RV6A down in Seattle area

Ron Wanttaja wrote:
On Mon, 18 Feb 2008 11:38:29 -0900, "Ron Webb" wrote:

As for the safety record of Lyc vs others, I have to grant that I'd have to
pick my examples pretty carefully to find an uncertificated homebuilt with a
better record. Such examples exist. http://www.rotaryaviation.com/ for one.

I did a study of homebuilt accidents over a ~8 year period. Didn't have fleet
sizes for Lycosaur and Auto conversions, but instead looked at how often the
engine was the *cause* of the accident.

Out of 744 homebuilt accidents involving Lycoming, Continental, Franklin,
Jacobs, or Pratt and Whitney engines, 104 were due to some form of engine
failure.

Out of 219 homebuilt accidents in the same period involving auto-engine
conversions, 63 were due to engine failure.

Lycosaur: 14%
Auto Engines: 28%.

Offhand, I'd say the Lycosaurs are safer.

For the purpose of my analysis, I counted the following as "due to engine
failure":

Internal failures (pistons, cranks, etc.)
Fuel System on the engine side of the firewall
Ignition systems
Drive systems (e.g., PSRUs)
Oil System
Carburetor or fuel injector failure
Cooling system failure
Undetermined loss of power


Ron Wanttaja


I've followed your articles on accident stats for several years; thank
you for doing the research. I wonder, though, if your conclusion about
Lycs is really valid.

If we factor in the reality that Lyc installations are more or less
'standardized', with help almost always available from knowledgeable
predecessors, compared to auto conversions where each is nearly unique,
and we factor in the unpleasant fact (sorry guys) that many of the
people most willing to do an auto conversion are the least qualified to
tackle it, how much should we weight the percentages? Only if you add
the word 'installation' to each category can you reach the conclusion
that Lycs are actually safer, in my opinion.

What do you think?

Charlie

"Peter Dohm" wrote

As far as the rotaries go, you seem to have missed that whole sequence by
at least ten years.

Other than the obvious poor fuel efficiency, which was probably no worse
than two-cycle engines, I really can't comment--because I never saw an
installation (or plans for one) with properly designed cooling.

There has been one at OSH for all of the 4 or 5 times I was there, that
seemed to get along quite well. Tracy Crook -
http://www.rotaryaviation.com/
--
Jim in NC

"Charlie" wrote

compared to auto conversions where each is nearly unique, and we factor in
the unpleasant fact (sorry guys) that many of the people most willing to
do an auto conversion are the least qualified to tackle it,

If you are trolling, nice try. Otherwise, how do you support this
conclusion?

Nice slap in the face to all those guys that have auto installations humming
happily along. There are bunches of them, and it WOULDN'T be a stretch to
say that they are pretty darn clever bunch, indeed.

Anyone capable of building a kit with all the holes drilled and all the
parts included can hang a Lyconental. It takes a clever person to use an
auto engine. I would hardly classify that as "least qualified."
--
Jim in NC

On Tue, 19 Feb 2008 20:44:57 -0600, Charlie wrote:

If we factor in the reality that Lyc installations are more or less
'standardized', with help almost always available from knowledgeable
predecessors, compared to auto conversions where each is nearly unique,
and we factor in the unpleasant fact (sorry guys) that many of the
people most willing to do an auto conversion are the least qualified to
tackle it, how much should we weight the percentages? Only if you add
the word 'installation' to each category can you reach the conclusion
that Lycs are actually safer, in my opinion.

What do you think?

I understand your logic, but don't agree with it. I look at the powerplant as a
*package*. If the engine itself is more reliable, but it's difficult to achieve
an installation that allows it to show its reliability, I don't feel that it
exonerates the engine as an aircraft powerplant. That's why my statistics
include fuel system problems FWF as an engine-related failure...if all else were
equal, Lycomings and, say, Fords should see the same rate of fuel FWF accidents.
If there's a difference, that means one is more picky as to the quality of the
fuel system install. FWIW, auto-engine conversions seem to have fewer instances
of FWF fuel system problems than certified engines.

The very standardization of the LyConts means that the average builder has a
better chance of achieving a reliable installation.

