Today's Message Index:
----------------------
1. 04:23 AM - Re: Re: Pressure Carburetor? (Matthew J. Hawkins)
2. 05:43 AM - Re: Re: Pressure Carburetor? (Matthew J. Hawkins)
3. 09:19 AM - Re: Re: Pressure Carburetor? (BobsV35B@aol.com)
4. 09:28 AM - Re: Re: Pressure Carburetor? (David Owens)
5. 09:49 AM - Re: Re: Pressure Carburetor? (Matthew J. Hawkins)
6. 10:57 AM - Re: Re: Pressure Carburetor? (BobsV35B@aol.com)
7. 11:10 AM - Re: Re: Pressure Carburetor? (Matthew J. Hawkins)
8. 05:34 PM - Re: Re: Pressure Carburetor? (Don)
9. 10:27 PM - Re: Re: Pressure Carburetor? (BobsV35B@aol.com)
10. 11:00 PM - Official Commander-List FAQ (Frequently Asked Questions) (Matt Dralle)
11. 11:03 PM - Official Commander-List Usage Guidelines (Matt Dralle)
12. 11:26 PM - Re: Re: Pressure Carburetor? (Don)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Wow! I had no idea my pressure carburetor question would spur this kind of discussion!
It's a good one though - quite important is seems.
N2760B is a very basic machine. CHT only on one cylinder for each engine - nothing
else. No EGT. No fuel transfer system. Sounds to me like best approach is
to run with mixtures "full rich" and let the pressure carb do it's job. Leave
mixtures "the stink" alone.
Matt
-----Original Message-----
From: owner-commander-list-server@matronics.com [mailto:owner-commander-list-server@matronics.com] On Behalf Of Bill Bow
Sent: Sunday, September 30, 2007 8:05 PM
Subject: RE: Commander-List: Re: Pressure Carburetor?
--> <bowing74@earthlink.net>
This is great!
It hasn't "hit the fan" like this since the "Sump-Gate" days of '01. bilbo
-----Original Message-----
From: owner-commander-list-server@matronics.com
[mailto:owner-commander-list-server@matronics.com] On Behalf Of N395V
Sent: Saturday, September 29, 2007 8:13 PM
Subject: Commander-List: Re: Pressure Carburetor?
<airboss@excaliburaviation.com>
> HI MILT. I am not picking on you, but need to make one other
> correction.
Not to worry JB I have a thick skin especially when my espousings are based on
science and data.
This is quite an important topic for any bathtub commander owner and neededs to
be thoroughly discussed.
--------
Milt
2003 F1 Rocket
2006 Radial Rocket
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=137190#137190
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Jb-
Thanks for this! Perfect description of what we're seeing.
Left engine (with properly re-built carb) does exactly as you say - rapid c
hange in engine operation as you get close to idle/cut-off. Right engine
seemed to lean somewhat like a "regular" engine. I'll double-check that th
is week. Right engine is the one that always seemed to run rich and foul p
lugs too.
We'll have a look at this when we can. Glad to hear that when "auto lean"
is not working properly the fallback in the design is to lean manually. Ma
kes good sense. In the short term, sounds like we just need to be aware of
whether or not the auto lean is running properly or not.
Good news is that all exhaust pipes are a nice ash grey - no black soot/res
idue. Perhaps engines are still bedding in?
What's your thought on the wire-type plugs?
Matt
-----Original Message-----
From: owner-commander-list-server@matronics.com [mailto:owner-commander-lis
t-server@matronics.com] On Behalf Of yourtcfg@aol.com
Sent: Sunday, September 30, 2007 12:54 AM
Subject: Re: Commander-List: Re: Pressure Carburetor?
HI TYLOR
You can generally tell if the autolean is operating by engine performance.
If the carb fails, it is designed to fail safe and run super rich. You ca
n then manually lean it until it can be repaired. On the Commander, look f
or the cyl temps to run the same on both engines, at climb and cruse. To c
heck normal operation, set cruse power and slowly lean the carbs manually (
one at a time thank you) The levers should travel about 1/2 way with littl
e or no change in engine operation. When the change comes, it should be ve
ry quick. It should go from running fine to idle cut-off in a very little
travel. Last, check the color of the exhaust pipes. They should be a nice
ash gray. jb
I do have a questions. Matthew's problem, how do you know the auto lean is
working?
How do you check it? It sounds like the rebuilt side is working and the old
er one may not?
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Good Morning Matt,
That may very well be the best answer for you and your airplane.
However, may I point out that even fifty years ago there were some who did
learn how to operate those engines safely and efficiently by judicious use of
the mixture control.
May I first ask just what style of Pressure Carburetor your engine has?
Does it have an AMC unit?
There seems to be a lot of mention about pressure carburetors implying that
all pressure carburetors have Automatic Mixture Controls installed.
That is definitely NOT true.
As was mentioned by Milt, the PS5c is not one that will provide any altitude
compensation at all, yet it is probably the most commonly used pressure
carburetor in the GA fleet.
The designers of the fuel controls had to be people who fully understood the
vagaries of engine operation.
They knew the difficulties present in trying to get even distributor of fuel
and air to each and every cylinder as well as the necessity for each
cylinder to be manufactured to close enough tolerances so that the compression
of
each cylinder was as close as possible to being identical and so that the
breathing efficiencies of the intake systems were identical.
They then designed a fuel delivery system that would work adequately for
engines that were at the edges of acceptability when evaluated for cylinder to
cylinder consistencies.
Have you ever heard a reference to the "Shaky Jakes", when one is discussing
Jacobs Aircraft Engines?
The reason they were described as shaky was because the early Jakes had a
very simple fuel delivery system that caused the lower cylinders to get a LOT
more fuel than the upper ones. Most of the later development of the Jacobs
engines were directed toward improving that mixture distribution.
Later, more modern, round engines used many schemes to provide better
distribution. It was thought by all, that it would be best if the pilot did not
have to operate any controls that would affect that mixture.
The development of the pressure injection carburetor with an AMC unit was an
effort toward simplifying the operation for the pilots of the day. It was
never completely successful. The best units that were ever made were those
that were fitted to the latest P&W R-2800s and the Curtiss Wright R-3350s which
were the engines that powered the last of the piston airline fleet.
When those engines were used in four engine long range airplanes, they
almost always had flight engineers assigned to operating the engines so that
adequate and proper leaning procedures could be used. For short haul airplanes,
the pilots normally just used the Auto Lean and Auto Rich functions. On those
rare occasions when range or endurance became an important consideration, even
we lowly aviators would do a bit of manual leaning.
What point am I trying to make?
You can do manual leaning of your aircraft even if you don't have the modern
equipment, but it takes a much greater understanding of the potential
vagaries of the combustion process than is generally made available to we aviators
in our basic training.
JB mentioned monitoring the tail pipes to ascertain whether or not the
mixtures being provided by your fuel delivery unit are adequate.
