Appendix 1 Figure 1-2. Integrated Capstrip/Field Blanket Replacement System Figure 1-3. Combination Fiberglass/Replacement Batting System A1-2
Appendix 1 Figure 1-4. Barrier Material Used in Conjunction with Fiberglass Figure 1-5. Barrier Material Used (including over frame) in Conjunction with Fiberglass A1-3
Appendix 1
Figure 1-6. Barrier Material Used in Conjunction with Fiberglass A1-4
Appendix 1
Figure 1-7. Barrier Material Used in Conjunction with Fiberglass A1-5
Appendix 1
Figure 1-8. Barrier Material Used in Conjunction with Fiberglass A1-6
Appendix 1 Figure 1-9. Encapsulating Film System Used in Conjunction with Fiberglass Figure 1-10. Encapsulating Film System Used in Conjunction with Fiberglass A1-7
Appendix 2 Appendix 2 Alternative Burner
1. Introduction. Section 25.856 specifies the test method required for compliance, but also allows for “other approved equivalent test requirements.” Generally, an equivalent test method is one that produces the same test results as the standard method, for any material tested.
Because there are several parameters that dictate the test results for a given material, it is not a simple matter to define an equivalent method. However, the FAA has developed an alternative to the burner discussed in part 25, Appendix F, part VII, that eliminates the most significant sources of variability in test results. This ‘Next Generation’ burner, or NexGen, relies on constant air mass flow and does not involve motor driven accessories.
2. Use of this alternative burner test method. The test method in this appendix is intended to be adopted in total, if it is used. Following one section of the test method from this appendix and another section of the test method from Appendix F, part VII, is not covered by this AC. If an applicant proposes to use sections from more than one version of a test method to show compliance, the applicant must first obtain approval from the cognizant FAA Aircraft Certification Office and an issue paper will likely be required. The applicant’s request should be coordinated with the Transport Airplane Directorate’s Transport Standards Staff.
3. Additional specifications. Note that this appendix specifies several parameters that are not covered in Appendix F, part VII. These are parameters that may have an influence on calibration or test results, although the exact effects have not been established. Because the NexGen burner eliminates the major sources of performance variation found in the standard burner, the influence (or potential influence) of secondary parameters is more easily seen. In order to provide the most reproducible results, we have eliminated as much variability as practicable.
Figure 2-1. General Arrangement A2-1
Appendix 2
4. General Description. The NexGen burner consists of a pressurized air and fuel supply to replace the existing motor driven pump and blower. The burner utilizes a sonic orifice to control the quantity of air supplied to the flame. This approach produces very consistent results compared with the standard burner. The components upstream of the air/fuel inlets (e.g., stators, igniter, burner cone) are the same as discussed in Appendix F, part VII. See figure 2-1 for the general arrangement. A more detailed description of the burner is available at:
http://www.fire.tc.faa.gov/reports/reports.asp.
5. Air supply. The air metering device supplied with the NexGen burner is a sonic orifice, which requires a constant, steady supply of compressed air in order to deliver a fixed mass flow rate of air to the burner. The attached pressure regulator comes ready to attach to the lab air supply via a 1” national pipe thread female connection. The compressed air supply required must provide a steady pressure of at least 57 pounds per square inch gauge (psig) in a 1” line, with a mass flow of at least 63 standard cubic feet per minute. The compressor must also maintain this pressure for extended periods of time (6 minute max test time). These figures are minimums, however, and a certain design factor should be added so that the equipment is not operated at or beyond its operating capability. An Ingersoll Rand SSR series, with an Ingersoll Rand Hydroguard™ refrigerated dryer provides acceptable performance.
The inlet air must also be conditioned prior to reaching the burner. Changes in the density (caused by temperature and water content) of the incoming air can affect the burner exit velocity, which is a critical component of the burnthrough time. Both the temperature and the moisture content can be controlled by installing an in-line heat exchanger followed by a water separator.
