Vivian Meazza wrote:
> y = -0.25x3 + 0.15x2 + 1.11x
> Thinking about the over-speed situation overnight, the Merlin was
> allowed to go to 3600 rpm for brief periods, and even then damage to
> the engine was possible. This is a normalised value of 1.2. The K
> Series will go to 9000 (don't try this on yours - it requires special
> valve lifters and crankshaft) or 1.28 normalised. The curve shown
> here:

Yes, but remember that the "normalization" RPM isn't guaranteed to be
a maximum speed.  It might be for your merlin configuration, but I can
guarantee you (seriously: 100% certainty) that if we include a model
that goes wacky in some regime, someone will come up with a
configuration to tickle the bug.  This has happened again and again,
often with your aircraft. :)

How about this one instead:

   ln(rpm_norm - 1) * (1 / ln(2))

It seems to qualitatively match the curve you posted (is there a
primary source for that curve?) without the nasty dropoff.  You can
see how it works, it just translates/scales a logarithm curve to pass
through the origin and (1,1).

Let me know.


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