an interesting in flight experiment

On Oct 18, 12:02*pm, Frank Stutzman wrote:
a wrote:
In my
case the engine ran a bit rougher -- rpms stayed where they were set,
of course, because prop pitch changed to accommodate the reduction in
power.

And if you were flying a 6 cylinder (or larger) engine, you may not have
even noticed the roughness. *

(I once failed to get the switch back to "both" after a run-up. *Managed
to take-off and fly for ~15 minutes before I noticed it. *The roughness
became more pronounced when I started leaning it out).

--
Frank Stutzman
Bonanza N494B * * "Hula Girl"
Boise, ID

The IO 360 has 4 cylinders -- the roughness was not really bad, and
you could be right -- with 6 may not have been noticeable.

My hand stays on the mag switch throughout a mag check so I want to
believe I won't forget to go back to both -- help us avoid making your
mistake: do you remember what distracted you enough to leave it
pointing to a single bank of plugs?

"a" wrote in message
...
My hand stays on the mag switch throughout a mag check so I want to
believe I won't forget to go back to both -- help us avoid making your
mistake: do you remember what distracted you enough to leave it
pointing to a single bank of plugs?

I agree, no reason to take your hand off the switch, but things can still go
wrong! I also took off on one mag once. I don't think I actually forgot to
return the switch to "both", but just made a sloppy job of it and somehow
ended up with the switch not quite in the detent. I still kick myself for
not aborting that takeoff. It turned out to be a butt-puckering trip around
the patch. I never did make it alll the way up to pattern height.

Now I visually verify the position of the switch before leaving the runup
pad.

Lesson learned!

Vaughn

On Oct 18, 2:24*pm, "vaughn"
wrote:
"a" wrote in message

...

My hand stays on the mag switch throughout a mag check so I want to
believe I won't forget to go back to both -- help us avoid making your
mistake: do you remember what distracted you enough to leave it
pointing to a single bank of plugs?

I agree, no reason to take your hand off the switch, but things can still go
wrong! *I also took off on one mag once. *I don't think I actually forgot to
return the switch to "both", but just made a sloppy job of it and somehow
ended up with the switch not quite in the detent. *I still kick myself for
not aborting that takeoff. *It turned out to be a butt-puckering trip around
the patch. *I never did make it alll the way up to pattern height.

Now I visually verify the position of the switch before leaving the runup
pad.

Lesson learned!

Vaughn

That's interesting. My primary flight instructor must have been burned
by something like that, because my training (which did not include
getting rapped across the knuckles with a stick -- that was from grade
school days) was to focus on the tach, go from both to left, note the
drop, back to both, see the tach get back to 1900, go to right, note
the drop, go to both, see the tach get back to 1900, and only then let
go of the mag switch.

He was the same guy who insisted controls like throttle and mixture
should be pushed with the palm, pulled with curled fingers, and never
grasped-- his point was that if can can only push or pull you are less
apt to move something in the wrong direction. Some old habits are
worth retaining. If he could have he would have replaced radio tuning
knobs with paddles.

Would you say he was compulsive?

On Sun, 18 Oct 2009 12:48:26 -0700 (PDT), a wrote:

On Oct 18, 2:24*pm, "vaughn"
wrote:
"a" wrote in message

...

My hand stays on the mag switch throughout a mag check so I want to
believe I won't forget to go back to both -- help us avoid making your
mistake: do you remember what distracted you enough to leave it
pointing to a single bank of plugs?

I agree, no reason to take your hand off the switch, but things can still go
wrong! *I also took off on one mag once. *I don't think I actually forgot to
return the switch to "both", but just made a sloppy job of it and somehow
ended up with the switch not quite in the detent. *I still kick myself for
not aborting that takeoff. *It turned out to be a butt-puckering trip around
the patch. *I never did make it alll the way up to pattern height.

Now I visually verify the position of the switch before leaving the runup
pad.

Lesson learned!

Vaughn

That's interesting. My primary flight instructor must have been burned
by something like that, because my training (which did not include
getting rapped across the knuckles with a stick -- that was from grade
school days) was to focus on the tach, go from both to left, note the
drop, back to both, see the tach get back to 1900, go to right, note
the drop, go to both, see the tach get back to 1900, and only then let
go of the mag switch.

He was the same guy who insisted controls like throttle and mixture
should be pushed with the palm, pulled with curled fingers, and never
grasped-- his point was that if can can only push or pull you are less
apt to move something in the wrong direction. Some old habits are
worth retaining. If he could have he would have replaced radio tuning
knobs with paddles.

Would you say he was compulsive?

No but he had a feckin' moron for a student.

"a" wrote in message
...

Would you say he was compulsive?

