The one and only one reason for flying small
aircraft is to have complete and utter
enjoyment leaving behind the stresses and worries aground.
Above, soaring through the air be it any kind of means
to lift one above the ground allows one to leave behind all
other thoughts and focus on that utter enjoyment of flight.
Sure, the views from above can be spectacular and if one is not
careful, cause distractions that overcome rightful thinking
forcing un-rightful decisions. On the other hand, when machines
are operating rightful, those machines speak in direct tones
without decision and distraction which will dictate a case
in point of rightful operation of engines. A clear example shows
us that cylinders with healthy compressions typically in the
seventies states that the engine is telling us that all is in
order for the most part or is it? Typically, the answer is
usually yes. Below, we will learn of two basic examples to
grow on.
The first example
shows a (O-320-160HP) chrome cylinder that showed zero over eighty on the first
compression test with exhaust blow-by heard from the exhaust
stack instructing a procedure to stake the valve to crush and
theoretically remove any debris (carbon / byproducts) to insure
a positive valve seat. Said procedure allowed a compression
reading of 72 over 80 (differential) and an engine runup of
normal parameters which indeed hid the real truth from
which
that was completely unforseen leaving post results that were
obviously undesireable. Click the pics below to enlarge and to
discover the result of excessively leaning (LOP) at full power.
pic#1
(torched)
pic#2
(hmmm, coin collector, yes?)
pic#3
(nice paper weight)
pic#4
(what's left of the valve stem)
--------------------------
The next example
clearly shows that an engine can operate normally without
indication of symptoms to the pilot until a basic compression
test during an ANNUAL inspection (the reason why annual
inspections are required) revealed a weak cylinder of 42 over 80
(differential). After staking the valves, peering in the
cylinder with a video probe, an engine run, and another
compression test, the order without hesitation was to pull the
cylinder without any further ado. Some may think that a stuck valve or possibly a
slightly bent valve could have been the culprit, but with many
many years of experience at play, removing the cylinder is by
far the easiest procedure to troubleshoot and repair any
deficiencies at hand and with that said, the pictures depicted
are worth a million in the hand. Click the pics below below to
reveal the secret that shows results of possible
shock cooling.
pic#1
pic#2
--------------------------
I agree that when a
situation arrives as far as troubleshooting, almost everybody or
anyone can debate one thing or another and every microscopic
iota involved including this or that as far as order of
procedures, or being just a "why person" instead of being
the "answer person". With that issue being questioned, I believe
in achieveing to be the "answer person" as the "why person" never
answers the question when troubleshooting and repair is necessary
for airworthiness and safety. As Larry the Cable Guy states,
"Jus Git-R-Dun", and never ever argue why inspections are
required.
What should I do? New or O/H?
Some think that is a
very difficult question to answer when it comes to the
replacement of cylinders. Actually, the question is very easy to
answer. Ask yourself these questions.
1) Do you know the
history of the cylinder (how many total hours since new)
2) Has the cylinder
been O/H before, or how many times
has it been O/H?
3) Is the cylinder capable of being O/H?
Without knowing how many total hours are on
an overhauled cylinder, that cylinder could last as long as
anybody's guess. That cylinder could have 100hrs on it, or it
could have 4K, 5K, or 6K hrs on it or more - no kidding! That's
a lot of pounding in the cylinder dome, whew!
Most cylinders can be overhauled twice
before the dimensions of the cylinder walls start to show signs
of significant wear under normal conditions. Then, when a
cylinder of such wear is measured, they can be chromed back to
standard, but that procedure has been nixed since the inception
of nickel, and nitrided cylinders.
So, if you do not know the history of a
cylinder, the best value is to surely buy NEW if your looking
for true and tried longevity, and if not - then BUYER BEWARE!
J
July 24, 2011
Joseph Gawlikowski
Contributing editor