That was, and still is, certainly one of the clues, but there are many
others.
Attendance at a good engine course such as is provided by The Advanced
Pilot's Seminar folks will provide the basics, but they start off by saying there
is no reason to try to learn the basics if the airplane is not equipped with
modern monitoring devices.
Having been an active aviator during the days when such stuff was not
available, I do have a few techniques which I can use to make a decision as to
whether or not it will be practical to operate at any setting other than full
rich.
Let's forget about what you are flying now, and consider whatever airplane
you used when you were a student pilot. Let's say it was a Piper Cherokee 140.
Once you were set up in cruise, you may have been taught to lean the engine
until it got rough, then richen until the operations smoothed. You were
probably also told not to lean at all below some pre selected altitude.
That method has good science behind it!
Before you can decide how much fuel is needed for the total engine, you must
determine how even the mixture is from cylinder to cylinder.
A very easy way to check on that when flying that Cherokee was to monitor
the RPM while leaning. If the engine got rough before any RPM drop was noted,
the mixture distribution was atrocious.
If you were able to get a fifty to sixty RPM drop before any roughness
occurred, the mixture distribution was reasonable.
As an aside, that DID NOT mean you should operate it with the fifty RPM
drop, that was merely a way to check for good distribution.
Cessna formerly recommended that the 170 with a fixed pitch propellor be
leaned until it encountered a two MPH drop in airspeed. That was a good method
of finding a point just barely on the lean side of best power and it would
probably have given an EGT reading of about fifty rich of peak had we had EGT
gauges back then. For any GA engine being operated at 65 per cent power or less,
there is nothing you can do with the mixture control that will hurt the
engine, so Cessna's method worked well and was very simple.
Back to the Cherokee!
If the engine kept operating smoothly all the way until all four cylinders
quit running, the mixture distribution was perfect.
With a constant speed propellor, the same sort of test can be performed by
watching the airspeed. Obviously, the air must be smooth and the pilot capable
of holding altitude and attitude very closely while performing the check, but
it did, and still does, work quite well.
If the distribution is good, you should be able to perceive an increase in
power by noting the increase in airspeed as the engine is leaned. Peak airspeed
will occur when the engine is developing peak power. That is, it will be
getting as much power as is possible from the fuel and air being delivered to
the engine.
For what it is worth, most small normally aspirated piston engine get their
peak power when the mixture is at a point corresponding to an EGT temperature
that is approximately eighty degrees Fahrenheit cooler than the peak EGT
number and on the rich side thereof.
Reason would tell us that the engine will run at it's hottest when the most
power is being developed, but tests have shown that to not be true. The CHTs
will be hottest when the engine is operated with an EGT set to somewhere
around fifty degrees rich of the Peak EGT temperature.
If we do not have an engine monitor, we cannot tell precisely where the
temperature is being set, but we can evaluate the performance of the airplane.
If we lean the engine so that the airplane is going just as fast as it will
go with the RPM and manifold pressure being used, the engine will be at the
best power mixture setting and it will be just a wee bit richer than the point
where the CHTs will be the hottest!
This is certainly NOT meant as a primer on how to lean your engine.
I just wanted to point out that there is no easy cake recipe style of
approach. If you wish to rely on the efficacy of the installed fuel control, that
is great, but you should understand the process well enough so that you can
determine whether or not your system is working as it was designed to work.
That part of the equation is very difficult if you DO NOT have modern engine
monitoring equipment. The potential for finding a mechanic with a proper
flow bench and all the skill and knowledge to use it well is very slim.
It has been ten to fifteen years since I last priced a rebuild on one of
those fancy fully automatic carburetors for an Aero Commander, but I was quoted
a price of fifteen thousand dollars per carburetor. The owner elected to
donate the aircraft to a mechanics school as it was not economically viable to
overhaul those units.
I have no idea whether or not any alternative carburetors were available for
that airplane, but installing a simple PS5c and modern monitoring equipment
would have been a lot cheaper alternative. The rub would be whether or not
it was FAA approved!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 10/1/2007 6:24:06 A.M. Central Daylight Time,
hawkins@cms.udel.edu writes:
N2760B is a very basic machine. CHT only on one cylinder for each engine -
nothing else. No EGT. No fuel transfer system. Sounds to me like best
approach is to run with mixtures "full rich" and let the pressure carb do it's
job. Leave mixtures "the stink" alone.
Matt
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Hey Chris! How you doin??? Dave Owens here with Aerial Viewpoint... Haven't
heard from you since your visit here at Hooks a few years back... Did
Dreamcatcher get sold or scrapped??? I heard stories. Looking forward to
hearing from you.
David Owens
Aerial Viewpoint
N14AV
AC-500A-Colemill
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Bob-
That's definitely something I've gleaned from this discussion. All pressur
e carbs are NOT created equal. I'll check on exactly what I have and let y
ou know.
Milt's view seems sound - if it can be leaned - you should do it. No sense
in wasting fuel/$$ However, seems like I don't have the engine monitorin
g systems to do it accurately or efficiently.
Next time we're up on a smooth day we'll try the airspeed method you sugges
t below.
Your description of manual leaning is exactly what I learned as a student p
ilot - and still use on a plane with no EGT. In fact, it's what my pilot w
ho flies the Commander was trying to do on the ground when engines were (ap
parently) running too rich. Sounds like we need to do it differently with
the constant speed prop.
Everything ran GREAT on our flight last week - think Summit got the final a
djustments right. Good mag checks, not rough running, nice grey ash in the
tubes (no black soot). Only question is whether or not the auto lean is w
orking on the right engine - and exactly what carbs we have (i.e. should it
have auto lean?).
The shop that did the final "tweak" on the left carb (and got it right) cha
rged us $795. Guess we did OK!
Milt sent me Chris Schuermanns PDF file that listed the other two recommend
ed shop in case we need for the right engine. We'll see.
I'm also going to check to see if we have the black gaskets or the newer or
ange.
Matt
-----Original Message-----
From: owner-commander-list-server@matronics.com [mailto:owner-commander-lis
t-server@matronics.com] On Behalf Of BobsV35B@aol.com
Sent: Monday, October 01, 2007 12:18 PM
Subject: Re: Commander-List: Re: Pressure Carburetor?
Good Morning Matt,
May I first ask just what style of Pressure Carburetor your engine has?
Does it have an AMC unit?
There seems to be a lot of mention about pressure carburetors implying that
all pressure carburetors have Automatic Mixture Controls installed.
That is definitely NOT true.
>
>
Let's forget about what you are flying now, and consider whatever airplane
you used when you were a student pilot. Let's say it was a Piper Cherokee 1
40. Once you were set up in cruise, you may have been taught to lean the en
gine until it got rough, then richen until the operations smoothed. You wer
e probably also told not to lean at all below some pre selected altitude.
That method has good science behind it!
>
>
With a constant speed propellor, the same sort of test can be performed by
watching the airspeed. Obviously, the air must be smooth and the pilot capa
ble of holding altitude and attitude very closely while performing the chec
k, but it did, and still does, work quite well.
