View Full Version : How does blue ice leave the plane ??

Lan Ding Gere
22nd May 2001, 16:09
Hi guys, I know it may sound like a dudd question. But I understand that blue ice is the water contents with blue disinfectant that leave the plane and freeze at a high altitude.

When you push the "Flush" button in the plane toilet, you can hear a high pressured suction noise and can also feel a very strong draft. Do the contents leave the plane at that point and how or how does it leave the plane at a later stage.

ickle black box
22nd May 2001, 17:01
I don't want to be boring, but it all stays in the plane. The noise is suction from a pump, to suck the [email protected] into a tank. The tank is emptied back at the airport.

If you think about it, there is no need to jetison anything out the plane anyway. The total weight of the plane isn't going to increase by keeping the waste water onboard, also the weight of water to flush the loo(which was onboard to start with) is a fraction of the weight of fuel. Fuel's burning continually, so the weight of the aircraft is continually reducing.

Turned and Slipped
22nd May 2001, 17:20

I think this is right, it's been a while since I did aircraft systems.

Blue Ice is caused by a failure of the doughnut seals in the toilet tank to shut properly, this allows the contents of the tank to seep out of the servicing port on to the fuselage where it freezes.

The suction noise is the vacuum pump used to transfer the 'deposits' from the toilet to the tank. The tank isn't dumped overboard, it's emptied on the ground into a service truck.

'Blue Ice' isn't always Blue. On more modern aircraft with vacuum systems, the offending material is just mixed with water and not the blue chemical.

I hope that answers your question about the great 'ka ka'.


Don't sweat the petty things and don't pet the sweaty things!