Ask Captain Dan: Our Resident Pilot Answers Flight Questions. January 23, 2012

CFN – Pilot Dan Baz is answering your flying questions here on the Cornwall Free News.

If you have a question about flying you can email Captain Dan or post below.


What happens to the waste from toilets and sinks ?Question asked by Christopher


Some say that as the flight progresses and everybody gets rid of their waste, the airplane gets lighter and flies faster. That is not really true. But here is what happens.
The waste water from washrooms and liquids  from galley sinks drain overboard. These liquids exit  through drain masts on the bottom of the airplane. The drain masts extend approximately 10 to15 cm’s below the skin of the fuselage.  The liquids evaporate or almost instantly turn to ice crystals, depending on the outside air temperature. The air temperature at airplane cruising altitudes can be as low as minus 70 degrees Celsius. To prevent these liquids from freezing onto the drain masts, the masts are electrically heated.
Waste from the toilets goes to holding tanks in the airplane. Some airplanes have a small tank for each toilet.  Most newer airplanes have two large holding tanks and vacuum pumps.  The waste from the toilets is drawn into the tanks by vacuum.  That is why you hear that whoooosh sound when the toilet is flushed. The tanks are emptied  on the ground into a tank on a truck. The airplane holding tanks are then flushed with clean water and a  pre-charge of small amount of sanitizing liquid is introduced into the tanks.  The truck will then dispose of the waste in a proper and sanitary manner.


A bit more about Captain Dan:

Captain Dan Baz enrolled in Flight School at the age of 16.

He has completed studies in Aircraft Engineering and Master of Business Administration. He has been at the controls of many different types of aircraft, from single engine Cessnas to large intercontinental jets on global routes.

Over the last four decades he has flown thousands of hours up in the blue sky.

Have a question for the Captain ?  Send it to Captain Dan Baz Every week a question from the readers will be selected and answer posted in this column.

Best Western Cornwall

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