The Man Who Fell to the Earth

[JonH]

The problem is it's not just low temp. In the winter it's always low temp. It's a combination of freeing temperature in the venturi and moist air that results in the formation of ice. If the air is dry, no carb ice, regardless of the temperature.

But either way, fuel injection does not suffer from carb ice.

Right. But, there is no humidity sensor. The only thing we have to work with it temp and it is more than enough. If you don't let the carb freeze, RH doesn't matter. Considering people pull carb heat based on RPM, I don't see a problem with pulling it based on temp.

 

[hindsight2020]

continental carb installations basically ought to have the carb heat safety-wired ON. That's how crappy an induction system they are. Ditto for side draft carbs in Lycomings, though to a lesser degree.

Pressure carburetors would be nice, but they were essentially replaced by FI systems, so might as well go FI. I don't even think it would be economic to retrofit to a pressure carb system. Actually it sounds like it would be more expensive than just going FI in the first place due to the lack of economy of scales of pressure carb in low power piston applications.

 

[RyanB]

I don't pull carb heat unless the engine gets rough or at the point I am abeam the numbers and drop the to 1500 rpm for my descent to the runway.

I certainly don’t intend to arm chair quarterback, but I have to ask...why?

Pulling carb heat only if you experience engine roughness isn’t how that lever is supposed to be used. That sounds like a problem waiting to happen.

 

[Rushie]

I certainly don’t intend to arm chair quarterback, but I have to ask...why?

Pulling carb heat only if you experience engine roughness isn’t how that lever is supposed to be used. That sounds like a problem waiting to happen.

I took it to mean he always puts it on as part of normal preparation to land also. That's how I was trained.

 

[RyanB]

I took it to mean he always puts it on as part of normal preparation to land also. That's how I was trained.

I didn’t take it like that, but maybe so. Sounds to me like during a decent from altitude, carb heat isn’t used unless his engine starts to cough. The only other time is while he’s downwind abeam and about to land.

 

[ircphoenix]

Thanks for surviving and coming back to share your experiences. Carb ice always worried me when I was flying my Cherokee. Why a 'modern' plane like a SkyCatcher would have been built with anything other than fuel injection is beyond me.

 

[azure]

Wow! I've never flown a Skycatcher and never realized Cessna was still making planes with carbureted engines after 2000. But one of the very first planes I flew during training, a late 1960s vintage 152, augured in at KPTK with a CFI on board due to carb ice, so it is something I was very attuned to when flying with a carb. Kudos to you for managing the best possible outcome from a very difficult situation, and for sharing your story here (and for an excellent writeup).

 

[Mtns2Skies]

continental carb installations basically ought to have the carb heat safety-wired ON. That's how crappy an induction system they are. Ditto for side draft carbs in Lycomings, though to a lesser degree.

Pressure carburetors would be nice, but they were essentially replaced by FI systems, so might as well go FI. I don't even think it would be economic to retrofit to a pressure carb system. Actually it sounds like it would be more expensive than just going FI in the first place due to the lack of economy of scales of pressure carb in low power piston applications.

It's amazing that ~half of the GA fleet survives every flight.

 

[Bill]

I took it to mean he always puts it on as part of normal preparation to land also. That's how I was trained.

In Cessnas, I was trained that anytime the RPMs were not in the green band, carb heat was to be on.

 

[jsstevens]

In Cessnas, I was trained that anytime the RPMs were not in the green band, carb heat was to be on.

Me too. Also, I've got quite a few hours in a 1963 C-172 with O-300 and the plane owner/CFI beat on me (metaphorically) to pull carb heat BEFORE pulling the throttle. He calimed it was much more prone to carb icing than the Lycoming installations.

 

[Brad Z]

It's amazing that ~half of the GA fleet survives every flight.

Not every flight. There are scores of accidents in the NTSB database of suspected carb icing causing engine failure. Besides, "just because that's the way we've always done it" is a terrible argument for a clear human factors design issue that is easily avoidable. These aircraft were designed in the early to mid 2000s, where fuel injected engines are readily available.

 

[Lowflynjack]

Not every flight. There are scores of accidents in the NTSB database of suspected carb icing causing engine failure. Besides, "just because that's the way we've always done it" is a terrible argument for a clear human factors design issue that is easily avoidable. These aircraft were designed in the early to mid 2000s, where fuel injected engines are readily available.

