Electric Carb Heaters?

[John A. Landry]

Greetings,

Does anyone have any experience (good or bad) with the electric carb
heaters that used to be sold to prevent carb icing on Bing side carbs?

The reason I ask is because I believe I had a couple of brief encounters
with carb icing on my dual carb Rotax 503 DCDI a couple of weeks ago when
flying in conditions of severe carb icing. The air temp was 40-45 degrees
and high humidity (visible in the air). Needless to say I didn't like
being scared like that and I don't care to experience it again.

As a result, I'm contemplating machining my own little adapters to press on
to the intake side of the carbs, each of which will hold a 30 watt
cartridge heater to be powered directly off the AC currant from alternator.
The pair of cartridge heaters should draw only 2.5 amps or less from the
alternator. How much heat the cartridge heaters will actually put out on
24 to 90 volts from the Rotax alternator is an unknown at this point.

Regarding carb ice...

Interestingly, I've never experienced any sort of carb icing symptom in
prior years when using premixed oil/fuel in my engine... and I flew in all
sorts of temperature and dew point conditions (short of flying in pouring
rain... which I did *once* and will never do that again either). The
flight where I experienced icing was only my second flight after upgrading
my 503 with an oil-injection system. The first flight since installing the
oil-injection system was in 35 degree air temps and low humidity. As one
would expect, no icing symptoms were experienced during that flight.

Can it really be true that oil in the fuel helps prevent carb icing? Based
on my very limited experience, it would seem so.

Anyway, I want something to guard against carb icing, and warming the carb
bodies electrically seems by far the simplest and fastest way to get there
(verses building a system to heat the intake air).

Thanks,

John L.
Shoreline, WA

[Jean-Paul Roy]

Hello John, I don't quite believe that oil in the fuel helps prevent carb
icing. But I do believe that the oil prevents icing from sticking on the
carb walls.
Just an opinion

Jean-Paul

Post by John A. Landry
Greetings,
Does anyone have any experience (good or bad) with the electric carb
heaters that used to be sold to prevent carb icing on Bing side carbs?
The reason I ask is because I believe I had a couple of brief encounters
with carb icing on my dual carb Rotax 503 DCDI a couple of weeks ago when
flying in conditions of severe carb icing. The air temp was 40-45 degrees
and high humidity (visible in the air). Needless to say I didn't like
being scared like that and I don't care to experience it again.
As a result, I'm contemplating machining my own little adapters to press on
to the intake side of the carbs, each of which will hold a 30 watt
cartridge heater to be powered directly off the AC currant from alternator.
The pair of cartridge heaters should draw only 2.5 amps or less from the
alternator. How much heat the cartridge heaters will actually put out on
24 to 90 volts from the Rotax alternator is an unknown at this point.
Regarding carb ice...
Interestingly, I've never experienced any sort of carb icing symptom in
prior years when using premixed oil/fuel in my engine... and I flew in all
sorts of temperature and dew point conditions (short of flying in pouring
rain... which I did *once* and will never do that again either). The
flight where I experienced icing was only my second flight after upgrading
my 503 with an oil-injection system. The first flight since installing the
oil-injection system was in 35 degree air temps and low humidity. As one
would expect, no icing symptoms were experienced during that flight.
Can it really be true that oil in the fuel helps prevent carb icing?

Based

Post by John A. Landry
on my very limited experience, it would seem so.
Anyway, I want something to guard against carb icing, and warming the carb
bodies electrically seems by far the simplest and fastest way to get there
(verses building a system to heat the intake air).
Thanks,
John L.
Shoreline, WA

[John Rockrohr]

HI John,
Here's some info, not sure if it's good or not. Goto Ebay and do a
search for "bing 54 carb heat", and an offer for plans to build carb heater
for about $30 should come up. I haven't ordered the plans yet, but I spoke
with the seller who assured me the parts were readily available for about
$100 from places like Wag-Aero, CPS, etc. If the offer is legit it sounds
like $130 will get them built.

