REFLECTOR:Rotarys, Lycosaurs, etc.
Wed, 5 Nov 2003 13:39:28 -0800 (PST)
Let me start by saying that I'm not against auto, rotary,
steam or any other type of conversion.
What I am against is comparisons with aircraft engines in
certified and experimental aircraft against them. First
(see my tutorial about aircraft engine overhauls). Al
mentions 500 hr. SMOH, do you know that an overhaul can
consist of nothing more that seals and gaskets!!! Unless
you know the type of overhaul including the work order you
don't know what was done. In an expert mental engine it is
I've seen Lyc's in trainers go 2000-2400 between overhauls
getting the daylights kicked out of them that most engines
wouldn't survive. I've also seen them fail in a lot less
To get real figures you need to start from a common
starting base and abuse all of them alike and maintain them
to the required standards to establish real life.
A closer comparison for automobile engines would be their
use in boats where they get far more abuse and continuous
HP output demands. I'll bet that they don't show any where
near where (personal experience also)the reliability of the
same engine in a car.
--- Jim Sower <email@example.com> wrote:
> I'm on your side here, but I get the impression of a
> standard in parts of your post that I find uncomfortably
> in the general discourse about auto conversions.
> <... get better performance and lower cost, no doubt
> about it;
> but the reliability is hard to achieve ...>
> Better performance at lower cost I agree with. What
> reliability? Admittedly, my own personal experience with
> Lycs (O-235, O-320, IO-360, ALL with less than 500 SMOH
> they came my way) has been abysmal - two jugs on EACH of
> for various reasons, a front seal on the 360, a mag or
> etc., etc. - ALL within 200 or 300 hours of operation.
> But let's not use my experience as typical. Show of
> hands boys
> and girls: how many of us have had, or have a personal
> who has had, a Lycoming make it to TBO without a major
> Now, let's go the other way - tell the truth now - how
> many have
> had or have a personal friend who has had a major failure
> less than, say, 1200 hrs. So much for reliability.
> <... pretty stout, reliable engines. Still, their
> failure modes
> are primarily related to valves, connecting rods, and the
> occasional crankshaft break ...>
> Let's don't forget jugs (worn out/broken rings, cracked
> scored barrels, etc. :o)
> Rightly enough, you don't count failures of peripherals
> they don't indicate engine problems. Sadly, most of the
> conversion "failures" ARE failures of peripheral systems,
> nonetheless are attributed to the engine. The type of
> standard that obscures efforts at rational, unbiased
> <... another engine with valves, connecting rods and
> stress it to the max, run it at high speeds, and add
> gearing; and put it in your airplane ...>
> In the 70s, I was in the auto repair business. The life
> expectancy of a V8 was 75k - 100k mi. Since then, thanks
> to CNC
> mills, electronic ignition and injection and unleaded
> gas, any
> average car will get a quarter million miles before the
> rots off the chassis with the engine still running
> Aircraft engines have NONE of these life extending
> ALL of the technology in my Lyc was in place, mature and
> SEVENTY YEARS AGO - like in the HOOVER administration -
> model-T engines were good for 20k or 30k miles. NO
> improvements since then other than minor metallurgy. So
> YES! I
> WOULD put one of these engines in my airplane.
> <... Do you know of any one of these that has gone 1500
> hrs in
> an airplane between major malfunctions ...>
> Yes. Matter of fact I do. Suppose we turn that around.
> many of us know PERSONALLY of anyone who has achieved
> that with
> Lycs and Conts? I know of two for sure. Don't know if
> actually DID get 1500 hrs with no failures, but they talk
> as if
> they did. Lots of peripheral failures, but no long block
> failures. Is it OK if I were to infer from the above
> that 1500
> hours failure free in a Lyc is only twice as common as
> hours failure free in a rotary? :o) Bottom line, how
> many of us
> know someone with 1500 hrs in their homebuilt airplane at
> <... it is very difficult to do a custom auto conversion
> installation and achieve a reliability as high as Lyc or
> Continental ...>
> "Custom" being the key word here. Actually, over the
> several years, more standard and proven conversion
> packages have
> been produced and "packages" are becoming more reliable
> by leaps
> and bounds.
