The world of aviation often intersects with automotive engineering, and one compelling example is Austro Engines. This company has carved a niche for itself by developing aircraft engines based on Mercedes-Benz automotive diesel technology. A recent discussion among aviation enthusiasts highlights the ongoing considerations and decisions surrounding Austro engines, particularly concerning the engine block material and the future direction of the company.
Austro Engines’ journey began with a strategic decision to leverage the proven reliability and performance of Mercedes-Benz engines. Initially, they utilized a large stock of Mercedes-Benz OM640 car engines. These engines, known for their robust cast iron blocks, became the foundation for Austro’s AE300 and AE330 aircraft engines. Austro’s process involved taking these OM640 engines, removing the car-specific accessories, and integrating essential aircraft components like gearboxes and Bosch ECUs. This approach allowed Austro to enter the market efficiently, capitalizing on Mercedes-Benz’s established manufacturing and component supply chains.
However, as time progressed and Austro engines gained popularity, a crucial question emerged: what happens when the supply of original Mercedes-Benz OM640 engines runs out? Mercedes-Benz has since moved on to newer generations of four-cylinder diesel engines, leaving Austro to consider its options. One point of discussion is whether Austro should continue manufacturing engines with cast iron blocks, essentially creating their own version of the OM640, or transition to a more modern design potentially featuring an aluminum block.
The debate around aluminum versus cast iron blocks brings several factors into play. Initially, Mercedes-Benz themselves used an aluminum block in a 1.7-liter engine that Thielert, another aircraft engine manufacturer, adapted. When Mercedes-Benz shifted to a 2.0-liter cast iron block, Thielert chose to develop their own aluminum block version. This decision, while aimed at maintaining engine weight and balance for aircraft compatibility, contributed to financial strain for Thielert. Austro, in contrast, opted for the readily available cast iron block Mercedes engine, and aircraft manufacturers like Diamond Aircraft adapted their airframes to accommodate the slightly heavier engine.
The advantage of an aluminum block is primarily weight reduction. Switching to aluminum could potentially reduce the engine weight by around 50kg, which translates to an increase in aircraft payload capacity. This is a significant benefit in aviation, where weight directly impacts performance and efficiency. However, the transition to an aluminum block is not straightforward. It would necessitate significant re-engineering and, crucially, a costly and time-consuming engine recertification process for aviation use. Furthermore, aircraft manufacturers would also likely need to recertify their airframes to accommodate any changes.
Cast iron blocks, while heavier, are known for their durability and robustness. One key difference highlighted in discussions is the overhaulability of cast iron blocks compared to aluminum blocks. Cast iron engines are often considered more amenable to overhauls, extending their operational lifespan. This is a critical factor in aviation, where engine longevity and reliability are paramount.
Ultimately, Austro Engines appears to have chosen a path of continuity and stability. Recent reports suggest that Austro has secured a license from Mercedes-Benz to manufacture the OM640 engine cores themselves. This strategic move ensures a consistent supply of engine cores without the need for major design changes or recertification hurdles. By manufacturing under license, Austro can maintain the proven design and reliability of the Mercedes-Benz-derived engine, focusing on production and meeting the demands of the growing market for their aircraft engines. While moving to newer engine technologies with aluminum blocks might seem appealing for weight savings, the complexities and costs associated with recertification, coupled with the reliability and established manufacturing processes for cast iron block engines, likely made continuing with the OM640 design the most pragmatic and economically sound decision for Austro Engines at this stage.
This reliance on a robust, if somewhat older, automotive engine design is not entirely unusual in the aviation world. Established piston engine manufacturers like Lycoming and Continental continue to produce engines based on relatively older technologies. The high costs and regulatory hurdles in aviation engine development and certification often favor evolutionary improvements over radical changes. Austro Engines, by building on the foundation of Mercedes-Benz automotive diesel technology, has successfully navigated this landscape, providing modern, reliable diesel power for general aviation aircraft.
