Thermal Management Solutions for enhanced Digital Flight Data Acquisition Unit in Avionics Applications

According to the Federal Aviation Administration, the commercial airline industry should expect to see the number of passengers traveling per year to grow from its current level of 750 million to nearly 1 billion by 2030. To meet this demand, airlines are placing orders for thousands of new aircraft over the next decade and beyond. With this increase in airline traffic, newer aircraft systems will generate an ever increasing amount of data per flight, data that allows airlines to further enhance their flight operations, flight safety, and reliability. For commercial avionics, the migration of the data acquisition and reporting functions from the traditional interface environments to newer, faster, and more network-centric architectures is creating a new generation of “smart” aircraft. Teledyne Controls' enhanced Digital Flight Data Acquisition Unit is an integral part of a new generation of aircraft and combines the functions of Mandatory Data Acquisition and Recording with a sophisticated Aircraft Conditioning Monitoring System that the aircraft operator uses to monitor the performance and reliability of each aircraft in its fleet. Some of the critical goals in the development of the Digital Flight Data Acquisition Unit are reducing the size and weight over previous generations, while maximizing performance and reducing cost. All of these opposing requirements make the design and fabrication very challenging. One such challenge includes dissipating high power in a confined space, and this makes thermal management a critical component of the overall LRU (line-replaceable unit) design. In addition, to increase the reliability over the lifespan of the unit, passive cooling systems are often required in place of internal fans. This presents another set of challenges, such as optimizing the airflow provided by the aircraft in the electronics bay compartment. This paper will present some of the critical elements in thermal management such as heat sinks, components placement, thermal interface materials, thermal vias, thermal links, packaging approaches and cooling strategy. The design and optimization of the system are based on analytical solutions, conjugated heat transfer and experimental results. The LRU should safely operate under various environmental conditions: ground operation, flight operation, high operating temperature and loss of cooling air where each environmental condition has different parameters for coolant airflow rate, effect of the surroundings, and ambient and coolant air temperature. Draw-Through and Blow-Through cooling analysis were performed using CFD (Computational Fluid Dynamics). The thermal analysis problems solved are conjugated heat transfer for laminar flow with radiation in steady-state or transient regimes. Multiple approaches were identified to remove heat from the critical components through optimization of the components and subsystems. These same approaches can also be used to increase the system's performance and reliability.