By Raymond (Lou) Roncase, Jr.
The Green On-Board Inert Gas Generating System (GOBIGGS), developed by Phyre Technologies Inc., has been selected by Sikorsky Aircraft Corp. as the next-generation system to inert explosive ullage gasses. GOBIGGS was selected as a component system of the Combat Tempered Platform Demonstration (CTPD) Project awarded to Sikorsky in 2012. The CTPD project is a $12-million demonstration program tasked to develop and integrate a suite of advanced technologies (some having previously low technology readiness levels [TRLs]) to increase the performance and survivability of U.S. military platforms. The best and most beneficial of these technologies will be matured and fully integrated into our next-generation or block upgrade aircraft to improve the performance and survivability of U.S. military aircraft. The aircraft chosen for this CTPD was the UH-60 BLACK HAWK series aircraft.
Phyre Technologies Inc. is a small, San-Diego-area-based research and development company founded in 2003. Its initial research efforts resulted in the development of Phyre’s Advanced De-Oxygenation System (PADS), a fuel deoxygenating system that capitalized on the properties of “Henry’s Law” to draw the oxygen out of fuel and process this oxygen through catalytic reaction to remove it in a closed-loop system (see Figure 1). Henry’s Law is best visualized by opening a bottle of soda and seeing and hearing the dissolved CO2 escape. Some of the benefits of deoxygenated fuel are the thermal stability, significantly decreased coking in the fuel delivery system, and the ability to elevate the fuel temperature, which can decrease fuel consumption and allow the fuel to be used as an on-board cooling medium for aircraft systems.
Developers soon realized the potential of the catalytic reaction, which removes the oxygen from the air in the PADS system, to also be used to remove the oxygen leg of the “fire triangle” to reduce the flammability of the ullage in a conventional fuel cell. A second benefit of this catalytic reaction is the removal of the hydrocarbons in the ullage air as well, resulting in a faster reduction in explosive gaseous components in the ullage mixture. Thus, GOBIGGS was developed to specifically target the explosive ullage air for the aviation industry.
The current system most deployed on U.S. military aircraft, the On Board Inert Gas Generating System (OBIGGS), is a membrane-based approach developed for the medical industry. The membrane divides the air particles by molecular weight into oxygen-enriched air (OEA) and nitrogen-enriched air (NEA). For medical use, the OEA is supplied to the patients and the NEA is discarded or stored (depending on the manufacturer). This system has also been adapted for use on aircraft and is called On-Board Oxygen Generating System (OBOGS). OBIGGS uses the NEA generated by the membrane and pumps the NEA into the flammable ullage to reduce the oxygen content in the ullage to below 9%; the excess gases are vented to the atmosphere. Although this system is considerably lighter than a liquid nitrogen type of system, it is heavy compared to GOBIGGS, and negative performance and maintenance issues have been documented.
As illustrated in Figure 2, GOBIGGS is simplicity in design and integration. It consists of nothing more than three small pumps to circulate the ullage gases and cool the heat exchanger and catalytic converter, a catalytic converter to burn off the oxygen and hydrocarbons, a small control unit that manages the system operation, and thermocouples that provide the inputs to the control unit. And all of this is contained in a small box (shown in Figure 3). External components consist of the tubing that will run between the fuel cells, isolation valves, and an overboard vent for the heat exchanger. The entire vent and gas transfer lines can be as lightweight and flexible as the other platform fuel system venting components, as GOBIGGS operates at the aircraft’s ullage pressure specifications. In addition, the system is scalable to large or small aircraft.
GOBIGGS was first demonstrated in 2006 to the Federal Aviation Administration (FAA) in Atlantic City, NJ, for use in the commercial aviation industry as a viable option to conventional ullage treatment systems to prevent another TWA Flight 800-type tragedy. As is typical in a developmental system demonstration, the system that was taken to Atlantic City was large and cumbersome. And although the FAA demonstration was successful at proving the technology, the low TRL and the lack of an established requirement to protect commercial aircraft fuel cells kept this technology on the shelf for several years.
However, the technology was eventually brought to the attention of the Joint Aircraft Survivability Program Office (JASPO), and in 2010 Phyre was awarded a contract to demonstrate GOBIGGS in a realistic environment, with the assistance of the engineers and technicians at the Naval Air Warfare Center-Weapons Division (NAWCWD) Weapons Survivability Lab (WSC) in, China Lake, CA. The test scenarios were designed to demonstrate the ability of GOBIGGS to inert a large fuel cell ullage volume, to inert during fuel offload/burn down conditions, and to operate at different catalytic converter temperatures.
The outstanding performance of the GOBIGGS system during the JASPO test series (the results of which were published in the fall 2012 edition of the Aircraft Survivability journal) brought GOBIGGS to the attention of the survivability engineers at Sikorsky. And through their efforts, the system was selected as one of the advanced technologies being demonstrated during the CTPD program cycle. GOBIGGS will exit the CTPD Program at TRL 6–7, as it has proven to be a viable ullage treatment option. The H-60 series aircraft do not currently have ullage protection, and GOBIGGS will provide the users with a level of protection not yet realized by other aircraft operating using the current OBIGGS system.
ABOUT THE AUTHOR
Raymond (Lou) Roncase, Jr., works as a vulnerability engineer in the Combat Survivability Division of the U.S. Naval Air Systems Command (NAVAIR) in China Lake, CA. He has almost 40 years of experience in LFT&E testing, including developmental/operational flight testing, sled track testing, explosive ordnance testing, and (for the last 13 years) vulnerability and JASP program management and testing at the WSL. Mr. Roncase has also served 8 years in the U.S. Marine Corps as an avionics technician, maintaining the AV8 A, B, and C series aircraft.