System Safety is an essential aspect of the aviation industry. To comprehend the analyses and studies conducted in this domain, it is vital to focus on the definition and explanation of safety. System Safety refers to the entirety of management and engineering methods applied during the design, development, production, operation, and maintenance stages of a system to minimize the probability of causing harm to human health, the environment, or property. It is a systematic and integrated approach to identifying, analyzing, assessing, and controlling safety risks. System Safety provides a continuously updated perspective throughout the lifecycle of aviation systems, including pre-flight, flight, post-flight, and maintenance stages, through various analyses and inputs.
The first stage of the safety concept involves identifying, exposing, and analyzing risks. Subsequently, efforts are made to eliminate these risks, or if elimination is not possible, mitigation activities are implemented to keep risks at an acceptable level. These mitigation efforts include various System Safety methods and analyses. The acceptable level of risk is directly proportional to the criticality of the system. Therefore, activities must be carried out using systematic approaches to understand the system and ensure System Safety.
In aviation, the primary purpose of the Fuel System is to supply sufficient fuel to the engine during all flight phases. The Fuel System performs essential functions such as storing fuel, delivering the stored fuel to the engine under the desired conditions, displaying the remaining fuel to the user, and providing information in case of abnormal conditions. Therefore, the Fuel System is a critical subsystem from a System Safety perspective. A reliable fuel system is required to ensure the engine operates safely, maintain proper weight distribution and performance, and support emergency management.
Ensuring a continuous supply of fuel to the engine is essential to prevent engine failures. Interruptions in fuel flow can lead to engine shutdowns, jeopardizing System Safety. Moreover, fuel management must be maintained to keep the helicopter balanced and ensure stable flight. A malfunction in fuel management can result in imbalances and control issues for the helicopter.
On the other hand, the components of the Fuel System pose a fire risk due to their direct interface with fuel. These risks can be minimized by addressing factors such as leaks, fuel vapors, overpressure, temperature, material-fuel compatibility, and electrical insulation.
Redundancy is another crucial focus area to minimize risks and enhance reliability. Redundant systems play a vital role, especially in emergencies, by providing users with greater control and flexibility for safe landings. The Fuel System is one of these redundant systems. Measures such as ensuring continuous fuel supply to the engine during a malfunction, preventing erroneous fuel level indications to the pilot, and diagnosing faults at an early stage enhance both System Safety and operational reliability of the helicopter.
In a helicopter, the redundant structures within the Fuel System typically include the following:
- Backup Fuel Tank: In case of a failure in one of the components responsible for fuel storage, the other component can fulfill this requirement.
- Backup Fuel Pump and Filter: If a failure occurs in one of the pumps supplying fuel to the engine, the other pump can continue fuel delivery.
- Dual Fuel Lines: If one line fails, fuel can be delivered to the engine via the other line.
- Emergency Line Shutoff Components: In potential engine emergencies, fuel supply may need to be cut off. Components responsible for shutting off lines are redundantly designed within the system architecture.
- Fuel Quantity Measurement Methods: In addition to multiple sensors for fuel quantity measurement, indicators can provide low-level information.
- Overpressure and Overfill Prevention Components: Breather lines and pressure relief components are used to prevent excessive pressure in fuel tanks. These components also prevent critical errors, such as overfilling during refueling, in case of float malfunctions.
In summary, the contributions of the Fuel System to System Safety in helicopter platforms are as follows: reliable engine performance, continuous fuel delivery to the engine even in the event of a failure through redundant designs, and maintaining the helicopter’s balance and stability. These features ensure that the helicopter can operate safely and/or perform a safe landing under both normal and emergency flight conditions.4o