ANNUAL, 2005 Redux...

: In any case, there are exactly two things "wrong" with aircraft engines. The
: spark timing is fixed and the mixture control is in the hands of the pilot.
: And you can't do anything about the first problem until you fix the second.

The first is a compromise, but generally works really well for aircraft
engines... they *do* run at a constant RPM all the time. The second isn't that big of
a deal if the pilot is properly trained to use the mixture knob. Trouble is most
aren't because of the great degree of OWT and misinformation out there on the subject.

I would argue that the #1 biggest problem with aircraft engines is that they
are still air-cooled. Removing the tremendous thermal stresses of having 450 degree
CHT's make most of the "routine" aircraft engine problems go away. Stuck valves,
cracked exhaust flanges and cylinder heads, ridiculous octane requirements (100 for
8.5:1?) due to the heat and low RPM, galled cylinders/pistons due to overheating,
shock-cooling, and cold-starts, etc.

Liquid cooling stabilizes everything, lets more power be made more efficiently
with greater reliability. It doesn't even have to add too much weight.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote in message
...
: In any case, there are exactly two things "wrong" with aircraft engines.
The
: spark timing is fixed and the mixture control is in the hands of the
pilot.
: And you can't do anything about the first problem until you fix the
second.

The first is a compromise, but generally works really well for aircraft
engines... they *do* run at a constant RPM all the time. The second isn't
that big of
a deal if the pilot is properly trained to use the mixture knob. Trouble
is most
aren't because of the great degree of OWT and misinformation out there on
the subject.

Except that the optimal spark timing is a strong function of the air fuel
ratio. To get the full benifit of leaning, you need to change the spark. You
can't optimize the spark for the mixture if you don't know what the mixture
is.

I would argue that the #1 biggest problem with aircraft engines is that
they
are still air-cooled.

Liquid cooling has it's advantages.

Removing the tremendous thermal stresses of having 450 degree
CHT's make most of the "routine" aircraft engine problems go away. Stuck
valves,
cracked exhaust flanges and cylinder heads, ridiculous octane requirements
(100 for
8.5:1?)

Octane requirement is a stong function of spark timing...
Of course, large, open combustion chambers with lower charge motion tend to
require higher octane too.

due to the heat and low RPM, galled cylinders/pistons due to overheating,
shock-cooling, and cold-starts, etc.

Liquid cooling stabilizes everything, lets more power be made more
efficiently
with greater reliability. It doesn't even have to add too much weight.


Getting rid of points would be an improvement also. Solid state magneto's
are not hard to make.

--
Geoff
the sea hawk at wow way d0t com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com writes:

I keep hoping that someone somehow will figure out a way to move
some of the massive tecnology improvements we use (and ignore) daily
in our cars into the fleet; but I sure don't know what that route
is...

The technology got into cars because the government mandated fuel economy
and emission improvements. It shouldn't be hard to figure out what it will
take to get it into aircraft.

Yes, this was the biggest push. But I believe once Detroit started
hiring EE's [they literally had ME's doing EE work for years...]
and got them into sync with the environment...[rotten power supply,
with 65V spikes seconds long, horrid temp & vibration issues, vicious
reliability demands, and oh, a NTE $0.25 price point...] they've NOW
gone a LONG way farther and continue to. That's because they have hungry
competitors who will not let them rest.

In any case, there are exactly two things "wrong" with aircraft engines. The
spark timing is fixed and the mixture control is in the hands of the pilot.
And you can't do anything about the first problem until you fix the second.

Agreed. They need what cars have had for years: FADEC's with one
lever power control.

FWIW, I write algorithms that do air fuel control and diagnostics at one of
the larger automobile manufacturers.

Then you know far more about this than greasy-knuckle folks like moi.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

The magnetos we pulled off Fat Albert date back further than we can
trace... They have been overhauled, rebuilt, massaged, tinkered, and
cobbled for 48 years... And they will go back to AVIAL who will strip
them down, regrind the bearing surfaces, replace the bushings,
remagnetize the rotors, replace the internal small parts, paint them
shiny black, and they will go fly another 20 years on someones'
motor... Tough to do that with microelectronics...

