Running an 0-235 well beyond TBO

How common is this? I am seeing some 152s for sale with engines as high
as 3000 hours SMOH. Surprising. (Well, to me!)

Related question (probably nearly impossible to answer): to what degree
is an engine's reliability related to it's time SMO? Obviously, it has
to be that a Lyc at 2200 hours is more likely to fail than one at 200,
but what are people's opinions? My FBO did just tell me of a gent who
had his O-320 put a rod through the crankcase at 140 hours.. and
apparantly Lyc isn't covering it. And this wasn't a hangar queen
sitting for years either.

Still lookin for the right plane. Since I'm going to be out of the
country for 9 days starting Friday I've held off on moving on anything.

Paul Folbrecht wrote:

My FBO did just tell me of a gent who
had his O-320 put a rod through the crankcase at 140 hours.. and
apparantly Lyc isn't covering it.

Lycoming gives a 1 year warrantee. They give a second pro-rated year on new
and remanufactured engines.

Bet it's an overhauled engine. Most people won't put 140 hours on a plane in a
year, so it's probably out of warrantee.

George Patterson
A diplomat is a person who can tell you to go to hell in such a way that
you look forward to the trip.

"Paul Folbrecht" wrote in message
hlink.net...
How common is this? I am seeing some 152s for sale with engines as high
as 3000 hours SMOH. Surprising. (Well, to me!)


It's not uncommon for a plane regularly flown and maintained (i.e., a good
flight school) to stretch way beyond TBO. Our club 172 was several hundred
hours beyond TBO and still going strong. TBO is only advisory for us.
small fry

Related question (probably nearly impossible to answer): to what degree
is an engine's reliability related to it's time SMO?

It's not.

Obviously, it has
to be that a Lyc at 2200 hours is more likely to fail than one at 200,

TBO is NOT Time Between Failures. It's just the manufacturer's idea of
when the thing needs to be opened up and inspected.

but what are people's opinions? My FBO did just tell me of a gent who
had his O-320 put a rod through the crankcase at 140 hours.. and
apparantly Lyc isn't covering it.

TBO isn't warranty either.

And this wasn't a hangar queen sitting for years either.

It doesn't need to sit for years...but I bet it took more than two years to get the 140
hours which doesn't mean it's flown regularly enough to maximumize the engine
life either.

Paul Folbrecht wrote:
Obviously, it has to be that a Lyc at 2200 hours is more
likely to fail than one at 200,

Without a careful statistical analysis of engine failures, it's
impossible to say if that's true or not.

Take a brand new engine right out of the factory. It's a reasonable
statement that it's more likely to make it to 200 hours than to 2200.
But, that's not the interesting question.

The interesting question is the one implied above, i.e. whether an
engine which has 200 hours on it is more likely to fail in the next 100
hours of operation as one which has 2200 hours on it. It's called
conditional probability. P(2300) is the probability of making it to
2300 hours. P(2300|2200) is the probability of making it to 2300 hours
GIVEN THAT is has already made it to 2200.

Roy Smith wrote:
Paul Folbrecht wrote:

Obviously, it has to be that a Lyc at 2200 hours is more
likely to fail than one at 200,


Without a careful statistical analysis of engine failures, it's
impossible to say if that's true or not.

Take a brand new engine right out of the factory. It's a reasonable
statement that it's more likely to make it to 200 hours than to 2200.
But, that's not the interesting question.

The interesting question is the one implied above, i.e. whether an
engine which has 200 hours on it is more likely to fail in the next 100
hours of operation as one which has 2200 hours on it. It's called
conditional probability. P(2300) is the probability of making it to
2300 hours. P(2300|2200) is the probability of making it to 2300 hours
GIVEN THAT is has already made it to 2200.

Yes, and what are these numbers for an O-235?

;-)

Paul Folbrecht wrote in message thlink.net...
How common is this? I am seeing some 152s for sale with engines as high
as 3000 hours SMOH. Surprising. (Well, to me!)

O-235's seem to last forever, with an utterly bulletproof bottom end.
Usually last even longer than an O-320, which is basically the same
engine but with larger bore.

Well.... more on our 172 M, purchased in Dec with 2600 SOH...
(we call "On conditio" here in Canada) ...

The bird sailed through it's anual/100 hr inspection requiring
3 cowl mounts...2 we knew about, one other was torn 1/2 way when I
yanked on it...

Borescoped the engine, valves/seats all look good, plugs clean
and burning well, burns 1 litre of oil in 11 hrs...

Compression "way above 70" (mechanics words) at all 12
points...

Engine pulls strong and very smooth, fires/starts in 1/2
rotation...

Came out of a flight school, 2600 hrs since June 2001...

Tach checks show 2350 RPM static when new, still shows 2350
static on the TO run...

We are going to run the sucker till something starts to
show...

Wish us luck!

Dave




On 8 Mar 2004 13:08:14 -0800, (One's Too Many)
wrote:

Paul Folbrecht wrote in message thlink.net...
How common is this? I am seeing some 152s for sale with engines as high
as 3000 hours SMOH. Surprising. (Well, to me!)

O-235's seem to last forever, with an utterly bulletproof bottom end.
Usually last even longer than an O-320, which is basically the same
engine but with larger bore.

wrote:
Well.... more on our 172 M, purchased in Dec with 2600 SOH...
(we call "On conditio" here in Canada) ...


snip

Compression "way above 70" (mechanics words) at all 12
points...

You have a 12 cylinder engine?

snip

Tach checks show 2350 RPM static when new, still shows 2350
static on the TO run...

On the T/O run is not "static".

snip

Dave
Remove SHIRT to reply directly.

Compression "way above 70" (mechanics words) at all 12
points...

You have a 12 cylinder engine?

Nope! Pressure checked at DTC, BDC & mid travel of piston in
each of 4 cyls.. Total 12 locations..

Hope I have the terminology right, new to me....

Sorry, no Merlin here...

snip

Tach checks show 2350 RPM static when new, still shows 2350
static on the TO run...

On the T/O run is not "static".

Good point, but holding on the brakes (short field procedure) ,
running to full RPM and then releasing...

Check RPM max before the roll...

Close enough?

Dave