Engine Dependability

I talked to TCM today to register that I am the new owner of one of
their engines. Just in passing, I mentioned that their engine failed
recently within a few hundred hours after major overhaul. They seemed
completely uninterested in knowing this fact. I asked if they kept
actual statistics on actual dependability of their engines. She said
that they did not, to the best of her knowledge. That seems quite odd.

Where do they get TBO numbers from. I always assumed there was some
serious historical statistical date to back these up. Does anyone keep
these statistics? Perhaps A&Ps report such failures? Overhaul shops
maybe? I sure hope someone is tracking the information.

-Sami
N2057M, Piper Turbo Arrow III

"O. Sami Saydjari" wrote in message
...
I talked to TCM today to register that I am the new owner of one of
their engines. Just in passing, I mentioned that their engine failed
recently within a few hundred hours after major overhaul. They seemed
completely uninterested in knowing this fact. I asked if they kept
actual statistics on actual dependability of their engines. She said
that they did not, to the best of her knowledge. That seems quite odd.

Ah, a new owner. Continental makes bulletproof bottom ends. Case, crank
and cam are terrific, they will never give you any problems. Avoid new
Continental cylinders like the plague. Total junk. I think ECI has the
better cylinders, some like Milleniums.



Where do they get TBO numbers from. I always assumed there was some
serious historical statistical date to back these up. Does anyone keep
these statistics? Perhaps A&Ps report such failures? Overhaul shops
maybe? I sure hope someone is tracking the information.

Nobody is tracking the info.

"O. Sami Saydjari" wrote:
Just in passing, I mentioned that their engine failed
recently within a few hundred hours after major overhaul.
They seemed completely uninterested in knowing
this fact.

No surprise. In the seven+ years I've been involved in general
aviation, I don't think I've ever heard anyone say anything nice about
TCM.
--
Dan
C172RG at BFM

On Mon, 19 Apr 2004 13:02:11 -0600, Newps wrote:


"O. Sami Saydjari" wrote in message
...
I talked to TCM today to register that I am the new owner of one of
their engines. Just in passing, I mentioned that their engine failed
recently within a few hundred hours after major overhaul. They seemed
completely uninterested in knowing this fact. I asked if they kept
actual statistics on actual dependability of their engines. She said
that they did not, to the best of her knowledge. That seems quite odd.

Ah, a new owner. Continental makes bulletproof bottom ends. Case, crank
and cam are terrific, they will never give you any problems. Avoid new
Continental cylinders like the plague. Total junk. I think ECI has the
better cylinders, some like Milleniums.



Where do they get TBO numbers from. I always assumed there was some
serious historical statistical date to back these up. Does anyone keep
these statistics? Perhaps A&Ps report such failures? Overhaul shops
maybe? I sure hope someone is tracking the information.

Nobody is tracking the info.

Well, I guess that puts us back to the original question. I, like the
orginal article's author, thought historical statistics were used to
establish TBO numbers. If no one is tracking this information, where do
the TBO numbers come from? Insurance liability statistics from wrecks?

"Greg Copeland" wrote in message
news

Well, I guess that puts us back to the original question. I, like the
orginal article's author, thought historical statistics were used to
establish TBO numbers. If no one is tracking this information, where do
the TBO numbers come from? Insurance liability statistics from wrecks?

TBO comes from two places.

1) Marketing

2) A Guess

On Mon, 19 Apr 2004 13:53:36 -0600, Newps wrote:


"Greg Copeland" wrote in message
news

Well, I guess that puts us back to the original question. I, like the
orginal article's author, thought historical statistics were used to
establish TBO numbers. If no one is tracking this information, where do
the TBO numbers come from? Insurance liability statistics from wrecks?

TBO comes from two places.

1) Marketing

2) A Guess

LOL! Is anyone else bothered by this? I guess it's not really saying
MTBF, it's just saying, your engine is ganna be tired when it hit this
number. So, I guess that really isn't all that bad after all.

