My first in-flight mechanical failure

Andrew Gideon wrote

Which would yield an unexpectedly "hot" prop with the switch in the
"off" position, yes?

No!

Bob Moore

Bob Moore wrote:

Andrew Gideon wrote

Which would yield an unexpectedly "hot" prop with the switch in the
"off" position, yes?

No!

Sigh

So that would only occur if the capacitor failed "closed"?

- Andrew

"G.R. Patterson III" wrote in message ...
Jay Honeck wrote:

I've often wondered how a failed magneto would manifest itself in flight.

If you don't have an engine analyzer (as Peter did), it shows up as a sudden 50 rpm
or so drop -- just like it does when you're doing your runup.

With the constant speed prop in the turbo'ed Bonanza, prop knob set
for cruise at 11000MSL (instead of full forward on the ground like at
runup), could you really sense that much of an rpm drop? Or would the
change in MP be more pronounced at the sudden loss of a mag?

Jay Honeck wrote:

So, since I *do* have a JPI engine analyzer, it won't do that?

Nope. There's a little section of the engine that knows you have an analyzer, and it
prevents the usual rpm drop when a mag fails. This is the same section of the engine
that causes a nearly imperceptible miss when you're about halfway across Lake
Michigan on the way to Osh.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

George,
If you have a Constant Speed prop you will not see the RPM drop as long
as you are within the authority of the governor.
You will see a change in Manifold pressure and eventually a slight drop
in Airspeed.
Speaking from experience.
Michelle

G.R. Patterson III wrote:

Jay Honeck wrote:


I've often wondered how a failed magneto would manifest itself in flight.



If you don't have an engine analyzer (as Peter did), it shows up as a sudden 50 rpm
or so drop -- just like it does when you're doing your runup.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.



--

Michelle P ATP-ASEL, CP-AMEL, and AMT-A&P

"Elisabeth" a Maule M-7-235B (no two are alike)

Volunteer Pilot, Angel Flight Mid-Atlantic

Volunteer Builder, Habitat for Humanity

"Andrew Gideon" wrote in message
online.com...
These capacitors fail with depressing regularity, but they usually
fail 'open' - that is, they stop doing their job and radio noise
increases, but the mag keeps working.

Which would yield an unexpectedly "hot" prop with the switch in the "off"
position, yes?

To elaborate on Bob's correct reply...

A broken p-lead would result in a "hot" prop even with the ignition off.
But the capacitor, not being the normal component used to short out the mag,
would have no such effect if it failed open.

The capacitor is in the circuit in parallel with the normal path of the
current. If it fails in the closed circuit state, this provides an
alternate route for the current coming from the magneto, shorting it out and
preventing a spark from being generated. But when it fails in the open
state, there is still the normal path of the current available for shorting
out the magneto when the ignition switch is in the off position.

Make sense?

Pete

"Michelle P" wrote in message
ink.net...
If you have a Constant Speed prop you will not see the RPM drop as long as
you are within the authority of the governor. [...]

You should perceive at least some drop. The prop governor cannot react
instantaneously, and the engine RPM will drop before the governor has time
to reduce the prop pitch and allow the RPM to come back to the set point.

Not all pilots are sensitive enough to the sounds their airplane is making,
but one who is should definitely note a momentary drop in RPM if a magneto
goes offline in an airplane with a constant speed prop.

In my airplane, I get much smaller fluctuations in power, caused by the
turbocharger's density controller "hunting" slightly during full-power
climbs in hot weather. The RPM change is barely perceptible on the gauge
(no more than 10 RPM up or down), but it's easily noticed by ear. A failed
mag would cause a much more significant change in RPM than that before the
prop governor can bring things back to the set point.

Speaking from experience.

If you failed to notice a change in RPM when your mag failed in a
constant-speed prop-equipped airplane, maybe some music lessons will help
you be more perceptive to what your airplane is telling you.

Pete

"Jay Honeck wrote in message I've often wondered how a failed magneto
would manifest itself in flight.

With some engines, you might not notice tht a magneto has failed in flight.
I was flying a C-310Q in cruise and one engine burped momentarily but
continued to run normally. While doing my run-up the next day, I discovered
what caused the burp. Nowadays, I train my charter pilots to check the mags
after landing so that if a mag has failed, maintenance has all night to fix
it.

D.

"Andrew Gideon" wrote in message
online.com...
Which would yield an unexpectedly "hot" prop with the switch in the
"off" position, yes?

No!

Sigh

So that would only occur if the capacitor failed "closed"?

No. If the capacitor failed closed, that would short out the magneto, and
prevent it from working. In fact, that's exactly what happened to the
original poster here. It would not result in a "hot" prop.

"Capt.Doug" wrote in message
...
With some engines, you might not notice tht a magneto has failed in
flight.
I was flying a C-310Q in cruise and one engine burped momentarily but
continued to run normally. While doing my run-up the next day, I
discovered
what caused the burp. Nowadays, I train my charter pilots to check the
mags
after landing so that if a mag has failed, maintenance has all night to
fix
it.

In addition to the "burp", you should also note increased fuel flow or
higher EGT/TIT temperatures (depending on whether you readjust the mixture
to compensate for the less-complete combustion). Nothing wrong with
checking the mags after landing, of course, but I've never heard of a mag
failing in flight where there was NO actual indication that it had failed.