Reducing the Accident Rate

"Richard Kaplan" wrote
What piston engine design would be more reliable? (Economics make turbine
engine comparisons unfair, even if turbines are more reliable -- and I am
not certain that they are.)

First off, turbine engines are not out of the questions at all. The
reason they are so incredibly expensive has a lot to do with the FAA
and milspecs. Second, turbine engines are inherently more reliable -
there are far fewer moving parts, and no reversals of direction. In
addition, they separate the combustion stages (suck, squeeze, bang,
blow) in space rather than in time - and that means only a relatively
small part of the engine has to be tough enough to accomodate the most
difficult portion of the cycle. In other words, pound for pound the
turbine will always be more reliable.

Second, we've learned a lot about piston engine reliability in the
past half century. Little of that has made it into aircraft engine
designs. For example, separate cylinders are disasters. There's not
sufficient mechanical stability, so everything moves too much. Note
that the two modern aviation piston engines - the Thielert and Orenda
- have abandoned that nonsense.

That's just one example. There are countless others in the ignition,
fuel, and other systems.

I have experienced a lot more engine problems driving cars than flying
airplanes for sure.

Driving cars made in the last 20 years? I find that amazing.

Experimental airplanes do not seem to have any lower incidence of engine
failures anecdotally, nor do I recall reading any data to suggest there
exists a more reliable experimental piston engine design.

Experimentals are amateur-designed. The engine installations are
amateur-designed too. The very fact that after the first 50 hours are
flown off the accident rate appears to even out with the certified
airplanes should suggest to you what a disaster the FAA-mandated
professional engineering is. Amateurs can do almost as well working
in their garages.

Michael

For example, separate cylinders are disasters.

What are "separate cylinders" and what's the alternative? (unless you mean the
wankel)

Jose


--
(for Email, make the obvious changes in my address)

Teacherjh wrote:

For example, separate cylinders are disasters.

What are "separate cylinders" and what's the alternative? (unless you mean the
wankel)

Each cylinder on a typical Lycoming or Continental engine can be removed
independently. All of the cylinders in a typical automobile engine are cast in a
single unit (known as the block). This is also true of many water-cooled aircraft
engines and many motorcycle engines.

George Patterson
In Idaho, tossing a rattlesnake into a crowded room is felony assault.
In Tennessee, it's evangelism.

(Teacherjh) wrote
What are "separate cylinders" and what's the alternative? (unless you mean the
wankel)

Separate cylinders are exactly that - you can unbolt a cylinder from
an engine and replace it without affecting the other cylinders. The
alternative is an engine block.

Michael

Thanks... now why are separate cylinders a disaster?

Jose

--
(for Email, make the obvious changes in my address)

(Teacherjh) wrote
Thanks... now why are separate cylinders a disaster?

Because the engine comes out either too heavy or not rigid enough.
The engine block provides rigidity. Separate cylinders provide none -
they just hang out there by themselves.

Insufficient rigidity is the cause of many ills. For example, if you
manage to crack the block on an engine, it will still continue to make
some power for at least a few minutes. Crack a cylinder, and you can
easily jam the piston/rod and seize the engine. Does that really
happen? Yes, I've lost friends that way.

Insufficient rigidity also contributes to valve/seat/guide problems.

Note that NONE of the new aviation engines (Orenda, Thielert, Honda,
Bombadier) have separate cylinders. No automotive engines do this
either. In fact, ONLY obsolete aviation engines do this.

The reason? It's a rare aviation cylinder, especially on a big
engine, that is built well enough to make TBO. The quality assurance
process mandated by the FAA is a bad joke, and in fact keeps
manufacturers from being able to improve the process.

Michael

Michael wrote:

Note that NONE of the new aviation engines (Orenda, Thielert, Honda,
Bombadier) have separate cylinders.

Just a quick look with Yahoo turned up the Morane Renault, Zoche, and Jabiru engines
- all new designs with separate cylinders. I'd bet the guys going to Oshkosh will be
able to provide other examples when they get back.

In general, separate cylinders are advantageous for air-cooled engines and blocks are
preferred for water-cooled designs, but this is not a universal rule.

George Patterson
In Idaho, tossing a rattlesnake into a crowded room is felony assault.
In Tennessee, it's evangelism.

"G.R. Patterson III" wrote
Just a quick look with Yahoo turned up the Morane Renault, Zoche, and Jabiru engines
- all new designs with separate cylinders.

A Jabiru is an all-new design? Looks loke a Lycoming shrunk to take
advantage of better metallurgy. Besides, it's a certified engine in
Australia, and I bet they have their own version of the FAA modeled
largely on ours.

I've been hearing about Zoche for years - long before I ever heard of
Thielert. Thielert now has actual production engines on actual
production aircraft. How about Zoche?

In general, separate cylinders are advantageous for air-cooled engines and blocks are
preferred for water-cooled designs, but this is not a universal rule.

I don't agree that it's a rule at all. If it were, we would see
separate cylinders SOMEWHERE outside aviation. And no, engines of
less than 4 cylinders don't count.

Michael

"Michael" wrote in message
om...

Note that NONE of the new aviation engines (Orenda, Thielert, Honda,
Bombadier) have separate cylinders. No automotive engines do this
either. In fact, ONLY obsolete aviation engines do this.

So why dont' we see lots of homebuilts eliminating separate cylinders?
There are some great minds in the homebuilt community and minimal FAA
regulation.

--------------------
Richard Kaplan

www.flyimc.com

"Richard Kaplan" wrote
So why dont' we see lots of homebuilts eliminating separate cylinders?

They do. Look at Rotax. It is essentially the standard for little
(Cub size and down) airplanes.

Also consider the Leeza Air-Cam. It is a professionally designed
airframe, purpose built as a camera platform twin for flight over
terrain that offered few viable forced landing options. Engine cost
wasn't really an issue. So what top-of-the-line certfied engines were
used? Right, none. They used Rotax.

Michael