Constant speed props

On Thu, 24 Jun 2004 12:30:03 +0000, EDR wrote:

In article , GE
wrote:

I'm taking delivery today of my first aircraft and it had a constant speed
prop. I have only flown fixed props thus far. I want to have as much
understanding of the c-s prop as possible before I get with my instructor. I
understand the basic difference in what the controls do, but I don't really
have a good understanding of the hows and whys of flying with them. Any
general information, explanations, and tips would be greatly appreciated.

Go to www.avweb.com
on the left side of the screen, select COLUMNS
scroll down to find THE PELICAN"S PERCH
there are articles on fuel injection, manifold pressure, constant speed
props, leaning, etc
Everything you ever want to know about operating a high performance
aircraft engine is in those articles.


Great link!

I started reading this
article, http://www.avweb.com/news/columns/186619-1.html, and have a
question. In the Runup section, when he starts to test for proper mag
operation, somethings seems odd there. Can someone help explain that? He
says, "Are the mags working? The leaner the mixture, the more mag drop
you'll see on one mag, and that's normal." He then goes on to say, "The
EGTs should rise on the first single-mag operation, stay there for the
second, then drop again on the return to BOTH. That rise is proof-positive
the entire ignition system is working, and working well, and the leaner
the mixture, the more diagnostic it is."

Can someone help explain the supporting logic there? If both mags are
working properly and you switch to a single mag, why would the EGT go up?
After all, in theory, you're producing less spark and thusly, a slightly
less effecient ignition of the fuel/air. I would of thought that EGT
would stay the same or go down *just slightly* when running off of one
mag. Likewise, if one mag is not working, I would fully expect to see a
big EGT drop for the given problematic mag, which he does agree with.
But, he further asserts that, "If any of them fail to rise or even drop
during single-mag operation, there is a problem with that plug, the wire,
or the mag."

So, why would running on one mag, versus two, always cause higher EGTs?
And why would no rise in EGT indicate a bad mag, wire or plug?

Anyone?


P.S. I cross posted because this seems like good student pilot material
too.

"Greg Copeland" wrote in message
news
On Thu, 24 Jun 2004 12:30:03 +0000, EDR wrote:

In article , GE
wrote:

I'm taking delivery today of my first aircraft and it had a constant
speed
prop. I have only flown fixed props thus far. I want to have as much
understanding of the c-s prop as possible before I get with my
instructor. I
understand the basic difference in what the controls do, but I don't
really
have a good understanding of the hows and whys of flying with them. Any
general information, explanations, and tips would be greatly
appreciated.

Go to www.avweb.com
on the left side of the screen, select COLUMNS
scroll down to find THE PELICAN"S PERCH
there are articles on fuel injection, manifold pressure, constant speed
props, leaning, etc
Everything you ever want to know about operating a high performance
aircraft engine is in those articles.


Great link!

I started reading this
article, http://www.avweb.com/news/columns/186619-1.html, and have a
question. In the Runup section, when he starts to test for proper mag
operation, somethings seems odd there. Can someone help explain that? He
says, "Are the mags working? The leaner the mixture, the more mag drop
you'll see on one mag, and that's normal." He then goes on to say, "The
EGTs should rise on the first single-mag operation, stay there for the
second, then drop again on the return to BOTH. That rise is proof-positive
the entire ignition system is working, and working well, and the leaner
the mixture, the more diagnostic it is."

Can someone help explain the supporting logic there? If both mags are
working properly and you switch to a single mag, why would the EGT go up?
After all, in theory, you're producing less spark and thusly, a slightly
less effecient ignition of the fuel/air. I would of thought that EGT
would stay the same or go down *just slightly* when running off of one
mag. Likewise, if one mag is not working, I would fully expect to see a
big EGT drop for the given problematic mag, which he does agree with.
But, he further asserts that, "If any of them fail to rise or even drop
during single-mag operation, there is a problem with that plug, the wire,
or the mag."

So, why would running on one mag, versus two, always cause higher EGTs?
And why would no rise in EGT indicate a bad mag, wire or plug?

Anyone?


P.S. I cross posted because this seems like good student pilot material
too.
The key is that with two plugs, the combustion _in the cylinder_ is more
complete, earlier. When one mag cuts, the fuel air mixture still fully
burns, but the burn is continued slightly latter (where it does less work on
the piston). This results in the gas coming out of the exhaust being a
little hotter (in some cases, it may even be still burning).

Best Wishes

On Thu, 24 Jun 2004 16:41:32 +0100, Roger Hamlett wrote:


"Greg Copeland" wrote in message
news
On Thu, 24 Jun 2004 12:30:03 +0000, EDR wrote:

In article , GE
wrote:

I'm taking delivery today of my first aircraft and it had a constant
speed
prop. I have only flown fixed props thus far. I want to have as much
understanding of the c-s prop as possible before I get with my
instructor. I
understand the basic difference in what the controls do, but I don't
really
have a good understanding of the hows and whys of flying with them. Any
general information, explanations, and tips would be greatly
appreciated.

