My first in-flight mechanical failure

Given my relative low time of 700 hours, I wanted to share the story of
my first in-flight mechanical problem, which happened today while
returning from southwest Pennsylvania to central NY.

Cruising along at 11,000 feet with the XM radio playing in my headsets
(thanks to an earlier thread here, my first flight with the new XM radio
was this flight), my scan suddenly noticed the JPI engine monitor, now
flashing an increasing turbo-inlet temperature.

A quick background: I fly a turbo-normalized Bonanza and was taught by
Tornado Alley (the manufacturers of the turbo add-on) to cruise at wide-
open throttle and 75 degrees lean of turbo-inlet temperature peak. Once
this optimum lean mixture is found, the turbo-inlet temperature will
remain relatively constant throughout the remaining cruise at that
altitude. Thus, watching this temperature continue to climb to a peak
temperature, I immediately knew something was amiss.

Not knowing what was the issue, my first order of business was to take
in all the gauges and sounds to see if the engine was suffering an
imminent failure (low oil pressure, etc.) or not. The results of this
scan would determine whether I would be landing immediately or
continuing to my home airport, some 60nm away.

Other than the high TIT, there was no indication of a problem. I then
tried re-adjusting the mixture to see if somehow it had vibrated loose.
The only way to reduce the temperature was to enrichen the mixture in
through peak to some point safely rich of peak, an action that
definitely indicated a problem.

With the mixture set rich of peak and the temperature down to a safe
number, the fuel flow jumped to 24 gallons per hour (compared to 16 per
hour at lean of peak during normal cruise). I had more than enough
fuel, so I opted to leave the mixture ROP to hold down the temperature
while I thought over my options and prepared the aircraft to land at any
nearby airport.

At this point, I was out of ideas as to what the problem was, so I began
thinking how I was going to explain this problem to the mechanic Monday
morning. That is when an idea crossed my mind.

Tornado Alley states in their white paper that in order for lean of peak
operation to properly function, the magnetos and the spark plugs must
all be in excellent working order. A problem with fouled plugs or a bad
magneto would show up as a rough running engine or high temperatures
when at lean of peak.

With this, I reached down and slowly turned the key from "Both" to
"L"eft. Nothing noticeable happened in either the engine sound or the
temperatures. Back to "Both." Slowly I turned the key from "Both" past
"L" and into "R"ight. Instantaneously, the engine QUIT! Damn, I
thought, and I quickly turned the key back to "Both," returning the
engine to life. My heart-rate just when up a little.

OK, there's the problem, a dead mag. Just about the time I discovered
this, Center called me to hand me off to my class C airport's approach
control. I acknowledged the hand-off and thought for a second on how
best to safely deal with this problem.

Although it was a severe clear VFR day, I was on an IFR flight plan.
I decided that one dead mag was not an emergency, but I didn't want
to be vectored all over while approach control sequenced airliners for
their arrival, either. So, I keyed the mike and said, "Syracuse
Approach, Bonanza 2845W, level one-one thousand, with a request."

"Bonanza 45W, altimeter 30.18, go ahead with your request," answered
Approach.

"Syracuse Approach, Bonanza 45W has a mechanical problem, it is not an
emergency yet, but I do need vectors straight to the airport for an
immediate landing and I would like to remain at altitude until I get
closer."

"Bonanza 45W, expect all that, and when you have time, could you tell me
the nature of your mechanical problem?"

Since I did have a moment, I replied, "Magneto failure. The aircraft is
equipped with two mags, but if the remaining one fails, my engine will
quit. Also, I am now unsure of how the aircraft will operate at low
power settings with the dead mag while on approach."

ATC answered, "Thank you and if there is anything you need, please
ask." Knowing what she was implying, I kept the "Declare Emergency"
call on my mind and ready to use had the engine began to run rough.

I then called the airport in sight, despite still being out about 30
miles, and ATC cleared me for a visual approach. At this time I began a
gentle descent until I knew I was close. With the field made, I dropped
gear and flaps and reduced power to 17 inches MP. Not knowing what to
expect, I was pleasantly surprised to discover that the engine continued
to deliver with no roughness.

Landing was uneventful and on roll-out, tower asked me where I was
parking on the field. I replied that I needed to park at the GA
maintenance facility, to which the controller laughed and stated that
she should have known that answer.

With the leaves beginning to change color here in central NY, I am now
hopeful that maintenance will be able to replace the mag sometime early
this week. I also now have one mechanical issue to add to my growing
experience. I am not eager for others...

--
Peter