Description:
OBJECTIVE: Develop a fiber-optic-distributed sensor system that will sense bleed air leaks in the propulsion, environmental control, and thermal management systems (TMSs) to increase survivability throughout the operating mission of advanced tactical aircraft. DESCRIPTION: Advanced tactical aircraft are required to provide protection to fire throughout the operating mission flight envelope. The aircraft structure is vulnerable to excessive temperatures over long periods of time when exposed to hot gas leaks from the propulsion, environmental control systems, and TMSs on the aircraft. The distributed temperature sensing technology would increase the survivability of fighter aircraft against bleed air leaks. The purpose of this technology would be to allow the fighter aircraft to extend the amount of time that it could engage in conducting its mission without restricting the overall flight time before a bleed air leak condition is detected. This technology allows greater accuracy in detection of bleed air leak by reducing the amount of nuisance trip indications by providing greater resolution into the high end of the trip-detection band. When a bleed air leak detect condition is reported, then this technology will decrease the maintenance support time by providing maintenance personnel with the information needed to exactly pinpoint where the root cause is located in the equipment bay or duct, improving the aircraft readiness rate. The purpose of this program is to develop a distributed temperature sensing system to provide more robust and accurate fire-protection, leak-detection alarm capabilities and improved fault diagnostic capabilities. The existing fire-protection bleed air leak detect system technology alarm trip conditions are highly dependent on multiple conditions. The individual alarm trip points can vary over very large tolerances and are dependent on mission flight profile, ambient temperature, air speed before and during the bleed air leak detect alarm condition, engine conditions, air flow through equipment bay, and temperature over the sensor. Future aircraft are continuing to look at enhanced mission operating characteristics that demand longer flight times at low and fast airspeeds in hot ambient environments. The current methods used for detecting bleed air leaks in fighter aircraft equipment bays will continue to push the limits of the conventional technology alarm trip points and diagnosing and isolating the exact fault location along the temperature sensors will become increasingly difficult on future aircraft. The new fiber-optic technology offers the ability to accurately sense the temperature of the air temperature in the surrounding area adjacent to the sensors with the ability to provide enhanced fault diagnostics for future fighter aircraft. Innovation is required to reduce the size and weight of the optical time domain reflector meter instrumentation and routing of the fiber optics inside a small fighter aircraft equipment bay. The fiber-optic-distributed temperature sensing electronic system must be able to sense up to 565 degrees for alarm temperatures in a hot air equipment bay environment up to 15 m in length in eight channels. The spatial resolution must be 0.127 m at an acquisition rate of 0.5 Hz. The maximum power consumption should be 33 W at 28 VDC. The aircraft interface shall be IEEE 1394b"Firewire"SAE AS5643 compliant to industry standards. The operating temperature ranges from -60 to 160 degrees F and pressures ranging from atmospheric pressure down to 50,000 feet in altitude. In addition, the sensor probe must be compatible with fuel and fuel vapors. The sensor system must be intrinsically safe and survive under shock and vibration loading during takeoff, landing, and mission profiles. Prime contractor collaboration is highly encouraged. PHASE I: Design and demonstrate feasibility of a fiber-optic-distributed temperature sensing used for detecting bleed air leaks in fighter aircraft. Control and operation of a feasible fiber-optic sensor system can be shown by laboratory investigations. Develop a transition plan and business case analysis. PHASE II: Full development of a production representative fiber-optic-distributed temperature sensor system and demonstrate in a simulated relevant fighter aircraft bay thermal environment. Abbreviated developmental survey testing of the system under MIL-STD. A full-scale, simple-to-operate working prototype system is desired for presentation and demonstration at WPAFB, and delivery to the Government at the completion of program for additional evaluation. Refine transition plan and business case analysis. PHASE III DUAL USE APPLICATIONS: The technology has applications both for military and commercial aircraft. This type of distributed temperature sensing has other potential applications in leak/fault detection in industrial cooling applications and power plants.
