage is applied. In case of discrepancies, e.g.
due to different update cycles of aircraft documentation, the
manufacturer should be contacted for further advice.
In engines and aircraft where biocides are approved for use, the
manufacturers provide procedures in their AMMs for the application of
these biocides into the aircraft fuel tanks. Several recent events have
been documented showing adverse engine effects on the ground and
in-flight after application of a biocide treatment of the aircraft. Two
of these events were the result of overdosing the fuel system beyond
the recommended dosage, however, one event has shown no evidence of
misapplication. While lack of clarity of the AMM procedures, or lack of
adherence to those procedures by the maintenance personnel, may have
contributed to the overdosing events, evidence suggests that some
engine models are more sensitive to Kathon FP1.5 concentration than
As a result, DuPont, the manufacturer and distributor of Kathon FP1.5,
has recommended discontinuing the use of Kathon FP1.5 for
aviation-related products. General Electric is also taking measures to
remove Kathon FP1.5 from the approved fuels additives across all their
engine products while additional testing is being conducted. This SAIB
provides recommendations in response to these recent events and notes
publications for the proper continued use of biocide in fuel for
products for which it is approved.
- Operators should consult
their Aircraft Flight Manuals (AFMs), AMMs, the latest service
documents, and communications from the manufacturers of their engines
and aircraft to determine which biocide additives are approved for use
on their aircraft and engines and adjust their procedures to reflect
the latest approvals.
- Gas turbine powered engine
and aircraft manufacturers and operators should review current biocide
application procedures and practices and consider the following
- Aircraft fuel tanks should have the following minimum volume of fuel upon completion of biocide treatment:
- 1/3 of tank volume for
the initial treatment of a tank with confirmed biological
contamination. This may be increased if the aircraft is not limited by
fuel weight for its intended mission.
- 100% of tank volume for a second treatment of a tank with confirmed biological contamination (if necessary).
- 10% of tank capacity for preparing aircraft for storage.
- The additive should be applied to an aircraft fuel tank as follows:
- For aircraft equipped
with underwing pressure refueling capability, the additive should be
injected with a metered injection cart at the concentration levels
shown in Table 1. The injection cart should be equipped with a
graduated additive vessel to allow the determination of the volume of
additive injected during a biocide servicing.
- For all other aircraft,
a means should be provided to blend the biocide additive into the jet
fuel upstream of a pump and/or filtering system prior to loading into
the aircraft fuel tank. This can be accomplished by blending the
biocide additive into a refueling vehicle or separate fuel tank and
then pumping the fuel into the aircraft.
- The resulting
concentration of biocide additive in the aircraft fuel tank should not
exceed the levels shown in Table 1. Prior to treatment, care should be
taken to account for residual biocide levels that exist in the tank,
either from previous treatments or from the fuel supplier.
- For each application of an approved biocide additive, record the following information:
- Type of biocide used
- Quantity of fuel in the aircraft tank before additive injection
- Quantity of fuel uplifted into the tank when injecting the biocide additive
- Quantity of fuel in the tank after injection of the biocide additive
- Quantity of biocide additive injected for each application
Maximum Recommended Concentrations in Jet Fuel
|Maximum Concentration of Biocide Additive in Uplifted Fuel
|Maximum Concentration of Biocide Additive in Aircraft Fuel Tank after Biocide Injection
||0.100 ml/L 3
- Operators, Repair Stations,
and FBOs should review their procedures, training requirements, and
training records of persons charged with adding biocide to affected
aircraft. They should also verify that their biocide application
procedures are consistent with those provided in the manufacturer's
AMM, and that maintenance personnel are adhering to those procedures.
- Operators and FBOs should
keep detailed records of any biocides applied to fuel farms and
uploaded to aircraft such that the proper end dosage can be determined
based on the fuel supplied.
- Operators should review
their records for potential unreported cases of fuel control damage or
contamination that may be the result of biocide contamination. If any
cases are found, they should be reported to the engine and aircraft
- Procedures for decontaminating fuel systems on aircraft should also consider:
- Maximum biocide concentration permitted in uplifted fuel and in the fuel in the aircraft tank are clearly specified.
- Proper quality controls
are included in the process such that real-time calculation are not
required by the crew trying to perform the decontamination tasks.
- Necessary caution
statements and warnings for administering any fuel additive that can
overdose the fuel system and cause hazardous engine effects are
- Environmental regulations
may restrict the use of certain aviation jet fuel biocides in some
localities. The FAA recommends that the engine and aircraft
manufacturers ensure that adequate procedures are in place to prevent
biological contamination of aircraft fuel tanks using alternative means
other than the restricted biocide.
- Engine and aircraft
manufacturers should survey their operators who may have experienced
biocide contamination of engine fuel system components and report the
results to their appropriate airworthiness authority.
For Further Information Contact
- Flight Standards Inspectors
and airworthiness authorities should focus audit activities on the
proper application of all biocides. Pay particular attention to those
steps that ensure the proper concentration of additive is blended into
Mark Rumizen, Senior Technical Specialist, AIR-600, Aircraft
Certification Service, 1200 District Avenue, Burlington, MA 01803;
phone: 781-402-4609; email: firstname.lastname@example.org.
1 0.135 ml of Kathon FP1.5 per liter of jet fuel is equal to 135 parts per million (ppm) by volume.
2 0.269 ml of Biobor JF per liter of jet fuel is equal to
269 parts per million (ppm) by volume (also equivalent to 364 ppm by
weight based on a minimum density jet fuel)
3 0.100 ml of Kathon FP1.5 per liter of jet fuel is equal to 100 parts per million (ppm) by volume.
4 0.199ml of Biobor JF per liter of jet fuel is equal to 199
parts per million (ppm) by volume (also equivalent to 270 ppm by weight
based on a minimum density jet fuel)