If the distribution is good, you should be able to perceive an increase in
power by noting the increase in airspeed as the engine is leaned. Peak airs
peed will occur when the engine is developing peak power. That is, it will
be getting as much power as is possible from the fuel and air being deliver
ed to the engine.
>
>
I just wanted to point out that there is no easy cake recipe style of appr
oach. If you wish to rely on the efficacy of the installed fuel control, th
at is great, but you should understand the process well enough so that you
can determine whether or not your system is working as it was designed to w
ork.
>
>
It has been ten to fifteen years since I last priced a rebuild on one of th
ose fancy fully automatic carburetors for an Aero Commander, but I was quot
ed a price of fifteen thousand dollars per carburetor. The owner elected to
donate the aircraft to a mechanics school as it was not economically viabl
e to overhaul those units.
Happy Skies,
Old Bob
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Good Morning Matt,
Sounds great!
Learning and sharing knowledge is what it is all about.
You may well have a pressure carburetor that is not easy to manually lean.
After all, that WAS the goal of the folks who designed it.
In any case, I urge you to read and study the data that is readily
available. A good start is to read John Deakin's articles on general engine
management.
I doubt if you will find very many folks who have current experience with
the fuel controllers on your airplane.
It is obvious that JB does have current information because he is so
insistent that your particular unit should only be leaned in an emergency.
I have no gripe with that philosophy, but I do think it is important that an
operator of such a unit be very knowledgeable as to just what it is supposed
to be doing.
I strongly recommend that you do instrument the engine so that you will be
able to ascertain whether or not the automatic controls are doing what they
were designed to do!
I believe checking it using the airspeed method is quite a bit beyond what
you should be doing with your current level of experience and lack of on board
monitoring equipment.. Those are highly stressed and sophisticated engines.
Treat them gently!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 10/1/2007 11:50:32 A.M. Central Daylight Time,
hawkins@cms.udel.edu writes:
That's definitely something I've gleaned from this discussion. All pressure
carbs are NOT created equal. I'll check on exactly what I have and let you
know.
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Good advise! Burning a bit of extra fuel won't hurt me too badly in the sh
ort term.
Matt
-----Original Message-----
From: owner-commander-list-server@matronics.com [mailto:owner-commander-lis
t-server@matronics.com] On Behalf Of BobsV35B@aol.com
Sent: Monday, October 01, 2007 1:56 PM
Subject: Re: Commander-List: Re: Pressure Carburetor?
I believe checking it using the airspeed method is quite a bit beyond what
you should be doing with your current level of experience and lack of on bo
ard monitoring equipment.. Those are highly stressed and sophisticated engi
nes.
Treat them gently!
Happy Skies,
Old Bob
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Bob;
I used to sit sideways in a Connie running R-3360 Turbo compound
engines, but its been a long time.
My question is this, since you remember more about those things, I
recall being told some where that aircraft engines use approximately 25%
of their fuel for cooling. At what point in leaning do we get to where
we save fuel, but shorten the engine life? And where is the crossover
point.
Thanks, Don
----- Original Message -----
From: BobsV35B@aol.com
To: commander-list@matronics.com
Sent: Monday, October 01, 2007 12:18 PM
Subject: Re: Commander-List: Re: Pressure Carburetor?
Good Morning Matt,
That may very well be the best answer for you and your airplane.
However, may I point out that even fifty years ago there were some who
did learn how to operate those engines safely and efficiently by
judicious use of the mixture control.
May I first ask just what style of Pressure Carburetor your engine
has?
Does it have an AMC unit?
There seems to be a lot of mention about pressure carburetors implying
that all pressure carburetors have Automatic Mixture Controls installed.
That is definitely NOT true.
As was mentioned by Milt, the PS5c is not one that will provide any
altitude compensation at all, yet it is probably the most commonly used
pressure carburetor in the GA fleet.
The designers of the fuel controls had to be people who fully
understood the vagaries of engine operation.
They knew the difficulties present in trying to get even distributor
of fuel and air to each and every cylinder as well as the necessity for
each cylinder to be manufactured to close enough tolerances so that the
compression of each cylinder was as close as possible to being identical
and so that the breathing efficiencies of the intake systems were
identical.
They then designed a fuel delivery system that would work adequately
for engines that were at the edges of acceptability when evaluated for
cylinder to cylinder consistencies.
Have you ever heard a reference to the "Shaky Jakes", when one is
discussing Jacobs Aircraft Engines?
The reason they were described as shaky was because the early Jakes
had a very simple fuel delivery system that caused the lower cylinders
to get a LOT more fuel than the upper ones. Most of the later
development of the Jacobs engines were directed toward improving that
mixture distribution.
Later, more modern, round engines used many schemes to provide better
distribution. It was thought by all, that it would be best if the pilot
did not have to operate any controls that would affect that mixture.
The development of the pressure injection carburetor with an AMC unit
was an effort toward simplifying the operation for the pilots of the
day. It was never completely successful. The best units that were ever
made were those that were fitted to the latest P&W R-2800s and the
Curtiss Wright R-3350s which were the engines that powered the last of
the piston airline fleet.
When those engines were used in four engine long range airplanes, they
almost always had flight engineers assigned to operating the engines so
that adequate and proper leaning procedures could be used. For short
haul airplanes, the pilots normally just used the Auto Lean and Auto
Rich functions. On those rare occasions when range or endurance became
an important consideration, even we lowly aviators would do a bit of
manual leaning.
What point am I trying to make?
You can do manual leaning of your aircraft even if you don't have the
modern equipment, but it takes a much greater understanding of the
potential vagaries of the combustion process than is generally made
available to we aviators in our basic training.
JB mentioned monitoring the tail pipes to ascertain whether or not the
mixtures being provided by your fuel delivery unit are adequate.
That was, and still is, certainly one of the clues, but there are many
others.
Attendance at a good engine course such as is provided by The Advanced
Pilot's Seminar folks will provide the basics, but they start off by
saying there is no reason to try to learn the basics if the airplane is
not equipped with modern monitoring devices.
Having been an active aviator during the days when such stuff was not
available, I do have a few techniques which I can use to make a decision
as to whether or not it will be practical to operate at any setting
other than full rich.
Let's forget about what you are flying now, and consider whatever
airplane you used when you were a student pilot. Let's say it was a
Piper Cherokee 140. Once you were set up in cruise, you may have been
taught to lean the engine until it got rough, then richen until the
operations smoothed. You were probably also told not to lean at all
below some pre selected altitude.
That method has good science behind it!
Before you can decide how much fuel is needed for the total engine,
you must determine how even the mixture is from cylinder to cylinder.
A very easy way to check on that when flying that Cherokee was to
monitor the RPM while leaning. If the engine got rough before any RPM
drop was noted, the mixture distribution was atrocious.
