Air Conditioning in a C172 or PA28?

Ted DuPuis said:
Malibus have been in production for over 30 years. Earlier ones have a much different price tag than the newer ones, and many would argue the earlier ones are better in a number of ways.

Regarding AC, the best thing to do is to get one of the ice units. That will take the edge off as you climb out, which will make cruise a lot more tolerable. One of the problems I find is that being heat soaked on the ground makes it take much longer to cool off at altitude. The 414 needs the air conditioning to work. June I flew it 40 hours and sweated about 40 gallons worth, it was just miserable even at altitude. As much as I'd love to save the 80 lbs, this is 80 lbs that's worth it.
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I am sure it's 100 times worse in a pressurized plane with out a/c.
 
I was snooping around and looking for 12 volt units (real vapor cycle air conditioner) that a guy could build one for his/her airplane, similar to the $5k one above. There are lot of different units out there for boats/rvs etc but I haven't found one that jumps out at me yet.

I'm wondering how much radio/intercom etc interference they may cause.
 
SoonerAviator said:
My understanding is that the ice (dry or otherwise) was just a heat transfer mechanism via a radiator. The air isn't being directly transferred across the bed of ice, so there shouldn't be much problem with sublimation of the CO2. I suppose it's dependent on the actual design of the cooling mechanism.



I wonder if something like antifreeze could be added in the sump system so that it would prevent the lines from freezing up. Obviously it would have to use something a bit better than general automotive antifreeze to withstand -100F, but I'm sure something exists that could work. It'd sure make for some really cold air!
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i made a closed loop w normal antifreeze. Dry ice froze it. Probably need something in between ice and dry ice. Do they make damp ice?
 
Checkout_my_Six said:
alcohol? :eek:
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It has the right thermal properties, but what are you going to make the heat exchanger out of?

Aluminum, copper, and brass all contract quite a lot with such cold. Gonna leak.

And blowing air through the heat exchanger will ice it if it's below freezing. So, it will be plenty cold, but the airflow will be zero. There is a reason a good air conditioner expansion valve is tuned to 34 deg F.
 
focal_plane said:
I was not terribly impressed with the performance after complete refurb. The air was cold but so little volume of air was provided that you were just hot. PA-28s just don't seem to flow much air through the overhead ducts (my archer without ac but with a blower is the same way). I don't have any experience with the 172.
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Yea honestly I'd probably just us one the aftermarket dc powered installations we've mentioned above.
 
Matthew K said:
Yea honestly I'd probably just us one the aftermarket dc powered installations we've mentioned above.
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Being the air condition junkie that I am, I thought those portable Freon units were pretty cool.
 
labbadabba said:
My only experience with factory air was that it didn't work that great on the ground (except during run-up) so it sort of defeated the purpose.

Once you get up to 5,500 or so it's not an issue anyway. That said, I wish CAP 182's had AC. Flying 1,000 AGL at 90kts for 2 hours makes for sweaty work. I can only imagine what those pipeline guys in Louisiana and Texas have to deal with.
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Mine blows freezing cold. Not surprisingly it depends with the installation. I'd expect 1970s GA AC to be about as poor as 1970s automotive AC while modern GA AC is competitive with a modern car.
 
Checkout_my_Six said:
maybe you weren't high enough.....? :D
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That was at altitudes up to 17k. I didn't want to take the plane into the flight levels with the horrendously awful baffling and current lack of engine monitor, especially with how hot it was. Plus at gross, its climb rate is pretty bad and it makes it hard to justify going really high, even on long trips.

Plus, as you know, you don't always want to go high. Sometimes it's better to stay lower for headwinds.

RudyP said:
Mine blows freezing cold. Not surprisingly it depends with the installation. I'd expect 1970s GA AC to be about as poor as 1970s automotive AC while modern GA AC is competitive with a modern car.
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It depends on the system and the plane. I think some of the newer planes (like Cirrus) make an effort to make the AC on par with a modern car. Also, the plane is pretty small. The 414 has a system that is more or less sized for a mid 70s Lincoln, with a much larger cabin. Not surprisingly, that makes the system less effective. However the real intent is to take the edge off on the ground, help keep things cooler in the climb, and on extremely hot days make it comfortable at cruise. The system adds 80 lbs to the plane, which it really can't afford, so if you imagine the weight to have it throwing snowballs...
 
