Threatened Engine Out in IMC

Threatened Engine Out in IMC

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I finally received confirmation of the ASRS submission so here's the story.

We were delayed three hours while waiting for the visibility and ceiling to
improve to the FBO's dispatch minimums for instrument rated pilots. I also had
to switch airplanes due to an inoperative autopilot in the original airplane.

After listening to the ATIS and picking up my clearance I taxied to the run-up
area. Run-up indicated fouled plugs on one magneto. I was able to burn-off the fouling without incident. No other concerns were detected, specifically the oil pressure and temperature were indicating normally. Departure was likewise uneventful and I made the normal call-out that pressure and temperature were green and airspeed was alive. We launched at approximately 12:50 local.

Climb was uneventful the sky condition was reported as OVC008 and coincided with our entry into IMC. We were sent to ATL departure, radar identified and given multiple altitude and vector assignments. We were turned over to another frequency and asked which approach we requested at KAHN. We levelled off at 5,000 feet and I engaged the autopilot. I began to setup for the ILS 27 into KAHN (I was previously setup for the ILS 25 back into KLZU as a standard precaution when launching into IMC.)

After an initial setup of the approach ILS 27 into KAHN. We were
above the first cloud layer in our immediate vicinity but below the
same layer in different areas. Visibility was poor and there was no
horizon. I considered flight by reference to instruments to still be
required.

I began to fine-tune the power and mixture settings for cruise and
noticed that the oil temperature was pegged hot off the scale. I
notified approach of our situation and requested a return to KLZU and
requested the ILS 25. It is my recollection that I never officially
declared an emergency. I'm not clear on the order of the following
exchanges: I recall the controller asking if I needed priority and
giving the position of another aircraft on the ILS. I recall thinking
that the other aircraft would be out of the way before I got there
and that I was not prepared for the approach at the moment anyway. I
declined. I recall the controller asking if I required assistance on
the ground. I declined, I expected no problems if we made it to the
runway.

During the descent and vectors I was cleared down to 4,000 and very
shortly afterwards to 3,000. *I recall trying to balance how much to
reduce power to try to save the engine but still stay in a relatively
normal configuration for an IFR descent. When given the initial
vector and descent *I tried to initiate the turn and descent
manually. When the autopilot resisted I disabled the autopilot and
resumed hand-flying. At this point I was also trying to setup the ILS
25 into LZU. At approximately 13:08 local the controller notified me
that she was indicating 2,500 and that I was assigned 3,000. I
remember thinking no, I'm at 3,500. She also cleared me for the
approach when assigning me 3,000 which I missed. I simply
acknowledged the altitude assignment. I discovered this as I
questioned the controller as I flew through the localizer. The
approach and landing were uneventful.

I learned later that the incident airplane was known to have a
problem with the oil temperature sensor. The latest attempt to fix it
had apparently not addressed the problem.

*These are keys in the "chain of events" in my mind. I was
overloaded, descending much more rapidly than I'm accustomed to in
IMC and when push comes to shove I'm clearly more comfortable handflying.
I need to get more comfortable with the autopilot and pay
special attention to altitude when overloaded.