Thanksgiving 2017 - Mystery Engine Issue
Added 12/2017 - Approx 1300 hours
Time is like a runaway freight train these days and suddenly I
found myself at Thanksgiving season here in Wisconsin. While
we've had an extraordinary run of good weather here again this
fall (as I write this on 12/3 it's 48F out, but turning bad later
tonight), it's becoming more common to see days drenched in grey
skies, with plenty of low and high altitiude winds affecting our
flying. But Thanksgiving day we caught a big break, which
made our plans to travel to the North Milwaukee area to visit
family, a lot more enjoyable. By car we spend nearly 4
hours, each direction, making any "down and back in one day" trip
a painful experience, where there is more time spent in the car
than there is with the people we go to see. But by air, it's
a simple 1.25 hour flight, depending on the winds. With this
break in the weather, we booked a car out of KMWC and planned to
do it all by air.
We didn't want to inconvenience anyone with the care of our dog,
so we stuck on his Mutt
Muffs and loaded him in the plane too. We have a
special table-like board that has a seat cushion on it that lays
over the tunnel and has a couple of legs to stabilize it, allowing
the dog to lay comfortbly in the middle, of course also sprawling
over the passengers as dogs tend to do. He does really well
on our flights, and loves to go anywhere we do.
Looking at the foreflight screenshot below, you can see that there
was plenty of traffic in the Minneapolis area, so today was
definitely going to be a day where people got to use their
airplanes for travel. Incidentally, this may be one of the
last foreflight screenshots that I post. Their lack of any
sort of Family plan is driving my cost up considerably for that
product, whereas my WingX, FlyQ, and Aerovie applications are
fully able to be used by my wife and daughter. Foreflight is
top-notch stuff, but with one kid in college and another one there
soon, budget cuts have to be made, and I'd rather sacrifice an app
than an airplane. WingX is still wonderful software these
days, and works very well for me, but FlyQ has now made enough
improvements in features and stability that it has become the
"go-to" app for us when we plan x/c flights. You see, I took
advantage of a black friday special long ago to get a lifetime
subscription to their EFB product, and that means my wife,
daughter, and myself use that app for free for the long
haul. This year's black friday special brought a variety of
great lifetime data options for people, and their new FlyQ EFB 3.0
version and FlyQ online are ready for prime time as well. My
black friday purchase this year was their FlyQ Merlin ADS-B
receiver, with included AHRS. I had been looking at
Foreflight's "scout" device, to be used when I'm doing my CFI job
for the loal FBO in their rental planes, but the Merlin offers a 4
hour battery, dual-channel ADS-B system, and an AHRS for gauge
redundancy, and it was on the black friday sale for the same $199
price as the scout. My first couple of flights with it since
receiving it show that the AHRS is actually a lot better than I
figured it would be. The system syncs up with my iphone and
iPad very quickly, and every time I looked at the synthetic vision
display, the horizon matched up with the horizon on my Chelton
system. It should make a great backup gauge system for the
RV-10, should I ever need it. I have the iLevil 3AW in the
RV-14, which is even better in that it adds pitot and static
information and integrates with my engine monitor, but at a price
6x greater than this Merlin cost me.
Well, time to get on to the flight!
We didn't take much for pictures on these 2 flights, but you'll
notice something a little different about the photos above.
This was a trip where I spent one leg in the back seat.
Andrea and Danielle did the flight down, flying in great skies
with plenty of daylight. The back seat was pretty quiet,
with my tired college student, Colleen, getting a good nap
in. Quiet that is except for a little back-seat instructing
I did. ;) I find it hard to not offer tips and advice
to help make people either fly a little better, or at least better
understand the "hows" and "whys" about exactly why some of these
piloting rituals are done as we fly. I feel that probably
nearly ALL of the students we turn out these days are vastly
un-prepared for understanding exactly what they are doing for
engine management, or especially troubleshooting issues.
Personally, I feel the only way you will learn these skills is to
either A) fly with a variety of instructors, and those instructors
must have a varied background with pretty long-term skill set, or
B) spend a LOT of time reading on forums or online and in books to
really understand what is happening in their engines, and the
effects on their engine when they move the various control levers
or knobs in their plane.
This engine understanding all came to a task on the trip down to
KMWC, as my sharp daughter noticed our #1 EGT seemed to be a
little erratic, climing and falling maybe 20 degrees or more on a
random cycle. The CHT's seemed stable at first glance, and
weren't WAY off or anything, so my initial thoughts seemed to be
it would end up being either a bad EGT probe, bad probe
connection, or perhaps a partially plugged injector. I sat
in the back seat watching the numbers myself and pondered the
situation, but was also comforted in the fact that not only was
the airplane in good hands, but these engines don't just
disintegrate spontaneously...at least it's very very rare.
The flight down went great, and we had a real good time visiting
Andrea's family. Good food, good people...you know, a real
thanksgiving!
When it was time to load up for the flight home, Danielle was the
pilot and we used the time to complete a long night x/c for her
private certificate. We droned along in beautiful smooth and
clear skies, able to see Milwaukee, Oshkosh, Madison, and the
Wisconsin Dells, all at the same time out various windows. I
showed her how to identify airports by their rotating beacons, and
we kept focused on finding I-94 below...something that is a little
comforting to have below you when you're flying x/c at night.
As we flew along, I noticed that although the CHT's were fairly
stable, they definitely did not fit my normal temperature pattern
on the IO-540 in N104CD. On nearly all flights in cruise,
CHT 1&2 are very close, and also closely match 5&6.
