Today's Message Index:
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1. 07:26 PM - Carb ice, or vapor lock? (Jimmy Young)
2. 07:33 PM - Re: Carb ice, or vapor lock? (Tommy Walker)
3. 08:13 PM - Re: Carb ice, or vapor lock? (bigdog@bentwing.com)
4. 09:14 PM - Re: Carb ice, or vapor lock? (Jim Baker)
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Subject: | Carb ice, or vapor lock? |
Don't know if many folks are still monitoring this list, but if so I've got a question.
Two weekends ago, I flew my Zenith 750, powered by a Cont. C-90, from Houston to
Arlington TX. I arrived at 10 am, had it topped off and parked it on the ramp.
Came back at 3 pm to depart. It was 102 degrees, and dew point approx. 65 degrees.
The plane had been parked outside in the sun for 5 hrs. Took off and climbed
to 2500' msl and was running at around 2350 rpm. Decided to climb up to
4000' to get in some cooler air.
About 12 minutes into the flight, the engine began to stumble and sputter, losing
rpm & power enough that I prepared for an off-field landing. Had a nice site
picked and made, and began to pump the throttle to see if the accelerator pump
could get some fuel going. Helped a little, but continued to stumble for the
next 15 minutes. I was able to maintain altitude and made it to another airport
about 11 miles away. My CHT's were climbing & peaked around 410 degrees,
even though I could only maintain 2000 - 2200 rpm. They normally stay between
335 & 360 when running 2350 rpm. My EGT's were climbing as well. This indicates
to me that I was running lean, if I am correct. I do have a mixture control,
but I leave it on full rich all the time and only use it to kill the engine
at the end of a flight. Just about the time I had that airport made, the engine
began to run normal & all temps returned to normal. I landed and began to try
& figure out what had happened.
My first mistake was, I never tried to pull my carb heat when the problem first
showed up. I f I had used my carb heat, I may have found the problem was carb
ice but at the time, I was more focused on landing off-field. I know it is possible
to develop carb ice in any weather, but after a year of flying this plane
over 200 hrs it has never stumbled once. This was the hottest weather I had
ever flown the plane in. I sumped the gascolator and all the tank sumps, no evidence
of water. I pulled the gascolator off and checked the fuel screen, it
was clean & no debri was in the bowl. I ended up spending the night in Dallas
after taking it back up that evening for a 20 minute full-power flight around
the pattern, during which time it ran perfect. Next morning, I departed for Houston
and the engine ran fine all the way home.
I began to suspect the possibility of vapor lock. I've got an ACS metal gascolator
on the firewall, located low. It has no heat shield or blast tube cooling.
From the gascolator to the MA3SPA carb, I've got a SS braided 3/8" fuel line
with firesleeve. I was running straight 100 LL fuel.
Last weekend I had an annual done on the plane. We checked the 2 screens on the
carb, both were clean. Compression testing showed 79/80, 79/80, 78/80, 78/80.
The engine was completely rebuilt in 2011 and had a total of 205 hrs of perfect
performance prior to this incident. I discussed it with my A&P and he suggested
either carb ice or vapor lock.
My question is, based on the high ambient temps, is carb ice a realistic possibility,
or is vapor lock the more likely cause? I have flown in much more carb
ice-prone WX over the past year than that particular day, and have never experienced
it. I have since wrapped my gascolator with a foil backed fiberglass insulated
blanket as a precaution. Any thoughts from more experienced pilots would
be appreciated.
Regards & thanks -
Jimmy Young
Houston TX
Zenith CH750, Cont. C-90
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=405454#405454
Message 2
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Subject: | Re: Carb ice, or vapor lock? |
Very interesting Jimmy. I would like to hear others reply. I'm still
trying to get my O200 Kitfox finished.
As you know I built two 701s.
Tommy,
Sent from my Xoom Tablet
On Jul 27, 2013 9:26 PM, "Jimmy Young" <jdy100@comcast.net> wrote:
>
> Don't know if many folks are still monitoring this list, but if so I've
> got a question.
