Cooling System Condensation


Well, flying to Oshkosh this week, I learned a lot about flight but also coming up with a lot of questions. I was fortunate to experience several different airliners to get to the show, an Embraer RJ, a Canada Air RJ (not 100% on that RJ but it wasn’t an Embraer), a 757 and an MD80. Not fond of all that plane in front of the engines on the MD80 but the landing sure is smooth. I’m noticing now that on my former favorite, the 757, it seems like the turbulance is easier to feel, but that could just be the circumstances of those flights.

My question is about the RJ (don’t remember which one it was). It’s probably totally irrelevant but it did peak my curiousity. While sitting at the gate before departure before pressurization, and during taxi, the cooling vents in the ceiling were spitting out ice crystals all over the passengers, so we essentially had light snow in the cabin. I asked the FA about this and her answer was “condensation…happens all the time.” I’ve never seen it on any of my flights. It is something that should be fixed? Or is it really common and just a little Christmas in July I’ve been missing out on?


I have seen the condensation inside cabins several times here in south MS. No ice crystals ,but more like a mist coming out of the air conditioning. It has to do with the humidity here mixing with the cool air coming out of the a/c on the plane. I flew GPT-LAS last month on Allegiant ,and that was about the worst misting I had seen inside a plane. We boarded right before it was about to rain, and you could cut the humidity with a knife. During the summer months here it is fairly common.


Hey “Neighbor”

You also see this with cars that have the AC thermostat cranked way down. First time I saw it, I thought the car had caught fire :smiley: :smiley:



I saw the same thing in an A321 on a very wet day in Phoenix.


Wet day / Phoenix in the same sentence? Wow what is this world coming to :smiley: :smiley: :smiley:


July-September is monsoon season.


Lieberma…check your PM.



It is a very common thing. I have experienced it on a flight that I was working on probably about 2 times. Never with ice crystals, but the AC vents were spitting out water. The most recent time that this occured, we handed out napkins to all the passengers and told them we would give them extra peanuts since it was inconvient to the passengers.


I’m a flight attendant and I’ve never seen ice crystals, but mist, and even dripping water is very common.


The best for this is the CRJ. The vents underneath the pilot’s windows pour out a solid stream of condensation so, for the PAX walking up to their airplane, it looks like the cockpit is on fire.


Same goes for the Challenger, (naturally).
I saw this in HPN a few weeks ago and walked over to the airplane to make sure it wasn’t smoke. It really comes out of there thick. It only happens on airplanes with air cycle machines. The Pilatus had both ACM and freon a/c. The ACM (through the Environmental Control System, ECS) would do it when it was extremely moist, but the freon A/C didnt because the A/C takes the moisture out of the air. The P180 only has freon air and it never blows condensate. The ECS in the P180 can cool the cabin air a little bit but, but only when the outside air temp is cool. It it primarily used for heating.


Happens on older Boeings a lot and usually occurs on very humid or wet days. It has an ACM and when the water separator bags get dirty it reduces their ability to handle all the moisture in the air.


Ditto if the water separator sock starts to freeze up…