777 cabin airflow system?

[Juud]

Flight attendant question.

On the 747, on the rare occasion there is a feeling that a bit more 'fresh' air would be good, asking the pilots for help often results in the friendly mentioning of 'packs' , some fiddling with same and a perceived positive result.

On the rather more frequent occasions that pax or crew feel that a bit more 'fresh' air would do wonders on a 777, asking the pilots for help most often results in an irritable reaction along the lines of "Oh, somebody´s imagining that they´re feeling faint? Shouldn´t believe everything you read. Nothing we can do about it anyway. No we got no packs. Just make it cooler in the cabin."
Some-happy-times though, there is mention of "recirc fans" and possible fiddling with those doing some good.


does switching off the recirc fans increase the amount of 'fresh air' in the 777 cabin? Or have I misunderstood the whole thing?


Or is it a case of nothing helps on a 777 anyway, and the pilots mentioning recirc fans are just being nice caps/chapesses and trying to make us feel 'listened to'? (appreciated in and by itself!)

T is puzzling for a coffee pourer like me that after so many years of the 777 being in service, I still get pax passing out on the triple more often than on any other type. It´s equally puzzling that the mere mention of air irritates the cr@p out of many of our triple pilots.

I´d like to properly understand the airflow of the 777.
I don´t want to irritate the pilots by asking for the impossible.
Equally, if there is anything that can be done to improve matters when the FAs start getting headaches and the pax start fainting, that´d be good to know.

Thank you in advance for any and all light that may be shed on this. :)

[seat 0A]

Hi Juud,

From the 777 FCOM 2:

When one or both RECIR FANS switches are OFF, the packs operate at full flow, the cabin air exchange rate is increased, and fuel consumption increases 0.7% for each fan switch OFF.


So there is an option to increase airflow.

There are several reasons not to do this (and perhaps causing irritation towards the asking party?)

- Fuel flow increases quite a bit
- Several investigations have shown that air quality in the 777 is not any different from other airplanes and cannot cause fainting
- in an ETOPS aircraft with only 2 packs you might not want to put them in unnecessary high flow mode with the accompanying higher stresses involved.
- generally speaking in present day hightech aircraft is not a good idea to use selfinvented procedures. There might be other consequences that are not mentioned in the FCOM. As pilots we only know very little about system behaviour outside of recommended procedures. Best to stay away from fiddling with the systems ouside the SOP's when not necessary to overcome bad situations........

Hope this helps. Would love to fly again with you one of these days......
See you around.

[Juud]

Hi there 0A :) thanks for taking the time.
At least when we fly together, I won´t ask you for more air after this. ;)


Now understand better the difference between the 2 types re air flow management. A step forward for me.
Also at least partly explains why I often get the testy reactions from 777 pilots to a question, however diplomatically phrased, about airflow.


You say that there is a, for various understandable reasons undesirable, option to increase the airflow also on the triple.


Switching off the recirc fans; does that mean that rather than being partially recirculated, all the air that flows into the cabin is then 'fresh' (bleed?) air?

And would you or anybody else happen to know the difference in O2 % in the cabin air with both recirc fans on and both of them off? Or is that kind of information not available?


I don´t mean to nitpick, just want to completely understand all the issues.
Makes it easier to deal with stuff when you understand the backgrounds and reasons.

[seat 0A]

Hi,

Well, the testy reactions are ofcourse uncalled for. Especially when the question is being asked diplomatically. (it's different when you're being told to switch on the oxygen switch..:ugh: )

The answer to your first question is "Yes".
The answer to your second question is to my best knowledge unavailable.

Regarding the 2 types of airflow management. There is only 1 type of airflow management on the 777. That's the one with recirculation fans on.
The reason the packs have two modes of operation is to compensate in the event of a system failure in one of the components that prevents the normal use of system number 1 :)