Why would they not use fuel injection? Cost? Weight? I know they were trying to keep the price down and of course it was LSA, so weight was a huge issue.

I know a lot of us were upset when Cessna not only crushed the planes, but the engines. For an old Cessna 140, this engine would have been an awesome upgrade.

 

[Brad Z]

Why would they not use fuel injection? Cost? Weight? I know they were trying to keep the price down and of course it was LSA, so weight was a huge issue.

I know a lot of us were upset when Cessna not only crushed the planes, but the engines. For an old Cessna 140, this engine would have been an awesome upgrade.

I suspect it was because Textron, who owns Cessna, also owns Continental, so they wanted to use their own engine. I'm don't believe they ever made a certified production IO-200 variant of the small displacement engine, so a carb'd O-200 it was. It was heavy, and one of the reasons the 162 Skycrasher failed as an LSA.

 

[bobmrg]

When I was learning to fly in Juneau my instructor had me pulling the carb heat full out every once in awhile "to clear the engine." Maybe not the best reason, but I was a noobie and it made sense at the time. I think that the POH recommendation for most carbed engines is full heat before power reduction, no exceptions. Partial heat is a no-no unless you have carb instrumentation.

Bob

 

[SkyDog58]

I suspect it was because Textron, who owns Cessna, also owns Continental, so they wanted to use their own engine. I'm don't believe they ever made a certified production IO-200 variant of the small displacement engine, so a carb'd O-200 it was. It was heavy, and one of the reasons the 162 Skycrasher failed as an LSA.

Textron owns Lycoming.

Continental is owned by AVIC.

 

[danhagan]

Fly a AA5B Tiger, nearly impossible to ice up the carb

 

[hindsight2020]

It's amazing that ~half of the GA fleet survives every flight.

I've always acknowledged and highlighted the captive audience nature to these engine decisions from the perspective of owners. It's just an opportunity cost like everything else. To suggest it's improbable or unlikely compared to the FI fleet is simply a case of seeing what one wants to see however. I owned a C-150 and Warrior II in the past (conti and lycoming carb respectively), so I've dealt with captive audience dynamics in this hobby. I had an instance of unconfirmed (and self-limiting...that time) carb icing one chilly clear night circa November many moons ago departing out of KOKC. Although it didn't really hit me of what had transpired, quick enough to not allow me to do much about it, I came to the conclusion it was not worth enough juice for the squeeze in what is a recreational pursuit for me, when I did have FI options available at a close enough price point. So I paid my monies and took my chances, and never looked back. It's not without opportunity costs; hot starts in the Lyco IO-360 are a PITA without return lines, which conti FI does have.

As to this thread, we lose another participant to the recalcitrant vestiges of the FAA and costs gridlock between the market share (OEMs and the like) and said requirements (the FAA), and we choose to play stump the dummy armchair QB with the victim in order to defend stupid float carburetors in 2018 because Stockholm Syndrome. We're our own worst enemy. I hate the pretentiousness of the #cirruslife crowd in this hobby (maybe only second to some of the more insufferable sub-circles of big piston/jet wardbird 'ol boy club), but the Cirroids are right: facilitating ease of use via tech improvements is a good thing for our avocation. Playing gatekeeper with old technology is a turn off.

 

[Dan Thomas]

I suspect it was because Textron, who owns Cessna, also owns Continental, so they wanted to use their own engine. I'm don't believe they ever made a certified production IO-200 variant of the small displacement engine, so a carb'd O-200 it was. It was heavy, and one of the reasons the 162 Skycrasher failed as an LSA.

Lycoming belongs to Textron. Cessna didn't want to use the Lyc in the 162 because of Lycoming's persistent crankshaft QA/AD hassles, so Textron allowed them to buy the O-200 for it.

Continental may have planned an injected version of the O-200 at one time. The cylinder heads have injector ports.

 

[Dan Thomas]

Considering people pull carb heat based on RPM, I don't see a problem with pulling it based on temp.

Pulling it on based on temp is needlessly losing power when the air is dry enough that ice won't form. The heat reduces the air density, costing power and requiring a mixture adjustment. Besides, the ice risk is related to both temp and throttle position, so a pilot should understand what causes carb ice, how it forms, in what conditions and flight regimes it can form, and what ambient conditions are conducive to it. THEN he can manage it sensibly instead of simply by rote.