Greg Copeland wrote:

On Mon, 19 Apr 2004 13:53:36 -0600, Newps wrote:


"Greg Copeland" wrote in message
news


Well, I guess that puts us back to the original question. I, like the
orginal article's author, thought historical statistics were used to
establish TBO numbers. If no one is tracking this information, where do
the TBO numbers come from? Insurance liability statistics from wrecks?

TBO comes from two places.

1) Marketing

2) A Guess


LOL! Is anyone else bothered by this? I guess it's not really saying
MTBF, it's just saying, your engine is ganna be tired when it hit this
number. So, I guess that really isn't all that bad after all.

I, for one, prefer to base my decisions on facts instead of
speculations. How do they know the engine will be tired after x hours?
What does tired mean? The only thing that would be meaningful to
owners is probability of failure at X hours.

It does not seem that collecting the data and calculating MTBF would be
that hard.

I sure hope the engineers who designed the engine did not use the same
attitude with respect to the components they used! "Crankshaft A is 20%
cheaper than Crankshaft B? Well, who cares, everyone knows that
everyone just makes the reliability numbers up anyway. Let's use
Crankshaft A." Arg!

There is too much variability in operation to accurately track
reliability/dependability of an engine.
TBO comes from the manufacturer's test stand and flight test data under
controlled conditions. Same place the 55/65/75% power data comes from.

OK. I have gone back through my logs and compiled the following
information on my aircraft.

Since my airplane was born around 10/13/1977, it has had 4 engine
overhauls (including the most recently one that I am having done now).
The Mean Time Between Failure has been 877 hours of operation, 7
calendar years. The most recent failure took place within 318 hours of
the last overhaul. The table below gives the details:

Overhaul 1....10/01/79...826 hrs...2 yrs
Overhaul 2....05/26/85..1901 hrs...5.6 yrs
Overhaul 3....11/18/89..1288 hrs...4.5 yrs
Overhaul 4....04/06/04.. 318 hrs..14.4 yrs.
-------------------------------------------
Average................. 877 hrs...7 yrs

This is a far cry from the 1400 TBO on the first engine
(overhaul 1) and the 1800 TBO on the second (overhauls 2,3 and 4).

If anyone else is willing to post their data, it might make for some
interesting information in a thread.

-Sami

O. Sami Saydjari wrote:

I talked to TCM today to register that I am the new owner of one of
their engines. Just in passing, I mentioned that their engine failed
recently within a few hundred hours after major overhaul. They seemed
completely uninterested in knowing this fact. I asked if they kept
actual statistics on actual dependability of their engines. She said
that they did not, to the best of her knowledge. That seems quite odd.

Where do they get TBO numbers from. I always assumed there was some
serious historical statistical date to back these up. Does anyone keep
these statistics? Perhaps A&Ps report such failures? Overhaul shops
maybe? I sure hope someone is tracking the information.

-Sami
N2057M, Piper Turbo Arrow III

EDR,

I am afraid that I beg to differ. You certainly may question the value
of an "average" TBO to decision-making, but you can track the numbers
quite accurately (assuming correct reporting). It would really only
take the cooperation of a small number of overhaul shops, some A&P
mechanics and such.

In the same way, one could question the value of the accident rate of
the "average" GA pilot. Granted that all of us are above average
(apologies to Garrison Keillor), but such statistics can be useful
starting points, for example, to see if trends are improving or if a
given measure is worthwhile. Similarly, average disease mortality rates
are useful for medical treatment, despite no person being average.

I do not mean to beat a dead horse, but I really think it would be a
good idea, from an engineering perspective, to collect and report this data.

-Sami
N2057M, Piper Turbo Arrow III

EDR wrote:

There is too much variability in operation to accurately track
reliability/dependability of an engine.
TBO comes from the manufacturer's test stand and flight test data under
controlled conditions. Same place the 55/65/75% power data comes from.