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The FAA microscale combustion calorimeter (MCC) operates by burning the evolved gases from a thermally degrading sample and measuring the oxygen consumption to calculate a heat release rate. Recent method developments using hyphenated MCC techniques enables measurements of the effect of vitiation on toxic combustion gas yields. Stoichiometric fuel to oxygen ratio tests were performed where a constant fuel to oxygen ratio relative to the stoichiometric ratio, Φ, in the combustor is controlled throughout the sample decomposition. When Φ < 1, combustion is fuel lean (over ventilated). When Φ > 1, combustion is fuel rich (vitiated).
The MCC was coupled with an infrared spectrometer (MCC-IR) and a multigas analyzer (MCC-Testo), which were used to monitor gases and evaluate combustion toxicity at different Φ and combustion temperature set points. These hyphenated techniques demonstrate a unique capability to elucidate the effect of constant fuel to oxygen ratios on combustion product yields. Measurements made at different Φ’s will help to better understand the flame chemistry and the mix of complete/incomplete combustion products for various aircraft materials throughout the different stages of a full-scale fire. Combustion equivalence ratios of 0.5, 1.0 and 1.5 were evaluated in this study. A set of hydrocarbon materials with elemental compositions, including C, H, N, O, and S, were examined to provide a spectrum of gaseous combustion products where a small set of potential toxic combustion products could be evaluated. Yields of the gaseous decomposition/combustion products were compared as a function of equivalence ratio for the set of materials. Trends in combustion products produced at different oxygen ratios correlate with large-scale fire test data from the literature and showed an increase in toxic product yields with increasing Φ.
This study introduces a novel approach to enhance fire protection in aircraft cargo compartments, motivated by the urgency to address catastrophic in-flight fires recorded between 2006 and 2011. The method uses ultra-high frequency (UHF) radio frequency identification (RFID) temperature sensing tags and advanced algorithmic analysis to enhance fire detection capabilities within unit load devices (ULDs). This approach significantly reduces detection times while minimizing false alarms.
The first objective was to create an economical, battery-free fire detection system with UHF RFID temperature sensing tags installed within ULDs. This positions the temperature sensing tags closer to potential fire sources than traditional cargo compartment ceiling-mounted smoke detectors. Wireless temperature sensing tags allow the ULDs to move in and out of aircraft. Passive sensors address the challenges of batterypowered systems, such as battery changes and thermal runaway risks.
The second objective sought to enhance the RFID-based system with near real-time temperature monitoring capabilities within ULDs. The system provides accurate temperature trend analysis by incorporating a moving average convergence divergence (MACD) algorithm adapted from financial markets. This significant advancement improves fire detection times and supports communication of conditions within ULDs to flight crews, enabling quicker response actions.
The number of thermal runaway incidents from portable electronic devices (PEDs) in the aircraft cabin is growing at a notable rate. Recent data indicates that lithium battery incidents occur on average more than once per week on passenger aircraft. In response to this problem, many airlines have adopted the use of fire containment products as a means to mitigate the spread of fire and toxic fumes. An evaluation was conducted by the FAA to assess the effectiveness of commercially available fire containment products and assess their capability to mitigate the release of smoke, flames and shrapnel produced from a PED fire.
Fire containment products were procured from five different manufacturers and tested with three different fire loads, a tablet containing a 30 Watt-hour (Wh) battery, a 96 Wh power bank and a 154 Wh video camera battery. Products were only evaluated according to the maximum capacity that the product was advertised to withstand.
Key findings from this study include:
Testing suggests that some containment products cannot currently meet the airlines’ present expectations for product performance. Further testing on the use of fire containment products may be needed to ensure the safety of aircraft occupants.
As a result of the COVID-19 (SARS-CoV-2) pandemic, over 12.7 billion vaccine doses were shipped and administered across 184 countries. Transportation via aircraft was a significant contributor in this effort. Many of the COVID-19 vaccines need to be stored at extremely low temperatures to maintain efficacy, therefore, dry ice has been used as a method to keep vaccines refrigerated throughout air shipments. Dry ice is categorized as a Class 9 (Miscellaneous) Dangerous Good. Dry ice undergoes a process called sublimation at normal pressure and temperatures, in which the solidified form transitions directly to gaseous CO2. This process can create an oxygen deficient environment in confined areas (including aircraft), which can produce shortness of breath, unconsciousness, or death if exposed over prolonged periods of time.
An assessment was conducted by the Federal Aviation Administration (FAA) to identify parameters pertinent to dry ice sublimation throughout air shipment. This study was motivated by minor sublimation rates (<1% per hour) claimed from container manufacturers. This has important safety implications as decreases in sublimation rates allow for exponential increases in permitted dry ice cargo. Further analysis was needed. Specifically, this study evaluated the following parameters’ impact: temperature, pressure, humidity, dry ice pellet size, container design and durability. Results indicate that dry ice pellet size, container design, and durability had a clear impact on sublimation rate. Sublimation rates differed significantly between the three containers evaluated within this study and were observed to increase as containers were reused. Furthermore, dry ice pellets with smaller nominal diameters were noted to sublimate at a higher rate than those with a larger diameter. Other evaluated parameters within this study produced no clear correlation. Although sublimation was observed to be affected by numerous parameters, data suggests a conservative approach to this subject is prudent. While some external conditions may produce only minor differences in sublimation rates, it would have a major impact on the allowable quantity of dry ice shipped.
This report summarizes the research effort undertaken by the Federal Aviation Administration (FAA) to develop an improved test methodology for determining the performance of aircraft evacuation slide materials when exposed to radiant heat. A laboratory scale test method was previously developed by the FAA circa 1983, which used a pressurized cylinder apparatus on which a sample of evacuation slide material is mounted. The slide sample material was exposed to an electrically powered radiant heat source that simulated the heat flux typical of a fully-developed jet fuel fire. The purpose of the test was to determine the ability of an evacuation slide to maintain pressurization when the material was exposed to radiant heat, as past aircraft accidents had shown that evacuation slides were losing pressure prematurely during exposure to jet fuel fires.
An adjustable voltage regulator was used to set the level of heat flux of the radiant heater before the test, as measured by the calorimeter. Once the heat flux was set, a test was conducted in which the slide material was exposed to the radiant heat source. During a test, it was possible for normal supply voltage fluctuations to increase or decrease the previously-set heat flux level of the radiant heater resulting in poor test repeatability.
An improved test method in which the electrical power input to the radiant heater was continuously monitored and adjusted for the duration of the test. This ensures that fluctuations in supply voltage are accounted for, to prevent any variability in the heat flux level generated by the heater. In addition to the adjustable voltage regulator, the improved methodology also requires a digital amp meter to measure the amount of electrical current entering the radiant heater.
Numerous trials were conducted to determine the repeatability of different radiant heaters and heat flux gauges to potentially improve the calibration method. The heat flux gauges proved to be much more consistent and require yearly recalibration making them essential for proper calibration of the evacuation slide test apparatus.
Federal Aviation Administration