SFTY440_3.3_Subsystem Hazard Analysis (SHA)_Assignment

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3.3 Assignment: Subsystem Hazard Analysis (SHA) My Name College of Aeronautics, Embry-Riddle Aeronautics University SUBSYSTEM HAZARD ANALYSIS 1. Loss of System Pressure Cause: Malfunctions in the bleed air and Auxiliary Power Unit systems may cause issues in pressurization for an aircraft. Effects: Effects may lead to operating failures in de-icing and air conditioning, as well as pressurization systems, which may cause substantial depressurization in the aircraft cabin. RAC: 1D Recommended Controls: 1. Engineers need to implement redundancies in case one system fails. This is to ensure that risks are properly prevented or deterred. 2. Develop comprehensive maintenance intervals that include quality checks completed by certified engineers. 3. Ensure oxygen supply is sufficient, certified, and regulated for certain aircraft models. Controlled RAC: 2D Standards: - 14 CFR 23.1438: Pressurization and Pneumatic Systems (Govino, 2016) - ARPA4754A – Guidelines for the development of civil aircraft and systems (SAE International, 2010) 2. Contamination Cause: Occurrences of improper filtration and progressing bleed air contaminants may cause toxic fumes in aircraft bleed air systems. Effects: Onboard passengers are exposed to harmful air/gasses that may have high toxicity levels and result in adverse health symptoms. RAC: 3D Recommended Controls: 1. Conduct proper and frequent cleaning/replacement procedures for air ducts, filtration systems, and bleed air components concerning the engine.

2. Install both high-energy particulate air and carbon-based gas-phase absorption filtration systems. 3. Alternative use of environmental control systems. Controlled RAC: 3E Standards : - 14 CFR 25.831 Ventilation (Michaelis, 2018) 4. Bleed Air Leakage Cause: Uncontrolled loss of bleed air due to ruptured air ducts and failure in the engine compressor. Effects: Direct effects of leakage would cause aircraft structures to lose structural integrity, various aircraft components to overheat, and an in-flight fire. RAC: 1C Recommended Controls: 1. Conduct regular inspections of the engine and valves to ensure the bleed air systems and their redundancies maintain good conditions and are working within safe limits. 2. Execute the bleed air leak detection systems, bleed air monitoring systems, and overheat detectors to warn against excessive temperatures. 3. Establish training programs to develop comprehensive knowledge for proper emergency decision-making and completion of maintenance inspections. Controlled RAC: 1E Standards : - 14 CFR 23.111 – Turbine engine bleed air system (GovInfo, 2005) - 14 CFR 33.66 Bleed air system, 2020) - ARP1796 – Engine Bleed Air Systems for Aircraft (SAI Global, 2015) 5. Corrosion Cause: Prolonged stress on the system or structure may result in corrosion. Severe changes in environmental conditions and situations of material incompatibility are also contributory causes. Effects: Corrosion at the ducts or valves can cause failures and leakages to the bleed air system. Corrosive attacks aggravated by erosion may also result in structural failure. RAC: 1C

Recommended Controls: 1. Frequent use of non-destructive inspection methods at ducts and valves for possible identification of cracks or fatigue developed by corrosion. 2. Implement corrosion inhibitor sealants or coatings to the metallic structures of the bleed air ducts and valves. Controlled RAC: 1D Standards: - 14 CFR 135.415 Service difficulty reports (GovInfo, 2008) - AC 43-4B – Corrosion Control for Aircraft (FAA, 2018) Risk Assessment and Recommendations Hazard 1: Contaminated Bleed Air Risk Assessment: The risk is assessed as Controlled Critical (B) due to potential health and safety risks. Recommendation: Implement and strictly adhere to rigorous maintenance and inspection protocols for the aircraft's engines to prevent engine leaks and contaminants from entering the bleed air system. Enhance contamination detection and filtration systems. Regular training of maintenance personnel in identifying and addressing engine leaks is essential. Hazard 2: Bleed Air Leaks Risk Assessment: The risk is assessed as Controlled Marginal (C) because of the risk of cabin pressurization loss. Recommendation: Regular inspections of bleed air system components, including ducts and connections. Maintain a robust maintenance schedule for repair and replacement of ducts to prevent leaks. Implement stringent quality control measures during manufacturing and assembly of these components. Crew members should receive thorough training in recognizing and addressing potential leaks during pre-flight checks. These recommendations aim to reduce the identified risks associated with these hazards in the aircraft's bleed air system. Proper maintenance, redundancy in critical systems, and continuous training are crucial aspects of risk mitigation in aviation. 6. Inadequate Anti-Icing/De-Icing Cause: Equipment malfunction, Human error.

