Here's one to get your attention....  Engine sputtering on climb out in
instrument conditions

This morning I was to fly from North East Philadelphia to Detroit.  Conditions
were a thick overcast in the Philly area, ceilings around1,000, rain and a
temp of +7 Celsius.  Things improved towards the west, in the direction of my
flight.

My LNC2 has an IO-360-B1F on board with the a 'Y' installed in front of the
throttle body.  The 'Y' allows me to switch between all filtered air (the
Bracket style filter is on the baffle in front of the number 1 cylinder) and
ram air.  The flapper is such that when ram air is selected, filtered air is
not closed off.

I took off in rain at about 10:30 am, normal except that I forgot two items on
the checklist that I normally check as I'm cleared onto the runway:
Transponder to Alt mode, and Induction air to ram position (for that extra 1.5
inches and the cooling benefit).  I entered the clouds at about the time I was
passed to Departure.  Departure asked me to turn on my transponder (they must
see this often) and I kicked myself for forgetting this.  But I did not think
any further than that.  Freezing level was at 4,000 feet or so.  As I passed
6,000 on my way to 14,000 I noticed (felt) the engine hesitate slightly.  This
wakes you up quick.  Is it a little water in the fuel?  My wings are not
picking up any ice yet.  Then at 7,000 I noticed the fuel flow was way down.
Normally it's at 17 gph in the climb and slowly drops to maybe 15 as I get
towards 10,000 feet or so.  I saw 10 gph on the VMS-1000!  Now I know
something was wrong, and at that moment, the engine sputtered a couple more
times.  The fuel pressure looked normal (23 psi) but I turned on the boost
pump just in case.  No effect.

I called departure and said I needed to turn back due to engine problems.
About this time, I noticed the manifold pressure had dropped into the teens,
(I saw 11 inches at one point), and my 'gear minder' starting asking I put the
gear down.  Sure enough airspeed had bled off to 90 kts. Over the nose went.
The engine started to run really rough, with a lot of popping noises.  ATC
asked if I needed assistance and if I wanted to declare an emergency, to which
I said Yes, I was declaring an emergency.  I've never done THAT before.  They
cleared me direct to North East Philly airport, but my response was, 'could
you please give me a vector?"  ATC gave me vectors from there.  I just did not
want to bother with fumbling with the 'direct to' button on the GPS yet.

It was a 180 degree turn back but I found that this and the rest of the flying
was not difficult by reference to the instruments.  ATC vectors really helped
because I did not have to divert attention to charts.  I had not gotten far
from the departure airport and would have the original 35 knot headwind now at
my back.  I had plenty of altitude to work with (I declared at 8,000 feet) and
the airport is at 120 feet MSL.  The engine ran a bit more happily with the
throttle pulled back quite a bit.  I guess my natural instinct is when the
engine is unhappy, pull the throttle back.  The manifold pressure was jumping
all over, but remained in the teens.  A few times I thought the engine was
going to die completely, but moving the throttle seemed to bring it back to
partial life.  One brief tug on the mixture control did not have any effect so
I left it all the way in.  I never thought of trying the mags, nor did I pull
out the emergency checklist I created for just such an event.  Hmmm.

ATC cleared me to 5,000 feet and asked whether I wanted the ILS or the Back
Course into the airport.  The ILS would have been the natural choice due to it
being into the prevailing wind direction, but it required a longer journey,
whereas the Back Course was closer to where I was coming from.  I had the Back
Course chart on my lapboard already, since it is what I had used to arrive two
days prior.  I asked ATC which approach was closer, they responded the Back
Course, so that's what I took.  ATC volunteered the localizer frequency, but
it was not the same one I used two days prior.  A minute later it became clear
they had given me a Philly International frequency, so we got that
straightened out.

Since I had partial power, I had hope.  The plane will fly on 14 inches, maybe
less.  It was handling fine.  I was able to think pretty well, enough to set
the HSI indicator to the reverse course for this approach and to the runway
heading.  I was strangely gratified to hear the controller talking to other
aircraft, since it meant that I was not bringing the whole system to a
screeching halt.  I mentioned that I had partial power so that probably helped
him.

Descending through 4,000 feet all of a sudden the engine surged (and
stabilized).  I began to think induction ice.  I glanced at the thermometer
and saw that it was two degrees above freezing.  Now, I needed to focus on
lining up with the final approach course.  I had already hit the direct to GPS
button and dialed in the airport so that I had a distance reading.  I was
cleared down to 2,000 feet prior to the final approach fix, and at 2,000 I was
catching a glimpse of ground.  The speed had picked up, so I needed to pull
power to get below gear extension speed.  ATC called the final fix and passed
me to tower.  I had a brief twinge of anxiety leaving Approach and going to
Tower since this guy had been assisting me.  Tower told me I would have a 7
knot tailwind.