One has to understand what statistics in these cases really *mean*. The fact
that 25% of aircraft accidents aren't caused by "N" DOESN"T mean that *you* have
a 25% chance of having an accident due to "N". It means, out of 100 owners, 25
of them will suffer that kind of accident. If "N" is due to installation
errors, and you spend extra care on your installation, get advice, use quality
materials, etc., then you are less likely to experience that kind of accident.

BTW, I do track installation errors (I call them "builder errors") in my
analyses.

Ron Wanttaja

On Tue, 19 Feb 2008 14:05:54 -0800 (PST), wrote:

Ron, do you have this stuff up on your web site? If not, it would be a
very valuable addition.

I don't, though I do write regular articles on these subjects and give talks at
local EAA Chapters. The EAA Chapters are the fun ones, 'cause then I brief the
accident rates for specific homebuilts. :-)

The auto engine vs. LyCont study I performed is the subject of a short article I
wrote for EAA Sport Aviation, it should be out pretty soon. Kitplanes has asked
for another comprehensive accident article; I'll be updating my database with
the 2005 and 2006 accidents pretty soon and starting to work. They usually have
the October issue as the "safety" one.

Ron Wanttaja

On Tue, 19 Feb 2008 21:16:53 -0500, "Morgans" wrote:

I intended to say that the PSRU ((_CAN_ )) be the weak link in an auto
conversion. Cooling, too, but you can generally tell you have a problem
with that, and deal with it without much catastrophic surprise.

You've actually nailed two of the three main areas where auto engine conversions
suffer reliability-wise vs. certified engines. The third is ignition system...
about 19% of the fixed-wing auto-engine failures involved the ignition, compared
to just 8% of the certified engines on fixed-wing homebuilts.

As far as "are auto engines strong enough internally for aircraft use," my
feeling is yes. The accident rates due to internal failures of the engines
(thrown rods, burned pistons, broken cranks, etc.) is just about the same as for
certified engines.

Ron Wanttaja

Well, my reference is 6 decades of banging around behind aircraft
engines of various makes, Lyc, Cont, P&W, Franklin, etc... In that
time period I have had one sudden engine failure, a Continental on T-
Craft that blew a jug landed in a field, fixed it, flew it out..
Also in that time period I have had at least a dozen or more, but
who's counting sudden engine failures in cars/trucks/boats...
Now for you statisticians, yes I have many more hours behind auto/boat
engines than aircraft... But if the auto engines had been maintained
to the standard of aircraft engines likely I would have had few or no
failures...

So, for me the issue is reliability... Based on my experience I will
stay with certified aircraft engines for my airplanes...
I do not claim that an auto engine is intrinsically less reliable when
used in an aircraft... But I can certainly tell from being around
experimental aircraft since the early 1960's that aircraft engine
installations are more reliable than auto conversion installations...
The major factor here is the quality of the engineering in the
installation/conversion...

You can argue that the aircraft engine is more reliable only because
of standardization of parts, installation, etc. and from continued
refinements from analyzing the failures that have occured - which is
why we have dual magneto's, etc...
And you can hypothesize that if Toyota were to get into the piston
airplane engine market that their level of engineering expertise and
the financial resources they can bring to bear would result in a
reliable auto engine conversion equaling any Lyc, etc... And you
would be right... And the cost to buy, install, and maintain, that
certified auto engine will not be one penny less than a certified
Lycosaurus - see the Mooney / Porsche if you don't believe it...

But that generalized certified auto conversion hasn't happened yet...
And the vast majority of shade tree mechanic installations in aircraft
have been less than world class in quality and reliability... So,
being a betting man every time I strap on a plane I will bet with
the odds not against...

denny

"Morgans" wrote in message
...

"Peter Dohm" wrote

As far as the rotaries go, you seem to have missed that whole sequence by
at least ten years.

Other than the obvious poor fuel efficiency, which was probably no worse
than two-cycle engines, I really can't comment--because I never saw an
installation (or plans for one) with properly designed cooling.