If you were able to get a fifty to sixty RPM drop before any roughness
occurred, the mixture distribution was reasonable.
As an aside, that DID NOT mean you should operate it with the fifty
RPM drop, that was merely a way to check for good distribution.
Cessna formerly recommended that the 170 with a fixed pitch propellor
be leaned until it encountered a two MPH drop in airspeed. That was a
good method of finding a point just barely on the lean side of best
power and it would probably have given an EGT reading of about fifty
rich of peak had we had EGT gauges back then. For any GA engine being
operated at 65 per cent power or less, there is nothing you can do with
the mixture control that will hurt the engine, so Cessna's method worked
well and was very simple.
Back to the Cherokee!
If the engine kept operating smoothly all the way until all four
cylinders quit running, the mixture distribution was perfect.
With a constant speed propellor, the same sort of test can be
performed by watching the airspeed. Obviously, the air must be smooth
and the pilot capable of holding altitude and attitude very closely
while performing the check, but it did, and still does, work quite well.
If the distribution is good, you should be able to perceive an
increase in power by noting the increase in airspeed as the engine is
leaned. Peak airspeed will occur when the engine is developing peak
power. That is, it will be getting as much power as is possible from the
fuel and air being delivered to the engine.
For what it is worth, most small normally aspirated piston engine get
their peak power when the mixture is at a point corresponding to an EGT
temperature that is approximately eighty degrees Fahrenheit cooler than
the peak EGT number and on the rich side thereof.
Reason would tell us that the engine will run at it's hottest when the
most power is being developed, but tests have shown that to not be true.
The CHTs will be hottest when the engine is operated with an EGT set to
somewhere around fifty degrees rich of the Peak EGT temperature.
If we do not have an engine monitor, we cannot tell precisely where
the temperature is being set, but we can evaluate the performance of the
airplane.
If we lean the engine so that the airplane is going just as fast as it
will go with the RPM and manifold pressure being used, the engine will
be at the best power mixture setting and it will be just a wee bit
richer than the point where the CHTs will be the hottest!
This is certainly NOT meant as a primer on how to lean your engine.
I just wanted to point out that there is no easy cake recipe style of
approach. If you wish to rely on the efficacy of the installed fuel
control, that is great, but you should understand the process well
enough so that you can determine whether or not your system is working
as it was designed to work.
That part of the equation is very difficult if you DO NOT have modern
engine monitoring equipment. The potential for finding a mechanic with a
proper flow bench and all the skill and knowledge to use it well is very
slim.
It has been ten to fifteen years since I last priced a rebuild on one
of those fancy fully automatic carburetors for an Aero Commander, but I
was quoted a price of fifteen thousand dollars per carburetor. The owner
elected to donate the aircraft to a mechanics school as it was not
economically viable to overhaul those units.
I have no idea whether or not any alternative carburetors were
available for that airplane, but installing a simple PS5c and modern
monitoring equipment would have been a lot cheaper alternative. The rub
would be whether or not it was FAA approved!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 10/1/2007 6:24:06 A.M. Central Daylight Time,
hawkins@cms.udel.edu writes:
N2760B is a very basic machine. CHT only on one cylinder for each
engine - nothing else. No EGT. No fuel transfer system. Sounds to me
like best approach is to run with mixtures "full rich" and let the
pressure carb do it's job. Leave mixtures "the stink" alone.
Matt
-------------------------------------------------------------------------
-----
See what's new="_blank">Make AOL Your Homepage.
-------------------------------------------------------------------------
-----
10/1/2007 6:59 PM
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Good Evening Don,
I have never heard that particular number and I believe we would have to
better define the terms before we could either disagree or agree with that 25%
assertion.
As to where does leaning cause additional wear, that is another tough one.
Running any engine too lean at high powers will cause big troubles. However
running one leaner than optimum at low powers will not hurt it all, but it
will burn more fuel per horsepower developed than is possible when the engine
is run so as to attain optimum BSFC (Brake Specific Fuel Consumption).
I do not know the number used by your airline to lean the Turbo Compound
R-3350, but most users utilized a ten percent BMEP drop from the peak BMEP.
The procedure used by my airline was as follows. We would first chose a
desired BMEP number from the power charts. Just for kicks, let's say that the
desired cruise BMEP was 254. We would start out with the mixture in Auto Rich.
The mixture would be slowly leaned until the BMEP started to rise. When it went
above 254, we would throttle back until it was at 254, then continue to lean
until it was steady at 254 and where any further leaning would take the BMEP
reading below 254. That procedure determined the peak BMEP (Peak power) for
the manifold pressure being used. At that time, we would continue leaning
the engine until the BMEP was reading 254 minus 24.5 or approximately 228 BMEP.
Once that spot ten percent leaner than peak power was found, the throttle
was used to add manifold pressure so as to bring the BMEP back to the desired
cruise power. We then checked the manifold pressure to be sure we were still
below the maximum allowed manifold pressure for the desired cruise power.
Sound familiar?
If we leaned the engine further, it would just lose power, but no harm was
done. However, if we richened it up a bit, the engine would overheat and it may
even go into mild detonation. It needed to be well lean of peak power to
cool properly.
I don't know if you recall, but there is a shaft on the rear of the engine
which connects the two fuel injection controllers together. One unit is for the
front row and the other feeds the rear. That shaft would occasionally slip.
When that happened, one row would be running substantially leaner than the
other. The one that was getting more fuel would be carrying more of the load
that was being developed by the engine. That row would burn the valves and
sometimes even have holes burned in the pistons while the row which was not
getting enough fuel would be running clean and comfortable.
The place where any engine is most likely to develop engine problems are
when the mixture is at that point where the peak BMEP or peak engine power is
being developed. If the engine is run at that same power with a richer than
needed fuel mixture, the extra fuel will slow down the rate of burn and move the
point of peak combustion pressure to a point where the engine is able to
operate relatively cool.
That function is what is normally referred to as cooling the engine with
fuel and it is how we kept our cool during takeoff and climb regimes!
Another way to cool the engine is to cool it with additional combustion air.
That is what happens when the engine is run well lean of best power. (Note
that I said best power, not Peak EGT. They do NOT occur at the same point) When
we leaned that nice big R-3350 ten percent lean of best power, we were
running at a mixture that was well lean of the best power point and the engine
was
being cooled by that surplus combustion air.
Normal cruise power for the 3350 was around 55 to 60 percent of rated power.
We were really running it quite conservatively. If we richened it without
reducing the manifold pressure, we defeated the air cooling effect and it would
overheat and cause all sorts of problems.
Leaner is cleaner and leaner is cooler. Cleaner and cooler is generally
considered to be better, is it not?
So, if you want to extend engine life, run it at relatively low power
settings and run the mixture on the lean side of best power!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 10/1/2007 7:35:20 P.M. Central Daylight Time,
dongirod@bellsouth.net writes:
Bob;
I used to sit sideways in a Connie running R-3360 Turbo compound engines,
but its been a long time.
