On one Mag? Temptation and decision

Absolutely, positively, do not fly on one mag if the engine is designed for
two! The second mag is not just for redundancy.

The two spark plugs light off the cylinder charge in two separate places.
Ever heard of burning your candle at both ends? The combustion takes place
faster so the burning is over when the exhaust valve opens and things have
time to cool down a bit. With one mag, the exhaust will be hotter and, in
some cases, combustion still taking place when the exhaust valve opens.
This can burn valves. On some engines, it can even damage the exhaust
piping.

Flying even 40 miles this way could be burning the engine's candle at both
ends and maybe even your own.

--
Roger Long

Roger Long wrote:
Geesh! Thanks Roger, something else to worry about..
Flew for about 1 hour and 40 minutes...don't know when the mag went
out... no engine indication roughness at all.

Terry

This can burn valves. On some engines, it can even damage the exhaust
piping.

Flying even 40 miles this way could be burning the engine's candle at both
ends and maybe even your own.

--
Roger Long

Well, in fairness, I've got to tell you all this little story.

I took my old CFI, who did most of my primary training for a flight the
other day after not flying with him since before I got my license. Of
course, I really wanted to look good and also show off the airplane I
manage.

I proudly showed him our digital tach and how the red LED's that come on
when either mag is off help keep you from taking off on just one mag. One
mag was a bit rough so I cleared it.

We took off and about 4000 agl, Joe looked over and said, "What's that red
LED on the tach mean?"

No apparent harm done except to my pride. I did notice that RPM was a
little low on roll out but figured it was just the weather.

There's a lot to be said for a sterile cockpit and not yacking away during
run up and take off.

--
Roger Long

Roger Long wrote:

No apparent harm done except to my pride. I did notice that RPM was a
little low on roll out but figured it was just the weather.

We flew into Asheville a few years ago, and the radio died during the approach.
They gave me a green light, but I was faced with handling the departure NORDO the
next day.

I called the tower and got instructions, taxied down, did my runup, got the green,
and took off. She didn't feel right climbing out, but I figured it was just the
mountains. She still didn't feel right in cruise either, though. I was into my
second panel check and considering landing at a nearby airport when I noticed I
was running on one mag. The distraction of dealing with the light gun and traffic
that I couldn't hear was enough to cause me to fail to cut the switch back all
the way to both during the runup.

George Patterson
Great discoveries are not announced with "Eureka!". What's usually said is
"Hummmmm... That's interesting...."

On Sun, 28 Dec 2003 19:14:30 GMT, "Roger Long"
om wrote:

Absolutely, positively, do not fly on one mag if the engine is designed for
two! The second mag is not just for redundancy.

The two spark plugs light off the cylinder charge in two separate places.
Ever heard of burning your candle at both ends? The combustion takes place
faster so the burning is over when the exhaust valve opens and things have
time to cool down a bit. With one mag, the exhaust will be hotter and, in
some cases, combustion still taking place when the exhaust valve opens.
This can burn valves. On some engines, it can even damage the exhaust
piping.


I would think with incomplete combustion it would be cooler in the
cylinder and hotter in the exhaust stacks.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair?)
www.rogerhalstead.com

Flying even 40 miles this way could be burning the engine's candle at both
ends and maybe even your own.

Roger Halstead wrote in message . ..
On Sun, 28 Dec 2003 19:14:30 GMT, "Roger Long"
om wrote:

Absolutely, positively, do not fly on one mag if the engine is designed for
two! The second mag is not just for redundancy.

The two spark plugs light off the cylinder charge in two separate places.
Ever heard of burning your candle at both ends? The combustion takes place
faster so the burning is over when the exhaust valve opens and things have
time to cool down a bit. With one mag, the exhaust will be hotter and, in
some cases, combustion still taking place when the exhaust valve opens.
This can burn valves. On some engines, it can even damage the exhaust
piping.


I would think with incomplete combustion it would be cooler in the
cylinder and hotter in the exhaust stacks.

And it's not that much hotter in the exhaust stacks either. On a
single mag, I usually see my EGT rise about 50 degrees. Unless you're
leaning hard and making lots of power, I wouldn't worry too much about
running on one mag.

John Galban=====N4BQ (PA28-180)