Carbureted automobiles used a vacuum-operated carb heat valve that was controlled by a thermostatic sensor in the air cleaner. It kept the induction air at around 70°F. That, combined with the carburetor base heated by exhaust gases, prevented icing in anything but the most adverse conditions, but it reduced available power. Such a system would be dangerous in a light airplane.

 

[FlySince9]

I added a Carburetor Temperature Gauge... That little gadget is highly enlightening as to the range of temperatures during different power settings... and resolves the ambiguous instructions offered in the POH...

 

[JonH]

Pulling it on based on temp is needlessly losing power when the air is dry enough that ice won't form. The heat reduces the air density, costing power and requiring a mixture adjustment. Besides, the ice risk is related to both temp and throttle position, so a pilot should understand what causes carb ice, how it forms, in what conditions and flight regimes it can form, and what ambient conditions are conducive to it. THEN he can manage it sensibly instead of simply by rote.

Carbureted automobiles used a vacuum-operated carb heat valve that was controlled by a thermostatic sensor in the air cleaner. It kept the induction air at around 70°F. That, combined with the carburetor base heated by exhaust gases, prevented icing in anything but the most adverse conditions, but it reduced available power. Such a system would be dangerous in a light airplane.

Have you flown a C-162? The carb temp doesn't get low enough to be a concern unless you reduce throttle. Since you're reducing throttle, a little performance loss isn't a factor. If you pull carb heat based on some RH figure you're guesstimating, that's great. I'll keep pulling carb heat based on RPM. I don't care about temps, and I don't care about RH. When I drop the throttle I don't care about a loss of RPM because of the heat.

I feel like we're talking about two different things and don't want to get into it on this thread.

Much respect to the OP, I'm out.

 

[hindsight2020]

prevented icing in anything but the most adverse conditions, but it reduced available power. Such a system would be dangerous in a light airplane.

..you mean other than the shooting, I mean induction icing?

 

[FlySince9]

The carb temp doesn't get low enough to be a concern unless you reduce throttle

Well let see, the other day at cruise power, my carb temp was 28 degrees... Just say'n...

 

[Dan Thomas]

Well let see, the other day at cruise power, my carb temp was 28 degrees... Just say'n...

Yup. Even at full throttle the temp will be lower. The venturi's pressure drop as well as vaporizing fuel will do it. Closing the throttle forms another couple of venturis between the throttle plate and carburetor bore wall, which is why reducing throttle increases the risk of ice.

 

[CC268]

That Cloud Ahoy Cockpit view is amazing...didn’t know you could do that. Is that something you can do with like a Stratus?

 

[Brad Z]

Lycoming belongs to Textron. Cessna didn't want to use the Lyc in the 162 because of Lycoming's persistent crankshaft QA/AD hassles, so Textron allowed them to buy the O-200 for it.

Continental may have planned an injected version of the O-200 at one time. The cylinder heads have injector ports.

Whoops, you're right. Makes it even more baffling that they didn't go with a Rotax.

FWIW, the round-the-world Rutan-built Voyager aircraft has a fuel injected IO-200 engine, so it's been used in at least one application.

 

[Salty]

That Cloud Ahoy Cockpit view is amazing...didn’t know you could do that. Is that something you can do with like a Stratus?

Yes. You can use just a phone, or a better gps, or even upload data from a glass instrument like the g300 in The skycatcher or a G5, etc

 

[Dan Thomas]

FWIW, the round-the-world Rutan-built Voyager aircraft has a fuel injected IO-200 engine, so it's been used in at least one application.

I think that was a liquid-cooled version as well. Different head.

 

[benyflyguy]

When I flew cherokees in training I pulled heat when checklist called for it, think it was just pattern. When I bought into a 182 club. My CFI drilled into me “carb heat!!” He would say it’s a Cessna thing. The carb is an ice maker in most Cessna he told me. I pull anytime I start a power off descent. Occ I summer heat when power gets real low on final the engine with cough a bit with heat on, mixture might be a bit too rich. So I’ll check carb temp and push in and monitor carb temp. Never partial pull -apparently that can make ice form deeper in carb I think I read.

 

[Let'sgoflying!]

possibly a good addition to the convo?

