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The microscale combustion calorimeter (MCC) was developed by researchers at the Federal Aviation Administration (FAA) as a tool to evaluate research quantities of new materials. The MCC was licensed by the FAA for manufacture. Since then, many have been made and sold around the world. The FAA performed an interlaboratory study under the guidance of the American Society for Testing and Materials (ASTM) to evaluate the precision and bias of the MCC test method, ASTM D7309. This study encompassed MCCs made by several vendors and run by operators in different laboratories. Identical sets of five polymeric materials were sent to the laboratories for evaluation in the MCC. The laboratories were asked to test the samples in triplicate and report the values obtained for heat release capacity, peak heat release rate, total heat release, peak heat release temperature, and residual mass. Over 20 laboratories were asked to participate in the study. Twelve of these laboratories were able to provide data. Statistical analysis was performed on the results from the different laboratories for comparison to each other. The repeatability and reproducibility of the equipment and method were examined. Additional tests were run in the fire science laboratory at the FAA using thermogravimetric analysis to calculate the properties that are measured in the MCC. These tests were used to validate the results obtained by MCC using an alternate technique. Results from the study were very good compared to other fire tests, with a repeatability of <1% to 3.8% and a reproducibility of 2.2% to 7.9%. Recommendations for modifying the MCC methodologies were formulated and are discussed in this report to improve the results for future studies.
In an effort to minimize uncertainties seen in bench scale tests, the sources of variability in fire test data were investigated. An earlier study―a PhD thesis written by Patel at the University of Central Lancaster, UK, in 2011 titled “Investigation of Fire Behavior of PEEK-based Polymers and Compounds”―on poly(arly ether ether ketone) (PEEK) showed that the fire performance parameters of this thermoplastic changed noticeably when exposed to moisture prior to the test. The present research is a follow-up study where a series of cone calorimetry tests were conducted on conditioned PEEK specimens to analyze the previously reported ignition time scatter and its relation to surface bubble formation. Pyrolysis modeling is, subsequently, carried out to relate the moisture content with the model parameters and to explain the possible physical mechanisms that cause the difference in ignition times between wet and dry samples.
This study has evaluated Equivalent Level of Safety (ELOS) Findings and Exemptions relating to the cabin safety requirements in Title 14 Code of Federal Regulations Part 25 that involved transport category airplanes with a maximum certificated passenger capacity of up to 60 seats. The results of this study can be used as an indication of the relevance and applicability of certain requirements to this airplane category, and could form a basis for future research studies.
A review of the Federal Aviation Administration database up to February 2006 found a total of 98 ELOS and Exemption applications appropriate for this study. The applications were classified under 15 categories, and the categories having more than 4 original applications were given further consideration. These Categories are related to:
It was found that some of these subjects are not exclusive to smaller transport airplanes. This is mainly because the applications were related to the type of operation and configuration that require specific features, such as executive interior or air ambulance configuration that can be installed in both large and smaller transport airplanes. However, some of these issues may be more prevalent in smaller transport airplanes. It was also found that other issues are related to the size of the airplane, in that the pertinent requirements may be considered more appropriate to larger transport airplanes.
Ice collection and blockages in fuel systems have been of interest to the aerospace community since their discovery in the late 1950s when a B-52 crashed. A recent growth of interest was provoked by several incidents that occurred within the last few years. This study seeks to understand the underlying principles of ice growth in fuel flow systems.
Tests were performed in a recirculated fuel system with a fuel tank that held approximately 115 gallons of Jet A-1 fuel, and ice accumulation was observed in two removable test pipes. The setup was in an altitude chamber capable of reaching -60°F, and the experiments involved fullscale flow components.
Initially, tests were performed (stage I) to better understand the system and the variables that affected accumulation. First, initial conditions within the test pipes were varied. Also, pipe geometry, pipe surface properties, initial water content of the fuel, and heat transfer from the fuel pipe were varied. As a result of the tests, observations were made about other effects involved in the study. The effects include the result of sequentially run tests, the effect of the fuel on the freezing temperature of the entrained water, the effect of ice accumulation on pipe welds, and the effect of the test pipe entrance and exit flow conditions on ice accumulation. The results of initial tests were qualitative. Later quantitative tests were performed (stage II) to demonstrate the dependence of temperature, Reynolds number, and heat transfer on ice accumulation. Tests were quantified with a pressure increase across the pipe sections that was normalized by the expected theoretical initial pressure. As a result of these tests the effect of contamination in the fuel was revealed.
The results of stage I showed that accumulation of soft ice was greatest when a layer of hard ice had initially formed on the pipe surface. Stainless steel collected more ice than Teflon®, and there was a lack of a preferential accumulation region downstream of a pipe bend. A greater heat transfer from the pipe increased ice accumulation for aluminum that was made rough with 80-grit sand paper and for Teflon. Water collected in the pipe system as the number of tests increased and the freeze temperature of either the hard or soft ice was about 0°C. Finally, results of stage I tests showed that stainless steel pipe welds were a preferred sight for ice to accumulate.
Repeatability was done first in stage II, and the normalized pressure increase for two 3/4 uninsulated pipe tests were within 7%. Normalized pressure increased across a pipe as the Reynolds number decreased. A 50% increase in the Reynolds number led to a 40% decrease in characteristic normalized pressure increase (CNPI). Tests were performed at three temperatures, and ice accumulated the most at -11°C. The CNPI at -11°C was about 3 times greater than the CNPI at -7°C and about 60 times greater than the CNPI at -1°C.
A greater heat transfer from the fuel pipe increased ice accumulation. For the amount of time that the tests ran, the total normalized pressure increase was about 0.9 greater for an uninsulated pipe than for an insulated pipe. Contamination in the fuel increased the amount of soft ice that collected in the system. The CNPI for the more contaminated fuel was more than double the case with less contaminated fuel.
Possible solutions for the prevention or decrease of ice accumulation in aircraft fuel systems based on the results of this study are insulated pipes, a change in the type of pipe material, a higher fuel flow rate, and cleaner fuel. The fuel temperature could also be altered to avoid temperatures where the most ice accumulates.
Adhesives are widely used in the aviation industry to construct lightweight and fatigue resistant aircraft cabin materials. Presently, there is no separate requirement for the flammability of adhesives, potting compounds, and fillers used in construction of cabin materials. The Flammability Standardization Task Group is an aircraft industry group that has proposed testing adhesives using the 12- and 60-second Vertical Bunsen Burner (VBB) Fire Tests requirements for cabin materials in Title 14 Code of Federal Regulations 25.853 to demonstrate that new adhesives have similar flammability to those used in certified cabin materials. Cabin materials pass or fail the VBB tests based on criteria for burn length, after-flame time, and time required for flaming drips to extinguish. The present study was conducted to determine whether the microscale combustion calorimeter (MCC) could also be used to establish similarity of aircraft adhesives, potting compounds, and fillers. To this end, thermal combustion properties were measured by MCC for 37 adhesives, edge fillers, and potting compounds, and the results were compared to VBB ratings to determine whether the former could be used to predict the latter.
Federal Aviation Administration