My passengers are always wrapping up in blankets and complaining I'm freezing them out! I tell them with All the glass in the front I'm just right. At cruise I usually just turn on the blower and move air around.
 
MAKG1 said:
It has the right thermal properties, but what are you going to make the heat exchanger out of?

Aluminum, copper, and brass all contract quite a lot with such cold. Gonna leak.

And blowing air through the heat exchanger will ice it if it's below freezing. So, it will be plenty cold, but the airflow will be zero. There is a reason a good air conditioner expansion valve is tuned to 34 deg F.
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Yeah, I didn't really think about the exchanger itself icing up. I wonder how long it would take to ice up . . .
 
Ted DuPuis said:
That was at altitudes up to 17k. I didn't want to take the plane into the flight levels with the horrendously awful baffling and current lack of engine monitor, especially with how hot it was. Plus at gross, its climb rate is pretty bad and it makes it hard to justify going really high, even on long trips.

Plus, as you know, you don't always want to go high. Sometimes it's better to stay lower for headwinds.
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I like to go high even if it means burning more fuel to get up there. Besides being cooler, you're above more weather and the weather you cannot top is easier to see if you're high. Being in the teens is in my opinion often the worst altitude when there is weather because you're in it. Honestly I'd rather be lower below 10k than be in the teens trying to punch through weather.
 
Cavorter said:
I like to go high even if it means burning more fuel to get up there. Besides being cooler, you're above more weather and the weather you cannot top is easier to see if you're high. Being in the teens is in my opinion often the worst altitude when there is weather because you're in it. Honestly I'd rather be lower below 10k than be in the teens trying to punch through weather.
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Weather is highly variable, as you know, so it depends on the specifics. There are many factors involved. This summer I was routinely flying in temps that were ISA+20C or higher, in a plane that had no engine monitor, horrible baffling, and an anemic climb rate. The higher you go the hotter the engines get, too, since there is less air to cool (even though that air you do have is cooler). Add in the low climb rate etc., and the mid teens worked well and also gave a comfortable cabin altitude of ~5k, which reduced fatigue significantly on the 8-10 hour days I fly regularly.

In the ~75 hours I put on the thing this summer, there was one leg where it would've been nice to go high. There was a solid line several hundred miles long that we had to cross. In reality it wouldn't have helped without on-board radar (currently inop on the plane) as the tops of this line were into RVSM range. So we ended up going down to 6k and visually found a hole.

I'm sure this winter I'll venture into the flight levels with it and likely next summer as well. I've got the right side baffles redone (left is next), the new props will help climb rate and engine cooling significantly, the winter temps will help horsepower all around, so that'll make the climb more worthwhile.
 
I'm sorry for some reason the idea of air conditioning in a C-172 just totally cracks me up.
I get this image in my head that there would be a placard on the panel that would read something like "You can run the air conditioning or fly the plane, but not both at the same time. Refer to the POH."
 
Shepherd said:
I'm sorry for some reason the idea of air conditioning in a C-172 just totally cracks me up.
I get this image in my head that there would be a placard on the panel that would read something like "You can run the air conditioning or fly the plane, but not both at the same time. Refer to the POH."
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I remember seeing a 172 with factory AC for sale a few years ago. Seemed like it was an M or an N but not sure. Never knew it was a factory option. Don't recall the numbers but useful load took quite a hit.
 
Shepherd said:
I'm sorry for some reason the idea of air conditioning in a C-172 just totally cracks me up.
I get this image in my head that there would be a placard on the panel that would read something like "You can run the air conditioning or fly the plane, but not both at the same time. Refer to the POH."
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Stingray Don said:
I remember seeing a 172 with factory AC for sale a few years ago. Seemed like it was an M or an N but not sure. Never knew it was a factory option. Don't recall the numbers but useful load took quite a hit.
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Honestly if I or whoever were to put a/c in a 172 or pa28 they wouldn't be worried about the weight. It'd most likely be only used for 1 or 2 people and they just want comfort while having a relatively cheap plane.
 