John Rockrohr

Post by John A. Landry
Greetings,
Does anyone have any experience (good or bad) with the electric carb
heaters that used to be sold to prevent carb icing on Bing side carbs?
The reason I ask is because I believe I had a couple of brief encounters
with carb icing on my dual carb Rotax 503 DCDI a couple of weeks ago when
flying in conditions of severe carb icing. The air temp was 40-45 degrees
and high humidity (visible in the air). Needless to say I didn't like
being scared like that and I don't care to experience it again.
As a result, I'm contemplating machining my own little adapters to press on
to the intake side of the carbs, each of which will hold a 30 watt
cartridge heater to be powered directly off the AC currant from alternator.
The pair of cartridge heaters should draw only 2.5 amps or less from the
alternator. How much heat the cartridge heaters will actually put out on
24 to 90 volts from the Rotax alternator is an unknown at this point.
Regarding carb ice...
Interestingly, I've never experienced any sort of carb icing symptom in
prior years when using premixed oil/fuel in my engine... and I flew in all
sorts of temperature and dew point conditions (short of flying in pouring
rain... which I did *once* and will never do that again either). The
flight where I experienced icing was only my second flight after upgrading
my 503 with an oil-injection system. The first flight since installing the
oil-injection system was in 35 degree air temps and low humidity. As one
would expect, no icing symptoms were experienced during that flight.
Can it really be true that oil in the fuel helps prevent carb icing?

Based

Post by John A. Landry
on my very limited experience, it would seem so.
Anyway, I want something to guard against carb icing, and warming the carb
bodies electrically seems by far the simplest and fastest way to get there
(verses building a system to heat the intake air).
Thanks,
John L.
Shoreline, WA

[John A. Landry]

On Mon, 7 Mar 2005 17:48:31 -0600, in rec.aviation.ultralight, John

Post by John Rockrohr
Here's some info, not sure if it's good or not. Goto Ebay and do a
search for "bing 54 carb heat", and an offer for plans to build carb heater
for about $30 should come up. I haven't ordered the plans yet, but I spoke
with the seller who assured me the parts were readily available for about
$100 from places like Wag-Aero, CPS, etc. If the offer is legit it sounds
like $130 will get them built.

Hi John,

Thanks for the pointer.

Yes... I've seen the guy's plans on eBay. He apparently uses a bolt
together approach, which is a logical method of course.

However, since I have my own hobby machine shop in my garage, I intend to
instead machine my adapters out of solid pieces of 6061 aluminum, and then
*press* them on permanently to the carb inlets. They'll be more compact
and less noticeable this way. I've already sketched out the design and I
hope to make them this coming weekend.

In the mean time, I've already bought 2-1/2" long x 1/4" diameter 30 watt /
120 volt cartridge heaters from www.mcmaster.com, and will press them into
the adapters right up under the carb inlet.

Best regards,

John L.
Shoreline, WA

[sleepy6]

Post by John A. Landry
On Mon, 7 Mar 2005 17:48:31 -0600, in rec.aviation.ultralight, John

Post by John Rockrohr
Here's some info, not sure if it's good or not. Goto Ebay and do

a

Post by John Rockrohr
search for "bing 54 carb heat", and an offer for plans to build carb

heater

Post by John Rockrohr
for about $30 should come up. I haven't ordered the plans yet, but I

spoke

Post by John Rockrohr
with the seller who assured me the parts were readily available for a

bout

Post by John Rockrohr
$100 from places like Wag-Aero, CPS, etc. If the offer is legit it s

ounds

Post by John Rockrohr
like $130 will get them built.

Hi John,
Thanks for the pointer.
Yes... I've seen the guy's plans on eBay. He apparently uses a bolt
together approach, which is a logical method of course.
However, since I have my own hobby machine shop in my garage, I intend to
instead machine my adapters out of solid pieces of 6061 aluminum, and then
*press* them on permanently to the carb inlets. They'll be more compa
ct
and less noticeable this way. I've already sketched out the design an
d I
hope to make them this coming weekend.
In the mean time, I've already bought 2-1/2" long x 1/4" diameter 30 w
att /
120 volt cartridge heaters from www.mcmaster.com, and will press them into
the adapters right up under the carb inlet.
Best regards,
John L.
Shoreline, WA

120 volt?

