Flushing toilet in a 747-400

[mingalababya]

I'm not sure where to post this question but thought this forum might be appropriate. Anyway, I was in a 747-400 recently and despite the notice to close the lid before flushing the toilet, I thought I'd be a bit daring and leave the lid open to see what happens. I've flushed a toilet in a 747-400 many times before not knowing whether it was suction that drew the stuff away or whether it was flushed like a conventional toilet on the ground. So, after flushing with the lid open, I was able to observe exactly what was happening and notice a fair degree of suction although not as much as what I was expecting. To my disappointment (I was expecting 100% suction and 0% water), some water did trickle down the side of the bowl, to wash away any stragglers that refused to go due to suction action .

Why I assumed 100% suction? Well, so that the aircraft doesn't need to carry much water for toilet flushing action thereby minimising its weight. Afterall, carrying extra weight for toilet flushing would penalise its payload and fuel. So, can someone from the airline industry specialised in toilet flushing please confirm this observation, and also provide some indication as to how much suction force is used in flushing the toilet of 747-400 series aircraft?

[Biggles' Apprentice]

MIng

747 loos are just bog standard for the industry.

[Jet II]

Potable water is used to rinse around the bowl - as for how much suction, well in flight it is whatever the pressure difference between the cabin altitude and aircraft altitude is - usually aroud 7-8 psi.

[Rainboe]

The 400 ones seems to have a stronger suction flush than the 737 loos. There is this enormous wet sucking noise when you can feel air being drawn into the compartment from every point and blowing over you in its hurry to go down that hole. The flight deck toilet seems particularly strong- I used to think it wouldn't surprise me at all if one day when it flushed, the whole compartment, including toilet, would fly out of the side of the aeroplane! The 737 is tame in comparison.

[Jet II]

are there any other aircraft types with windows in loos?

newer A330's

[oncemorealoft]

Mr Fogg

First Class BA B747s!

[WHBM]

The old 748 (the real one from BAe, not the new one coming from Boeing) had not just a window but the emergency exit door in the WC compartment (rear right), behind the toilet unit, complete with a small ladder if I remember correctly (it's been a few years). It must have been a hoot doing an emergency disembarkation in one of those !

[Phileas Fogg]

The old, the real, 748 came from Avro, no such thing as BAe in those days and what did they construct, the ATP :yuk: , the 748 came from the same stable as the Lancaster, the Shackleton and the Vulcan. Didn't appreciate it had a window in the loo though

[Golf Charlie Charlie]

Am pretty sure some MD-80s and maybe MD-90s also have a window in the lavatory.

[Capt Claret]

as for how much suction, well in flight it is whatever the pressure difference between the cabin altitude and aircraft altitude is - usually aroud 7-8 psi.

Now I have to wonder. When the aircraft's on the ground, doors open, pressure diff of zero; how does the dunny flush?

[gas path]

...Vacuum blower that operates upto around 15k feet when cabin diff is good enough to shift even the stiffest of turds:uhoh:

[derekl]

The old 748 (the real one from BAe, not the new one coming from Boeing) had not just a window but the emergency exit door in the WC compartment (rear right), behind the toilet unit, complete with a small ladder if I remember correctly (it's been a few years). It must have been a hoot doing an emergency disembarkation in one of those !

Er, don't you mean an emergency evacuation:}

[Bolty McBolt]

744 toilets.

I have seen a good trick. On a night flight and you have access to toilets close to the front of the aircraft or better still the upper deck.
Grab a cup full of ice and flush them. The cubes rattling down the pipes reaching sonic speeds in the quiet of the night puts many a puzzled face on pax trying to work out what caused the strange noise

:=

[carro]

Just wondering, where does the waste go? Are there septic tanks or does it get sucked out to land on some indian farmer??

[Bolty McBolt]

Carro
That question is to silly to answer :ok:

[Capt Claret]

Carro,

In really old aeroplanes - into a holding tank, usually located immediately under the toilet seat. The tank is lifted out and emptied by cleaning personel.
In old aeroplanes - into a holding tank, again susally under the seat but plumbed to an external drain so that the honey cart (so named because of the not so pleasant odour that wafts about it) can connect and empty the tank. In installations with forward and aft lavs, the honey cart would have to connect to multiple drains.
In modern aeroplanes - vacuum system draws all waste into a central tank, meaning the honey cart need only connect at one point to service the lavs.

[tu154]

The loo on a Saab 2000 is best, it has a window in the loo thus one can have a sit down and look out of the window at the same time, are there any other aircraft types with windows in loos?

The Tu 134 loo has a nice little porthole looking upwards.
Also liked the nice touch at the emergency exits. In case of emergency, use escape rope! :E

[carro]

Hey Bolty,

Yeah, silly it was.. as was intended!! lol But honestly think of the weight saving!!! and the poor Indian farmer:eek:

[spekesoftly]

One hopes that all these aircraft loo windows are frosted or fitted with blinds? :p

[mingalababya]

Carro,

In old aeroplanes - into a holding tank, again susally under the seat but plumbed to an external drain so that the honey cart (so named because of the not so pleasant odour that wafts about it) can connect and empty the tank. In installations with forward and aft lavs, the honey cart would have to connect to multiple drains.


