Aircraft Cargo Compartment Minimum Performance Standard
This technical note establishes the minimum performance standard (MPS) that a Halon 1301 replacement aircraft cargo compartment fire suppression system must meet. This MPS was developed in conjunction with the International Aircraft Fire Protection Systems Working Group, formerly known as the International Halon Replacement Working Group. It describes the tests that shall be performed to demonstrate that the performance of the replacement agent and system provides the same level of safety as the currently used Halon 1301 system. The results of these tests will be used to determine the required concentration levels to adequately protect an aircraft cargo compartment against fire and hydrocarbon explosions. The Supplemental Type Certificate applicant shall provide the minimum agent protection concentration, density, etc., to the Federal Aviation Administration (FAA) Aircraft Certification Office with an objective way of measuring it. Currently, the FAA Transport Airplane Directorate, in conjunction with the Joint Aviation Authority, is developing an advisory circular to address the certification of an aircraft cargo compartment fire extinguishing or suppression system. This MPS update replaces the standard reported in FAA Technical Note DOT/FAA/AR-TN03/6, "Minimum Performance Standard for Aircraft Compartment Halon Replacement Fire Suppression Systems."
The four different MPS fire test scenarios that new cargo compartment fire suppression systems must meet are bulk-load fire, containerized-load fire, flammable liquid fire (surface burning), and an aerosol can explosion simulation. The bulk- and containerized-load fires, which are deep-seated fire scenarios, use shredded paper loosely packed in cardboard boxes to simulate the combustible fire load. The difference between these two tests is that in the bulk-load fire scenario the boxes are loaded directly into the cargo compartment, while in the containerized-load fire scenario, the boxes are stacked inside an LD-3 container. The surface-burning test (Class B fire) uses 0.5 U.S gallon (1.89 liters) of Jet A as fuel. The aerosol can explosion simulation tests are executed by using an aerosol can simulator containing a flammable and explosive mixture of propane, alcohol, and water. This mixture ignites or explodes when it is exposed to an arc from sparking electrodes. At least five tests per MPS scenario must be conducted. These tests shall be performed in a 2000-ft3 simulated aircraft cargo compartment.
The suppression performance of a new agent, once the data is collected and analyzed, is then compared with the standard acceptance criteria to determine if it passes or fails the fire tests. None of the peak temperatures and areas under the time-temperature curves may exceed the values specified in the acceptance criteria table. The acceptance criteria are as follows:
- For the bulk-load fire scenario, the average of the five test peak temperatures shall not exceed 720°F (382°C), starting 2 minutes after the suppression system is initially activated until the end of the test. In addition, the average of the five test peak areas under the time-temperature curve shall not exceed 9940°F-min (5504°C-min). The area should be computed from 2 minutes (t3) after the time of initial suppression system activation (t2) to 28 minutes after t3.
- For the containerized-load fire scenario, the average of the five test peak temperatures shall not exceed 650°F (343°C), starting 2 minutes after the suppression system is initially activated until the end of the test. The average of the five test peak areas under the time-temperature curve shall not exceed 14,040°F-min (7,782°C-min). The area should be computed from 2 minutes (t3) after the time of initial suppression system activation (t2) to 28 minutes after t3.
- For the surface-burning fire scenario, the average of the five test peak temperatures shall not exceed 570°F (299°C), starting 2 minutes (t3) after the suppression system is initially activated until the end of the test, 3 minutes after t3. In addition, the average of the five tests peak areas under the time-temperature curve shall not exceed 1230°F-min (665°C-min) for the same period mentioned in the previous sentence.
- For the aerosol can explosion simulation scenario, no evidence of an explosion shall be present in the compartment at the time the simulator is activated, such as no overpressure (0.0 psig) or deflagrations. In addition, when the agent concentration is below its inert concentration, the explosion intensity and peak pressures shall not be greater than the values exhibited during an explosive event when no suppression agent is present in the compartment.
Appendix A presents a table showing how the acceptance criteria values were determined based on the Halon 1301 test data. Appendix B contains the aerosol can explosion simulator drawings.
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