I've had outboard motors with transistorized, CD, ignition... The
ignition was a constant source of problems and sudden failures... On
an airplane I want a magneto to back up the electronic ignition, just
in case on a dark and stormy night...

denny - older than dirt

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com writes:

George Patterson" wrote in message
Yeah. I heard an ad on the radio about a shop that had the gear to read
the computer chips for diagnosis in cars. That set me thinking about the
diagnosis technique frequently used with aircraft; replace parts until
something works. It seems to me that it wouldn't be hard to get the FAA to
sign off on at least a diagnostic chip.

Right. Now a mechanic just replaces parts until the fault codes go away...

See my last rant...about alternators..

It's nearly impossible to narrow things down to just one part, so even with
diagnostic codes to point the way, mechanics still tend to replace the easy
stuff first.
For example if you get a "oxygen sensor not switching" code, 9 times out of
10, the mechanic will replace the sensor. Then, only when that doesn't solve
the problem, will they will actually start to look for the cause of the
mixture problem (vacuum leak, etc.). Of course, there are those who will
just replace the sensor again. And again. And again... After a few tries,
they then complain that there is something wrong with the diagnostic
software.

BT,DT,GtTS!

Thirty years ago a friend had a job teaching the folks at a certain
western Ohio weight measuring company how to fix their new load cell
scales. These guys had fixed huge mechanical scales for years and
were ....resistant... to change. Every time he got a board-swapper;
he'd put them on the rigged unit with ...intermittent.. backplane
wiring. They soon learned.

Good diags and error codes are tremendous timesavers, but they are
no substitute for a brain, logical thinking and a rigorous
problem-solving approach.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Capt. Geoffrey Thorpe wrote:

Right. Now a mechanic just replaces parts until the fault codes go away...

I've not found that to be the case. Not in the last 15 years, at least.

It's nearly impossible to narrow things down to just one part, so even with
diagnostic codes to point the way, mechanics still tend to replace the easy
stuff first.
For example if you get a "oxygen sensor not switching" code, 9 times out of
10, the mechanic will replace the sensor. Then, only when that doesn't solve
the problem, will they will actually start to look for the cause of the
mixture problem (vacuum leak, etc.).

The one time that showed up on my vehicle, they checked for (and found) a vacuum
leak first thing.

George Patterson
Coffee is only a way of stealing time that should by rights belong to
your slightly older self.

Capt. Geoffrey Thorpe The Sea Hawk at wow way d0t com wrote:
: In any case, there are exactly two things "wrong" with aircraft engines. The
: spark timing is fixed and the mixture control is in the hands of the pilot.
: And you can't do anything about the first problem until you fix the second.

You are spot-on. I would argue, though, that you can't fix the second
problem until you eliminate the first.
--
Aaron C.

On 9-Jan-2006, Aaron Coolidge wrote:

Capt. Geoffrey Thorpe The Sea Hawk at wow way d0t com wrote:
: In any case, there are exactly two things "wrong" with aircraft engines.
The spark timing is fixed and the mixture control is in the hands of the
pilot.
: And you can't do anything about the first problem until you fix the
second.

You are spot-on. I would argue, though, that you can't fix the second
problem until you eliminate the first.


And after we resolve the magneto/mixture knob vs. electronic
ignition/automatic mixture control issues we can discuss the fact that here,
in the year 2006, manufacturers are still making aircraft engines with
CARBURETORS! And the "advanced" engines have MECHANICAL (rather than
electronic) fuel injection!

Still, in terms of reliability and durability piston aircraft engines score
pretty well. How long would a typical Detroit V6 engine last if it was
called upon to deliver full rated power for several minutes a few times a
day, and 75% of full rated power for several hours at a stretch?
--
-Elliott Drucker

Don't remember if I gave the ending to the group... The rebuilt mags
went on without problems and the engines started promptly... I have
flown 10+ hours at this point and have no complaints about the mags
(didn't have complaints before)... I did have one fouled plug on the
3rd flight (leaded crap ought to be outlawed) that cleared with the ol
full throttle with lean mixture trick, but the tanks have been pretty
well flushed of lead now by topping off with the cheapest, nastiest,
mogas I can find... The engines running smooth and loving every drop of
it...
Total bill was $3200 parts and labor for the annual, lots better than
the $12K+ last year... Sooner or later I'm going to get an annual for
just his shop rate (yeah, right!, cept I did notice some oil on the
bottom plugs on 2 cylinders on the starboard engine sigh, so I can
see an overhaul in my future... I'm busily collecting new cylinders
and overhaul parts...

denny and Fat Albert the Apache