AOPA Pilot Magazine - May 2020 - 89

position. Quite a bit of interesting analysis
can be done with this data.
In 2012 my company launched a free
web-based digital engine data analysis
platform at SavvyAnalysis.com. Since then,
owners have uploaded data from more than
10,000 piston GA aircraft to the platform,
and our database now contains data from
some 2.5 million flights. From inception,
this platform has automatically flagged
exceedances such as high CHT. In recent
years, we've been developing and incorporating more sophisticated predictive
analytics algorithms.
Failing (burned) exhaust valves
are "rare events," but they're the leading cause of cylinder replacement, and
exhaust valve failure is a significant cause
of piston engine power-loss incidents. I've
long observed that failing exhaust valves
often cause small, slow, rhythmic EGT
oscillations that are fairly easy to spot in
a graphical plot of the data. In 2015, we
developed a heuristic algorithm called
FEVA (Failing Exhaust Valve Analytics)

that scans all uploaded engine monitor
data for this signature. We've been using
this to alert owners to the possibility that
they may have a failing exhaust valve and
that a borescope inspection of the cylinder
is suggested. But to be honest, we've been
less than thrilled about the accuracy of the
FEVA algorithm.
Over the past year, we've been developing a new algorithm (FEVA 2.0) that
uses machine learning techniques, and
we've trained the algorithm on thousands of flights involving known-good
and known-failing exhaust valves. The
result is a significantly higher accuracy
rate and fewer false positives than the
heuristic FEVA 1.0.
In the meantime, we've been working hard to develop another algorithm
(SEVA) to detect the sticking exhaust
valve syndrome that especially afflicts
Lycoming engines and is often referred
to as "morning sickness."
A st i c k i n g ex h a u st va l ve t y p ically starts off causing fairly

innocuous roughness when the engine is
first started cold, and which goes away as
the engine warms up. But if not detected
and addressed early, a sticking exhaust
valve can progress to the point that it
results in a bent pushrod and power
loss, and occasionally a valve strike and
catastrophic engine failure. It's obviously important to catch this condition
early when it's still in the incipient stage.
This seems like a perfect candidate for
predictive analytics, and the preliminary results of our R&D have been very
encouraging.
Predictive maintenance is clearly
the wave of the future. The more sensors we have in our airplanes, the more
comprehensive and powerful it will
become. Over time, it will increasingly
be our aircraft-not our mechanics-
that tell us what maintenance needs to
be done.
AOPA
MIKE BUSCH is an A&P/IA.
EMAIL mike.busch@savvyaviation.com

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AOPA Pilot Magazine - May 2020

Table of Contents for the Digital Edition of AOPA Pilot Magazine - May 2020