Posted for J H Webb <airmale4@yahoo.com>:

Dear Friends,
 
     I have been doing a great deal of flying mostly long cross countries and
Check rides. Mostly in Cessna 310's, 404, and 421 aircraft and this came up
which I thought it was very interesting so  I am sharing it with you.. This
engine was running well and made no unusual sounds and developed normal power,
but at the oil change (every 50 hours about 20 days per change) the oil did
not run out in a straight circular stream but was split.  The mechanic who was
doing the change was very observant and wondered why. He probed in to the sump
and found that there was something loose in the bottom of the oil pan. So they
took the sump off and discovered this mess.  Most of the broken parts are over
1" in the principle dimension. Three of the pistons had both skirts broken
off. As far as we know at the this point most of the metal was from the
pistons. It was very surprising that the engine ran.
    The source of the problem is that pilot who was taking the airplane
(Cessna 310) home to an airport near his home where there was no preheat
available. So he was putting a light bulb inside of the cowl to keep it warm.
We had told him not to try a start below 20 degrees.  He did a start after the
airplane sat overnight at approximately 10 degrees F. Then almost immediately
the other engine developed a crack in the cylinder.  We wondered if it was
related to the unacceptable start. Then a few days later and many flying hours
it came in for an oil change.
    We are flying 14 Cessna aircraft and most of them fly close to 100 hours
per month.  Almost without exception the engines make it to overhaul without a
top. This engine was an IO470 which is a very similar design to our engines. 
Most of our engines are IO 520's and turbo GTSIO 520's. Unfortunately this is
anidotal but something can be learned for this expensive mistake.
    Enclosed find two pictures of the junk in the oil pan and one picture of
an example piston.
 
Jack Webb
Ohio
L360, LIV