If the PA28 is a Warrior or something similar, I'd agree with you. But I'd expect an Archer or something bigger could tolerate the extra weight, and still be a 3 person aircraft.
 
MAKG1 said:
If the PA28 is a Warrior or something similar, I'd agree with you. But I'd expect an Archer or something bigger could tolerate the extra weight, and still be a 3 person aircraft.
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I'd expect it to also be. I'm just saying the type of person who would put a/c in a base plane most likely wouldn't expect to have more than 1 passenger on most flights anyways.
 
Shepherd said:
I'm sorry for some reason the idea of air conditioning in a C-172 just totally cracks me up.
I get this image in my head that there would be a placard on the panel that would read something like "You can run the air conditioning or fly the plane, but not both at the same time. Refer to the POH."
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Actually it's in the Cessna POH but as I recall it's buried since it wasn't a popular option. The AC must be off for critical flight phases like takeoff and landing and any time maximum power is needed.

The commercially made checklist for my C-182 that's all pretty and laminated made it clear by digging it out of the back of the POH and includes it on the appropriate sections of the checklist.

Which is always a chuckle for me on a hot day with passengers as I read it, "Air Conditioner - Off ... see, you didn't know this thing even had that! Nah, not really. It was an option, but we will be cooler in a few minutes, I promise."

They did that on this checklist for all of the possible factory options. AC - Off, is right above Autopilot - Off... which ironically I *do* have, but it doesn't work worth crap... so my response for that call out to myself is... "And we'll be leaving it off because it sucks..." :)

Or sometimes in the OfficeSpace voice, "I wouldn't really call it an Autopilot, Bob... but it's off."
 
Shepherd said:
I'm sorry for some reason the idea of air conditioning in a C-172 just totally cracks me up.
I get this image in my head that there would be a placard on the panel that would read something like "You can run the air conditioning or fly the plane, but not both at the same time. Refer to the POH."
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Certainly true for an O-300 powered variant (or maybe even an O-320), but a 180 HP 172 like the one I learned to fly in, it'd be just fine.

Stingray Don said:
I remember seeing a 172 with factory AC for sale a few years ago. Seemed like it was an M or an N but not sure. Never knew it was a factory option. Don't recall the numbers but useful load took quite a hit.
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The system in the 414 is around 80 lbs. There's not a whole lot you can shrink in 1970s tech for the 172, so I imagine it'd still be around 80 lbs. Honestly, I'd be more concerned about the useful load hit in the 414 since there you're talking OEI performance issues.

The PA-28-181 I did my instrument rating in (and flew around 130 hours total) had a place on the panel for the factory AC switch. It was not so equipped. Personally, I don't think a 172 or PA28 needs air conditioning unless you operate in a particularly hot climate (Texas, etc.).
 
Love the factory a/c in our arrow, even though it adds between 60- 80# as stated before, I haven't looked at the poh recently to see the actual weigh. But the a/c works great on the ground, especially during longer taxis.
 
My Pa-28 had air when new. Gone now, gained almost 70 lbs. I believe, in useful load and you had to turn off for take off.
 
I built my own from a cooler, Home Depot 4" pvc elbow, a Walmart 12v fan and 7 blue ice plastic re-freezable doohickies. The fan can be powered by the cigarette lighter but I bought a 12v lawnmower battery at Walmart to power it - all for about $60.

It doesn't freeze anyone out but it knocks the heat down quite a bit and only weighs about 30 pounds including the battery.
 
Timbeck2 said:
I built my own from a cooler, Home Depot 4" pvc elbow, a Walmart 12v fan and 7 blue ice plastic re-freezable doohickies. The fan can be powered by the cigarette lighter but I bought a 12v lawnmower battery at Walmart to power it - all for about $60.

It doesn't freeze anyone out but it knocks the heat down quite a bit and only weighs about 30 pounds including the battery.
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Why didn't you by a deep cycle battery? Would put out power for much longer.
 
Spotter626 said:
My Pa-28 had air when new. Gone now, gained almost 70 lbs. I believe, in useful load and you had to turn off for take off.
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I just looked ours up yesterday. 68.6 lbs. And yes, off for takeoff, but you could turn it on in the climb if you wanted to.
 
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