Fiber Optic Pressure Sensing for Military Aircraft (MIL-Aero) Environments
Navy SBIR 2019.2 - Topic N192-076
NAVAIR - Ms. Donna Attick -
Opens: May 31, 2019 - Closes: July 1, 2019 (8:00 PM ET)


TITLE: Fiber Optic Pressure Sensing for Military Aircraft (MIL-Aero) Environments


TECHNOLOGY AREA(S): Air Platform, Electronics ACQUISITION PROGRAM: JSF Joint Strike Fighter

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.


OBJECTIVE: Develop fiber optic pressure sensing technology for detecting failures prior to flight and throughout the operational mission flight envelope for military aircraft applications.


DESCRIPTION: Advanced aircraft are required to provide failure detection prior to flight and throughout the operating mission flight envelope. Aircraft hydraulic systems, fuel filters, and many other systems rely on differential pressure sensors to ensure the aircraft hardware is functioning normally. Electro-Hydrostatic Actuators (EHAs) onboard aircraft use multiple pressure transducers. The high pressure ripple environment and high accuracy requirements are pushing the limits of passive pressure transducers. As a result of this limitation, some EHAs require an active pressure transducer design, however, due to electromagnetic interference (EMI) filtering must be implemented. Current pressure transducer designs rely on a strain gage attached to a diaphragm. Leads are then soldered to the strain gage. Active pressure transducer designs are complex, expensive, and can be prone to reliability issues. If the transducers are active, they may be inherently prone to EMI. Mechanical failure modes can be addressed with a fiber optic pressure sensor, which is also immune to EMI.


Fiber optic pressure sensing capability may also have application to differential pressure sensors present in fuel- burning turbine engines. These engines have their own fuel control and sense pressure across a fuel filter. This measured differential pressure is usually less than 10 pounds per square inch (psi). Fuel systems however have been shown to damage the sensor with pressure spikes that are caused by fuel system valve closures and can exceed 100 psi. Low-pressure differential pressure sensors cannot handle these pressure spikes. Fiber optic pressure sensing technology could increase the availability of military aircraft by improving component reliability. A fiber optic

pressure sensor would allow sensing without direct contact with the diaphragm, and also provide immunity to EMI and radiofrequency interference (RFI). Innovation is required to take the current pressure sensor technology and modify it for use in military aircraft EHA and fuel filter operational and mechanical environments. The fiber optic pressure sensor signal will need to be converted to an analog signal that matches that of a passive pressure transducer. Signal processing located away from the sensor should make implementation possible without exceeding the mechanical envelope of a typical active sensor.


The actual sensor device should fit within a 3-inch long by 1-inch diameter mechanical envelope volume. If the fiber optic sensor device includes a light source and receiver electronics within the mechanical envelope volume, then the sensor will be expected to work off 28-volt direct current power. If the light source and/or receiver electronics are remote from the sensor, then a fiber optic interconnect may be used to interface between the light source and/or receiver electronics and the sensor. The sensor will need a sample rate of 560 Hertz and if not remoted, be able to operate at 28 volts direct current. For fiber optic pressure sensing technology to be used in aircraft EHA applications, the high fiber optic pressure sensing systems must be able to accurately measure between 10 and 4,500 psi and be able to withstand pressure spikes up to 6,000 psi, with a pressure measurement resolution of plus or minus 1 percent. The aircraft interface must comply with industry standards such as SAE AS5643. The high fiber optic pressure sensor operating temperature ranges from -65F to 275F with altitudes ranging from sea level up to 50,000 feet. In addition, the high pressure sensor probe must be compatible with MIL-H-5606B hydraulic fluid. The sensor system must be intrinsically safe and survive under shock and vibration loading as described in MIL-STD- 810. The sensor design life is 30 years of operation, or 8,000 flight hours and 4,000 ground hours of operational usage.


Establishing a working relationship with relevant original equipment manufacturer(s) (OEM), while not mandatory, will greatly enhance the probability of successful development and transition.


PHASE I: Design a fiber optic pressure sensing system to be used to monitor hydraulic pressures and fuel filter pressures. Ensure that the hydraulic pressure sensor is housed within an actuator installed on a military aircraft in accordance with the parameters in the Description And that the fuel filter pressure sensor is housed within an airtight structure in compliance with the environmental parameters defined in the Description. Demonstrate, through laboratory investigations, feasibility of control and operation of the fiber optic sensor systems. The Phase I effort will include prototype plans to be developed under Phase II.


PHASE II: Complete full development of a production representative fiber optic pressure sensing system prototype for both hydraulic and fuel filter applications. Demonstrate the sensing system prototypes in a simulated relevant aircraft environment. Conduct abbreviated developmental survey testing of the system under MIL-STD-810. A full- scale, simple-to-operate working prototype system is desired.


PHASE III DUAL USE APPLICATIONS: Further test and qualify the pressure sensors in aircraft representative actuator and fuel systems. Transition the fiber optic pressure prototypes demonstrated in Phase II for subsequent production as Commercial-Off-The-Shelf items. Private sector industries that would benefit from successful technology development include commercial aviation, space vehicles, oil drilling, and chemical plants.



1.   MIL-H-5606B Military Specification Hydraulic Fluid, Petroleum Base; Aircraft, Missile, and Ordnance. Department of Defense, 1963.


2.   MIL-DTL-9490E Detail Specification Flight Control Systems - Design, Installation, and Test of Piloted Aircraft, General Specification For. Department of Defense, 2008. DTL/MIL-DTL-9490E_10979


3.   MIL-STD-810G Environmental Engineering Considerations and Laboratory Tests. Department of Defense, 2008.

4.   MIL-PRF-5503G Performance Specification Actuators: Aeronautical Linear Utility, Hydraulic, General Specification For. Department of Defense, 2013. PRF-5503G_54119/


5.   DO-160F Environmental Conditions and Test Procedures for Airborne Equipment. Radio Technical Commission for Aeronautics (RTCA), 2007.


6.   Actuators: Aircraft Flight Controls, Power Operated, Hydraulic, General Specification For ARP1281. SAE International, 2002.


7.   IEEE-1394b Interface Requirements for Military and Aerospace Vehicle Applications AS5643. SAE International, 2004.


KEYWORDS: Pressure Sensor; Fiber Optic; Aircraft; Actuator; Fuel Filter; Packaging



Brian Mc Dermott





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