There has been one at OSH for all of the 4 or 5 times I was there, that
seemed to get along quite well. Tracy Crook -
http://www.rotaryaviation.com/
--
Jim in NC

Thanks Jim,

I could probably squirm out by saying that it hadn't actually seem it, which
is true, but the fact is that I simply forgot and I stand corrected. Tracy
Crook, and his work are quite famous (especially in the RV community) and I
would really like to take a look at his installation to see just how much
radiator he needed in a tractor installation with plenty of ram air--a good
look with the pilot/builder present is sure to be informative and I would
like to hear his opinion of other installations. I would be especially
curious what he thinks about pushers with ducted intakes because consistent
cooling has been somewhat elusive in southern Florida.

Peter

"Denny" wrote in message
...
Well, my reference is 6 decades of banging around behind aircraft
engines of various makes, Lyc, Cont, P&W, Franklin, etc... In that
time period I have had one sudden engine failure, a Continental on T-
Craft that blew a jug landed in a field, fixed it, flew it out..
Also in that time period I have had at least a dozen or more, but
who's counting sudden engine failures in cars/trucks/boats...
Now for you statisticians, yes I have many more hours behind auto/boat
engines than aircraft... But if the auto engines had been maintained
to the standard of aircraft engines likely I would have had few or no
failures...

So, for me the issue is reliability... Based on my experience I will
stay with certified aircraft engines for my airplanes...
I do not claim that an auto engine is intrinsically less reliable when
used in an aircraft... But I can certainly tell from being around
experimental aircraft since the early 1960's that aircraft engine
installations are more reliable than auto conversion installations...
The major factor here is the quality of the engineering in the
installation/conversion...

You can argue that the aircraft engine is more reliable only because
of standardization of parts, installation, etc. and from continued
refinements from analyzing the failures that have occured - which is
why we have dual magneto's, etc...
And you can hypothesize that if Toyota were to get into the piston
airplane engine market that their level of engineering expertise and
the financial resources they can bring to bear would result in a
reliable auto engine conversion equaling any Lyc, etc... And you
would be right... And the cost to buy, install, and maintain, that
certified auto engine will not be one penny less than a certified
Lycosaurus - see the Mooney / Porsche if you don't believe it...

But that generalized certified auto conversion hasn't happened yet...
And the vast majority of shade tree mechanic installations in aircraft
have been less than world class in quality and reliability... So,
being a betting man every time I strap on a plane I will bet with
the odds not against...

denny

That is absolutely the best summation that I have read in a long time!

Peter

"Peter Dohm" wrote

I could probably squirm out by saying that it hadn't actually seem it,
which is true, but the fact is that I simply forgot and I stand corrected.
Tracy Crook, and his work are quite famous (especially in the RV
community) and I would really like to take a look at his installation to
see just how much radiator he needed in a tractor installation with plenty
of ram air--a good look with the pilot/builder present is sure to be
informative and I would like to hear his opinion of other installations.

His installation that I saw (he has since put a newer engine in) used two GM
air conditioner condensers as radiator, and strangely enough, that is a
pretty popular choice. I don't know if he started that trend, or if he got
the idea from someone else. I have also seen Ford 3.8's and Chevy 4.3's in
airplanes with the same setup.

As I recall, he used them parallel in the cooling line, and had them placed
directly behind the standard cowl twin inlets.

The other popular radator placements I have seen use the radiator back at
the firewall, with the top of the engine baffled off from the bottom, and
had the cooling air go past the top of the engine, through the radiator,
then into the engine compartment, then out the normal lower outlet.

I would be especially curious what he thinks about pushers with ducted
intakes because consistent cooling has been somewhat elusive in southern
Florida.

Indeed. Use of NACA type of inlets have usually failed, badly. The type of
scoop that works the best is a P-51 type of scoop, mounted above or below
the engine.

The key is to have the air flow through the radiator first, then past the
engine, (or directly out into the air) because if the air picks up engine
heat then goes through the radiator, it is sure to fail.

The other key to this type of arrangement is getting the outlet into a good
low pressure area. I have seen some that looked like the twin round inlets,
only they are the outlets. They are indeed tricky to get right, it seems.
--
Jim in NC