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Effects: Inadequate anti-icing/de-icing measures can lead to ice build-up on critical aircraft surfaces, compromising aerodynamics and affecting safety. RAC: 2C Recommended Controls: 1. Frequent anti-icing system checks, maintenance, and testing. 2. Enhanced training of personnel 3. Clear procedures for de-icing to prevent ice build-up Controlled RAC: Standards: Hazard Condition Item 1: Aircraft Cabin Bleed Air Contamination Quality air distribution throughout the cockpit and cabin during air transportation in a pressurized aircraft is extremely critical to human health (Day, 2015). Improper filtration of the bleed air systems and fumes can severely affect the health of passengers and the aircrew on board. Improper filtration of air due to air contaminants could also impair crew efficiency or cause physical discomfort to the pilots or physical distress or injury to the cabin crew and passengers (Michaelis, 2018). Risk Assessment 1 The severity of such occurrence is "Marginal" as exposure to harmful gasses can affect the health of the passengers and cabin crew. However, due to the system's safety design and environmental control systems, the severity of risk can be "Minimal." Also, the probability of a mishap of this nature is categorized as "remote" due to the rare occurrence of air quality events in an aircraft cabin cockpit (Day, 2015). However, it is still important to note when designing a sampling strategy for hazardous constituents for bleed air (Day, 2015). The risk assessment matrix assigns these risks a classification of "3D," which, according to Table 2.3 Chapter 2, is acceptable but requires management review. Recommendation Thorough research can be done to develop effective air cleaning technology for the engine bleed air supplied to the cockpit and cabin of the pressurized aircraft (FAA, 2013). This is backed up by the requirements of the FAA Modernization and Reform Act of 2012, HR 658 (the Act), Section 917 (FAA, 2013). Airworthiness ventilation and heating requirements under 14 CFR 25.831 should be strictly followed. The requirement would be that each crew compartment has enough fresh air, enabling crew members to perform duties without undue discomfort or fatigue, and require crew and passenger compartments to be free of harmful or hazardous concentrations,

gasses, or vapors (Michaelis, 2018). As such, provisions must be made to mitigate risk if the ventilating or pressurization system fails (Michaelis, 2018). The ventilation requirement under 14 CFR 25.831will also help manufacturers be aware of the design requirements so that any probable failure of the bleed air system, the ventilation system would be able to provide enough uncontaminated air to the cabin and cockpit so that the crew members can perform their duties effectively. As such, even though a RAC of 3D is considered acceptable with a review, there is still a need to reduce the risk and ensure the following recommendations listed above can be adhered to. With that, it would further reduce the probability of occurrence to an improbable level. Once the recommended control actions are in place, a controlled RAC of 3E (Marginal/Improbable) can be assigned. Hazardous Condition Item 2 Bleed Air Ducts/Valves Leakage High temperature and high-pressure bleed air can structurally degrade aircraft structures, and leakage can occur (Johnson, 1987). The high bleed air temperature is due to compression, and the bleed air extracted from the engine can be hotter than necessary, so it passes through a precooler before it reaches the other systems (National et al. [U.S.], 2002). Long and heavy usage of the bleed air system, the precooler may malfunction, and ducts might leak or get damaged, which can cause the overheating of aircraft components and possibly lead to a fire. Risk Assessment Due to the long and heavy usage of the bleed air system, the probability of such occurrences can be categorized as "Occasional." The severity of such a mishap can be considered "Catastrophic" as fire and multiple degradations can severely damage the aircraft structure and cause the aircraft to be uncontrollable, which could lead to a crash. The risk assessment matrix assigns this risk classification of 1C, which, according to Table 2.3 in Chapter 2, is unacceptable, and changes must be made. Recommendation The usage of tough and corrosion-resistant materials during the production of the bleed air ducts and valves is highly recommended to prevent or reduce the risk of leakage and to ensure a long- life service and durability of the parts. Another effective way to reduce risk would be to apply an air leak detection system. This bleed air leak detection system monitors the pneumatic ducting for high-temperature bleed air leaks, and it will automatically shut down the respective bleed system when a leak is detected (CRJ Regional Jet, n.d.). This safety device will help protect the other system components from further damage. Using bleed air monitoring systems can help to sense the loss of pressure caused by a duct failure, and it can send a warning signal to the flight deck (Home, 2011). Regular inspections of engines and bleed air ducts/valves must be conducted to ensure the systems are operating within safe parameters. Conduct required training so the engineers and operators know the dangers of such risks and how to prevent them. The ARP 1796 (Engine et al. for Aircraft) is the aerospace recommended practice (ARP), which involves design philosophy, system, and equipment requirements, and this could help manufacturers design the

system with minimal risk. With all these recommendations and ARP in place, it would significantly reduce the hazard risk associated with this condition. Therefore, the controlled RAC of 1E (catastrophic/improbable) could be assigned to this condition once the recommended controls are implemented. References: CRJ Regional Jet. (n.d.).Chapter 19 - Pneumatic. Retrieved from http://www.smartcockpit.com/docs/CRJ-00_and_00-Pneumatic.pdf Day, G. (2015). Aircraft cabin bleed air contaminants: A review. Retrieved from https://www.faa.gov/data_research/research/med_humanfacs/oamtechreports/ 2010s/media/201520.pdf Federal Aviation Administration. (2013). to Congress on engine and APU bleed air supplied on pressurized aircraft. Retrieved from https://www.faa.gov/about/plans_reports/congress/media/ Report_to_Congress_on_Engine_and_APU_Bleed_Air_Supplied_on_Pressurized_Aircraft.pdf Horne, T. A. (2011, March 1). System synopsis: Bleed air malfunctions. Retrieved December 8, 2019, from https://www.aopa.org/news-and media/all-news/2011/march/01/system-synopsis-bleed-air- malfunctions. Horne, T. A. (2011, March 1). System synopsis: Bleed air malfunctions. Retrieved December 8, 2019, from https://www.aopa.org/news-and-media/all-news/2011/march/01/system- synopsis-bleed-air-malfunctions . Johnson, A. (1987). Effects of aircraft engine bleed air duct failures on surrounding aircraft structure. Retrieved from https://apps.dtic.mil/dtic/tr/fulltext/u2/a181071.pdf Michaelis, S. (2018) Aircraft Clean Air Requirements Using Bleed Air Systems. Engineering, 10, 142-172. doi: 10.4236/eng.2018.104011. Vincoli, J. W. (2014).Basic guide to system safety (3rd ed.). Hoboken, NJ: John Wiley & Sons.

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