21 minutes ago, jspilot said:

That heat knob is for cabin heat.  That system works by sucking some air from the engine compartment and pumping that back into the cabin.  In real life you really have to be careful using cabin heat in a 152 or 172 to avoid carbon monoxide poisoning.  That’s why most single engine piston planes that rely on this system for heating have a CO2 indicator stuck on a window somewhere to notify if the CO2 levels rise within the cabin.

Technically speaking it  takes ram air outside engine. To be specific via wings inlets. Then air passes to through the shroud over exhaust pipe and heated. 

I have never see CO2 indicator stuck on window, mostly on panel upholstery. But those sticky CO2 indicators are utterly useless as they warn pilot too late - after carbon monoxide poisoning already happens. The way around it is to by electric expensive CO2 detector. But they are expensive and have to be changed ever so often..

Then there is de-icing fluid ...

Edited October 27, 20205 yr by Glenn Fitzpatrick

13 minutes ago, Glenn Fitzpatrick said:

Then there is de-icing fluid ...

Yes and also pneumatic boots, bleed air heated and etc But none of those in 172 !

If you hit icing in a 172 at cruise, your service ceiling is probably lower than the 3,000 feet you need to get higher into clear skies.

Descend below freezing level or do a 180.

Funny enough, I was coming to the forum to ask exactly the same question after being surprised by ice accumulation on windows during a flight last night in a C172.

I guess it's not a coincidence: temps have been dropping in the Great White North over the last few days 😉

The key is proper flight planning, especially if planning to fly IFR or in and out of IFR conditions.  If using live weather, or one of the few live weather mods, you can check for icing conditions at sites such as Windy.com (see below).  In this example I have selected the Temperature map depiction (black arrow near the upper right).  Then adjusted the altitude slider (middle black arrow) to various altitudes and let the map refresh; and then used the color bar (lowest black arrow) to evaluate where icing is likely at the chosen altitude.  Looking for any shade of blue on that map.  This is the USA depiction right now at 3,000 ft.  A green perimeter around blue, such as you can see around west Texas, would clearly be marginal as well.

6 hours ago, sd_flyer said:

Technically speaking it  takes ram air outside engine. To be specific via wings inlets. Then air passes to through the shroud over exhaust pipe and heated. 

I have never see CO2 indicator stuck on window, mostly on panel upholstery. But those sticky CO2 indicators are utterly useless as they warn pilot too late - after carbon monoxide poisoning already happens. The way around it is to by electric expensive CO2 detector. But they are expensive and have to be changed ever so often..

Right-  good point about not being stuck to the windows.  I’ve flown probably 500 hours in mostly 172’s and now that I’m thinking about it you are right.  Almost all were mounted on the panel somewhere.

Your point about them being useless is a good one.  That’s why I said in real life the cabin heat is used pretty sparingly( at least I don’t use it often.) Id rather be a bit chilly then die of Carbon Monoxide poisoning but to each his own I guess!

 

I saw your other response about the different types of icing.  I hear what you are saying and totally understand but sometimes I try and just keep explanations in laymen’s terms so everyone reading it can understand.  Your explanation is much more of what would be expected for a PPL oral exam! No knock at all— still trying to figure out how this board operates!

8 minutes ago, jspilot said:

Right-  good point about not being stuck to the windows.  I’ve flown probably 500 hours in mostly 172’s and now that I’m thinking about it you are right.  Almost all were mounted on the panel somewhere.

Your point about them being useless is a good one.  That’s why I said in real life the cabin heat is used pretty sparingly( at least I don’t use it often.) Id rather be a bit chilly then die of Carbon Monoxide poisoning but to each his own I guess!

 

I saw your other response about the different types of icing.  I hear what you are saying and totally understand but sometimes I try and just keep explanations in laymen’s terms so everyone reading it can understand.  Your explanation is much more of what would be expected for a PPL oral exam! No knock at all— still trying to figure out how this board operates!

Yes I hear you. I rarely use cabin heater. But I also fly in Southern California which doesn't have cold winter, so it sound like a cheat! LOL

1 hour ago, sd_flyer said:

Yes I hear you. I rarely use cabin heater. But I also fly in Southern California which doesn't have cold winter, so it sound like a cheat! LOL

The cabin heat in a 1972 Cherokee is like having an asthmatic breathe on you anyway. I always have a CO2 detector (one of the sticky ones) on the panel - are they no good? I don’t mind spending a bit of money. I have a pulse oximeter as well, for example. 

8 hours ago, sd_flyer said:

 

Before it gets messy. There are two type of equipment anti-icing and de-icing. Anti-icing is turned on before icing condition as preventive measure. While de-icing is turned to remove icing that start forming.

Among icing there are types  induction and structural. Carb heat is to prevent induction icing

Pito heat, prop heat, windshield heat are anti-icing equipment 

Wouldn’t pitot heat and windshield deice be both actually? The both prevent and remove ice. Not that the distinction really matters...

Just now, mtr75 said:

The cabin heat in a 1972 Cherokee is like having an asthmatic breathe on you anyway. I always have a CO2 detector (one of the sticky ones) on the panel - are they no good? I don’t mind spending a bit of money. I have a pulse oximeter as well, for example. 

Yes I went to seminars five years ago where they show cased by the time paper indicator show CO2 pilot will be impaired. I'm using electronic one Sentry

3 hours ago, sd_flyer said:

Yes I went to seminars five years ago where they show cased by the time paper indicator show CO2 pilot will be impaired. I'm using electronic one Sentry

Thanks for the tip!

6 minutes ago, mtr75 said:

Thanks for the tip!

It's not entirely just CO2 it's add on for Foreflight  ADS-B IN and +CO2 detector

https://foreflight.com/support/sentry/

12 hours ago, sd_flyer said:

Technically speaking it  takes ram air outside engine. To be specific via wings inlets. Then air passes to through the shroud over exhaust pipe and heated. 

I have never see CO2 indicator stuck on window, mostly on panel upholstery. But those sticky CO2 indicators are utterly useless as they warn pilot too late - after carbon monoxide poisoning already happens. The way around it is to by electric expensive CO2 detector. But they are expensive and have to be changed ever so often..

In the real world, do most GA pilots typically avoid using cabin heat for this reason (CO poisoning risk)?

1 hour ago, Mace said:

In the real world, do most GA pilots typically avoid using cabin heat for this reason (CO poisoning risk)?

I think it is possibility but not the end result. Pilots usually mitigate risk with all known safety approaches. I personally don't use heater because I don't really need when I fly. But somewhere up north it's not a an option.