 

[vman]

I didn’t take it like that, but maybe so. Sounds to me like during a decent from altitude, carb heat isn’t used unless his engine starts to cough. The only other time is while he’s downwind abeam and about to land.

poh for a beech sport

DESCENT
1.Altimeter-SET.
2.Carburetor Heat- WHEN REQUIRED.
3. Power-AS REQUIRED (avoid prolonged idle settings which may cause low cylinder head temperatures).
4. Mixture - ENRICH AS REQUIRED

for landing carb heat - "as required"

 

[Stingray Don]

possibly a good addition to the convo?
View attachment 69975

What is this “Celsius” that you speak of?

 

[Rushie]

poh for a beech sport


for landing carb heat - "as required"

Well that certainly clears it up.

If it turns out you would have needed it, then you should have used it. Story of my life.

 

[WannFly]

Well that certainly clears it up.

If it turns out you would have needed it, then you should have used it. Story of my life.

Same in archer POH

 

[hindsight2020]

I always got a chuckle at the carb charts. The entire year if you live somewhere where water is present in gas form (aka planet Earth most places) is in the operating window of a piston airplane where induction icing is possible lol. Which is why you have to have a means to keep the carb heated full time. Lycomings of the oil sump bolted variety accomplish this in an indirect way. The rest of the float type lot? Not so much. Yous pays your monies yous takes your chances.

 

[Doug F]

Just some thoughts after watching the Cloud Ahoy replay (talk about fascinating you had this on)

Around 40:20 to 48:00 you were in very gradual descent for most of it. Maybe you picked up some ice there? Then it looks like you backed off some power for a very nice -500fpm descent at 48:00. And then it would seem you pitched for best glide around 49:21.

I did a see a few -200ft (from 4500) corrections before that gradual descent at 40:20. Not questioning your altitude keeping skills (mine are way worse). But I was wondering if you had already lost some power and had to correct a couple of times. Then that ever so slow nearly 7min descent iced it up even more. I know you probably had the same throttle/rpm but just wondering if it played a role?

Sorry about the delay responding; I didn't get updates on people responding. I'll be playing catch up tonight!

The +/- altitude changes were due to two factors; 1. I climbed to about 4700 and drifted east to avoid an area that might have had aerobatics going on (none happening). The valley around US441 was a bit windy. I was sightseeing and let the plane climb/descend because I wasn't paying attention. Once I noticed I was off my target altitude, I'd correect that.
My guess is that I picked up the ice when I dropped throttle from 2350 to about 2200 and started the slow descent. That most likely killed the engine, which cooled off, and carb heat was not possible. The 162's carbeurator is a bit isolated from the engine and doesn't get a lot of heat from the engine (new news and now part of the flight school's training).

I use ForeFlight to generate track logs. Those are pushed to CloudAhoy which has a much better interface for debriefing. I use(d) it all the time. It's hard to lie to yourself when you can see the numbers played back!

 

[Doug F]

so glad you’re ok i have 200 hrs in the Skycatcher and can recall only one flight with suspected carb ice. nothing like what you experienced and my flight continued as planned once i pulled carb heat on but i sure can relate to your experience. congratulations on your walk-away crash.

The flight school is going to start having students pull carb heat any time they drop throttle as a preventive measure. If nothing else, watch your carb temp like a hawk any time you pull throttle; that would probably kept me out of trouble.

 

[Doug F]

Not all 162s have carb temp sensors.

Did not know that. The flight school is likely to recommend carb heat any time you pull the throttle back. I think that would go double if you can't see the temp.

 

[Doug F]

I always got a chuckle at the carb charts. The entire year if you live somewhere where water is present in gas form (aka planet Earth most places) is in the operating window of a piston airplane where induction icing is possible lol. Which is why you have to have a means to keep the carb heated full time. Lycomings of the oil sump bolted variety accomplish this in an indirect way. The rest of the float type lot? Not so much. Yous pays your monies yous takes your chances.

When I was training, we never really spent a lot of time going over the weather prior to a flight and never discussed things like temp/dew point spread and what it might mean. We looked at ceiling, visibility, and wind on the ground. In retrospect, a more complete discussion about all the 'weather crap that could kill you' might have been a good idea!

 

[Doug F]

+1.

Not to mention, the G300 has a carb temp sensor, and a readout, why can't it have an annunciator for low temp?

Yes yes 1000 time yes. The damn thing screams at you for a dozen other things why not let you know the carb is getting cold; it's just freaking software!