My question is this, since you remember more about those things, I recall
being told some where that aircraft engines use approximately 25% of their fuel
for cooling. At what point in leaning do we get to where we save fuel, but
shorten the engine life? And where is the crossover point.
Thanks, Don
Message 10
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Official Commander-List FAQ (Frequently Asked Questions) |
Dear Listers,
Please read over the Commander-List Frequently Asked Questions (FAQ) below. The
complete Commander-List FAQ including the Usage Guidelines can be found at the
following URL:
http://www.matronics.com/FAQs/Commander-List.FAQ.html
Thank you,
Matt Dralle
Matronics Email List Administrator
[ Note: This FAQ was designed to be displayed with a fixed width font such as
Courier. Proportional fonts will cause display formatting errors. ]
_-*************************************************************************-_
_-* Commander List Co-Sponsored by the Twin Commander Flight Group (TCFG) *-_
_-* *-_
_-* Please see the link below for a welcome message from the TCFG *-_
_-* directory, Jim Metzger. Jim can be reached at 360-835-1090 or via *-_
_-* email at: YOURTCFG@aol.com *-_
_-* *-_
_-* List Welcome Message from Jim Metzger: *-_
_-* *-_
_-* http://www.matronics.com/commander-list/TCFG-welcome.html *-_
_-* *-_
_-* TCFG Website *-_
_-* *-_
_-* http://www.aerocommander.com *-_
_-* *-_
_-*************************************************************************-_
This FAQ can also be viewed in HTML online at the following address:
http://www.matronics.com/FAQ/Commander-List.htm
************************************************************
******* LIST POLICIES AND FREQUENTLY ASKED QUESTIONS *******
************************************************************
PLEASE READ. This document contains Commander-List policies and information
for new and old subscribers. Understanding the Commander-List policies will
minimize problems for the Administrator, and will help keep the Commander-List
running smoothly for all of us.
******************************************
*** Quick Start Guide to List Features ***
******************************************
There are many features available on the Matronics Email Lists and each
one is described in detailed below. However, using the List Navigator
you can quickly access the complete set of features available for this
List. The List Navigator can be found at the following URL:
http://www.matronics.com/Navigator?Commander-List
****************************************
*** How to Subscribe and Unsubscribe ***
****************************************
Simply go to the Web Page shown below and enter your email address and
select the List(s) that you wish to subscribe or unsubscribed from. You
may also use the handy "Find" function to determine the exact syntax of
your email address as it is subscribed to the List. Please see the
complete instructions at the top of the Web Page for more information.
The Subscribe/Unsubscribe web page is:
http://www.matronics.com/subscribe
Note that you will receive TWO conformation emails regarding your subsciption
process. The first verifies that your subscription/unsubsciption request
was received, and the second confirms that the process has been completed.
You should receive the first email within a few minutes of your request.
The second conformation will arrive in less than 24 hours. You cannot post
until you receive the second conformation email message.
*****************************
*** How to Post a Message ***
*****************************
Send an email message to:
commander-list@matronics.com
Your message will be redistributed to everyone currently subscribed
to the List.
*****************************************************
*** SPAM Fighter - You Must be Subscribed to Post ***
*****************************************************
When a new post is received by the system, the From: line of the message
is checked and compared against the current subscription list. If the
email address is found, the message is passed on to the List Processor.
If the email address isn't found in the current list of subscribers, it
is dumped. This serves to very effectively thwart 99% of the SPAM that
gets posted to the Lists.
Remember, however, that the syntax of your email address is very important
with regard to the configuration of your email application such as Outlook
or Eudora. For example, the following two email addresses may be
functionally equivalent, but only one would pass the Matronics Email SPAM
test depending on which was syntax was subscribed to the given List:
smith@machine.domain.com
smith@domain.com
Either email address syntax is alright, just be sure that you configure
your email application to match *exactly* the address you've subscibed to
the List.
**************************************
*** Enclosure Support on the Lists ***
**************************************
Limited posting of enclosures such as pictures, documents, and spreadsheets
is supported on the Lists. There are a number of restrictions, and these
are detailed below. Please abide by the rules put forth regarding the
content of enclosures.
These are some of the features and limits of enclosures on the Matronics
Lists:
1) Enclosures will only be posted to the Real Time version of the Lists.
2) Enclosures will NOT be included in the Daily Digest version of the Lists.
3) Enclosures WILL BE forwarded on to the BBS Forum Web site.
4) Enclosures will NOT be appended to the Archives.
5) Enclosures will NOT be available in the List Browse feature.
6) Only the following file types and extensions will be allowed:
bmp doc dwg dxf gif jpg pdf png txt xls
All other enclosures types will be rejected and email returned to
sender. The enclosure types listed above are relatively safe from
a virus standpoint and don't pose a particularly large security risk.
7) !! All incoming enclosures will be scanned for viruses prior to posting
to the List. This is done in real time and will not slow down
the process of posting the message !!
Here are some rules for posting enclosures. Failure to abide by these rules
could result in the removal of a subscriber's email address from the Lists.
1) Pay attention to what you are posting!! Make sure that the files
you are enclosing aren't HUGE (greater that 1MB). Remember that there
are still people checking they're email via dial up modem. If you post
30MB worth of pictures, you are placing an unnecessary burden on these
folks and the rest of us, for that matter.
2) SCALE YOUR PICTURES DOWN!!! I don't want to see huge 3000 x 2000
pictures getting posted that are 3 or 4MB each. This is just
unacceptable. Use a program such as Photoshop to scale the picture
down to something on the order of 800 x 600 and try to keep the
file size to less-than 200KB, preferably much less.
Microsoft has a really awesome utility available for free that allows
you to Right-Click on a picture in Explorer and automatically
scale it down and resave it. This is a great utility - get it, use it!
http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx
Look for the link "Image Resizer"
3) !! This would seem to go without saying, but I'll say it anyway. Do not
post anything that would be considered offensive by your grandmother.
And you know what I'm saying; I don't want to see anything even
questionable. !!
4) REMEMBER THIS: If you post a 1MB enclosure to a List with 1000 members
subscribed, your 1MB enclosure must be resent 1000 times amounting
to 1MB X 1000 = 1 Gigabyte of network traffic!! BE CAREFUL and
BE COURTEOUS!
Also see the section below on the Matronics Photo and File Share where
you can have your files and photos posted on the Matronics web server
for long time viewing and availability.
*******************
*** Digest Mode ***
*******************
Each day, starting at 12 midnight PST US, a new 'digest' will be started.
This digest will contain the same information that is currently appended
to the archive file. It has all of the headers except for the "From:"
and "Subject:" lines removed, and includes a message separator consisting
of a line of underscores.
Each day at 23:55 PST US, the day's messages as described above will be
combined and sent as a single message to everyone on the digest email list.