The heat exchanger uses cool water to remove heat from the air stream, and the water separator will remove any water that has condensed due to cooling. For the heat exchanger, McMaster Carr part number 43865K78 is suitable. For the water separator, McMaster Carr part number 43775K55, is suitable.
6. Fuel supply. The fuel nozzle installed in the burner requires a steady supply of pressurized fuel at 120 psig. The suggested method of fuel pressurization is to construct a pressure vessel capable of containing fuel and compressed gas (nitrogen or air) at 120 psig. The layout of the fuel supply system is shown in figure 2-2. The use of a mechanical pump driven by an electric motor may also work, but should be shown to provide an equivalent level of performance to the pressurized fuel tank system.
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Appendix 2 Pressure Regulator (in the range of 0-150 psig)
e.g., Bellofram Type 70 Pressure Regulator, 2- 150 psig, max 250 psig inlet, approx Compressed gas from bottled Nitrogen or Air, High pressure liquid level sight or air gauge (e.g., compressor, if McMaster Carr it is capable p/n: 3706K23) Nozzle 5.5 GPH 80 deg-PL Solenoid or manual ball valve Fuel Air/N2 @ ~120 psig Ven t Air Inlet Fuel Fill Fuel Outlet Ice Solenoid or manual ball valve Solenoid or manual ball valve Pressurized venting or outdoors Pressure Vessel (for example, McMaster-Carr p/n 1584K7, ASME-Code Vertical Pressure Tank W/O Top Plate, 15 Gallon Capacity, 12" Dia X 33" L, ) or any suitable pressure vessel that can withstand pressures of around 150 psig.
This schematic is pretty basic. You can supplement this design with whatever instrumentation you would Needle valve to control Vent to lab like to obtain the required data or to make for easier operation. Some examples would be a pressure transducer, remotely operated solenoid valves, fuel flow meter, etc.
Bath H2O Figure 2-2. Fuel System Schematic
7. Fuel and Air Temperature. Experience has shown that the temperature of the fuel and air can influence test results to some degree. This is really only critical with materials with burnthrough performance that is relatively close to the pass/fail criteria. Nonetheless, the consistency of the tests can be improved if the air and fuel temperature is controlled. A schematic of a heat exchange system can be seen in figure 2-3.
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Appendix 2 Water Pump Air From Compressor Condensate Separator McMaster-Carr p/n 43775K55 BurnerCooler Heat Exchanger McMaster-Carr p/n 3865K78 Blue = Water Lines Orange = Fuel Lines Black = Air Lines Fuel Tank Figure 2-3. Heat Exchange System Schematic
a. Fuel temperature. The fuel temperature must initially be between 32°- 40°F, and must not vary more than 10°F for the length of a test. A 5° variation is not unusual. This can be achieved by using an ice bath to chill the incoming fuel, and using insulation to cover all of the fuel lines and gauges to protect them from flame radiation.
b. Air temperature. The air temperature should not vary outside of the 40°-60°F range during the length of a test. This can be achieved by using the in-line heat exchanger discussed in paragraph 4, above. If the water temperature is not cold enough to attain this temperature range, the water can be run through the same ice bath to further cool the incoming air. Run the air for 5-10 minutes before testing, to ensure that the air has reached a quasi-steady temperature, and is well within the 40°- 60°F range during the test. All exposed air lines should be covered in insulation as well, to protect from being heated by burner flame radiation.
8. Fuel and Air Pressure. The pressure of the fuel and air can similarly influence performance.
The fuel pressure should be measured just upstream of the fuel temperature measurement point.
The fuel pressure should be set to 120 psig. As noted in the air supply discussion above, a minimum continuous 57 psig is necessary for consistent operation.
A2-4
Appendix 2
9. Calibration. When the burner is set up as described above, the heat output of the burner is essentially determined by the fuel and air settings. Therefore, it is not necessary to calibrate the burner for heat flux. It is necessary to confirm proper temperature calibration, because this becomes more a measure of the shape and uniformity of the flame. It may also be useful to periodically check the heat flux calibration, to confirm the consistency of the burner, but this measurement is not required to perform certification tests.
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