TITLE: Low-Density, Low-Volume Explosion Suppression Material for Aircraft Fuel Tanks
TECHNOLOGY AREA(S): Air
ACQUISITION PROGRAM: PMA-261
H-53 Heavy Lift Helicopters
OBJECTIVE: Develop a
lightweight fuel tank explosion suppressant that fits within a wide range of
aircraft fuel tank geometries, and is easily installed and removed.
DESCRIPTION: The Navy has two
Fuel Tank Explosion Suppression (FTES) methods operating within the fleet for
air vehicles: On Board Inert Gas Generating System (OBIGGS) and Explosion
Suppression Foam (ESF) [Refs 1, 2]. The OBIGGS protects the fuel tanks
internally by constantly generating inert gas (typically nitrogen) and
supplying it to the fuel tank ullage space to maintain an oxygen depleted
environment, thus suppressing an explosion. ESF (urethane foam) protects by
filling the fuel tank with reticulated foam and keeps a ballistically-induced
or electrical failure-induced flame front and explosion from propagating
throughout the fuel tank. Air vehicles use only one of these suppression
systems if vulnerability reduction is required due to the platform’s mission
ESF has a few practical limitations in the fleet. Routine maintenance of fuel
tanks requires that the ESF be removed until maintenance is complete, at which
point the ESF is reinstalled in the fuel tank. ESF is often difficult to remove
and reinstall, increasing the amount of time required for routine repairs and
time out of service for the air vehicle. The second limitation has to do with
the density and volume of ESF. The nominal density of ESF is 1.3 pounds per
cubic feet [Ref 1]. ESF can displace up to 2.5 percent of fuel by volume and
retain up to 2.5 percent of fuel by volume.
An innovative FTES material to replace ESF, while meeting the explosion
suppression performance properties, is needed. The new FTES material must not
displace more than one percent fuel volume, and must not retain more than one
percent fuel volume in any given fuel tank. The new FTES material must have a
uniform nominal density not to exceed 0.9 pounds per cubic foot and should
perform with JP-4, JP-5, JP-8, and commercial Jet A fuels (including military
additives (i.e., static dissipater additive, corrosion inhibitor/lubricity
improver, fuel system icing inhibitor, and may include antioxidant and metal
deactivators)) [Ref 11]. No toxicity hazard to personnel who maintain or come
in contact with the FTES material can occur [Ref 1]. Material color should be
uniform throughout and cannot be blue, orange, yellow, or red. It must be easy
to install and remove per SAE AIR 4170B [Ref 2] during routine maintenance for
a wide range of complex fuel tank geometries. There should be a 10-year
maintenance requirement to check and remove if necessary and a storage life of
3 years. All of the material must be removable during maintenance and no
foreign object debris (FOD) can detach from the FTES material. SAE AIR 4170B
[Ref 2] provides examples and diagrams of common obstacles that must be taken
into account during installation and removal of the new FTES material. These
obstacles include valves, pumps, pipes, and fuel inlets.
The developed material will be expected to pass several tests similar to those
detailed in MIL-F-87260 [Ref 1]. Uniform density will be tested using a
material specimen 3 inches (width) x 4 inches (height) x 10 inches (length).
The results will be reported to the nearest 0.1 pounds per cubic foot. Ten
locations on the specimen will be randomly chosen and the density will be
measured at those locations. Tear resistance will be tested in accordance with
ASTM D3574 Test F [Ref 5]. Fuel displacement will be tested at standard
conditions using a 1000 mL capacity cylinder filled to the 900 mL mark with
approved fuel. The material specimen will be cut to the diameter of the
cylinder and to the length of the 900 mL mark of the cylinder. Then the
specimen will be submerged in the fuel for 24 hours, to obtain maximum swelling
effects. The fuel level of the cylinder will then be measured for fuel
displacement. The fuel will be transferred to a second cylinder and measured to
determine fuel retention.
PHASE I: Develop a concept
for an innovative explosion suppression material that is low density and low
volume. Determine technical feasibility through demonstration of the material’s
proposed suppression capabilities. Produce plans for prototype development in
PHASE II: Develop and
demonstrate a prototype FTES capable of meeting desired suppression capabilities
and ease of installation and removal on representative air vehicle fuel tanks.
Validate, through testing, the ability of the new FTES material to meet the
qualification requirements including a uniform density test, tear resistance
test, and a fuel displacement test (see Description section above).
PHASE III DUAL USE
APPLICATIONS: Complete validation and verification of the FTES material.
Transition the technology for implementation on existing Navy air vehicle fuel
tanks. Lightweight fuel tank explosion suppression technology can transfer to
commercial aviation, automotive and transportation industries, providing
protection of tanks containing fuel, hazardous materials, and other liquids.
1. MIL-F-87260, Foam
Material, Explosion Suppression, Inherently Electrostatically Conductive, For
Aircraft Fuel Tanks. (07-FEB-1992). http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-F/MIL-F-87260_46748/
2. “Reticulated Polyurethane
Foam Explosion Suppression Material For Fuel Systems And Dry Bays.” Society of
Automotive Engineers, Inc. (SAE), SAE AIR 4170B. http://standards.sae.org/air4170b/
3. MIL-T-5624, Turbine Fuel,
Aviation, Grade JP-4, JP-5, and JP-5/JP-8 ST. (29-SEP-1992). http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-T/MIL-T-5624P_30850/
4. MIL-B-83054, Baffle and
Inerting Material, Aircraft Fuel Tank. (17-MAY-1998). http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-B/MIL-B-83054B_14045/
5. “Standard Methods of
Testing Flexible Cellular Materials - Slab, Bonded, and Molded Urethane Foams.”
American Society for Testing and Materials International, 1 December 2011, ASTM
6. “AC 25.981-1C - Fuel Tank
Ignition Source Prevention Guidelines.” Federal Aviation Administration (FAA),
September 19, 2008. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_25.981-1C.pdf
7. “AC 25.981-2A - Fuel Tank
Flammability Reduction Means.” Federal Aviation Administration (FAA), September
19, 2008. https://www.faa.gov/documentlibrary/media/advisory_circular/ac_25.981-2a.pdf
8. MIL-DTL-27422F, Tank,
Fuel, Crash, Resistant, Aircraft (Non Self-Sealing and Self-Sealing). http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-DTL/MIL-DTL-27422F_49706/
9. MIL-DTL-5624, Turbine
Fuel, Aviation, Grades JP-4 and JP-5. http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-DTL/MIL-DTL-5624U_5535/
10. MIL-T-5578C, Tank, Fuel,
Aircraft, Self-sealing. http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-T/MIL-T-5578C_13565/
11. MIL-DTL-83133E, Turbine
Fuel, Aviation, Kerosene Type, JP-8 (NATO F-34), NATO F-35, and JP-8+100 (NATO
Fire-protection; Explosion Protection; Fuel Tank; Survivability; Low Density
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