Introduction:
Safety is of paramount importance in all developments associated with the commercial airline industry. Through rigorous qualification and acceptance testing, dramatic technological improvements have brought tremendous advancements in air travel. A highly successful example is development of the Boeing 777 jetliner. Requiring coordination of an incredibly complex network of developers and suppliers, the substantial impact that a seemingly small design detail can have on overall cost and schedule effectiveness of a larger development program becomes very clear. When one critical supplier for the power plant development effort encountered such a problem, Single Iteration was able to step in and provide an alternative solution that avoided a costly delay.
Customer Challenge:
The supplier of a new synthetic engine fluid was well behind schedule. The new fluid was intended to increase lubrication flow for faster in-flight starts and reduced engine wear under cold start conditions. The engine test program could not proceed until the new fluid was available. The engine manufacturer determined that an alternative fluid could be used if critical engine components were preheated for cold starts. The engine manufacturer approached Single Iteration for assistance after their other development partners were unable to provide the resources and expertise to address the heating problem.
Single Iteration Solution:
As the engine design and development program was largely complete pending qualification testing, the addition of heating could not add more than 2.5 pounds of additional weight nor could it impact the existing physical design envelope and mounting interfaces. To address these constraints, Single Iteration concentrated on a "heated part" approach; whereby, non-structural components were replaced with form and fit heaters cast into the shape of the existing mounting envelope. In addition, analysis determined a redundant sensor probe could be eliminated from the engine without affecting system performance or reliability. Single Iteration developed a heater in the shape and configuration of the probe. This allowed heat to be efficiently applied to a critical bearing interface. Through the use of self-limiting heater elements, the need for closed loop sensing and control was also avoided. This allowed the heaters to self adjust their power dissipation based on the engine temperature, eliminating the need for discrete controllers, sensors, and additional wiring. A Built-In-Test (BIT) circuit was designed into the thermal system such that operating health and status could be monitored by existing on-board computers. Following delivery and integration of prototypes, extensive testing for environmental, reliability, maintainability and performance resulted in successful completion of the engine development program.
Through this development, Single Iteration enabled the customer to overcome a major thermal management problem that had halted their development. Creative analysis of requirements and consideration of alternatives allowed us to provide a solution with minimal impact to the existing customer design and development schedule.