Perhaps he just had a will to live? Back in my sailplane instructing days,
I taught my students to not wrap their fingers around certain controls,
particularly on takeoff. Reason? A jolt (we took off on grass) could make
you accidently pull a control. That could disconnect you from the towplane
if you pulled the release (the same as your engine quitting on takeoff)
or...if you accidently pulled the spoilers open, our towplane would no
longer be powerful enough to keep us flying.

Vaughn

On Oct 18, 5:18*pm, Franklin "Franklin
wrote:
On Sun, 18 Oct 2009 12:48:26 -0700 (PDT), a wrote:
On Oct 18, 2:24*pm, "vaughn"
wrote:
"a" wrote in message

....

My hand stays on the mag switch throughout a mag check so I want to
believe I won't forget to go back to both -- help us avoid making your
mistake: do you remember what distracted you enough to leave it
pointing to a single bank of plugs?

I agree, no reason to take your hand off the switch, but things can still go
wrong! *I also took off on one mag once. *I don't think I actually forgot to
return the switch to "both", but just made a sloppy job of it and somehow
ended up with the switch not quite in the detent. *I still kick myself for
not aborting that takeoff. *It turned out to be a butt-puckering trip around
the patch. *I never did make it alll the way up to pattern height.

Now I visually verify the position of the switch before leaving the runup
pad.

Lesson learned!

Vaughn

That's interesting. My primary flight instructor must have been burned
by something like that, because my training (which did not include
getting rapped across the knuckles with a stick -- that was from grade
school days) was to focus on the tach, go from both to left, note the
drop, back to both, see the tach get back to 1900, go to right, note
the drop, go to both, see the tach get back to 1900, and only then let
go of the mag switch.

He was the same guy who insisted controls like throttle and mixture
should be pushed with the palm, pulled with curled fingers, and never
grasped-- his point was that if can can only push or pull you are less
apt to move something in the wrong direction. Some old habits are
worth retaining. If he could have he would have replaced radio tuning
knobs with paddles.

Would you say he was compulsive?

No but he had a feckin' moron for a student.

Thanks so much for your insight. So far his moronic student had 3000
safe odd hours in a complex single, so his instruction worked. You, on
the other hand -- your remark is the QED of that -- clearly failed in
social skills..

On Oct 18, 5:22*pm, "vaughn"
wrote:
"a" wrote in message

...

Would you say he was compulsive?

Perhaps he just had a will to live? *Back in my sailplane instructing days,
I taught my students to not wrap their fingers around certain controls,
particularly on takeoff. *Reason? *A jolt (we took off on grass) could make
you accidently pull a control. *That could disconnect you from the towplane
if you pulled the release (the same as your engine quitting on takeoff)
or...if you accidently pulled the spoilers open, our towplane would no
longer be powerful enough to keep us flying.

Vaughn

Good habits are often validated in the real world. I doubt that things
like pushing with palm, pulling with fingertips, have saved lives, but
the ingraining of bits and pieces like those in total probably do.
That old saw -- a superior pilot uses superior judgement to avoid
circumstances where he (or she) has to use his (or her) superior
skills really is true.

"a" wrote in message
...
On Oct 18, 10:40 am, "Peter Dohm" wrote:
"Morgans" wrote in message

...

"twdeckard" wrote

I am sure you know all of this (grin), I just chimed in becuase its a
check best done on the run-up pad.

He did not say you shouldn't do it at run-up. He was just pointing out
that your engine could run very rough if you lose one side while
cruising.

--
Jim in NC

I am really not sure exactly what he tried to say; but, in his initial
post,
it was clear that he had lost the use of all of one mag and a part of the
other--or the plugs or wires attached to it.

The problem with that is that mags have a couple of failure modes that
are
common to all breaker point ignition systems in addition to the failure
modes that are peculiar to magnetos.

As far as I know, it is still a common practice to simply set the timing
and
perform a runup type mag check as part of an annual and not open the mags
to
gap and visually check the points. That leaves the door a lot farther
open
for the failure modes involving erosion of the points--which is related
to
one of the two failure modes of the capacitor a/k/a condenser--and also
to
wear of the cam follower. Both of those failure modes usually make the
engine harder to start long before they will fail in flight, or at runup
test; but are masked sufficiently by electric starters that they can go
virtually unnoticed--unless the pilot is so dilligent as to carefully
prime
and set the throttle and then count the blades on nearly every start.

Peter

To put several of your minds at ease, of course I did the conventional
both-right-both-left mag check at runup, but at 1900 RPM. I had not
had one bank of spark plugs go in/op ever until the in flight failure
a little while ago, and my post was simply to suggest pilots go to one
mag while at cruise rpm and engine loading to see what happens. In my
case the engine ran a bit rougher -- rpms stayed where they were set,
of course, because prop pitch changed to accommodate the reduction in
power.

