Avionics systems are complex and often interdependent, as demonstrated in an aircraft cockpit that houses control, monitoring, communication, navigation, weather and anti-collision systems. These highly regulated electronics are among the most expensive and standardized products available—considerable investments that are expected to perform for up to 30 years, making the determination of product lifetime reliability a top priority.
Commercial and military aircraft are exposed to a myriad of rugged environmental conditions including extreme temperature, shock, pressure, vibration and moisture. Therefore, accurately assessing reliability in the design phase is difficult. To address these complexities, reliability engineers must approach testing and prediction of long-term avionics reliability through product lifecycle simulations.
Reasonable assumptions for simulation are often based on certain things like components conforming to datasheet values, manufactured assembly quality and anticipated behavior of components. However, there are specific factors related to avionics that, if overlooked in deference to assumptions, can be causes for concern and potentially costly in time, money and reliability:
Environment-related thermal stresses
Given the inherent mobility of aircraft, avionics undergo temperature fluctuations that are largely determined by the weather in the takeoff and landing locations, the number of flights per day, and the duration of the flights. More complex than either diurnal fluctuations or simple flight cycles, these thermal stresses in the environment must be accounted for and mitigated within the design.
Product-related thermal stresses
By understanding which components will dissipate any significant power, their contribution to the thermal stress inside of the enclosure can be calculated by using powerful thermal simulation tools. In addition, avionics stack configurations that retain heat and and distribute it throughout the entire line replaceable unit (LRU) can cause overall temperatures to rise and can also be assessed using the same thermal simulation tools.
Mechanical stresses in the environment
Avionics are known to be highly influenced by two failure-inducing mechanical stresses: Vibration and shock (particularly from landing gear deployment, speed brake use and landing impact). Estimating the frequency of shock and vibration events helps accurately define the environment, predict probability of failure and ultimately inform design decisions.
Naturally, the duty cycle impacts avionics systems reliability because the more a component is used the sooner it will wear out. Determining an accurate measurement of the proportionate time of operation (duty cycle) to predict reliability requires specific knowledge and simulation of time in use, cycles per day, flights per year, dormant conditions, intensity of use, low to high power cycles and low data rates versus maximum loads.
Tools like Sherlock Automated Design Analysis™ software address these challenges and more, ensuring accurate product lifecycle simulation and proven reliability for avionics systems. To learn more, access our webinar Guarantee Reliability with Vibration Simulation and Testing. Click the button below.