My first in-flight mechanical failure

On Fri, 01 Oct 2004 00:52:11 GMT, "Capt.Doug"
wrote:

"zatatime" wrote in message My answers would be oil temp going up for a
couple miutes and then going down when there isn't enough oil to be
sensed left in the engine. Cylinder head temps would go up.

You're on the right track. In 4 oil loss situations that I've experienced,
the oil dumped out over a period of time, not instantaneously. The CHTs may
have risen slightly, and a good gauge should have shown the slight rise, but
the ancient OEM gauges in front of me didn't show it. The oil pressure
dropped off slowly. Most oil lines to the pressure gauge have a small
orifice that restricts oil flow in case the line breaks. I theorize that the
orifice damps out the fluctuations of the pressure changes as air bubbles
make their way through the oil passages. The oil temperature never did rise.
It dropped slowly. I theorize the temperature sensor releases some of the
heat it receives from the oil into the air bubbles passing over it thus
showing a cooler temperature. On the Continental TSIO-520 series, the first
indication of low oil shows up as fluctuating manifold pressure. Air bubbles
passing through the waste-gate controller cause this. On some engines, the
propeller RPMs will indicate low oil before the gauges do as air bubbles
passing through the prop governor cause the RPMs to fluctuate. I just
remembered a fifth time. The engine was a Garrett turboprop. The first
indication was oil pressure. The temp was normal. I was on short final and
simply feathered the engine.

D.

Thanks for the reply!

z

Many magneto installations can be tuned so
that there is no perceptible rpm drop during a mag check.

Then they are tuned incorrectly, no? If there's no perceptible drop, how do you
know your P-leads and ignition switch are working correctly?

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.

Why does the MP change? (disregarding that governors are not perfect) the engine
speed hasn't changed, and the throttle setting hasn't changed. How can the MP
change?