Go to www.avweb.com
on the left side of the screen, select COLUMNS
scroll down to find THE PELICAN"S PERCH
there are articles on fuel injection, manifold pressure, constant speed
props, leaning, etc
Everything you ever want to know about operating a high performance
aircraft engine is in those articles.


Great link!

I started reading this
article, http://www.avweb.com/news/columns/186619-1.html, and have a
question. In the Runup section, when he starts to test for proper mag
operation, somethings seems odd there. Can someone help explain that? He
says, "Are the mags working? The leaner the mixture, the more mag drop
you'll see on one mag, and that's normal." He then goes on to say, "The
EGTs should rise on the first single-mag operation, stay there for the
second, then drop again on the return to BOTH. That rise is proof-positive
the entire ignition system is working, and working well, and the leaner
the mixture, the more diagnostic it is."

Can someone help explain the supporting logic there? If both mags are
working properly and you switch to a single mag, why would the EGT go up?
After all, in theory, you're producing less spark and thusly, a slightly
less effecient ignition of the fuel/air. I would of thought that EGT
would stay the same or go down *just slightly* when running off of one
mag. Likewise, if one mag is not working, I would fully expect to see a
big EGT drop for the given problematic mag, which he does agree with.
But, he further asserts that, "If any of them fail to rise or even drop
during single-mag operation, there is a problem with that plug, the wire,
or the mag."

So, why would running on one mag, versus two, always cause higher EGTs?
And why would no rise in EGT indicate a bad mag, wire or plug?

Anyone?


P.S. I cross posted because this seems like good student pilot material
too.
The key is that with two plugs, the combustion _in the cylinder_ is more
complete, earlier. When one mag cuts, the fuel air mixture still fully
burns, but the burn is continued slightly latter (where it does less work on
the piston). This results in the gas coming out of the exhaust being a
little hotter (in some cases, it may even be still burning).

Best Wishes

Makes perfect sense! Thanks!

The key is that with two plugs, the combustion _in the cylinder_ is more
complete, earlier. When one mag cuts, the fuel air mixture still fully
burns, but the burn is continued slightly latter (where it does less work on

I can confirm that an engine running on one mag will show a higher EGT than on
both mags.

I went through the preflight, run-up, took off and during full-power climbout,
I noticed a significantly higher EGT than I was used to.

Startled me until I discovered that in the pre-takeoff mag check I had left the
mag switch on only one mag - I took off and was climbing on a single mag. Duh!

Switching to both mags brought the EGT back down to normal.

I don't wish to sound like a smartass here, but what's your problem with
getting a full checkout in this airplane from a competent pilot current
in the aircraft?
It sounds like you might benefit from a bit of complex training here!!!
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please replace
the z's with e's.
dhenriquesATzarthlinkDOTnzt
"Greg Copeland" wrote in message
news
On Thu, 24 Jun 2004 12:30:03 +0000, EDR wrote:

In article , GE
wrote:

I'm taking delivery today of my first aircraft and it had a
constant speed
prop. I have only flown fixed props thus far. I want to have as
much
understanding of the c-s prop as possible before I get with my
instructor. I
understand the basic difference in what the controls do, but I
don't really
have a good understanding of the hows and whys of flying with them.
Any
general information, explanations, and tips would be greatly
appreciated.

Go to www.avweb.com
on the left side of the screen, select COLUMNS
scroll down to find THE PELICAN"S PERCH
there are articles on fuel injection, manifold pressure, constant
speed
props, leaning, etc
Everything you ever want to know about operating a high performance
aircraft engine is in those articles.


Great link!

I started reading this
article, http://www.avweb.com/news/columns/186619-1.html, and have a
question. In the Runup section, when he starts to test for proper mag
operation, somethings seems odd there. Can someone help explain that?
He
says, "Are the mags working? The leaner the mixture, the more mag drop
you'll see on one mag, and that's normal." He then goes on to say,
"The
EGTs should rise on the first single-mag operation, stay there for the
second, then drop again on the return to BOTH. That rise is
proof-positive
the entire ignition system is working, and working well, and the
leaner
the mixture, the more diagnostic it is."

Can someone help explain the supporting logic there? If both mags are
working properly and you switch to a single mag, why would the EGT go
up?
After all, in theory, you're producing less spark and thusly, a
slightly
less effecient ignition of the fuel/air. I would of thought that EGT
would stay the same or go down *just slightly* when running off of one
mag. Likewise, if one mag is not working, I would fully expect to see
a
big EGT drop for the given problematic mag, which he does agree with.
But, he further asserts that, "If any of them fail to rise or even
drop
during single-mag operation, there is a problem with that plug, the
wire,
or the mag."