[John A. Landry]

Post by sleepy6
120 volt?

120 volts is the maximum the cartridge heater is rated to continuously
withstand. There's no reason why less voltage can't be applied to it.

According to the tech literature from California Power Systems, the modern
Rotax 503 alternator 503 puts out from about 24 volts at idle to 90+ volts
at 6800 rpm.

Best regards,

John L.
Shoreline, WA

[sleepy6]

Post by John A. Landry

Post by sleepy6
120 volt?

120 volts is the maximum the cartridge heater is rated to continuously
withstand. There's no reason why less voltage can't be applied to it.
According to the tech literature from California Power Systems, the mo
dern
Rotax 503 alternator 503 puts out from about 24 volts at idle to 90+ v
olts
at 6800 rpm.
Best regards,
John L.
Shoreline, WA

Thats at no load. The voltage drops rapidly even under a light load.
You probably will not get enough voltage to push much current through
that resistance. The end result will be very little heat.

[John A. Landry]

Post by sleepy6
Thats at no load. The voltage drops rapidly even under a light load.
You probably will not get enough voltage to push much current through
that resistance. The end result will be very little heat.

Of course the voltage will drop under load!

However, as long as the AC voltage drop isn't significant enough to affect
rectified DC current downstream (as in below 15-16 volts), it shouldn't a
problem.

I'll test the circuit this weekend (heat output of the cartridges and the
voltage drop of both AC and rectified DC circuits) and report the results
here.

Regards,

John L.
Shoreline, WA

[Q]

If more voltage is needed it would be easy enough to add a small
transformer to get whatever voltage is necessary.

Q

Post by John A. Landry

Post by sleepy6
Thats at no load. The voltage drops rapidly even under a light load.
You probably will not get enough voltage to push much current through
that resistance. The end result will be very little heat.

Of course the voltage will drop under load!
However, as long as the AC voltage drop isn't significant enough to affect
rectified DC current downstream (as in below 15-16 volts), it shouldn't a
problem.
I'll test the circuit this weekend (heat output of the cartridges and the
voltage drop of both AC and rectified DC circuits) and report the results
here.
Regards,
John L.
Shoreline, WA

[sleepy6]

Good idea if he can determine what voltage the altenator actually puts
out under whatever his normal load might be. I did some experiments
way back when and the AC voltage swings all over the place depending on
rpm and load. A 120 volt to 24 VAC at 2 or 3 amp transformer hooked up
backwards might be a good place to start experimenting but that's just
a guess.

Post by Q
If more voltage is needed it would be easy enough to add a small
transformer to get whatever voltage is necessary.
Q

On Wed, 09 Mar 2005 00:37:01 GMT, in rec.aviation.ultralight, sleepy

Post by sleepy6
Thats at no load. The voltage drops rapidly even under a light load

.

Post by sleepy6
You probably will not get enough voltage to push much current throug

h

Post by sleepy6
that resistance. The end result will be very little heat.

Of course the voltage will drop under load!
However, as long as the AC voltage drop isn't significant enough to

affect

rectified DC current downstream (as in below 15-16 volts), it should

n't a

problem.
I'll test the circuit this weekend (heat output of the cartridges an

d the

voltage drop of both AC and rectified DC circuits) and report the re

sults

here.
Regards,
John L.
Shoreline, WA

[Smitty]

Post by John A. Landry

Post by sleepy6
Thats at no load. The voltage drops rapidly even under a light load.
You probably will not get enough voltage to push much current through
that resistance. The end result will be very little heat.

Of course the voltage will drop under load!
However, as long as the AC voltage drop isn't significant enough to affect
rectified DC current downstream (as in below 15-16 volts), it shouldn't a
problem.
I'll test the circuit this weekend (heat output of the cartridges and the
voltage drop of both AC and rectified DC circuits) and report the results
here.
Regards,
John L.
Shoreline, WA

Don't forget that power doesn't drop proportionally to voltage, it drops
proportionally to the square of voltage (W = V*V/R.) Putting 85 volts
through a heater designed for 120 will cut your heating power in half.
If the loaded alternator puts out only 60 volts, you'll cut the heat
output of those cartridges to 25%. But hell, who's to say that isn't
enough? Let us know what happens...

