gph, and injected bottom-induction
Continentals often have a spread of 1. 5 gph
or more. Some carbureted engines (e.g.,
Continental O-470-series) can have spreads
in the 2-3 gph range. Experience indicates
that if your engine has a GAMI spread above
1.0 gph, it probably won’t be able to run
smoothly at LOP mixtures.
Figure 2 shows a mixture distribution
test that reveals a GAMI spread of 0.5 gph,
which is quite good. Note that this engine
monitor is configured to capture fuel flow
information, making the analysis very easy
and eliminating the need to record the fuel-flow information manually.
I recommend performing this test every
12 months or 100 hours, whichever comes
first, and also anytime any sort of engine
anomaly is suspected.
INDUCTION LEAK TEST
This in-flight test is an effective method for
detecting leaks in the engine’s induction
system. It is best accomplished in level
cruise flight at about 5,000 feet MSL. It
consists of a pair of tests: the high-MP test
and the low-MP test.
Mike Busch, EAA 740170, was the 2008 National Aviation
Maintenance Technician of the Year and has been a pilot for
44 years, logging more than 7,000 hours. He’s a CFI and A&P/
IA. E-mail him at mike.busch@savvyaviator.com. Mike also
hosts free monthly online presentations as part of EAA’s
webinar series on the first Wednesday of each month. For a
schedule, visit www.EAA.org/webinars.
