All historical jet aircraft had single-spool engines. How should the N1 and N2 related values for a such be chosen? Will making sure N1 always equals N2 work? Or is this an untested edge case and in reality one should pretend that the engine has two spools and just tweak the values and tables until the performance matches the documented performance of the real aircraft?
I’ll check two add-on aircraft from my Community folder that have single-spool engines, Sim Skunk Works’s TF-104G, and Tyler Gladman’s Bristol 188.
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The TF-104G has a J-79 engine. The engines.cfg makes some effort to ensure that N1 equals N2. For instance low_idle_n1=67 and low_idle_n2=67. It uses a n2_to_n1_table where for the most part N1 indeed equals N2. Except at the higher N1 (and N2) values, where N2 exceeds N1. I have no idea whether this is just an oversight or whether the thing would not work otherwise. Also some other values are different for N1 and N2, like min_n1_for_combustion=10 but min_n2_for_combustion=19.4.
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The Bristol 188 has a de Havilland Gyron Junior engine. In its engines.cfg there doesn’t seem to be any attempt to tell that there is no separate N1 and N2. For instance, low_idle_n1=25 and low_idle_n2=61. But the rated_N2_rpm=9200 which presumably is in the right ballpark and much too low to match more modern two- or even three-spool engines that have a much higher N2 RPM, don’t they, that’s the point of having separate spools, the LP one with larger fan, compressor, and turbine blades needs to spin slower than the core one with small compressor and turbine blades.