Re: Aircraft Toilets

From:         geohull@ditell.com (George Hull)
Organization: DirecTell L.C. - Park City, UT. - 1.801.647.0214
Date:         02 May 95 13:27:43 
References:   1
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In article <airliners.1995.509@ohare.Chicago.COM>, Neil Harding
<neil.harding@hertford.oxford.ac.uk> wrote:

> My girlfriend does not believe me when I tell her that certain older,
> currently flying airliners deposit their sanitary waste out of the back
> of the aircraft during flight. Which leads to the phenomenon known as
> 'blue ice'.
>
> Please could someone inform me of types of aircraft which do this, as
> this matter is currently forming a bet for a dinner!

I know of no modern airliners which allow sanitary waste to be dumped
overboard.  All of the airliners with which I am familiar store that waste
in storage tanks which are serviced on the ground.  The only vents that I
know of are for the sink drains.  Those vents are heated so that any
liquid which flows from them will not become an ice formation at the drain
itself and subsequently come loose as solid ice.

Blue ice is created when the seals at the lavatory service recepticles do
not work correctly and some of the "blue fluid" is allowed to escape past
the seal.  The buildup of such "blue ice" is considered very undesirable
for a couple of reasons.  On some aircraft (B-727 particularly) the lav
service area is forward of the right wing.  If the seal leaks and ice
accumulates it can eventually break loose and flow over the wing and into
the right pod-mounted engine.  There have been instances in which the ice
has actually caused that engine to separate from the fuselage and fall to
the ground (fast-turning engine encounters large ice chunk and tries to
stop . . centrifugal force of turning parts causes bolts to fail as they
are designed to do and engine leaves the airframe).  Sometimes you can see
the path that this ice would take if you look at the right side of a 727
where streaks of blue fluid sometimes take the path of the airflow over
the wing.

So, the short version of that story is that there "should" be no blue ice
falling from the sky . . but it happens.

I'm sorry if this causes you to have to take your girlfriend out for
dinner . . perhaps others have different information to share so you can
get her to take you.

George