On Fri, 25 Jul 2003 15:22:20 GMT, Kevin Horton
wrote:


It is difficult to compare the aviation engine type certification tests
with the automotive durability tests, as the two tests are doing
different things. The automotive test is trying to find problems that
will cause the manufacturer grief in automotive service.

I would say that any manufacturer of aircraft engines would be looking
for the same thing, only in aviation service.

Unfortunately, the configuration tested may be quite different from the
one we would use in an aircraft, as there is no PSRU, and there may be
substantial differences in ignition and fuel delivery systems. The
aviation engine test is supposed to test the whole engine, PSRU, etc,
in a configuration that is suitable for airborne use.

I agree. I guess I'm reacting from the old Paul Lamar episodes where
he declared that the short block itself by dint of it's V type
configuration, use of a cast steel crank and close cast cylinders was
inherently fragile and that the crank would "crumble to dust" and the
engine be unable to cool properly. What shocked me about this
attitude was that he used to work with Chaparal racing when this
little group was standing sports car racing on it's head with it's
innovation in aerodynamics and transmissions. He was an aerodynamics
engineer (I think) who's job was to make what Jim Hall dreamed up
happen. They made racing history. Now, 20 years later, he was
declaring that the very same type of engine that ran successfully in
his race cars (V engines), sometimes for 24 hours, cooling all the
way, would now not cool for even five minutes of climb at greatly
reduced rpm from the race track. It didn't make sense. I knew of no
crankshafts that had broken as he declared they would at that time,
and now almost 10 years later, I still haven't heard of any.

The engines themselves appear robust enough to handle the power
requirements. As you say, it's the ancillary components that can be
problematic.

Continuing airworthiness issues also come into play here. The aviation
engine manufacturers are required to inform us about any major problems
they learn about. For automotive engines you may only learn about
problems and fixes through the grapevine (e.g. Ford V-6 coolant leaks
into the oil system).

So, in the end, the only way to figure out whether a given automotive
conversion will work is do fly it and find out. Eventually we'll have
enough service history to know what works, and what doesn't.

Well how many hours should that necessarily be? Bruce can cite two
examples that have reached 2,000 hours and beyond. There are many
models of aircraft engines that must be overhauled long before then.

I'm not anti-automotive conversion - I'm considering a Mazda conversion
for my next project (please don't tell my wife I'm considering another
project - she still expects to get the garage back once my RV-8 is
flying).

We've been walking around the fuselage in the shop for so long that
it's become a fixture. It keeps getting more stuff put on it from
time to time.

Corky Scott