>
> Two weekends ago, I flew my Zenith 750, powered by a Cont. C-90, from
> Houston to Arlington TX. I arrived at 10 am, had it topped off and parked
> it on the ramp. Came back at 3 pm to depart. It was 102 degrees, and dew
> point approx. 65 degrees. The plane had been parked outside in the sun for
> 5 hrs. Took off and climbed to 2500' msl and was running at around 2350
> rpm. Decided to climb up to 4000' to get in some cooler air.
>
> About 12 minutes into the flight, the engine began to stumble and sputter,
> losing rpm & power enough that I prepared for an off-field landing. Had a
> nice site picked and made, and began to pump the throttle to see if the
> accelerator pump could get some fuel going. Helped a little, but continued
> to stumble for the next 15 minutes. I was able to maintain altitude and
> made it to another airport about 11 miles away. My CHT's were climbing &
> peaked around 410 degrees, even though I could only maintain 2000 - 2200
> rpm. They normally stay between 335 & 360 when running 2350 rpm. My EGT's
> were climbing as well. This indicates to me that I was running lean, if I
> am correct. I do have a mixture control, but I leave it on full rich all
> the time and only use it to kill the engine at the end of a flight. Just
> about the time I had that airport made, the engine began to run normal &
> all temps returned to normal. I landed and began to try & figure out what
> had happened.
>
> My first mistake was, I never tried to pull my carb heat when the problem
> first showed up. I f I had used my carb heat, I may have found the problem
> was carb ice but at the time, I was more focused on landing off-field. I
> know it is possible to develop carb ice in any weather, but after a year of
> flying this plane over 200 hrs it has never stumbled once. This was the
> hottest weather I had ever flown the plane in. I sumped the gascolator and
> all the tank sumps, no evidence of water. I pulled the gascolator off and
> checked the fuel screen, it was clean & no debri was in the bowl. I ended
> up spending the night in Dallas after taking it back up that evening for a
> 20 minute full-power flight around the pattern, during which time it ran
> perfect. Next morning, I departed for Houston and the engine ran fine all
> the way home.
>
> I began to suspect the possibility of vapor lock. I've got an ACS metal
> gascolator on the firewall, located low. It has no heat shield or blast
> tube cooling. From the gascolator to the MA3SPA carb, I've got a SS braided
> 3/8" fuel line with firesleeve. I was running straight 100 LL fuel.
>
> Last weekend I had an annual done on the plane. We checked the 2 screens
> on the carb, both were clean. Compression testing showed 79/80, 79/80,
> 78/80, 78/80. The engine was completely rebuilt in 2011 and had a total of
> 205 hrs of perfect performance prior to this incident. I discussed it with
> my A&P and he suggested either carb ice or vapor lock.
>
> My question is, based on the high ambient temps, is carb ice a realistic
> possibility, or is vapor lock the more likely cause? I have flown in much
> more carb ice-prone WX over the past year than that particular day, and
> have never experienced it. I have since wrapped my gascolator with a foil
> backed fiberglass insulated blanket as a precaution. Any thoughts from more
> experienced pilots would be appreciated.
>
> Regards & thanks -
>
> Jimmy Young
> Houston TX
> Zenith CH750, Cont. C-90
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=405454#405454
>
>
Message 3
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Subject: | Carb ice, or vapor lock? |
I'm based at Hooks in Houston but back in the late 70's I had a Taylorcraft with
an A-65 based at Clover Field (now Pearland Intergalactic). Returning from a
run to the beach near Matagorda Island I had a similar experience. It was a hot
summer day with high humidity like we've had this week. While I did pull carb
heat I didn't leave it on long enough. With the power continuing to drop I
managed to limp into Lake Jackson and had the engine stop on the runway. By the
time I could get some tools to remove the cowling the ice had evaporated and
there was no evidence of other problems. I started up and flew home without problems.
That was the only time it's ever happened to me. The A & C-series are
known for susceptibility to carb ice and I learned afterward that it's possible
even on hot days. I would not discount carb ice. I fly behind an IO-550B now
so don't have the issue but I'm restoring an L-2 and will need to contend with
it again when that is flying.
