Emergency

And what became of the 'no-show' 3rd leg pilot? I hope you called
your dispatcher and mentioned it.

T o d d P a t t i s t wrote in
:

"Peter Duniho" wrote:

I've never quite figured out why carb heat is designed this
way.

I suspect it's a matter of keeping the design simple.

I'm sure you're right.

I recognize that there are rare circumstances when one would
want to bypass the filter (impact iced over). Nonetheless,
it seems to me that accidents due to fiddling with the carb
heat after landing are at least as much of a concern.

How so? Induction icing can cause a forced landing, if not a crash.
Assuming the pilot has their priorities straight, fiddling with the
carb heat after landing should pose no risk at all.

As for the induction icing issue, I wasn't proposing getting
rid of the alternate air. As for the pilot's priorities, I
agree, if you do it right, you shouldn't have an issue, but
it is always a competing concern. I'd like my engine to get
filtered air as soon as possible, particularly when the dirt
is flying, yet I know I've got to fly the taildragger until
it's absolutely safe to reach for the carb heat.

Oddly enough, in reviewing the certification requirements, I found two
paragraphs that my own airplane doesn't appear to meet.

Very interesting.


You may find interesting as well, the Rotex 912UL (80 or 100hp)version
has as an option full time "carb heat". coolent from the engine is
circulated up to a fitting that is attached to the carb body. This
heats the carb body, but not the incoming air. "Carb heat" is always on
with no drop in performance since the air stays cool. I suppose it's
still possible for ice crystals to form in the incoming air, but they
will not stick to the warm pieces of the carborator. This engine is
almost the defacto standard for now in most of the new light sport
aircraft (although the full time carb heat is not "standard" on any but
the StingSport)

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

I can't find anything in the discussion of carb ice in The Lycoming Flyer to
make me think that full throttle somehow obviates carb ice when conditions
are conducive to icing. If ice is forming on the interior of the venturi,
the position of the throttle plate won't make much difference. Lycoming does
say that ice is more likely at low power settings, but I think we all know
that.

Bob Gardner

"Dan Luke" wrote in message
...
It was the 3rd leg of an Angel Flight and I wasn't even supposed to be
flying it. I'd already flown the second leg from Natchez, MS to
Monroeville, AL, but the 3rd leg pilot had mysteriously failed to show--no
call, no nothin'. It was late, I was tired and I was mad. I had two pax
aboard.

We were in the clouds and in the dark in a Cutlass RG approaching Macon,
GA (MCN). The outside temperature was 13 C and moisture was streaming
back on the windshield. The throttle was fully open, the RPM was set for
2500 and the mixture was leaned to 10.5 gph. The autopilot was holding
course and altitude. I was studying the ILS approach plate when I noticed
the AP's "up" trim warning light illuminate.

A quick scan of the instruments showed the IAS at 100 and falling;
normally it would indicate 125 at that altitude. I had detected no change
in the engine sound. I immediately hit the AP disable switch to prevent
its stalling the airplane. This was right and wrong, as I now had to do
all the flying while troubleshooting the problem. What I should have done
was disable the altitude hold and allow the AP to continue keeping us on
course and wings level.

Any attempt to lift the nose resulted in a sickening drop in airspeed.
The situation was now officially scary: we were going down on a dark,
rainy night over central Georgia.

I shoved the prop and mixture full forward, confirmed the throttle was
wide open and the primer was in. No improvement. There was no unusual
vibration. The engine still sounded good and was still making 2500 rpm,
but the prop was probably in flat pitch to do it. I tried the electric
fuel pump: no joy. I glanced at the JPI engine analyzer and saw that all
four cylinders showed roughly even EGTs. All this took much less than a
minute; maybe only 30 seconds.

Finally, I pulled the carb heat. Within a few seconds I felt a surge of
power and we began to climb. I don't know for sure what a death row inmate
feels like when the governor calls at the last minute, but I'm guessing it
feels something like that.

My heart was pounding in my chest and I was so stoked on adrenalin my
hands were shaking. The front seat passenger was looking at me
wide-eyed--he didn't know what was happening, but he had figured out
*something* wasn't right. I had wandered 40 deg. off course and Atlanta
Approach was repeating a frequency change instruction. In a few moments I
had us back on course and altitude but I was still somewhat rattled and
blew the readback on Atlanta's initial approach instructions. Got that
sorted out and made an uneventful ILS approach to runway 5 at MCN.

Not a totally satisfying performance. I ended up doing the right thing
and we lived; that's the good news. The bad news is that allowed myself
to rush things. A moment's thought would have prevented the autopilot
mistake. A calmer, more orderly flow through the engine controls would
have led me to the carb heat sooner and saved a few unnecessary extra
seconds of high anxiety. Next time I have an emergency (please: NO next
time!) I'll try to take it a little slower.

I'm still surprised that the carb iced up at full throttle. Conditions
were in the bad area of the carb ice chart, but my engine has never seemed
prone to the problem. In 650+ hours I've only detected carb ice once
before, and that was after a long taxi on a cool, rainy day.

--
Dan
C172RG at BFM

"MaulePilot" wrote:

And what became of the 'no-show' 3rd leg pilot?

Never heard from the guy, despite several messages left on cell & home
phones.

I hope you called
your dispatcher and mentioned it.

I did. I also mentioned it in the remarks on the mission report.

