Constant Speed Prop and Carb ice
Peregrine
I apply carb heat as a sign that carb ice is clearing. With a constant speed
prop, does the manifold pressure gauge give me similar info? Also, will I
feel the same kind of engine roughness that is possible in a fixed prop as
an indicator of carb ice?
Bob Gardner
the reduction is the result of ice or caused by throttle movement. And yes, the
engine will express its displeasure at being deprived of breathing air in the
same manner. But *most* planes with constant speed props have fuel injected
engines, so carb ice is not a problem (but intake icing is still a hazard).
(Please, lurkers, do not provide me with a list of airplanes that have constant
speed props and carbs.)
Bob Gardner
Colin Rasmussen
In article <371F5930...@halcyon.com>, Bob Gardner <bob...@halcyon.com>
wrote:
> Yes, the manifold pressure gauge becomes your loss-of-power indicator, whether
> the reduction is the result of ice or caused by throttle movement. And yes,
the
> engine will express its displeasure at being deprived of breathing air in the
> same manner. But *most* planes with constant speed props have fuel injected
> engines, so carb ice is not a problem (but intake icing is still a hazard).
> (Please, lurkers, do not provide me with a list of airplanes that have
constant
> speed props and carbs.)
>
> Bob Gardner
Lots of them do. I have yet to fly anything with fuel injection, and unless
I win a lottery soon , likely won't. The GA fleet is 20 years old or so,
and so there's plenty of carb fed bangers out there.
The rest of the answer is correct re MP.
Colin
Trevor Fenn
Bob Gardner wrote:
> Yes, the manifold pressure gauge becomes your loss-of-power indicator, whether
> the reduction is the result of ice or caused by throttle movement. And yes, the
> engine will express its displeasure at being deprived of breathing air in the
> same manner. But *most* planes with constant speed props have fuel injected
> engines, so carb ice is not a problem (but intake icing is still a hazard).
> (Please, lurkers, do not provide me with a list of airplanes that have constant
> speed props and carbs.)
Well ok, as you wish but that list is quite extensive.
Trevor Fenn
>
>
Jack
> Yes, the manifold pressure gauge becomes your loss-of-power indicator
What _was_ I thinking?
Yes of course, MP on constant speed props and RPM on fixed pitch.
These damned piston engines are just too complicated. If God meant for things to
go up and down instead of 'round and 'round he would have ... oh, never mind.
Jack
Jack
But *most* planes with constant
speed props have fuel injected
engines, so carb ice is not
a problem (but intake icing is still a hazard).
(Please, lurkers, do not provide
me with a list of airplanes that have constant
speed props and carbs.)
That's asking for a lot, here on "rec.aviation.flamethyneighbor"
Got to be way more 182s than 185s and 210s still flying. Who knows how many other examples?
But if your point is that MP is your indicator on both types of props,
I must agree.
Jack
Marcus Vinicius
>
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>Bob Gardner wrote:
>
>But *most* planes with constant speed props have fuel injected
>engines, so carb ice is not a problem (but intake icing is still a hazard).
>(Please, lurkers, do not provide me with a list of airplanes that have constant
>speed props and carbs.)
>
>That's asking for a lot, here on "rec.aviation.flamethyneighbor"
>
>Got to be way more 182s than 185s and 210s still flying. Who knows how many
> other
>examples?
Dakota
John - N8086N
Wise man says "Never use a bank with the initials F. U."
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Erik Shilling
<co...@fungus.usask.ca> writes:
>
>
>In article <371F5930...@halcyon.com>, Bob Gardner
<bob...@halcyon.com>
>
>
>> Yes, the manifold pressure gauge becomes your loss-of-power
being deprived of breathing air in the same manner. But *most* planes
with constant speed props have fuel injected engines, so carb ice is
not a problem (but intake icing is still a hazard).
There is one type of icing that has not been address, which is impact
icine of the impact tube on a fu;el injected engine.
With this type of icing the engine quites as though you used idle
cut-off.
MP does not change since air flow is not restricted but impact tubing
ice stops fuel flow because the signal is that there is no ram. and
cuts fuel flow.
karl gruber
cut-off."<<
Not so. The alternate door just opens and flight continues without you
even knowing something happened.
Karl
N29348
roughness is easier to tell ( by sound, vibration) for fixed pitch props.
CSP does mask slight engine roughness.
highflyer
>
> Yes, the manifold pressure gauge becomes your loss-of-power indicator, whether
> engine will express its displeasure at being deprived of breathing air in the
> same manner. But *most* planes with constant speed props have fuel injected
> engines, so carb ice is not a problem (but intake icing is still a hazard).
> speed props and carbs.)
>
>
You mean like all of mine, as well as most C-182's, etc.
Anyway, the MP gauge does indicate the power status and yes, they
do get rough, even with a constant speed prop.
