Newbie question on relationships between TT, TBO and SMOH

[H.P.]

If a plane (C172S) has 1600 TT but is at 250 hrs SMOH on an original engine
that's spec'd for 2000hrs TBO, does this mean that the engine went in for
overhaul prematurely? For what possible reason and how would I find out?

[Mark Hansen]

On 8/1/2005 15:32, H.P. wrote:

> If a plane (C172S) has 1600 TT but is at 250 hrs SMOH on an original engine
> that's spec'd for 2000hrs TBO, does this mean that the engine went in for
> overhaul prematurely? For what possible reason and how would I find out?
>
>

Remember that TBO is based on hours run as well as calendar time. How
long was the engine in the airplane, and what does it's manufacture
recommend for calendar time to overhaul?

--
Mark Hansen, PP-ASEL, Instrument Student
Sacramento, CA

[RST Engineering]

The 172S model is a 1999-2001 model year if I'm not mistaken. 6 years (less
how long it has been since SMOH) is way below any reasonable manufacturer's
recommendations.

Jim


"Mark Hansen" > wrote in message
...
> On 8/1/2005 15:32, H.P. wrote:
>
>> If a plane (C172S) has 1600 TT but is at 250 hrs SMOH on an original
>> engine that's spec'd for 2000hrs TBO, does this mean that the engine went
>> in for overhaul prematurely? For what possible reason and how would I
>> find out?
>
> Remember that TBO is based on hours run as well as calendar time. How
> long was the engine in the airplane, and what does it's manufacture
> recommend for calendar time to overhaul?
>
> --
> Mark Hansen, PP-ASEL, Instrument Student
> Sacramento, CA

[Michael]

> If a plane (C172S) has 1600 TT but is at 250 hrs SMOH on an
> original engine that's spec'd for 2000hrs TBO, does this mean that
> the engine went in for overhaul prematurely?

In this case, yes.

> For what possible reason and how would I find out?

For many possible reasons. It could have had a prop strike and the
owner opted to major since the insurance was paying for the teardown
and rebuild anyway. The engine could have grenaded itself (bearings or
whatever). The jugs might have worn out and the owner decided to major
rather than top because it wasn't that much more money or downtime
(which isn't true, but...) The factory might have done a ****ty job of
building the engine, and it just didn't last.

Look in the logs around the time of the overhaul and prior. Was there
airframe repair at the same time? Then it was a prop strike, or maybe
an engine failure resulting in an off-airport landing. Did the engine
have a history of replacing jugs? Maybe the owner just got fed up with
it.

Really, unless there are issues with unrepaired or improperly repaired
airframe damage, I would worry a lot more about HOW the engine was
overhauled rather than WHY.

Michael

[BTIZ]

yes...
look in the engine log book.. sometimes a reason for overhaul is not
specifically mentioned..
but information like declining compression readings etc may yield and answer
or something like "engine overhauled at xxxhours due to propeller strike,
crank passed inspection"

BT


"H.P." > wrote in message
. ..
> If a plane (C172S) has 1600 TT but is at 250 hrs SMOH on an original
> engine that's spec'd for 2000hrs TBO, does this mean that the engine went
> in for overhaul prematurely? For what possible reason and how would I
> find out?
>

[Dave Butler]

H.P. wrote:
> If a plane (C172S) has 1600 TT but is at 250 hrs SMOH on an original engine
> that's spec'd for 2000hrs TBO, does this mean that the engine went in for
> overhaul prematurely? For what possible reason and how would I find out?

1. Yes
2. Too many possible reasons to enumerate.
3. Ask the owner?

[Paul kgyy]

Engines commonly do not reach TBO unless flown regularly (i.e. daily or
hourly) and properly operated. I wouldn't be concerned about an
overhaul at 1350 hrs as long as the overhaul was properly done.