--
Dan
C-172RG at BFM

"Bob Gardner" wrote:

I can't find anything in the discussion of carb ice in The Lycoming Flyer to
make me think that full throttle somehow obviates carb ice when conditions
are conducive to icing. If ice is forming on the interior of the venturi,
the position of the throttle plate won't make much difference. Lycoming does
say that ice is more likely at low power settings, but I think we all know
that.

Apparently I'm guilty of believing what I was told by instructors without
checking the facts. Carbs can ice any time ambient conditions are right for
it. My tiedown neighbor with a Skylane tells me I'd have figured this out a
long time ago if I had a TCM O-470 182.

--
Dan
C-172RG at BFM

Jose wrote:
I had carb ice in the =runup= in a Dakota that had never had any kind of
carb ice problems before. It was warm and humid, ideal conditions, but
the engine hadn't been running for ten minutes yet. I applied runup
power and checked mags and such, no issue. Then I pulled the power all
the way back and the engine died. Tried it a few times, then took it
back to have it looked at. Nothing amiss. Final conclusion is that it
was probably carb ice.

Never happened before, or since.

Jose

In beautiful MN in the winter months I occasionally get carb ice while
on the ground checking ATIS. It's just like in the textbook ... an
unexplained loss of RPM. Usually the dew point spread is at least a few
degrees, so it is odd (and memorable) when it happens.

This has happened in both C172s and a Piper (can't remember if it was
the Archer or the Warrior).




Mike

"Dan Luke" wrote in message
...

"Bob Gardner" wrote:

I can't find anything in the discussion of carb ice in The Lycoming Flyer
to make me think that full throttle somehow obviates carb ice when
conditions are conducive to icing. If ice is forming on the interior of
the venturi, the position of the throttle plate won't make much
difference. Lycoming does say that ice is more likely at low power
settings, but I think we all know that.

Apparently I'm guilty of believing what I was told by instructors without
checking the facts. Carbs can ice any time ambient conditions are right
for it. My tiedown neighbor with a Skylane tells me I'd have figured this
out a long time ago if I had a TCM O-470 182.

--


That is because iced carbs will have the motor *stop* at idle settings
simply because the venturi is "choked", while they may continue to run quite
well at cruise settings with the venturi open. So they kept telling us to
carb heat at low power and eventually we started to believe we only *needed*
carb heat at low power because nobody told us different.

I finally found an instructor in the latter stages of my training who set me
straight on a number of things, including that one.

....and he was the one who emphasized the need to use a "cruise checklist"
every 15 minutes at least, which would be approximately like:

HI to compass heading
oil temps and pressures
fuel gauges; fuel switch correct tank as necessary
rpm/MP; pull carb head momentarily and check drop
tweak power; tweak mixture

have to disagree, on that one. A proficient pilot never puts himself in a
situation like that, in the first place, ideally.

Yeah, that sounds great - in theory.

The difference between theory and practice is much greater in practice
than it is in theory.

In theory, it may be possible to become a capable, experienced, and
proficient pilot by taking a cautious approach, not making boneheaded
mistakes, and not scaring oneself. But in practice, I've never seen it
happen. In practice, capable and proficient pilots are the ones who
survive their many little crises - usually of their own making, at
least in part.

Michael

"T o d d P a t t i s t" wrote in message
...
[...]
Oddly enough, in reviewing the certification requirements, I found two
paragraphs that my own airplane doesn't appear to meet.

Very interesting.

Well, I had a chance to ask my mechanic about this today. Unfortunately, he
wasn't completely certain about the answer either. However, it *appears*
that it's related to the original type certificate being issued under CAR 3,
rather than FAR 23.

The thing that he couldn't figure out (nor could I) is that on the TC Data
Sheet says (for my airplane type) "Certification Basis: 1. 14 CFR Part 23,
18 December 1964, Amendments 23-1 to and including 23-23, Subparts A, B, D,
E, F, and G." It goes on to also say "2. CAR 3...", but I don't understand
why they would list all the bits of FAR 23 if the type doesn't actually have
to meet the requirements of that Part.

However, it is true that my airplane shares the exact same TCDS number as
the original CAR 3 airplane from which it was derived (in spite of being
about as similar to it as a Cessna 206 is to a Cessna 150). So maybe that's
the answer, regardless of the mention of Part 23 in the TCDS. I have to
admit, it's a bit entertaining reading through the TCDS, seeing the
evolution of the type. Each new version is described as "exactly like the
previous, except...". Some of the exceptions are pretty broad.

It does appear that generally the requirements in question (manual override,
pilot indication) are met by other aircraft with automatic alternate air
induction sources, or at least two of them. The guys at the shop all agreed
that the Piper Navajo and Seneca both have those features to go along with
their automatic alternate air (I don't know firsthand myself...I'm just
taking their word for it).

If there's anyone out there who actually knows something about how aircraft
type certificates are granted who wants to take a look, here's the TCDS:
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/e906cc8a49ec031586256f7e0064e791/$FILE/1a13.pdf

The URL looks suspiciously to me as though it may contain a session ID, and
so it may not be valid by the time anyone else reads this post. But you can
navigate to the sheet by going he
http://www.airweb.faa.gov/Regulatory...e?OpenFrameSet
and then looking up the TCDS direction (it's 1A13, just like the name of the
PDF file in the previous link).

Anyway, fun with type certificates...

Pete

Glad you found the problem in time. Did your manifold pressure drop?

That was my first question, too. Dan?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"