On Apr 2, 4:34 am, Denny wrote:
As I said, catastrophic failure can happen, but is the exception in
engine stoppages...

Morning sickness: for example... I can't even begin to estimate the
number of engines I have heard on the ramp, at fly-in's, where ever,
that the engine starts up and shakes like a wet dog for 30 seconds
before it begins to run halfways right - yet these Einsteins just gun
the hell out of it until the valve breaks loose and go take off...

Bad rings: They start up with a big puff of blue smoke, pilot waves,
smiles, puffs out his manly chest and away he goes...

Bad mag: Uncountable times I have heard a run-up where the engine
runs rough on one mag and yet, away they go...

Dripping oil on the ramp: Hot shot pilot just jumps in and off he
goes...

And in hanging around the mechanics shop I am flabbergasted at the
condition of some of the planes brought in:
Mechanic says, 'the plugs are bad, the wires are bad and one is
broken'..
Owner says, 'well, just fix the broken wire I need to be in Pittsburg
today'...

Mechanic said: 'there's a mandatory AD on the fuel servo' (this
happened just last week)
Owner said with a scowl: 'how much is that going to cost?'
Notice that the owner did not ask and did not care what the AD was,
all he focused on was cost... After considerable discussion the
mechanic then said that he could not sign the aircraft out as
airworthy - and stomped off to work on my plane... Owner threw a fit
like a three year old... In the end he agreed to have the AD
performed... The plug on the fuel servo was finger turn loose and
likely would have put the plane into the weeds, sooner rather than
later...
This same engine has 2800 hours smoh and is burning considerable
oil... Owner refuses to overhaul it and if/when it does fail in flight
it wil be another "sudden engine stoppage" (not!)....

denny

Got to agree with you, Denny. I've had two engine failures, both on
poorly-maintained engines. Properly-maintained engines are much, much
less inclined to let you down, because the mechanic will find wear or
other developing problems and correct them well before they cause
trouble.
Magnetos are a prime example, and most of them are supposed to
come off every 500 hours and get opened up and inspected. We usually
find that at the 1000-hour mark they need new points and sometimes
other stuff. Sometimes the impulse couple is falling apart. A failed
magneto can do more than just quit: it can start firing at the wrong
time when its internal distributor gears wear out, and really screw
things up. A Bendix dual mag really needs watching, as both mags are
driven by one gear and impulse coupling. Don't know how they ever got
that certified. Those impulse couplings have an AD against them.
Owners are sometimes warned about falling compression. A leaking
exhaust valve is going to burn, and a burning valve head can separate
from its stem and end up in the cylinder. Pistons don't like
compressing valve heads. And engines that sit a lot can get corroded
valve stems; corrosion pits weaken them so they'll break off even if
they're not burning.
Propeller strikes are often ignored. Dangerous, since
crankshafts often acquire cracks just this way.
Engine fluid hoses should get replaced every few years. Oil
cooler hoses get old and hard and can fail in flight, pumping all the
oil overboard. The engine seizes, sometimes in a rather spectacular
manner. Is that the engine's fault?
Once in a great while an engine will fail because of
manufacturing flaws (like a few of Lyc's cranks), but it's really
rare. Most failures are engines that were given the cheapest
maintenance the owners could find.
The pilot is the next big threat to the engine; abusing it, just
like abusing your car's engine, will shorten its life expectancy.
Pushing that throttle open too fast, overboosting, or misusing the
prop control can all do damage. We could built idiot-proof engines,
but they'd be too heavy to fly.

Dan