[Mark Smith]

Post by Smitty

Post by John A. Landry

Post by sleepy6
Thats at no load. The voltage drops rapidly even under a light load.
You probably will not get enough voltage to push much current through
that resistance. The end result will be very little heat.

Of course the voltage will drop under load!
However, as long as the AC voltage drop isn't significant enough to affect
rectified DC current downstream (as in below 15-16 volts), it shouldn't a
problem.
I'll test the circuit this weekend (heat output of the cartridges and the
voltage drop of both AC and rectified DC circuits) and report the results
here.
Regards,
John L.
Shoreline, WA

Don't forget that power doesn't drop proportionally to voltage, it drops
proportionally to the square of voltage (W = V*V/R.) Putting 85 volts
through a heater designed for 120 will cut your heating power in half.
If the loaded alternator puts out only 60 volts, you'll cut the heat
output of those cartridges to 25%. But hell, who's to say that isn't
enough? Let us know what happens...

The alternator is rated by Rotax at about 150 watts.

Use as you like but the current at 15 volts is about 6 amps at best.

I like the idea of the 120 volts !

[John A. Landry]

On Wed, 09 Mar 2005 09:47:24 -0800, in rec.aviation.ultralight, Smitty

Post by Smitty
Don't forget that power doesn't drop proportionally to voltage, it drops
proportionally to the square of voltage (W = V*V/R.) Putting 85 volts
through a heater designed for 120 will cut your heating power in half.
If the loaded alternator puts out only 60 volts, you'll cut the heat
output of those cartridges to 25%. But hell, who's to say that isn't
enough? Let us know what happens...

Smitty,

You have a darn good point I completely overlooked!

Another thing a friend pointed out to me in an email today is this...

When using a shunt type rectifier/regulator on the alternator output, any
excess voltage above what the rectifier/regulator uses is dumped to ground,
thus effectively limiting (clamping) the AC voltage (present on the
alternator wires) to between 12 and 15 volts. My KeyWest
rectifier/regulator puts out 14.6 to 14.8 volts, so assuming what my friend
told me is correct, I'd never get more than that from my alternator.

Assuming the alternator voltage clamped at 14.7 volts, that means a 30 Watt
cartridge heater would put out a mere 0.45 Watts! I can't believe that'll
do any good.

Hmmm... heating the intake air in the convention manner is starting to
sound attractive again. :)

John L.
Shoreline, WA

[Q]

Yet another possibility is using a little inverter. I use one on my
machine to power a heating pad that I stuff inside my snowmobile suit.

Q

Post by John A. Landry
Smitty,
You have a darn good point I completely overlooked!
Another thing a friend pointed out to me in an email today is this...
When using a shunt type rectifier/regulator on the alternator output, any
excess voltage above what the rectifier/regulator uses is dumped to ground,
thus effectively limiting (clamping) the AC voltage (present on the
alternator wires) to between 12 and 15 volts. My KeyWest
rectifier/regulator puts out 14.6 to 14.8 volts, so assuming what my friend
told me is correct, I'd never get more than that from my alternator.
Assuming the alternator voltage clamped at 14.7 volts, that means a 30 Watt
cartridge heater would put out a mere 0.45 Watts! I can't believe that'll
do any good.
Hmmm... heating the intake air in the convention manner is starting to
sound attractive again. :)
John L.
Shoreline, WA

[Smitty]

Post by John A. Landry
On Wed, 09 Mar 2005 09:47:24 -0800, in rec.aviation.ultralight, Smitty

Post by Smitty
Don't forget that power doesn't drop proportionally to voltage, it drops
proportionally to the square of voltage (W = V*V/R.) Putting 85 volts
through a heater designed for 120 will cut your heating power in half.
If the loaded alternator puts out only 60 volts, you'll cut the heat
output of those cartridges to 25%. But hell, who's to say that isn't
enough? Let us know what happens...