Capt Claret, thanks for the info .. interesting stuff. I remember as a young boy waiting for a flight in Denpasar, I saw a Garuda DC9 emptying its tanks, but without the honey cart .. they just let it all drop on to the tarmac. hehehe ..

Thanks all for the interesting accounts of various loos in different aircraft. I would love to occupy a loo with a window... you probably wouldn't get me out of there in a hurry either. I guess it gives another meaning to the term "business class". ;)

Anyone know if pilots need to know the workings of the sewage system on aircaft as apart of their type ratings? (I'm serious ...) :O

[A2QFI]

A point raised by David Gunston in his humorous monlogue "What goes up must Come Down"

[tom775257]

<<Anyone know if pilots need to know the workings of the sewage system on aircaft as apart of their type ratings? (I'm serious ...)>>

Well not at least on the A320 it certainly wasn't of any note, however I did read a little about it at the back of the manual (FCOM1), certainly I wasn't tested on it!

[helopat]

Can't believe nobody has asked...does the water swirl clockwise or counterclockwise:confused:

[stilton]

I miss the old chemical toilets.

I don't need any more noise and violence in such a small space!

[JediDude]

Can't believe nobody has asked...does the water swirl clockwise or counterclockwise:confused:

Depends on the shape of the bowl. Don't believe that Northern/Southern hemisphere crap, it's an urban myth.

[NoRedPortLeft]

Depends on the shape of the bowl. Don't believe that Northern/Southern hemisphere crap, it's an urban myth.


Just as I suspected all along! The Earth really is flat!!:p

[Bolty McBolt]

Depends on the shape of the bowl. Don't believe that Northern/Southern hemisphere crap, it's an urban myth.


Are we saying that the "coreolus" effect does not exist...

Dam it. I wasted so much time learning how IRS/INS systems worked only to find now the world is flat :ok:

[Tod]

(In modern aeroplanes - vacuum system draws all waste into a central tank,

On the 744 it goes into four tanks at the aft end of the plane.
Two are 85 gallons and the other two are 65 gallons.

Tod

[FLCH-SPD]

Wow, do the loos really use cabin pressure to create suction???

I'll keep my flushing brief next time, wouldn't want to depressurize the cabin! :bored:

[Swedish Steve]

I'll keep my flushing brief next time, wouldn't want to depressurize the cabin! :bored:
The flushing time is controlled by a timer. You have no control.

Also, when an aircraft has more than one tank (B767 2 tanks, B777 3 tanks, B744 4 tanks) each tank is treated as a separate system. A set of toilets feed one tank. If this tank is full these toilets will stop working, but others connected to a different tank will continue to function.

[g10]

Why? In case a birdy sees your birdy? :p :)

Or possibly to prevent engineers carrying out unwanted crack inspections :)

[ONE GREEN AND HOPING]

[quote=tom775257;2857749]<<Anyone know if pilots need to know the workings of the sewage system on aircaft as apart of their type ratings? (I'm serious ...)>>


Don't recall ever being required to know much about latrine plumbing for type ratings. However, as a callow youth, I was thrillingly dispatched to Seattle for a conversion course on the 707. I have long since forgotten the limitations on load shuffle tolerance and max weight mid section over the centre tank, but annoyingly remember quite clearly being told all about the pretty blue fluid, and that all matter was reduced to 400 microns by some hideous unseen mashing unit. ( straying momentarily from the thread, soft slippers were issued before being allowed a look-see on the first production 747 )

Also did the 747-400 course around the time we were picking the first ones up new from the shop. I guess there was the standard three tape and slide stuff on each system, but although I remember there being something about the engines, there was nothing much on bogs. Since, in the early stages they were often packing up, and there was no latrine tab in the ' Abnormals ', we rapidly became entirely self taught..........hence the discovery of the sensor degreasing action of a bucket full of ice cubes into the cockpit or upper deck lavatories, and the puzzled reaction from below stairs as the cubes rattled at an alarming rate towards the collection tanks at the rear end. Bearing in mind that the pneumatic system was a novelty for most in my airline at that time, it was ( so I'm told ) a popular demonstration to bowl a toilet roll down the cabin so that it was undone to its full length, then someone would hit the button, whereupon it would vanish with astonishing speed into the cubicle accompanied by a certain amount of clapping and cheering from the audience.

Finally........... a moments silence for all those heroes who over the years have been caught under a misfunctioning gate valve at the wrong moment, and sacrificed their freshness for the convenience of others.......

[Tod]

747-400 . . . . .hence the discovery of the sensor degreasing action of a bucket full of ice cubes into the cockpit or upper deck lavatories, and the puzzled reaction from below stairs as the cubes rattled at an alarming rate towards the collection tanks at the rear end.

Although it is not nearly as fun (or noisy), you can accomplish the same corrective action by dumping the ice in the aftmost lav connected to the tank in question.



Finally........... a moments silence for all those heroes who over the years have been caught under a misfunctioning gate valve at the wrong moment, and sacrificed their freshness for the convenience of others.......

Always be respectful of the man with the blue stains on his raincoat.:eek:

Tod

[ulflarsson]

There is another way to check the suction, this is a classic so I guess some of you have allready tried this: :}

Take a roll of toilet paper and put one end in the toilet and place the center hole of the toilet paper around your index finger and flush. Half of the roll will dissapear in seconds.

Not good for the airlines toilet budget but a lot of fun on long flights :O