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<< Lancair Builders' Mail List >>
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George, Fred and Brent:
The responses to your thoughtful and educated
suggestions to the "supercharger" project should
only serve to convince you further what an utter
waste of time it is to offer facts, engineering, and
experience into the world of wishful thinking
and perpetual motion.
<<<...Right now @ 42in. MAP our inlet temp is
150F so I do not see a need for coolers yet on
the Normalized version...>>>
AHA, someone has (yet again) repealed the fundamental
laws of thermodynamics.
Although a multistage axial compressor can be more
thermally efficient (85%) (oops, 0.85 for Eric) than the
best of the single-stage centrifugal compressors such
as found on turbochargers (typically around 75% in a small
operating-efficiency island), the temperature-rise numbers
assuming hot-day inlet-air (as they do for certification)
suggest that 150F cylinder-inlet temperature at
42" MAP might be the product of faulty instrumentation.
But hey, real data might burst the bubble.
<<<...Testing as you know tells all...>>>
Actually, testing DOES NOT tell all.
Testing proves only the EXISTENCE of flaws,
not the absence, of flaws.
<<<...But in normal operation you do not run 100% power at high
flight levels and therefore the heat is less of a problem than
you state...>>>
I don't recall Fred suggesting that the problem was limited to
the regime of 100% operation. The problems Fred described
have been experienced, documented and worked-on by
real engine experts, but hey.....
As you probably suspected, George, all those people
who have worked on reducing the detonation-sensitivity
of the TIO-540's and GTSIO-520's (Chieftan, P-Nav, 421,
AC-685, etc.) must have had no grip on what they were
doing, because they found that, with inlet air temps of
150F (and EXTERNAL-SURFACE CHT's above 400F)
there was a distinct propensity for destructive
detonation, which they could only remedy by
calibrating in fuel flows which produced BSFC's
of 0.7 at high power operation.
<<<...we are going to photo the panel on all flights
for data storage...>>>
During the flight test program for the STC-engine retrofit
of the Orenda V8 into the Aero Commander 685, I found
that the only reasonable way to collect comprehensible
flight test data (with sufficient detail and real-time
correlations to actually troubleshoot problems instead
of guessing) was with a computerized data acquisition
system.
I put together a system which took inflight data readings
at one second intervals, then downloaded the data
(postflight), post-processed the raw data to
produce flight data and engine data, and produced both
onscreen and hardcopy graphical (trend analysis) and
numeric data from the flight.
The raw data recorded were: Pitot pressure, Static pressure,
OAT, MAP, RPM, Compressor Discharge Temp & Pressure
(CDT, CDP), Intercooler Discharge Temp & Pressure
(IDT, IDP), air-delta-P and delta-T across all 3 heat
exchangers (Coolant, Oil, Intercooler), fluid delta-P and
delta-T across all 3 heat exchangers, oil pressure, oil temp,
coolant pressure, coolant temp, all 8 EGT's, TIT,
turbochanger RPM, pilot-inpit "MARK" button,
and 3-axis accelerations. (a bit more than is likely
to be available on the instrument panel of a Lancair,
even with a $100k (!!!!!!!) panel.)
Postprocessing produced flight data (pressure
altitude, density altitude, ROC, IAS, TAS, etc.)
and engine data sufficient to define and remedy
installation problems (many) quickly.
This system came into being after I found that it
was simply impossible to record sufficient data
with sufficient accuracy from the large panel of
(mostly digital) instrumentation I built into the
rear cabin of the test aircraft, with a dedicated
data-taking person at the panel.
Lest you think this was done on some
government-funded debacle, the total cost of the
DAQ system was less than $9k (of which,
a large percentage was sensors).
Jack Kane
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LML website: http://members.olsusa.com/mkaye/maillist.html
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Please send your photos and drawings to marvkaye@olsusa.com.
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