Going of ver recommended TBO

[gman]

Hello All,
Where I fly, the density altitude on the tarmac is typically more than
7000ft even on cold days (>9000ft on hot days). As a result, non-turbo
engines cannot develop any more than 70% of rated power.

The consensus around here is that as long as the engines are blessed by
the mechanics and checked for compression, one can exceed the
recommended TBO sometimes by a factor of 2x.

My question is this: Is this practice safe? What about material fatigue
in the engine components (i.e. crank shaft, pistons, rods, valves etc)?
Would this practice make the chances of an engine failure more likely?

Thanks.

[Kobra[_3_]]

> The consensus around here is that as long as the engines are blessed by
> the mechanics and checked for compression, one can exceed the
> recommended TBO sometimes by a factor of 2x.
>
> My question is this: Is this practice safe?

I'm no expert, but it is NOT safe. There are things deep in the engine that
a mechanic has no idea about...such as...the main bearing. If one of those
goes, so does the engine.

As far as cylinders, pistons, rings, valves go...well...they can be
monitored and you can get a "Top Overhaul" to keep those components in
working order. BUT it's the bottom half that really needs the Major
Overhaul. The bearings, seals, crankshaft, cam shaft, connecting rods that
can and will cause an engine failure.

Going over TBO by 50 to 100 hours is one thing...but 1000 or 2000 is totally
an unacceptable risk.

My partner and I fund an Engine Account with 17.00 dollars per hobbs flying
hour. We have 12,000.00 dollars in that account now with 800 hours left to
go. When we hit 2000 we will have 90% or more of the money for an overhaul.

Don't stick your head in the sand and fly, fly, fly and never save for the
overhaul. You'll only be fooling yourself that when the time comes you'll
have the money or that you'll get 4000 hours out of that engine. It won't
happen. The next time you blink you'll be at TBO and no way to replace the
engine. Then you'll be forced to sell the plane for much less than you
bought it for.

Kobra

[Doug[_1_]]

The altitude does help because it limits power developed by the engine
and that causes wear. Safe? As the engine ages, the chances of a
breakdown increase. There is an increased chance of a breakdown
immediately after rebuild also. The 2000 hours is not regulatory for
Part 91 aircraft and many owners exceed it. Even Part 135 operators can
exceed it if they get a waiver from the FAA (and they can if they
monitor their engines and get it all approved etc). YOU will have to
decide where your level of risk is. But I would think some hours past
2000, perhaps 500 would be economic and not incur signifigant
additional safety risks. Cut open your oil filters and do oil analysis
and keep an eye on oil consumption, and do frequent compression checks.
Any anamolies with those tests indicate time to rebuild (if you are
past TBO). Good luck!

gman wrote:
> Hello All,
> Where I fly, the density altitude on the tarmac is typically more than
> 7000ft even on cold days (>9000ft on hot days). As a result, non-turbo
> engines cannot develop any more than 70% of rated power.
>
> The consensus around here is that as long as the engines are blessed by
> the mechanics and checked for compression, one can exceed the
> recommended TBO sometimes by a factor of 2x.
>
> My question is this: Is this practice safe? What about material fatigue
> in the engine components (i.e. crank shaft, pistons, rods, valves etc)?
> Would this practice make the chances of an engine failure more likely?
>
> Thanks.

[Robert M. Gary]

gman wrote:
> The consensus around here is that as long as the engines are blessed by
> the mechanics and checked for compression, one can exceed the
> recommended TBO sometimes by a factor of 2x.

Wow, I don't know about a factor of 2x. I think the most important
factors are
1) How recent was the last overhaul
2) What the engine factory overhauled, new, or field overhauled last?

I know some operators that go as much as 300 hours past TBO but they
reach TBO every few years. An engine that has been 20 years since
overhaul is probably due before TBO, regardless of how its run.
Also, I would expect a factory new engine would do better past TBO than
a field overhauled.
I have a factory new engine installed in 97. I expect to be able to go
about 200 hours past. However I have the following going for me 1) It
was factory new 2) It has only been 10 years and 3) I have a complete
record of oil analysis since installation.

-Robert

[Tony Cox]

"gman" > wrote in message
ups.com...
>
> The consensus around here is that as long as the engines are blessed by
> the mechanics and checked for compression, one can exceed the
> recommended TBO sometimes by a factor of 2x.

The Oct '06 edition of "Light Plane Maintenance" fielded
a question on exceeding TBO with a Lycoming O-320
in a Cessna 172 (you didn't say what engine you have).
The engine burns 1qt/8 hours and the compressions are
all in the low 70s. The owner recently did a valve wobble
check.

Biggest concern: exhaust valve break up, which apparently
nearly always happens in flight, but which is usually
preceded by said valve getting burnt, then getting hot, and
then failing.

Recommendation: Continue flying until engine gives a
reason for overhaul. Increase monitoring, especially by
doing frequent compression checks (25 hours) and attention
to oil (filter/screen + oil analysis). Compression check
verifies both cylinder & valves not seating properly. Investigate
if any cylinder showing compression in the low 60s.

[Jim Macklin]

Wear and friction are not less because the power output is
reduced at altitude. Bearing wear increases clearances and
oil pressure will decrease. You can detect some of the wear
by careful inspection of an assembled engine. There are
some things that can't be checked without engine
disassembly. If you tear the engine down, you might as well
complete the overhaul.
TBO is only mandatory in commercial operations. Because of
the cost of being sued, most FBO do overhauls at TBO because
juries decide. Private owners are free to do what they
want. Compression can be checked and since aircraft engines
use individual cylinders, rings and valves can be repaired
one cylinder at a time as required. That does not alter TBO
time.
Overhaul includes all components and accessories, such as
magnetos. A freshly overhauled engine [or a new one] is
suspect for the first 100 hours.


