UA840 venting something from rear of aircraft over Bankstown

[Lee G]

I just happened to be watching outside when UA840 YMML - YSSY went overhead Bankstown at about 7000ft. It was venting something from the right hand rear of the aircraft forward to the Horizontal Stabiliser.

My immediate thought was APU however it went on for a considerable time.

Does anyone have any idea what this might have been?

[Tony P]

Someone flushed the dunny.

[Lee G]

Yup thought of that one too ... then decided the thought was too grose! ...( photo taken while holding umbrella and looking for UFO's )

[Tony P]

Well it is flying over Bankstown. No one would know the difference!!

[NickN]

I have seen the same thing from a Hawaiian 767 overhead the control tower at YSSY as it was joining a left downwind leg for a 16R arrival. Would have been lower than 7000ft though. Would like to know what it is.... Maybe dumping any extra potable water prior to landing?

[Raymond Rowe]

More than likely someone pouring something out of the rear galley.

[Stephen B]

I thought aircraft couldn't dump anything overboard (especially untreated effluent) except in case of emergency. And do they even have the ability to dump anything in that way aside from fuel?

[David Knudsen]

I believe the sinks in the lavs/galleys flow directly outside? A former Ansett engineer once told me that the big brown stain under most 737's was from leftover coffee going down the drain

[Brian Wilkes]

Plasma matter from the warp core?

[Mike Scott]

F/A grey matter (hair or hair colouring ) coming from the rear jumpseat !!!!