Smitty,
You have a darn good point I completely overlooked!
Another thing a friend pointed out to me in an email today is this...
When using a shunt type rectifier/regulator on the alternator output, any
excess voltage above what the rectifier/regulator uses is dumped to ground,
thus effectively limiting (clamping) the AC voltage (present on the
alternator wires) to between 12 and 15 volts. My KeyWest
rectifier/regulator puts out 14.6 to 14.8 volts, so assuming what my friend
told me is correct, I'd never get more than that from my alternator.
Assuming the alternator voltage clamped at 14.7 volts, that means a 30 Watt
cartridge heater would put out a mere 0.45 Watts! I can't believe that'll
do any good.
Hmmm... heating the intake air in the convention manner is starting to
sound attractive again. :)
John L.
Shoreline, WA

Hmm, I'm surprised they'd waste all that potential power by shunting it
to ground. Maybe you can isolate the heater from the regulator. But, you
could also get low voltage cartridges. Here's a company that sells
physically diminutive heaters with supply voltages as low as three
volts. These babies were used to keep liquid nitrogen valves from
freezing up, so maybe they'd work in a carburetor.

http://www.sunelectricheater.com/

[John A. Landry]

Post by Smitty
Hmm, I'm surprised they'd waste all that potential power by shunting it
to ground. Maybe you can isolate the heater from the regulator. But, you
could also get low voltage cartridges. Here's a company that sells
physically diminutive heaters with supply voltages as low as three
volts. These babies were used to keep liquid nitrogen valves from
freezing up, so maybe they'd work in a carburetor.
http://www.sunelectricheater.com/

Thanks Smitty.

I stumbled across similar heaters on a different web site, but the same thing.
Let me ask you this though, what would be the difference of using a normal
sized (cheaper) cartridge heater and simply taking into consideration the
decreased heat output by using one with a higher rating to start with? For
example, a 120 volt / 200 watt cartridge heater would be 2 watts at 12 volts.

Even though it's pretty low, I'll bet 5-10 watts, maybe even less, would be
enough to heat the carb body adequately. The other day I was trouble shooting
and replacing some tail lamps on my vehicle. I darn near burned my fingers
while trying to remove a lit backup lamp. I don't know how many watts that
was, it can't be much, but boy was it hot!

Regards,

John L.

[Smitty]

Post by John A. Landry

Post by Smitty
Hmm, I'm surprised they'd waste all that potential power by shunting it
to ground. Maybe you can isolate the heater from the regulator. But, you
could also get low voltage cartridges. Here's a company that sells
physically diminutive heaters with supply voltages as low as three
volts. These babies were used to keep liquid nitrogen valves from
freezing up, so maybe they'd work in a carburetor.
http://www.sunelectricheater.com/

Thanks Smitty.
I stumbled across similar heaters on a different web site, but the same thing.
Let me ask you this though, what would be the difference of using a normal
sized (cheaper) cartridge heater and simply taking into consideration the
decreased heat output by using one with a higher rating to start with? For
example, a 120 volt / 200 watt cartridge heater would be 2 watts at 12 volts.
Even though it's pretty low, I'll bet 5-10 watts, maybe even less, would be
enough to heat the carb body adequately. The other day I was trouble shooting
and replacing some tail lamps on my vehicle. I darn near burned my fingers
while trying to remove a lit backup lamp. I don't know how many watts that
was, it can't be much, but boy was it hot!
Regards,
John L.

Well, that's a good question. It's true that the power dissipation would
be equal. But, if you put two watts into a two watt resistor it's going
to get hotter than a fifty watt resistor with two watts on it. I think
you have to take into account that if the power is being dissipated over
a larger area, less of it is going to warm the carb, which is, of
course, your ultimate objective.

And do you think that the carb is going to sink a lot of heat and
dissipate it to the outside air before it starts to warm up?

I know this is a low budget sport, but I wouldn't let cost get in the
way of preventing carb ice. That's a comparatively serious issue, maybe
not up there with structural failure, but at least on a par with fuel
exhaustion.