Greg Young
-----Original Message-----
From: owner-continental-list-server@matronics.com [mailto:owner-continental-list-server@matronics.com] On Behalf Of Jimmy Young
Sent: Saturday, July 27, 2013 9:26 PM
Subject: Continental-List: Carb ice, or vapor lock?
--> <jdy100@comcast.net>
Don't know if many folks are still monitoring this list, but if so I've got a question.
Two weekends ago, I flew my Zenith 750, powered by a Cont. C-90, from Houston to
Arlington TX. I arrived at 10 am, had it topped off and parked it on the ramp.
Came back at 3 pm to depart. It was 102 degrees, and dew point approx. 65 degrees.
The plane had been parked outside in the sun for 5 hrs. Took off and climbed
to 2500' msl and was running at around 2350 rpm. Decided to climb up to
4000' to get in some cooler air.
About 12 minutes into the flight, the engine began to stumble and sputter, losing
rpm & power enough that I prepared for an off-field landing. Had a nice site
picked and made, and began to pump the throttle to see if the accelerator pump
could get some fuel going. Helped a little, but continued to stumble for the
next 15 minutes. I was able to maintain altitude and made it to another airport
about 11 miles away. My CHT's were climbing & peaked around 410 degrees,
even though I could only maintain 2000 - 2200 rpm. They normally stay between
335 & 360 when running 2350 rpm. My EGT's were climbing as well. This indicates
to me that I was running lean, if I am correct. I do have a mixture control,
but I leave it on full rich all the time and only use it to kill the engine
at the end of a flight. Just about the time I had that airport made, the engine
began to run normal & all temps returned to normal. I landed and began to try
& figure out what had happened.
My first mistake was, I never tried to pull my carb heat when the problem first
showed up. I f I had used my carb heat, I may have found the problem was carb
ice but at the time, I was more focused on landing off-field. I know it is possible
to develop carb ice in any weather, but after a year of flying this plane
over 200 hrs it has never stumbled once. This was the hottest weather I had
ever flown the plane in. I sumped the gascolator and all the tank sumps, no evidence
of water. I pulled the gascolator off and checked the fuel screen, it
was clean & no debri was in the bowl. I ended up spending the night in Dallas
after taking it back up that evening for a 20 minute full-power flight around
the pattern, during which time it ran perfect. Next morning, I departed for Houston
and the engine ran fine all the way home.
I began to suspect the possibility of vapor lock. I've got an ACS metal gascolator
on the firewall, located low. It has no heat shield or blast tube cooling.
From the gascolator to the MA3SPA carb, I've got a SS braided 3/8" fuel line
with firesleeve. I was running straight 100 LL fuel.
Last weekend I had an annual done on the plane. We checked the 2 screens on the
carb, both were clean. Compression testing showed 79/80, 79/80, 78/80, 78/80.
The engine was completely rebuilt in 2011 and had a total of 205 hrs of perfect
performance prior to this incident. I discussed it with my A&P and he suggested
either carb ice or vapor lock.
My question is, based on the high ambient temps, is carb ice a realistic possibility,
or is vapor lock the more likely cause? I have flown in much more carb
ice-prone WX over the past year than that particular day, and have never experienced
it. I have since wrapped my gascolator with a foil backed fiberglass insulated
blanket as a precaution. Any thoughts from more experienced pilots would
be appreciated.
Regards & thanks -
Jimmy Young
Houston TX
Zenith CH750, Cont. C-90
Message 4
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Subject: | Re: Carb ice, or vapor lock? |
X-mailer: Pegasus Mail for Windows (4.61)
When ice accumulates, that richens the mixture, not leans it. EGT and CHT
would decrease.
http://www.stinsonclub.org/newBB3/viewtopic.php?f=4&t=215
http://flighttraining.aopa.org/students/presolo/skills/carbicing.html
^^^
Each time a normally aspirated, four-cycle engine (which describes the engines
in most trainers and simple four-place aircraft) completes two crankshaft
revolutions, it draws a volume of air equal to the engine's displacement (less
small losses because of throttle position and system friction) through the
carburetor. Given a constant throttle position, this volume essentially remains
the same whether the carburetor is wide open or clogged with ice.
