Snecma M53 - Design and Development

Design and Development

Although an entirely new design, the M53 is very similar in concept with the previous family of SNECMA military engines, the ATAR 9C and 9K, in that it has a single shaft driving both the fan and the high pressure compressor. Although this made it rather “dated” in comparison to other engines of the same generation, this gave the M53 some very desirable traits for a military engine. It allows for carefree operation, whereas a two-spool engine of the same generation required much more care during its operation; this is ironic in that 2-spool turbofans were originally invented to avoid the problems that single stage fans encountered during abrupt throttle movements. When one compressor section stalls on a single-spool fan, it directly effects the entire spool. When one compressor stalls in a 2-spool type, the remaining compressor and turbine continue to function independently, maintaining partial thrust and making it easier to get the stalled compressor working again, without relying on "windmilling" to ensure the engine will start. The M53's maintenance is vastly simplified, being of modular construction (subassemblies or modules do not require calibration when exchanged), and engine parts are changed “on condition”, that is, they do not expire after a given amount of hours of operation or time since installed, but rather on the general condition of the part or subassembly at the moment of inspection, which cuts down on maintenance costs. It is a simple engine in general, having no variable stators and less moving parts, it is reliable and pilot friendly, free of operational restrictions (extremely important in combat). However, it is the only known single-spool turbofan extant as of 2013, and it's manufacturer transitioned to a more "conventional" two-spool design in subsequent engines, such as the Snecma M88.