To subscribe to the digest list, use the same subscription web form
described above, and just select the Digest version of the List.
http://www.matronics.com/subscribe
Note that you *can* be subscribed to both the realtime and digest versions
of the List at the same time. This is perfectly acceptable.
Now some caveats:
* Messages sent to "commander-list-digest" will be forwarded to the standard
email list. In other words, you cannot post messages only to the
digest List.
* If you are subscribed to both the regular List and the digest List, you
will receive the realtime postings as well as the digest at the end of
the day.
* If you reply to the digest email, your message will be forwarded to the
normal list associated with the digest. Important Note: Please change
the subject line to reflect the topic of your response! Also, please
*do not include all or most of the digest in your reply*.
****************************
*** List Digest Browser ***
****************************
An archive of all the List Digests can be found online in either plain text
or HTML format. These archives contain the exact Digest that was posted to
the Digest email list on the given day. The Digest Archives can be found
at the following location:
http://www.matronics.com/digest
*****************************************
*** The "DO NOT ARCHIVE" Message Flag ***
*****************************************
At times, your message may concern something that is revelent only to a very
small number of persons or to a limited area, and you may not wish to archive
it. In such a case, simply put the following phrase anywhere in the
message:
do not archive
Your message will not be appended to the archive, but will be sent to List
email distribution as normal.
**********************************************
***** READ THIS - Automatic Unsubscribes *****
**********************************************
Note that if your email address begins to cause problems such as bounced
email, mailbox is filled, or any other errors, your address will be promptly
removed from the List. If you discover that you are no longer receiving
messages from the Commander-List, go to the following Web page, and look
for your email address and a possible reason for your removal.
The Matronics Email List uses utility called the "Email Weasel" that
automatically looks though the day's bounced email for addresses that
caused problems due to common things like "user is unknown", "mailbox
full", etc. If the Email Weasel removes your email address from the
Lists you will find record of it at the following URL:
http://www.matronics.com/unsubscribed
If the problem listed on the web site above has been resolved, please feel
free to resubscribe to the Lists of your choice.
*******************************
*** List Member Information ***
*******************************
If you have not done so already, please email me your phone numbers and
paper mail address in the following format:
smith@somehost.com
Joe Smith
123 Airport Lane
Tower, CA 91234-1234
098-765-1234 w
123-456-7890 h
Please forward this information to the following email address:
requests@matronics.com
I have a file of such things, that I typically use to contact you when
there are problems with your email address. The information will NOT
be used for any other commercial purpose.
****************************************
*** Realtime Web Email List Browsing ***
****************************************
Recent messages posted to the Commander-List are also made available on
the Web for realtime browsing. Seven days worth of back postings are
available with this feature. The messages can be sorted by Subject,
Author, Date, or Message Thread. The Realtime List Browser indexes are
updated twice per hour at xx:15 and xx:45. You can also reply to a message
or start a new message directly from the List Browser Interface (coming soon).
You do not have to be subscribed to the given list to use the List
Browser Interface in view-mode.
http://www.matronics.com/browselist/commander-list
*******************************************
*** Web Forums Bulletin Board Interface ***
*******************************************
A phpBB BBS web Forums front end is available for all Commander-List content.
content. The Forums contain all of the same content available via the email
distribution and found on the various archive viewing formats such as the
List Browse, etc. Any posts on the web Forums will be cross posted to the
respective email List, and posts to the Email List will be cross posted to
the web Forums.
You may view all List content on the Forums without any special login.
If you wish to post a message via the Web Forum interface, however, you
will need to Register. This is a simple process that takes only a few
minutes. A link to the Registration page can be found at the top of the
main web Forums page. Note that registering on the Forum web site also
enables you to send email posts to the Lists as well. You will also need to
Subscribe to the respective Email List as described above to receive the
Email Distribution of the List, however.
The Matroincs Email List Web BBS Forums can be found at the following URL:
http://forums.matronics.com
*********************************
*** Matronics Email List Wiki ***
*********************************
In an attempt to make it easy to store and find structured and often accessed
information, Matronics has installed a Wiki at:
http://wiki.matronics.com
The Wiki allows individuals to create web pages to contain useful information
for other users of the mailing lists and web site. Unlike an ordinary web page
where the content needs to be submitted to Matronics for inclusion, the Wiki
permits the users to construct their own pages and have them visible immediately.
While constructing pages for the Wiki is not difficult, some may not be
comfortable building pages. In that case, simply prepare the text and any
images and email it to:
wiki-support@matronics.com
One of the volunteers on that list will take your submission and construct
a Wiki page for you.
Often someone produces a particularly useful posting in email one one of the
Lists that would be of general interest. In that case Matronics may take that
post and convert it into a Wiki page.
*********************
*** List Archives ***
*********************
A file containing of all of the previous postings to the Commander-List is
available on line. The archive file information is available via the
Web and FTP in a number of forms. Each are briefly described below:
* Commander-List.FAQ
- Latest version of the Commander-List Frequently Asked Question
page (this document).
* Commander-Archive.digest.complete
- Complete file with most of the email header info removed and
page breaks inserted between messages.
* Commander-Archive.digest.vol-??
- Same as the file above, but broken up into small sections that
can more easily handled.
* Commander-Archive.digest.complete.zip
- Same as the Commander-Archive.digest.complete file above, but
in PKZIP format. Use "binary" data transfer methods.
* Commander-Archive.digest.complete.Z
- Same as the Commander-Archive.digest.complete file above, but in
UNIX compress format. Use "binary" data transfer methods.
Download Via FTP
----------------
The archive file is available via anonymous FTP from ftp.matronics.com
in the "/pub/Archives" directory. It is updated daily and can be found in
a number of formats as described above. (All filenames are case sensitive.)
ftp://ftp.matronics.com/pub/Archives
Download Via Web
----------------
The archives are also available via a web listing. These can be found
toward the bottom of the following web page:
http://www.matronics.com/archives
******************************************
*** Complete List Web Archive Browsing ***
******************************************
All messages posted to the Commander-List are also available using the
Email List Archive Browsing feature. With this utility, all messages
in the List are indexed, and individual sub-archives can be browsed.
http://www.matronics.com/archive/archive-index.cgi?Commander
*****************************************
**** High-Speed Archive Search Engine ***
*****************************************
You can use the custom, high-performance Matronics Email List Search Engine
to quickly locate and browse any messages that have been posted to the
List. The Engine allows the user to easily search any of the currently
available List archives.
http://www.matronics.com/search
****************************
*** File and Photo Share ***
****************************
With the Matronics Email List File and Photo Share you can share pictures
and other data with members of the List without having to forward a
copy of it to everyone. To share your Files and Photos, simply email
them to:
pictures@matronics.com
!! ==> Please including the following information with each submission:
1) Email Lists that they are related to.
2) Your Full Name.
3) Your Email Address.
4) One line Subject description.
5) Multi-line, multi-paragraph description of topic.