CHT's 3&4 are usually a little lower and also very similar to
eachother. It's a benefit of hours of experience in your
plane, when you know what temperature patterns you can
expect. On this flight, I noticed that CHT #1 was
lower than CHT's 2,5&6. That wasn't normal. So now
I had an EGT that was fluctuating and a CHT on that same cylinder
that was low. That pointed to a definite cylinder issue on
#1. The only question was, how bad was it and what exactly
was it. I could now rule out the bad EGT probe and bad probe
connection, at least...but depending on the issue, it could be
more expensive than if it were those options. We made it
safely home and the engine sounded just fine. I only wish I
had looked closer at the EGT's when we did the runup, as perhaps I
would have noticed something there. I didn't, because prior
to this I was expecting it to be a probe issue.
When we got back in the hangar, I downloaded the engine logs, and
sent them up to SavvyAnalysis to review, and once I could see them
in graph form, it was much easier to see the variations.
Notice below that even on the full flight view, you can see the
ripples in EGT 1. But you also see places where CHT 1 takes
some dips. The EGT and CHT both have variation from the
other cylinders at various points of flight. Looking at the
graphs, again, clearly something isn't right, but, I didn't
exactly know what to expect. I was still thinking Injector
plugging, or spark plug issue, or if something were really going
nasty, maybe a valve issue.
It took me all of 10 minutes to yank the top cowl, pull the top
plug, and stick the borescope cam in and have a peek. I saw a
fairly clean cylinder, with a nice dry piston top, but when I
flipped the camera around to check the valves, I got my
diagnosis. Looking at the bottom spark plug that was still
installed, you could see it did NOT look right at all. You
could tell that either something had melted or broken on the
plug. With all the deposits in that area, it was hard to
really see for sure what to expect, as they distracted me from the
big picture. On the good side though, I had a VERY nice
picture of both my intake and exhaust valves and those looked
wonderful. So the expensive issues were now ruled out.
A $75-80 fine-wire spark plug was probably the worst thing I'd
face.
I pulled the bottom cowl and plug, yanked the plug, and you could
see the ugliest lead-fouled booger I'd ever seen in my life!
It came out easily with a pick, and the plug was easily
cleaned. This is the FIRST fully fouled plug I'd ever had on
the RV-10 in 1300 hours. My top plugs, with Lightspeed
Ignition, have never had any fouling whatsoever. My bottom
plugs, however, occasionally have gotten some lead gobs in
them. The bottoms are much more susceptible to such things,
as they not only have a much weaker spark, driven by a magneto,
but also are inverted, acting as a little "cup" for the
lead. This plug was cleaned, and returned to service, and
after that the engine ran just fine with no more EGT/CHT issues.
Looking back at my logs, this did not happen on our trip to see
the eclipse in August, but started some time after that.
Looking at the time after that last trip, I had done some long
idling periods, and flights where we did landing practices with
the mixture often kept full rich throughout multiple
landings. It doesn't take much time at full rich on the
ground to foul a set of plugs. As a reminder to all pilots,
the best thing you can do for your plugs is to do a couple of
things: 1) Do the "Mixture Full Rich" landing
checklist item just as you turn from Base to Final. i.e.
don't fly the whole pattern or start the "full rich" segment when
abeam the numbers. People may argue with me about this, and
I accept your arguments as valid points, but if you want your
engine to perform well, only be full-rich when also at full
power. 2) as soon as you are on the ground, or, before
you taxi, lean your engine as far as you can possibly lean it
without it running rough and quitting. Lean it so far that
if you push the throttle forward, the engine wants to die. It's
when you are UNABLE to give it full power that you are doing it
right. This will give you a very lean mixture for taxi, and also
prevent you from accidentally taking off without going full-rich
first. This has been my common practice for nearly 20 years
now. I don't expect a new private student to be able to keep
the pace up all the time when flying touch and go's in an RV, as
things happen very quickly when you're flying patterns in an RV.
But, as they progress and can handle drinking from the fire hose a
bit better, it's something that be improved on to encourage good
engine management at all times during a flight....from engine
start, to engine shutdown. One more short paragraph below...
First, an engine shutdown tip: Before shutting down your
engine, first run the RPM to about 1800 RPM approx. Then,
drastically lean your engine until it stumbles. Watch for
your EGTs to hit 1200 for a few seconds, then pull back the
throttle to idle and once it's idling, mixture full cut-off.
Doing this will help burn off the lead before you shut down.
You have to get to 1200 degrees or so before it will help and make
a difference.
Now for a pet peeve... Yes, there's a lot going on during an
engine start, and yes, hot starts can be harder than cold starts.
This issue happens easily during hot starts but I see it happen
during cold starts as well. When you fire up and
engine, none of the bearing surfaces yet have their oil film
barrier to keep the engine parts from touching. Once the oil
pump is operating, the film of oil prevents direct metal to metal
contact. But you first have to have oil pumping.
(unless you have a pre-oiler, which I sure wish I had) This
means that during startup you DEFINITELY don't want to go
immediately from not-running to high RPM. Advance the
throttle only enough for about 1000 RPM during startup. If
you advance it more, such as during a hot start when you're doing
Wide-Open throttle and mixture off, you want to be very quick on
the throttle lever once it fires, and get that mixture rich and
throttle to idle a.s.a.p. It's just one more thing that can
keep your engine intact for more hours, and these engines aren't
cheap.
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