Maybe you can make your own custom heater. You can get some resistance
wire and wind it around a mandrel of suitable size and shape, and
encapsulate it in some ceramic, with an insulating layer on the outside
to keep the heat radiating inwards. This could end up becoming a
marketable product, you could make millions, save some lives, get your
five minutes of fame, and buy a learjet, stocked with plenty of, uh,
stewardesses.

[Mark Smith]

Post by sleepy6

Post by John A. Landry
On Mon, 7 Mar 2005 17:48:31 -0600, in rec.aviation.ultralight, John

Post by John Rockrohr
Here's some info, not sure if it's good or not. Goto Ebay and do

a

Post by John Rockrohr
search for "bing 54 carb heat", and an offer for plans to build carb

heater

Post by John Rockrohr
for about $30 should come up. I haven't ordered the plans yet, but I

spoke

Post by John Rockrohr
with the seller who assured me the parts were readily available for a

bout

Post by John Rockrohr
$100 from places like Wag-Aero, CPS, etc. If the offer is legit it s

ounds

Post by John Rockrohr
like $130 will get them built.

Hi John,
Thanks for the pointer.
Yes... I've seen the guy's plans on eBay. He apparently uses a bolt
together approach, which is a logical method of course.
However, since I have my own hobby machine shop in my garage, I intend to
instead machine my adapters out of solid pieces of 6061 aluminum, and then
*press* them on permanently to the carb inlets. They'll be more compa
ct
and less noticeable this way. I've already sketched out the design an
d I
hope to make them this coming weekend.
In the mean time, I've already bought 2-1/2" long x 1/4" diameter 30 w
att /
120 volt cartridge heaters from www.mcmaster.com, and will press them into
the adapters right up under the carb inlet.
Best regards,
John L.
Shoreline, WA

120 volt?

You think maybe he shoulda bought the plans ?

[Jan Nademlejnsky]

I am very experienced "Rotax Flyer" with iced up carburetors. I fly (try to fly) in the winter, but the carburetor icing drives me crazy. When I was flying single cylinder Rotax 272 or Yamaha 286 it was easy. I carried on board hair dryer. As soon as I heard the engine coughing, I landed, removed carb, run to nearest car plugging, plugged in hair dryer *), melted ice, installed carb and flew again. This is not as easy now, with dual carb on my Rotax 582. The last time I flew, I did not feel or hear anything, but when I removed the air filter I saw the carb full of ice. It is scary and I do not know how the 582 would behave. Would it suddenly quit or is there any warning. I always wondered how people do it to fly in the winter with 2 stroke above hostile territory without fear the engine would quit.


*) I live in Canada, where everybody has outdoor car plug to keep car from freezing (-45C).

Jan Nademlejnsky
http://members.shaw.ca/jannadem/home.htm

Post by John A. Landry
Greetings,
Does anyone have any experience (good or bad) with the electric carb
heaters that used to be sold to prevent carb icing on Bing side carbs?
The reason I ask is because I believe I had a couple of brief encounters
with carb icing on my dual carb Rotax 503 DCDI a couple of weeks ago when
flying in conditions of severe carb icing. The air temp was 40-45 degrees
and high humidity (visible in the air). Needless to say I didn't like
being scared like that and I don't care to experience it again.
As a result, I'm contemplating machining my own little adapters to press on
to the intake side of the carbs, each of which will hold a 30 watt
cartridge heater to be powered directly off the AC currant from alternator.
The pair of cartridge heaters should draw only 2.5 amps or less from the
alternator. How much heat the cartridge heaters will actually put out on
24 to 90 volts from the Rotax alternator is an unknown at this point.
Regarding carb ice...
Interestingly, I've never experienced any sort of carb icing symptom in
prior years when using premixed oil/fuel in my engine... and I flew in all
sorts of temperature and dew point conditions (short of flying in pouring
rain... which I did *once* and will never do that again either). The
flight where I experienced icing was only my second flight after upgrading
my 503 with an oil-injection system. The first flight since installing the
oil-injection system was in 35 degree air temps and low humidity. As one
would expect, no icing symptoms were experienced during that flight.
Can it really be true that oil in the fuel helps prevent carb icing? Based
on my very limited experience, it would seem so.
Anyway, I want something to guard against carb icing, and warming the carb
bodies electrically seems by far the simplest and fastest way to get there
(verses building a system to heat the intake air).
Thanks,
John L.
Shoreline, WA

[Q]

Jan,

I fly in the winter here in the high desert of Central Oregon and have
experienced carb icing many times on my 582. First thing is that I don't
fly over hostile terrain because I've been forced to land several times
to let the ice melt. Only once did I have to land in a place that was
too small to take off again, and that was a real hassle.

