ANNUAL, 2005 Redux...

"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:
: 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.

Agreed. All I'm saying is that the for the aircraft application, the
operating regime (cruise) is a very small window of operating conditions. If it can
be optimized within that window, but made simultaneously safe to operate outside of
it, that'd be enough. I haven't thought it through completely, so they may be
mututally exclusive.

: 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.

Isn't it a stronger function of compression ratio and CHT, though? Timing
will help manipulate the time at which the peak pressure occurs, but the detonation
margin has very little to do with timing.

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

Agreed. Points suck. Making them lightning-robust might take some
thought, however...

All of these things (solid-state "points," variable timing intelligently
dependent on RPM and manifold pressure, etc) would be very difficult to accomplish
mechanically to aviation robustness standards. Computers like FADEC would make it
easier to implement, but still quite difficult to certify.

-Cory


--

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

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.

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

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

Well, Steve survived his Part 135 review and is now a full fledged for
hire air carrier...
So, today when I bopped in (after driving half the length of the state
- gawd I hate driving) I found him replacing the rear wall of the
baggage compartment on Fat Albert after he apparently inspected the
cables to the tail planes, tested the ELT, etc...
We pulled all the other planes out of the hangar, including his
newly-135 Aztec, and proceeded to fire up Fat Albert's engines for the
first time with the new mags... Gee, they even ran... Mag drops are 100
on the left mag and 125 on the right mag... Same on both engines...
Adjusted the idle and it looks like I will get the fat boy back on
Friday (ceilings indefinite with 1/2 mile viz at this time) after they
button things up...

denny

In article Lk0xf.5150$sa4.3381@trnddc07,
wrote:


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?

an 6 liter automotive V8 can make 200hp all day long...

--
Eduardo K. | Some say it's forgive and forget.
http://www.carfun.cl | I say forget about forgiving just accept.
http://e.nn.cl | And get the hell out of town.
| Minnie Driver, Grosse Point Blank

Eduardo K. wrote:
In article Lk0xf.5150$sa4.3381@trnddc07,
wrote:


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?


an 6 liter automotive V8 can make 200hp all day long...


And what is the maximum HP of this engine that you have in mind?

Matt

Eduardo K. wrote:
: In article Lk0xf.5150$sa4.3381@trnddc07,
: wrote:
:
:
: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?

: an 6 liter automotive V8 can make 200hp all day long...

A 6-liter IO-360 can make 200 HP all day long as well.
--
Aaron C.