6-x) One-line Description of each photo or file
Prior to public availability of the files and photos, each will be scanned
for viruses. Please also note that the process of making the files and
photos available on the web site is a pseudo-manual process, and I try to
process them every few days.
Following the availability of the new Photoshare, an email message will be
sent to the Email Lists enumerated in 1) above indicating that the new
Share is available and what the direct URL to it is.
For a current list of available Photoshares, have a look at the Main
Index Page:
http://www.matronics.com/photoshare
**************************
*** List Archive CDROM ***
**************************
A complete Matronics Email List Archive CD is available that contains
all of the archives since the beginning of each of the Lists. The archives
for all of the Lists are included on the CD along with a freeware search
engine written by a list member. The CD is burned the day you order it
and will contain archive received up to the last minute. They make
great gifts!
http://www.matronics.com/ArchiveCDROM
**********************************
*** List Support Contributions ***
**********************************
The Matronics Lists are run *completely* through the support of it members.
You won't find any PopUpAds, flashing Banner ads, or any other form of
annoying commercialism on either the Email Messages or the List web pages
associated with the Matronics Email Lists. Every year during November
I run a low-key, low-pressure "Fund Raiser" where, throughout the month,
I ask List members to make a Contribution in any amount with which they
are comfortable.
I will often offer free gifts with certain contribution levels during the
Fund Raiser to increase the participation. The gifts are usually donated
by companies that are themselves List members.
Your Contributions go directly to supporting the operation of the Lists
including the high-speed, business-class Internet connection, server
system hardware and software upgrades, and to partially offset the many
many hours I spend running, maintaining, upgrading, and developing the
variety of services found here.
Generally Contributions range from $20 to $100 and are completely voluntary
and non-compulsory. I ask only that if person enjoys the Lists and obtains
value from them, that they make a Contribution of equal magnitude.
Contributions are accepted throughout the year, and if you've just
subscribed, feel free to make a Contribution when you've settled in.
The website for making SSL Secure Contributions is listed below. There are
a variety of payment methods including Visa and MasterCard, PayPal, and
sending a personal check.
If you enjoy and value the List, won't you make a Contribution today to
support its continued operation?
http://www.matronics.com/contributions
Thank you!
Matt Dralle
Email List Administrator
******************************************************************************
Commander-List Usage Guidelines
******************************************************************************
The following details the official Usage Guidelines for the Commander-List.
You are encouraged to read it carefully, and to abide by the rules therein.
Failure to use the Commander-List in the manner described below may result
in the removal of the subscribers from the List.
Commander-List Policy Statement
The purpose of the Commander-List is to provide a forum of discussion for
things related to this particular discussion group. The List's goals
are to serve as an information resource to its members; to deliver
high-quality content; to provide moral support; to foster camaraderie
among its members; and to support safe operation. Reaching these goals
requires the participation and cooperation of each and every member of
the List. To this end, the following guidelines have been established:
- Please keep all posts related to the List at some level. Do not submit
posts concerning computer viruses, urban legends, random humor, long
lost buddies' phone numbers, etc. etc.
- THINK carefully before you write. Ask yourself if your post will be
relevant to everyone. If you have to wonder about that, DON'T send it.
- Remember that your post will be included for posterity in an archive
that is growing in size at an extraordinary rate. Try to be concise and
terse in your posts. Avoid overly wordy and lengthy posts and
responses.
- Keep your signature brief. Please include your name, email address,
aircraft type/tail number, and geographic location. A short line
about where you are in the building process is also nice. Avoid
bulky signatures with character graphics; they consume unnecessary
space in the archive.
- DON'T post requests to the List for information when that info is
easily obtainable from other widely available sources. Consult the
web page or FAQ first.
- If you want to respond to a post, DO keep the "Subject:" line of
your response the same as that of the original post. This makes it
easy to find threads in the archive.
- When responding, NEVER quote the *entire* original post in your
response. DO use lines from the original post to help "tune in" the
reader to the topic at hand, but be selective. The impact that
quoting the entire original post has on the size of the archive
can not be overstated!
- When the poster asks you to respond to him/her personally, DO NOT
then go ahead and reply to the List. Be aware that clicking the
"reply" button on your mail package does not necessarily send your
response to the original poster. You might have to actively address
your response with the original poster's email address.
- DO NOT use the List to respond to a post unless you have something
to add that is relevant and has a broad appeal. "Way to go!", "I
agree", and "Congratulations" are all responses that are better sent
to the original poster directly, rather than to the List at large.
- When responding to others' posts, avoid the feeling that you need to
comment on every last point in their posts, unless you can truly
contribute something valuable.
- Feel free to disagree with other viewpoints, BUT keep your tone
polite and respectful. Don't make snide comments, personally attack
other listers, or take the moral high ground on an obviously
controversial issue. This will only cause a pointless debate that
will hurt feelings, waste bandwidth and resolve nothing.
- Occassional posts by vendors or individuals who are regularyly
subscribed to a given List are considered acceptable. Posts by
List members promoting their respective products or items for sale
should be of a friendly, informal nature, and should not resemble
a typical SPAM message. The List isn't about commercialism, but
is about sharing information and knowledge. This applies to
everyone, including those who provide products to the entire
community. Informal presentation and moderation should be the
operatives with respect to advertising on the Lists.
-------
[This is an automated posting.]
do not archive
Message 11
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Official Commander-List Usage Guidelines |
Dear Listers,
Please read over the Commander-List Usage Guidelines below. The complete
Commander-List FAQ including these Usage Guidelines can be found at the
following URL:
http://www.matronics.com/FAQs/Commander-List.FAQ.html
Thank you,
Matt Dralle
Matronics Email List Administrator
******************************************************************************
Commander-List Usage Guidelines
******************************************************************************
The following details the official Usage Guidelines for the Commander-List.
You are encouraged to read it carefully, and to abide by the rules therein.
Failure to use the Commander-List in the manner described below may result
in the removal of the subscribers from the List.
Commander-List Policy Statement
The purpose of the Commander-List is to provide a forum of discussion for
things related to this particular discussion group. The List's goals
are to serve as an information resource to its members; to deliver
high-quality content; to provide moral support; to foster camaraderie
among its members; and to support safe operation. Reaching these goals
requires the participation and cooperation of each and every member of
the List. To this end, the following guidelines have been established:
- Please keep all posts related to the List at some level. Do not submit
posts concerning computer viruses, urban legends, random humor, long
lost buddies' phone numbers, etc. etc.
- THINK carefully before you write. Ask yourself if your post will be
relevant to everyone. If you have to wonder about that, DON'T send it.
- Remember that your post will be included for posterity in an archive
that is growing in size at an extraordinary rate. Try to be concise and
terse in your posts. Avoid overly wordy and lengthy posts and
responses.
- Keep your signature brief. Please include your name, email address,
aircraft type/tail number, and geographic location. A short line
about where you are in the building process is also nice. Avoid
bulky signatures with character graphics; they consume unnecessary
space in the archive.
