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As an old school A&P can you tell me why the recip transports usually had
a
BMEP guage which was given its (oil press) signal from the torque nose of
the (HamStandard) prop? If it is true BMEP is a mathematical construct, and
it is, how and with what error was the Tq given as BMEP? Is it just a
piston era relic? Do modern turbine Tq guages have any intrinsic misleading
error?<<
This repeats a little from the previous excellent post, but it might be
worthwhile for its simplicity: As far as I know the torque sensing for the
old radial engines and the new turbine engines are essentially the same.
Both use planetary gear speed reducers and use the torque reaction of the
stationary element to push on a hydraulic cylinder. The pressure is
directly proportional to engine torque and is displayed in units that are
understandable (psi wouldn't do it). For piston engines BMEP is a number
that will translate well between different engines and will correlate to
textbook information. For turbines I believe they just display it in
percent of rated or something to that effect. There are no inherent errors
in this approach, just the normal errors do to friction, tolerances, etc.
Gary Casey
ES project
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