So far I have only had carb ice problems when the temp was below 35 F
and there was fog within a couple miles. First thing I notice is my EGTs
going down to below 1000 F, then below 900, and I know it's starting to
ice up. At that point I start working the throttle from full closed to
full open to try to break the ice off the carb slide. The ice sometimes
breaks off and the engine coughs a couple of times then continues to
run. Sometimes it gets bad enough that the carb slides are totally
stuck. At that point I choose a place to land, turn off the engine, and
do a dead stick landing.

Anyway the key for me is keeping an eye on the EGTs.

One more thing. After ice in the carbs melts, some of that water can run
down through the needle jets into the float bowls. That drop of water
can freeze into a pea sized ice pellet and block the main jet. Always
dump the float bowls after an icing event!

Q

Post by Jan Nademlejnsky
I am very experienced "Rotax Flyer" with iced up carburetors. I fly (try to fly) in the winter, but the carburetor icing drives me crazy. When I was flying single cylinder Rotax 272 or Yamaha 286 it was easy. I carried on board hair dryer. As soon as I heard the engine coughing, I landed, removed carb, run to nearest car plugging, plugged in hair dryer *), melted ice, installed carb and flew again. This is not as easy now, with dual carb on my Rotax 582. The last time I flew, I did not feel or hear anything, but when I removed the air filter I saw the carb full of ice. It is scary and I do not know how the 582 would behave. Would it suddenly quit or is there any warning. I always wondered how people do it to fly in the winter with 2 stroke above hostile territory without fear the engine would quit.
*) I live in Canada, where everybody has outdoor car plug to keep car from freezing (-45C).
Jan Nademlejnsky
http://members.shaw.ca/jannadem/home.htm

[Mark Hansen]

Post by John A. Landry
Greetings,
Does anyone have any experience (good or bad) with the electric carb
heaters that used to be sold to prevent carb icing on Bing side carbs?

One issue I can see is a typical use case: Generally, turning on
carb heat is the first step in diagnosing an engine failure. If
the carb heat is run via generator/alternator output, this won't
be of much help.

Of course, if you keep the heat on all the time, you're reducing
engine performance due to the higher density altitude induced by
the warmer air.

Post by John A. Landry
The reason I ask is because I believe I had a couple of brief encounters
with carb icing on my dual carb Rotax 503 DCDI a couple of weeks ago when
flying in conditions of severe carb icing. The air temp was 40-45 degrees
and high humidity (visible in the air). Needless to say I didn't like
being scared like that and I don't care to experience it again.
As a result, I'm contemplating machining my own little adapters to press on
to the intake side of the carbs, each of which will hold a 30 watt
cartridge heater to be powered directly off the AC currant from alternator.
The pair of cartridge heaters should draw only 2.5 amps or less from the
alternator. How much heat the cartridge heaters will actually put out on
24 to 90 volts from the Rotax alternator is an unknown at this point.
Regarding carb ice...
Interestingly, I've never experienced any sort of carb icing symptom in
prior years when using premixed oil/fuel in my engine... and I flew in all
sorts of temperature and dew point conditions (short of flying in pouring
rain... which I did *once* and will never do that again either). The
flight where I experienced icing was only my second flight after upgrading
my 503 with an oil-injection system. The first flight since installing the
oil-injection system was in 35 degree air temps and low humidity. As one
would expect, no icing symptoms were experienced during that flight.
Can it really be true that oil in the fuel helps prevent carb icing? Based
on my very limited experience, it would seem so.
Anyway, I want something to guard against carb icing, and warming the carb
bodies electrically seems by far the simplest and fastest way to get there
(verses building a system to heat the intake air).
Thanks,
John L.
Shoreline, WA