- DON'T post requests to the List for information when that info is
easily obtainable from other widely available sources. Consult the
web page or FAQ first.
- If you want to respond to a post, DO keep the "Subject:" line of
your response the same as that of the original post. This makes it
easy to find threads in the archive.
- When responding, NEVER quote the *entire* original post in your
response. DO use lines from the original post to help "tune in" the
reader to the topic at hand, but be selective. The impact that
quoting the entire original post has on the size of the archive
can not be overstated!
- When the poster asks you to respond to him/her personally, DO NOT
then go ahead and reply to the List. Be aware that clicking the
"reply" button on your mail package does not necessarily send your
response to the original poster. You might have to actively address
your response with the original poster's email address.
- DO NOT use the List to respond to a post unless you have something
to add that is relevant and has a broad appeal. "Way to go!", "I
agree", and "Congratulations" are all responses that are better sent
to the original poster directly, rather than to the List at large.
- When responding to others' posts, avoid the feeling that you need to
comment on every last point in their posts, unless you can truly
contribute something valuable.
- Feel free to disagree with other viewpoints, BUT keep your tone
polite and respectful. Don't make snide comments, personally attack
other listers, or take the moral high ground on an obviously
controversial issue. This will only cause a pointless debate that
will hurt feelings, waste bandwidth and resolve nothing.
- Occassional posts by vendors or individuals who are regularyly
subscribed to a given List are considered acceptable. Posts by
List members promoting their respective products or items for sale
should be of a friendly, informal nature, and should not resemble
a typical SPAM message. The List isn't about commercialism, but
is about sharing information and knowledge. This applies to
everyone, including those who provide products to the entire
community. Informal presentation and moderation should be the
operatives with respect to advertising on the Lists.
-------
[This is an automated posting.]
do not archive
Message 12
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Pressure Carburetor? |
Good Evening Bob;
I flew the Connie on the Shuttle Backup out of DCA, and yes it does
sound familiar. But that was a long, long time ago,(67) I was in the
last class of Connie engineers. I have all three ratings of F/E which
with about $ 5 will get you a cup of coffee at most Starbucks. I only
slid off the wings ( 14 ft.) twice in the winter snow, now it would
break my leg, then it just 'stung' like crazy. I remember we were
always happy to get a G as it had gas heaters and we could pre heat the
cabin. I was so happy to get out of the wing walking to check the fuel
and climbing out on the engine to check the oil, times sure have
changed. But your procedures sound familiar, how do you remember all
this stuff? My hard drive gets full, and when I left an aircraft, I
tried to forget it so I could remember the new aircraft and not get them
confused.
As to the 25% it is probably just a figure that some one once told me,
hanger talk, might be true at one particular power setting, might be
false, not sure. I always figured that was part of the reason aircraft
engines were not very efficient in a power verses specific fuel
consumption. Now that aught to start another discussion!
Don
----- Original Message -----
From: BobsV35B@aol.com
To: commander-list@matronics.com
Sent: Tuesday, October 02, 2007 1:27 AM
Subject: Re: Commander-List: Re: Pressure Carburetor?
Good Evening Don,
I have never heard that particular number and I believe we would have
to better define the terms before we could either disagree or agree with
that 25% assertion.
As to where does leaning cause additional wear, that is another tough
one.
Running any engine too lean at high powers will cause big troubles.
However running one leaner than optimum at low powers will not hurt it
all, but it will burn more fuel per horsepower developed than is
possible when the engine is run so as to attain optimum BSFC (Brake
Specific Fuel Consumption).
I do not know the number used by your airline to lean the Turbo
Compound R-3350, but most users utilized a ten percent BMEP drop from
the peak BMEP.
The procedure used by my airline was as follows. We would first chose
a desired BMEP number from the power charts. Just for kicks, let's say
that the desired cruise BMEP was 254. We would start out with the
mixture in Auto Rich. The mixture would be slowly leaned until the BMEP
started to rise. When it went above 254, we would throttle back until it
was at 254, then continue to lean until it was steady at 254 and where
any further leaning would take the BMEP reading below 254. That
procedure determined the peak BMEP (Peak power) for the manifold
pressure being used. At that time, we would continue leaning the engine
until the BMEP was reading 254 minus 24.5 or approximately 228 BMEP.
Once that spot ten percent leaner than peak power was found, the
throttle was used to add manifold pressure so as to bring the BMEP back
to the desired cruise power. We then checked the manifold pressure to be
sure we were still below the maximum allowed manifold pressure for the
desired cruise power.
Sound familiar?
If we leaned the engine further, it would just lose power, but no harm
was done. However, if we richened it up a bit, the engine would overheat
and it may even go into mild detonation. It needed to be well lean of
peak power to cool properly.
I don't know if you recall, but there is a shaft on the rear of the
engine which connects the two fuel injection controllers together. One
unit is for the front row and the other feeds the rear. That shaft would
occasionally slip. When that happened, one row would be running
substantially leaner than the other. The one that was getting more fuel
would be carrying more of the load that was being developed by the
engine. That row would burn the valves and sometimes even have holes
burned in the pistons while the row which was not getting enough fuel
would be running clean and comfortable.
The place where any engine is most likely to develop engine problems
are when the mixture is at that point where the peak BMEP or peak engine
power is being developed. If the engine is run at that same power with a
richer than needed fuel mixture, the extra fuel will slow down the rate
of burn and move the point of peak combustion pressure to a point where
the engine is able to operate relatively cool.
That function is what is normally referred to as cooling the engine
with fuel and it is how we kept our cool during takeoff and climb
regimes!
Another way to cool the engine is to cool it with additional
combustion air. That is what happens when the engine is run well lean of
best power. (Note that I said best power, not Peak EGT. They do NOT
occur at the same point) When we leaned that nice big R-3350 ten percent
lean of best power, we were running at a mixture that was well lean of
the best power point and the engine was being cooled by that surplus
combustion air.
Normal cruise power for the 3350 was around 55 to 60 percent of rated
power. We were really running it quite conservatively. If we richened it
without reducing the manifold pressure, we defeated the air cooling
effect and it would overheat and cause all sorts of problems.
Leaner is cleaner and leaner is cooler. Cleaner and cooler is
generally considered to be better, is it not?
So, if you want to extend engine life, run it at relatively low power
settings and run the mixture on the lean side of best power!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 10/1/2007 7:35:20 P.M. Central Daylight Time,
dongirod@bellsouth.net writes:
Bob;
I used to sit sideways in a Connie running R-3360 Turbo compound
engines, but its been a long time.
My question is this, since you remember more about those things, I
recall being told some where that aircraft engines use approximately 25%
of their fuel for cooling. At what point in leaning do we get to where
we save fuel, but shorten the engine life? And where is the crossover
point.
Thanks, Don
-------------------------------------------------------------------------
-----
See what's new at AOL.com and Make AOL Your Homepage.
-------------------------------------------------------------------------
-----
10/1/2007 6:59 PM
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|