So, why would running on one mag, versus two, always cause higher
EGTs?
And why would no rise in EGT indicate a bad mag, wire or plug?

Anyone?


P.S. I cross posted because this seems like good student pilot
material
too.

On Thu, 24 Jun 2004 16:08:47 +0000, Dudley Henriques wrote:

I don't wish to sound like a smartass here, but what's your problem with
getting a full checkout in this airplane from a competent pilot current
in the aircraft?
It sounds like you might benefit from a bit of complex training here!!!
Dudley Henriques


I wondered the same thing, but you're replying to the wrong person. I'm a
student and GE posted the original question.

Cheers!

I caught that right after I posted it :-) I had cleaned out OE last
night back to four days old and missed the pickup. Thought I had
deleted this but obviously it didn't work!
Anyway.....it looks to me like the IP needs a complete checkout in this
airplane before flying it. His questions just seem way out of line for
someone taking delivery of an airplane they are rated and competent to
fly!
Sorry about the mispost :-)
DH
"Greg Copeland" wrote in message
news
On Thu, 24 Jun 2004 16:08:47 +0000, Dudley Henriques wrote:

I don't wish to sound like a smartass here, but what's your problem
with
getting a full checkout in this airplane from a competent pilot
current
in the aircraft?
It sounds like you might benefit from a bit of complex training
here!!!
Dudley Henriques


I wondered the same thing, but you're replying to the wrong person.
I'm a
student and GE posted the original question.

Cheers!

On Thu, 24 Jun 2004 17:47:41 GMT, "Dudley Henriques"
wrote:

I caught that right after I posted it :-) I had cleaned out OE last
night back to four days old and missed the pickup. Thought I had
deleted this but obviously it didn't work!
Anyway.....it looks to me like the IP needs a complete checkout in this
airplane before flying it. His questions just seem way out of line for
someone taking delivery of an airplane they are rated and competent to
fly!
Sorry about the mispost :-)
DH
"Greg Copeland" wrote in message
news
On Thu, 24 Jun 2004 16:08:47 +0000, Dudley Henriques wrote:

I don't wish to sound like a smartass here, but what's your problem
with
getting a full checkout in this airplane from a competent pilot
current
in the aircraft?
It sounds like you might benefit from a bit of complex training
here!!!
Dudley Henriques


I wondered the same thing, but you're replying to the wrong person.
I'm a
student and GE posted the original question.

Cheers!



I applaud the original poster. He said, " I have only flown fixed
props thus far. I want to have as much
understanding of the c-s prop as possible before I get with my
instructor." He's trying to learn a little something in advance so he
doesn't start completely cold with the instructor. He is seeking
complex training and proactively preparing in advance for that
training.
Rich Russell

"Richard Russell" wrote in message
news
On Thu, 24 Jun 2004 17:47:41 GMT, "Dudley Henriques"
wrote:

I caught that right after I posted it :-) I had cleaned out OE last
night back to four days old and missed the pickup. Thought I had
deleted this but obviously it didn't work!
Anyway.....it looks to me like the IP needs a complete checkout in
this
airplane before flying it. His questions just seem way out of line
for
someone taking delivery of an airplane they are rated and competent
to
fly!
Sorry about the mispost :-)
DH
"Greg Copeland" wrote in message
news
On Thu, 24 Jun 2004 16:08:47 +0000, Dudley Henriques wrote:

I don't wish to sound like a smartass here, but what's your
problem
with
getting a full checkout in this airplane from a competent pilot
current
in the aircraft?
It sounds like you might benefit from a bit of complex training
here!!!
Dudley Henriques


I wondered the same thing, but you're replying to the wrong person.
I'm a
student and GE posted the original question.

Cheers!



I applaud the original poster. He said, " I have only flown fixed
props thus far. I want to have as much
understanding of the c-s prop as possible before I get with my
instructor." He's trying to learn a little something in advance so he
doesn't start completely cold with the instructor. He is seeking
complex training and proactively preparing in advance for that
training.
Rich Russell

You hope!!!

Could be, and most likely it's an ok scenario, but the correct answer I
believe is still to tell him to get the checkout; at least tell him this
along with supplying the data requested.
This is one of the drawbacks of aviation Usenet. You never know if
someone is taking a "shortcut" or seeking a head start going in the
right direction. You are probably right, but I notice that no one
answering this poster suggested that he get the checkout along with
supplying the data requested. :-)

Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please replace
the z's with e's.
dhenriquesATzarthlinkDOTnzt

Dudley Henriques wrote:

You hope!!!

Granted, he could be lying to us. But he did write "get with my
instructor". Admittedly, this is imprecise, but I took it to mean "...for
a checkout".

- Andrew