I am sure I make lots of inadvertent errors when flying: missing a mag
check is not one of them.

I was not trying to suggest that you failed to check the mags prior to
takeoff, and I do not have an opinion as to whether an in-flight check would
necessarily tell anything of value.

The problem that I have personally observed was a case of points which had
gradually "closed up" on a 65 horsepower Piper Cub until the engine could
not be manually started--and then was started on the first "lave" pull after
the points had been dressed and gapped. A second case, that was only
confirmed much later, involved a Cessna 172 which occasionally required
manual starting for an assortment of stupid reasons; but started very
reluctantly in those instances...

The salient point is that both aircraft passed all tests normally available
to a pilot; but, based upon the number of hours that each was operated,
probably had one or both mags out internal tolerances for multiple years.
So there are failure modes that the pilot can not necessarily
overcome--including damaged insulation on a p-lead, or a shorted mag switch,
amoung others.

By the way, what were the problems later identified on your aircraft?

Peter

a wrote:
....
Even on run up you lose some RPMs when on a single bank of spark
plugs.

Usually. At a 1700 rpm run up this morning, - I couldn't find a
drop either side. So I did a dead cut (at 1200rpm) with the usual effect.

Brian W

On Oct 18, 6:39*pm, "Peter Dohm" wrote:
"a" wrote in message

...



On Oct 18, 10:40 am, "Peter Dohm" wrote:
"Morgans" wrote in message

...

"twdeckard" wrote

I am sure you know all of this (grin), I just chimed in becuase its a
check best done on the run-up pad.

He did not say you shouldn't do it at run-up. He was just pointing out
that your engine could run very rough if you lose one side while
cruising.

--
Jim in NC

I am really not sure exactly what he tried to say; but, in his initial
post,
it was clear that he had lost the use of all of one mag and a part of the
other--or the plugs or wires attached to it.

The problem with that is that mags have a couple of failure modes that
are
common to all breaker point ignition systems in addition to the failure
modes that are peculiar to magnetos.

As far as I know, it is still a common practice to simply set the timing
and
perform a runup type mag check as part of an annual and not open the mags
to
gap and visually check the points. That leaves the door a lot farther
open
for the failure modes involving erosion of the points--which is related
to
one of the two failure modes of the capacitor a/k/a condenser--and also
to
wear of the cam follower. Both of those failure modes usually make the
engine harder to start long before they will fail in flight, or at runup
test; but are masked sufficiently by electric starters that they can go
virtually unnoticed--unless the pilot is so dilligent as to carefully
prime
and set the throttle and then count the blades on nearly every start.

Peter

To put several of your minds at ease, of course I did the conventional
both-right-both-left mag check at runup, but at 1900 RPM. I had not
had one bank of spark plugs go in/op ever until the in flight failure
a little while ago, and my post was simply to suggest pilots go to one
mag while at cruise rpm and engine loading to see what happens. In my
case the engine ran a bit rougher -- rpms stayed where they were set,
of course, because prop pitch changed to accommodate the reduction in
power.

I am sure I make lots of inadvertent errors when flying: missing a mag
check is not one of them.

I was not trying to suggest that you failed to check the mags prior to
takeoff, and I do not have an opinion as to whether an in-flight check would
necessarily tell anything of value.

The problem that I have personally observed was a case of points which had
gradually "closed up" on a 65 horsepower Piper Cub until the engine could
not be manually started--and then was started on the first "lave" pull after
the points had been dressed and gapped. *A second case, that was only
confirmed much later, involved a Cessna 172 which occasionally required
manual starting for an assortment of stupid reasons; but started very
reluctantly in those instances...

The salient point is that both aircraft passed all tests normally available
to a pilot; but, based upon the number of hours that each was operated,
probably had one or both mags out internal tolerances for multiple years.
So there are failure modes that the pilot can not necessarily
overcome--including damaged insulation on a p-lead, or a shorted mag switch,
amoung others.

By the way, what were the problems later identified on your aircraft?

Peter

My in-flight check in fact produced something of value, Peter. The
engine in cruise went a little rough and stayed that way with mixture
adjustments. When I went to a single bank of spark plugs the engine
noise went from rough to none: I was flying on half the spark plugs.
That told me two things -- to land for a repair, and what to tell the
A&E.

My suggestion in the OP was that pilots learn what their engine does
when on a single bank of plugs when at cruise. It might be
instructive, it might not be. The failure mode I experienced was in
the high voltage lead between the magneto and the distributer. The
voltage impulse found a gap more convenient than the one at the spark
plugs, this on an engine that was only about 1100 hours (on a 2000
hour engine) since last major overhaul. I continued on my trip in less
than 2 hours. Clearly the aviation gods smiled on me.