dang that Murphy

Just when I thought we had the Skyhawk ready to blast off next week for Florida.....we took a little ride Saturday and on the way
back she ran rough for milliseconds on two occasions. The 1st time was so fast, Donna didn't even notice. The second time she was
expecting it.

Any ideas?

The cylinders were gone through about 200 hrs ago.

In-flight mag check was fine. The mags are newish and maintained.

Leaned according to the POH.

We did seem to be picking up a bit of carb ice. (and by the way, how rough is rough when the ice melts)

Should I worry? Maybe do a MMO injection and a special dance? Plan to drive to Florida because the wx will be crap anyway?

Mike Z

Any chance of water in the fuel line? We had a similar incident (C172)
on the way to OSH last summer. The plane was parked at BTV all night
before being topped off early the next morning. Since we had just added
some nitrogen to the strut and all of our camping stuff was in the back,
the plane sat a bit nose high, even when taxiing. The problem didn't
appear until we leveled off at 10,000 ft. Just after leveling off, the
engine sputtered for a few seconds. (I think it took me about 2 seconds
to pull the carb heat on and set the mixture to full rich.) It was,
understandably, a bit of an eye opener. It subsided quickly. I thought
it might be carb ice and the carb heat cleared it up (although we were
developing full power all the way up). But it happened again a minute
or so later. I was within seconds of declaring an emergency and was
already looking for the airport the GPS indicated was closest when the
problem went away. Since we were at 10,000 ft, I was not too
uncomfortable continuing (we had 3 airports within gliding distance).
The problem never resurfaced. I presume that we had bit of water in the
tanks that missed the sump due to the attitude of the plane on the
ground and during the climb. That was at least 200 hours ago, and the
plane has been fine since. Just a thought.



Mike Z. wrote:
Just when I thought we had the Skyhawk ready to blast off next week for Florida.....we took a little ride Saturday and on the way
back she ran rough for milliseconds on two occasions. The 1st time was so fast, Donna didn't even notice. The second time she was
expecting it.

Any ideas?

The cylinders were gone through about 200 hrs ago.

In-flight mag check was fine. The mags are newish and maintained.

Leaned according to the POH.

We did seem to be picking up a bit of carb ice. (and by the way, how rough is rough when the ice melts)

Should I worry? Maybe do a MMO injection and a special dance? Plan to drive to Florida because the wx will be crap anyway?

Mike Z







--
Remove "2PLANES" to reply.

Mike Z. wrote:


We did seem to be picking up a bit of carb ice. (and by the way, how rough is rough when the ice melts)

Apples and Oranges, but winter conditions (OAT ~20deg F) at 10,000 ft
near any clouds causes the Skylane to stumble. Have to fly with some
continuous carb heat. I have a Carb Temp gauge, so I apply just enough
heat to keep the carb temp at ~ +5degC...

MikeM
Skylane '1MM (O470R)

I used to fly out of Boeing Field in Seattle and our school used old
Skyhawks for primary instrument trainers. As part of teaching holding
procedures we reduced to best endurance, which required a partial throttle
setting. The NW is known for its party-like atmosphere (lots of ice) so
those old birds would always make some carb ice if at all possible.

Students would forget the carb-heat and just keep adding throttle to make up
for the rpm drop. Finally, they'd catch on an grab a handful of heat.
Naturally the ice would all melt at once and I swear you could almost see
the prop hesitate as the engine choked. I'm sure it wasn't really that
dramatic, but having the only fan choke while in the soup always gets your
attention. The students learned to 1) not forget the carb heat, and 2) if
they forgot #1, not to yank it out when they remembered.

The hesitation didn't last long, but it certainly got their attention.

--
Jim Carter
Seen on a bumper sticker:
If you can read this, thank a teacher
If you can read this in English, thank a soldier.


"Mike Z." wrote in message
hlink.net...
...
We did seem to be picking up a bit of carb ice. (and by the way, how rough
is rough when the ice melts)

Mike Z

I haven't had a chance to fly the plane again but it does sure sound like I ingested a dab of water from somewhere.

Mike Z




"mikem" wrote in message ...

Mike Z. wrote:


We did seem to be picking up a bit of carb ice. (and by the way, how rough is rough when the ice melts)

Apples and Oranges, but winter conditions (OAT ~20deg F) at 10,000 ft
near any clouds causes the Skylane to stumble. Have to fly with some
continuous carb heat. I have a Carb Temp gauge, so I apply just enough
heat to keep the carb temp at ~ +5degC...

MikeM
Skylane '1MM (O470R)