--
James H. Macklin
ATP,CFI,A&P


"gman" > wrote in message
ups.com...
| Hello All,
| Where I fly, the density altitude on the tarmac is
typically more than
| 7000ft even on cold days (>9000ft on hot days). As a
result, non-turbo
| engines cannot develop any more than 70% of rated power.
|
| The consensus around here is that as long as the engines
are blessed by
| the mechanics and checked for compression, one can exceed
the
| recommended TBO sometimes by a factor of 2x.
|
| My question is this: Is this practice safe? What about
material fatigue
| in the engine components (i.e. crank shaft, pistons, rods,
valves etc)?
| Would this practice make the chances of an engine failure
more likely?
|
| Thanks.
|

[Ron Natalie]

gman wrote:
> Hello All,
> Where I fly, the density altitude on the tarmac is typically more than
> 7000ft even on cold days (>9000ft on hot days). As a result, non-turbo
> engines cannot develop any more than 70% of rated power.
>

TBO is advisory only for non-commerical operators. Flight school
aircraft that are flown and maintained regularly, even down here
at sea level, typically will make TBO without working hard. We
had a skyhawk here that was still going strong at 2400 hours SMOH.
It had spent the first 2000+ hours as an Embry Riddle plane and
then the next 3000+ or so in a well-run club. It's still flying
traffic reports in the DC area.

Most privately owned aircraft that fly 100-200 hours a year aren't
going to make it to TBO without a lot of luck.

[NW_Pilot]

"gman" > wrote in message
ups.com...
> Hello All,
> Where I fly, the density altitude on the tarmac is typically more than
> 7000ft even on cold days (>9000ft on hot days). As a result, non-turbo
> engines cannot develop any more than 70% of rated power.
>
> The consensus around here is that as long as the engines are blessed by
> the mechanics and checked for compression, one can exceed the
> recommended TBO sometimes by a factor of 2x.
>
> My question is this: Is this practice safe? What about material fatigue
> in the engine components (i.e. crank shaft, pistons, rods, valves etc)?
> Would this practice make the chances of an engine failure more likely?
>
> Thanks.
>

I would rather fly a over tbo engine with a clean bill of health & good oil
analysis trend than a freshly overhauled or factory new engine with 0 hours!

[Jim Macklin]

Agreed, the first 100 hours are all a test flight for
material and workmanship.



--
James H. Macklin
ATP,CFI,A&P

"NW_Pilot" > wrote in
message . ..
|
| "gman" > wrote in message
|
ups.com...
| > Hello All,
| > Where I fly, the density altitude on the tarmac is
typically more than
| > 7000ft even on cold days (>9000ft on hot days). As a
result, non-turbo
| > engines cannot develop any more than 70% of rated power.
| >
| > The consensus around here is that as long as the engines
are blessed by
| > the mechanics and checked for compression, one can
exceed the
| > recommended TBO sometimes by a factor of 2x.
| >
| > My question is this: Is this practice safe? What about
material fatigue
| > in the engine components (i.e. crank shaft, pistons,
rods, valves etc)?
| > Would this practice make the chances of an engine
failure more likely?
| >
| > Thanks.
| >
|
| I would rather fly a over tbo engine with a clean bill of
health & good oil
| analysis trend than a freshly overhauled or factory new
engine with 0 hours!
|
|

[Paul Tomblin]

In a previous article, Ron Natalie > said:
>TBO is advisory only for non-commerical operators. Flight school
>aircraft that are flown and maintained regularly, even down here
>at sea level, typically will make TBO without working hard. We
>had a skyhawk here that was still going strong at 2400 hours SMOH.
>It had spent the first 2000+ hours as an Embry Riddle plane and
>then the next 3000+ or so in a well-run club. It's still flying
>traffic reports in the DC area.

Our flying club aircraft regularly make 2400 or more hours, although our
Warrior only made 1800. Our Lance currently has 2700 hours on its IO-540.
Club aircraft get lots of hours, over the whole year, so that helps keep
the rust off. Plus, they're well maintained, and flown by people who
treat the planes like they own them.

When an engine is getting near to or over TBO, we do an oil analysis every
oil change instead of every other to see if it starts making metal, and we
watch compressions.

--
Paul Tomblin > http://blog.xcski.com/
My name is *ozymandias[], array of arrays
Look on my stack trace, ye mighty, and despair.

[nrp]

I've had a 172M for 31 years, now with 1700 hrs TTSN that still makes
compression (which never never has been that great) and still gets over
25 hrs/qt. It has been preheated religiously, run on Shell 15W50,
mostly autofuel, & mostly cruised at ~55% power. Oil analysis still
shows low and declining ppm metal contamination. It has a full flow
filter.

Given your operating conditions, you shouldn't break anything from
simple fatigue. You will eventually wear it out at some prolonged
point, corrode it internally or damage it on a cold start. All these
should give warning.

But I don't think you can make 2X TBO. You should critically look for
any signs of deterioration as you approach or exceed TBO. I assume
you have a full flow filter. Given the quality problems the
manufacturers seem to be having with recent OH components, I'd think it
safe vs an unnecessary overhaul.

Let me guess it is also an O-320 in a Cessna installation. I think
Cessna has better cooling provisions than Piper or especially Grumman
etc.