You're new to the aircraft and concerned about the engine unexpectedly needing a top overhaul
and other unscheduled work.
A top overhaul
is basically what it sounds like: Remove and overhaul or replace the "top end" of the engine: cylinders, pistons and valves.
5 times, and the minimum interval for top overhaul
has been extended to 1.
The tops and insides of pistons that were changed during a 20,000-hour top overhaul
showed only a lightly baked-on white caking of silicate.
Worse is that the top overhaul
, replacement of all cylinders, is almost never necessary--a sick cylinder is not infectious--yet it is still done with alarming frequency.
Many owners who weren't flying lots--say, 250 or more hours a year--were going through at least one top overhaul
on their way to TBO.
The thornier question involves a top overhaul
or having the exhaust system apart for other reasons.
I did a top overhaul
last year as my almost 1000-hour cylinders were using too much oil.
Most engines probably make it to their TBO with little more than oil changes and some spark plugs, or maybe a top overhaul
, But a few engines roll over long before that.
If the airplane is going to be down anyway--like for a top overhaul
or other lengthy work--getting your local prop shop to take a look is a good idea.
Even if I do a top overhaul
halfway to TBO and replace the mags and vacuum pump twice, my operating costs through TBO will be less.
The shop recommends a complete top overhaul
, perhaps surmising that if two jugs are bad, the rest can't be far behind.