> <... in a certified aircraft ...>
> When did we start talking about certified aircraft. How
> Lycs and Continentals in homebuilt aircraft? Why is it
> they seem so much less reliable than the same engines
> in certified planes?
> All of that having been said, I find that the reputation
> for "
> proven reliability and dependability" of certified
> engines is
> largely "theological" - that is, it owes a lot more to
> faith in what we've been told many many times than to
> examination of all the evidence. Certified engines have
> countless failure modes that would be unacceptable to us
> in say,
> our automobiles. The thing is, these failure modes and
> defects have been so well documented and described over
> decades that they have somehow morphed into acceptable
> attributes. When a failure occurs, everyone is right
> there with
> "... yeah, the old front seal falls out for reasons best
> to itself syndrome ..." or something of the sort, and the
> slob who it happened to is left feeling that since it
> seems so
> common, he must have been remiss is not anticipating it
> preventing it. To me, this widespread attitude has all
> intellectual allure of blaming a rape victim for the
> because she wore a short skirt.
> I could go on forever with failures and shortcomings of
> Lyc and
> Cont engines that NONE of us would EVER accept in our
> automobiles, but regard as inevitable and therefore
> somehow OK
> in our airplanes.
> I find this attitude puzzling in folks who are so
> regarding quality in the airplane they build.
> Man, I DO take the bit in my teeth from time to time,
> don't I
> :o)... Jim S.
> Al Gietzen wrote:
> > Gentlemen,
> > I hope I don't offend with this. But I just spoke
> > Lance Wheeler of NSI the other day and he told me he's
> > ready to produce a 2.5L (4 cyl) turbocharged Subaru FWF
> > that his dyno says puts out 300 hp. I'll bet one
> > It'll be a lot quieter than those rotary.
> > You put a turbo on a rotary and it is pretty quiet as
> > But I donít think quiet ranks at the top of the
> > criteria.
> > Before I selected the rotary I did a critical review of
> > about every possible engine option. The three main
> > were reliability, performance/weight, and cost. At one
> > I was very near choosing the 250 hp turbocharged 2.2L
> > conversion (I think it was Cross-Flow Aero). Pretty
> much the
> > same thing NSI is offering, just a bit smaller.
> > is attractive. When you added it all up, it was quite
> > expensive; but after asking a lot of questions, the
> reason I
> > crossed it off was uncertain reliability. Pushing 2
> > in. makes for high stress levels. Running in a race
> car Ė
> > OK. You can overhaul between races and you can pull
> into the
> > pits when something goes wrong. You can learn a lot
> > engine reliability talking to folks that race cars for
> > living.
> > Certified aircraft engines are pretty stout, reliable
> > engines. Still, their failure modes are primarily
> related to
> > valves, connecting rods, and the occasional crankshaft
> > And their performance is derated by running them slower
> > eliminate reduction gearing. Do you really want to
> > another engine with valves, connecting rods and
> > stress it to the max, run it at high speeds, and add
> > gearing; and put it in your airplane? Do you know of
> any one
> > of these that has gone 1500 hrs in an airplane between
> > malfunctions or overhaul?
> > In my opinion, it is very difficult to do a custom auto
> > conversion installation and achieve a reliability as
> high as
> > Lyc or Continental in a certified aircraft. (Uh-oh;
> now even
> > the other auto conversion guys wonít speak to me). You
> > get better performance and lower cost, no doubt about
> it; but
> > the reliability is hard to achieve. The statistics
> > arenít there. The basic engine can be reliable, but
> there are
> > many first time, one-of-a-kind aspects to most
> > Suitable reliability can be achieved, but it takes
> > scrutiny and engineering every step of the way. And
> then some
> > careful, rigorous testing.
> > Anyway, thatís my 2 cents worth.
> > And, yes; we are building experimental aircraft.
> > Al
> Jim Sower
> Crossville, TN; Chapter 5
> Long-EZ N83RT, Velocity N4095T
James F. Agnew
Velocity 173 Elite Aircraft Completed & Flying