If the carburetor venturi is constricted because of ice, the velocity of the flow
must increase because the amount of air flowing to the cylinders is constant.
This increase in velocity is much more significant than the small decrease in
mass flow caused by the restriction in the venturi because of ice.
An increase in velocity, Bernoulli says, will cause a further decrease in static
pressure within the venturi, which means the ambient static pressure acting on
the fuel in the float bowl will push more fuel through the metering jet, resulting
in
a richer mixture.
***
If your EGTs and CHTs went up, I'd look for another cause.
Subject: Continental-List: Carb ice, or vapor lock?
From: "Jimmy Young" <jdy100@comcast.net>
Date sent: Sat, 27 Jul 2013 19:25:59 -0700
Send reply to: continental-list@matronics.com
>
> Don't know if many folks are still monitoring this list, but if so I've got a
question.
>
> Two weekends ago, I flew my Zenith 750, powered by a Cont. C-90, from Houston
to Arlington TX. I arrived at 10 am, had it topped off and parked it on the ramp.
Came back at 3 pm to depart. It was 102 degrees, and dew point approx. 65
degrees. The plane had been parked outside in the sun for 5 hrs. Took off and
climbed to 2500' msl and was running at around 2350 rpm. Decided to climb up
to 4000' to get in some cooler air.
>
> About 12 minutes into the flight, the engine began to stumble and sputter, losing
rpm & power enough that I prepared for an off-field landing. Had a nice site
picked and made, and began to pump the throttle to see if the accelerator
pump could get some fuel going. Helped a little, but continued to stumble for
the next 15 minutes. I was able to maintain altitude and made it to another airport
about 11 miles away. My CHT's were climbing & peaked around 410 degrees,
even though I could only maintain 2000 - 2200 rpm. They normally stay between
335 & 360 when running 2350 rpm. My EGT's were climbing as well. This indicates
to me that I was running lean, if I am correct. I do have a mixture control,
but I leave it on full rich all the time and only use it to kill the engine
at the end of a flight. Just about the time I had that airport made, the engine
began to run normal & all temps returned to normal. I landed and began to
try & figure out what had happened.
>
> My first mistake was, I never tried to pull my carb heat when the problem first
showed up. I f I had used my carb heat, I may have found the problem was carb
ice but at the time, I was more focused on landing off-field. I know it is
possible to develop carb ice in any weather, but after a year of flying this plane
over 200 hrs it has never stumbled once. This was the hottest weather I had
ever flown the plane in. I sumped the gascolator and all the tank sumps, no
evidence of water. I pulled the gascolator off and checked the fuel screen, it
was clean & no debri was in the bowl. I ended up spending the night in Dallas
after taking it back up that evening for a 20 minute full-power flight around
the pattern, during which time it ran perfect. Next morning, I departed for
Houston and the engine ran fine all the way home.
>
> I began to suspect the possibility of vapor lock. I've got an ACS metal gascolator
on the firewall, located low. It has no heat shield or blast tube cooling.
From the gascolator to the MA3SPA carb, I've got a SS braided 3/8" fuel line
with firesleeve. I was running straight 100 LL fuel.
>
> Last weekend I had an annual done on the plane. We checked the 2 screens on the
carb, both were clean. Compression testing showed 79/80, 79/80, 78/80, 78/80.
The engine was completely rebuilt in 2011 and had a total of 205 hrs of perfect
performance prior to this incident. I discussed it with my A&P and he suggested
either carb ice or vapor lock.
>
> My question is, based on the high ambient temps, is carb ice a realistic possibility,
or is vapor lock the more likely cause? I have flown in much more carb
ice-prone WX over the past year than that particular day, and have never experienced
it. I have since wrapped my gascolator with a foil backed fiberglass
insulated blanket as a precaution. Any thoughts from more experienced pilots
would be appreciated.
>
> Regards & thanks -
>
> Jimmy Young
> Houston TX
> Zenith CH750, Cont. C-90
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=405454#405454
>
>
>
>
>
>
>
>
>
>
Jim Baker
Elmore City, OK
580.788.2779 home
405.426.5377 cell
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