HF
Capt Over
I had just departed ABQ and was flying through the tops of a snow shower at
16,000 ft. I was in an older Mooney 231 with the old Alt air door (doesn't open
automatically). I was woried more about structural ice than engine ice so I was
keeping a good eye on the wings. I started to lean the engine out and when the
EGT's started going down I started to richen a little bit. The EGTs kept going
down rather than going back up to peak. I started to re-richen the mixture
again to start over and the EGTs went to nothing. I confirmed the reading with
the ship's gauge and its true. EGT was less than the scale. Glanced over at
the Manifold Pressure and it read 12 inches (@ 16,000 ft, it should have been
27"). I looked over at the airspeed and it was about 90 KIAS (should have been
140). The autopilot had tried to keep me level so the airplane was slowing
down. I pulled the alt air on and the engine surged but then went back to 12".
This whole time, there had been very little sound cues to the ailing engine. No
roughness and no significant change in the engine noise. My guess at this point
was that the turbo had spun down and I wasn't going to get any real engine power
until I got down to 10,000. I told center I had an induction problem and asked
for a 180 back to ABQ and a descent down (did I mention this was IMC?). Center
came back with direct ABQ and a descent down to 10,000. I asked them for a
vector and they gave it too me. With no air going to the engine, the mixture
was very rich so I had to play with the mixture to keep the engine running.
About 10,000 feet, I was able to get about 50% power back and limped back to
ABQ.
I have talked earlier on this newsgroup about reducing distractions. After all
of the training I have been through, I could not beleive how difficult it was to
maintain a heading and a descent IMC while trying to trouble shoot the engine,
play with the mixtrure to keep the engine running, get set up for the approach
back into ABQ and keep working with center to get back down without hitting an
airplane or dirt. I have been a CFI for several years and don't beleive that we
can simulate that level of distraction short of Ernest Gann's lit match under
the nose on final from Fate is the Hunter (great book if your interested).
I have since complied with the SB that replaces the old alt air door with one
that pops open when needed. I've also since learned the importance of the
'preventative' use of alt air when flying a turbocharged airplane at altitude.
Once the turbo spins down, you will have to descend until you can get more air
into the engine.
Back to the point of this thread. MP will probably be your only indication that
something is amiss with a fuel injected CSP. If you have the AP engaged, you
may not notice it at all untill the AP disconnects. My side point about
emergencies that I will continue to preach is "Keep it simple. Fly the
airplane."
Blue Skies!
Capt Over
Brett Rabe
Two things:
1) Not all alternate doors are automatic.
2) I'm under the impression that some of the alt doors
are magnetically latched and, with a build-up of gunk
over the years, might be prone to sticking and not
opening.
Are either or both of those true?
Brett
--
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Systems Administrator - U S West Phone : 612.664.3078
Interact - 3S Pager : 612.613.2549
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Just because you're smart does not mean that the other guy is stupid.
n55bz
system is located in the servo assembly (Throttle body) which is downstream
of the alternate air door. Unless the air filter or the intake scoop had
already iced over, the alternate air door would not open of its own accord.
I think in this case you would also get ice accumulation on the venturi and
the throttle butterfly. I am not sure that ice blockage of the impact tube
would cause fuel cut off to the engine, but it would be serious. Especially
since alternate air is drawn in from the engine compatment and not over the
exhaust as in a carburator heat system and does not have the de-icing
capability of a carb. heat system.
In my opinion, alternate air is an anti-icing and not a de-icing system and
must be employed prior to entering icing conditions.
karl gruber wrote in message <372296F1...@worldnet.att.net>...
>>>"With this type of icing the engine quites as though you used idle
>cut-off."<<
>
>Not so. The alternate door just opens and flight continues without you
>even knowing something happened.
>
>Karl
>
n55bz
Capt Over wrote in message <372510C6...@me.com>...
>My only experience with this problem was this.
>
Norfolk in late September in a Navy EP-2H which had R3350 supercharged,
turbo compound engines with pressure injection carburetors. On climbout we
started picking up wing ice and were cycling the wing and empenage heaters
to take care of that when the flight engineer called out a reduction in
torque pressure (BMEP) and a reduction in MAP. He said that he thought that
we had picked up carb ice. The engines continued to run as smoothly as
always. These engines had carbuetor alcohol de-ice and alternate air for
anti-ice so the FE activated the carb alcohol, then adjusted the alternate
air doors to increase carb. air temp. The only engine roughness we
encountered was when the alcohol dislodged the ice in the carburetors and it
passed throught the engines.
The indications of induction icing were a reduction in manifold pressure and
a reduction in engine power output. Very few of us have horsepower, torque
pressure or BMEP gauges in our small aircraft, so the manifold pressure
gauge is our best indicator of the onset of icing. We may or may not
encounter engine roughness.
The two additional crew members and the aircraft systems made this encounter
with induction icing a non-event.
Michael Richmann
>karl gruber wrote:
>>
>> >>"With this type of icing the engine quites as though you used idle
>> cut-off."<<
>>
>> Not so. The alternate door just opens and flight continues without you
>> even knowing something happened.
>
>
>1) Not all alternate doors are automatic.
>
>2) I'm under the impression that some of the alt doors
> are magnetically latched and, with a build-up of gunk
> over the years, might be prone to sticking and not
> opening.
>
>Are either or both of those true?
Both. I've seen each scenario described in the Light Plane Maintenance
series of books...
--
Mike
C-182 N2406R
My opinions, not Argonne's...