At the fix, I headed down towards 600 feet, the minimum descent altitude.  My
heading control could have been better but the needle stayed close enough.  It
doesn't take much distraction to find yourself 30 degrees off heading.  I got
to 1,000 and about 3 miles out on the GPS and still nothing yet.  The clouds
were solid.  At 800 feet, the runway came into view.  Visibility was about 2
miles due to mist.  The landing was smooth.

I was asked to wait by my aircraft while Security came for a look.  The event
closed the airport until the security guys would approve reopening it.  I told
the firemen sent over as a matter of course that I suspected induction ice.
All 6 guys dutifully nodded their heads in serious understanding, as if to
say, "That seems reasonable to us".  The Security guy just wanted to look at
my license and that was it.

The adrenaline surge and fear lasted only between the time of "hey, something
seems off here!" to "we're going back and this engine may not make it."  After
that, there was too much to do.  Also, it was immediately clear that I had
partial power, so it was by no means as scary as a dead stick situation.

Now the head scratching started.  I wanted to be in Detroit, not stuck in
Philly.  The weather might improve in Philly for a few hours, but with the
dropping temperature associated with the passing cold front, snow was being
forecast for later.  It was 11:30 am on Sunday.  Why had the engine
misbehaved, and was it fixable?

Fortunately, I had packed a few tools, so I could get the cowlings off
(kindly, the FBO moved me into a dry hangar).  I figured any trace of ice
would be gone by now, but looking at the front of the airplane is when I
noticed that the ram air was closed.  Hmmm, I must have forgotten to set that
on takeoff, since I did not remember closing it in flight.  I opened the ram
air, and saw nothing but the usual puddle of liquid in the intake system (my
throttle body is rotated forward 90 degrees so fluid (fuel I believe running
down from the fuel injectors through the intake pipes).  I removed the upper
cowl and noticed the intake filter in front of number 1 cylinder was sopping
wet.  Ahhhhhh,  did that filter freeze over in the higher altitudes, choking
off the intake system?  It certainly was raining during the takeoff and
initial climb.  In my installation, the filter is small.  It is the same part
number used on a C-150.  It's all that would fit in that space.  Since it
allows 28.5 inches manifold pressure at sea level, I've figured it was OK.

I removed the bottom cowl to make sure none of the linkages had come loose,
possibly explaining the problem.  Everything looked normal, the engine was
dry, etc.  Since I had lost my autopilot altitude hold on the trip out, I
looked into that.  Also, my VMS-1000 fuel tank readings were dropping out on
the left and right tanks sporadically this particular day.  Maybe water
getting into a connector?  Thirdly, my feet got wet on the trip out descending
through the rain into my destination.  Obviously, the canopy front seal
(silicon bead) was not doing its job.

I decided that the most likely cause of my problems was air filter icing.
I've escaped this in the past by flying with ram air, but this time I forgot.
I decided to re-attempt the flight home provided the engine performed well on
a run up and the weather looked reasonable, preferable with no more rain.

The run-up was fine.  The weather was iffy, rain at departure and reports of
ice through the first half of the trip.  But the tops were reported as 6,000
to 7,000 so as long as I stayed up, I'd be fine.  The wind was against me, 35
knots on the nose.  But with 190 knots available, that was manageable.  Also,
I knew I had some altitude range to work with since I had climbed to 19,000
feet to get over some icing two days prior.  Climb rate had been 500 fpm, with
115 knots indicated in the climb and 130 indicated in cruise at 19,000 (180
true I recall).  I think the manifold pressure was 14.5 inches up there.  Even
with short wings, the planes have a lot of capability.  (Don't forget those
wonderful Mountain High O2 systems with EDS flow metering)  With the fuel tank
senders on the fritz, I'd have to be careful.  The VMS-1000 fuel totalizer has
always been excellent.  So, as long as I know how much fuel I have on board,
the totalizer will tell me how much flying time I have left and the Garmin
tells me the time to destination.  Make sure you have an hour reserve and it
has always worked out.  The center tank read out was not being unreliable
(different connectors?) and my automatic fuel transfer system runs on relays
and tank switches anyway.

The takeoff was much the same except no forgotten checklist items.  There was
no ice above the freezing level and the engine never faltered.  But you can't
help it.... Was that slight engine tone change a problem, or just a change in
climb rate and airspeed?  The 4 cylinder engines are not the smoothest to
start with.  I leveled off at 12,000 and soon the sun came out.  That's a
cheerful event.  With 8.7 gph, 20 inches, and 2300 rpm, I was seeing 190 kts
true.  The fuel flow and manifold pressure fluctuated only by their normal
amounts.  The rest of the trip to Detroit was uneventful, although the
altitude hold still doesn't work and the left wing fuel level indicator never
came back.

So, does everyone agree that induction icing, more specifically, air filter
icing was the likely culprit?  If so, why doesn't this happen more often,
since air filters are universal, and some, like Cessna, are right in front in
the open?  Could it be an installation problem in my case?

Best Regards,
Ed de Chazal (N361DC)