Lincoln From United States of America, joined Nov 2004, 3887 posts, RR: 8 Posted (5 years 6 months 2 weeks 4 days 11 hours ago) and read 1959 times:
I was on ship 420 (flight 1045) this morning doing CLE-IAH... and aside from one of the most attractive and closest-to-my-age flight attendants I've seen working mainline (and the F cabin) the aircraft was equipped with the Live TV gear... a bit of a suprise considering the flyfo said inseat power but no IFE.
I noticed, though, that despite having an LCD display in front of every passenger a manual safety demo was done... no welcome video from Uncle Larry, not even the oxygen/seatbelt/evac stuff... but FAs standing in asiles holding seatbelts and oxygen masks.
Anyone know why? As much as I like the personal touch of the manual demo, it seems like a bit of a step backwards technologically speaking.
These questions may be better off in their own thread, but
(a) Is it possible to turn off the display besides just turning the brightness way down? I can see how a couple hours of the "Bouncing DirecTV Logo" could get a little annoying
(b) What's the purpose of the plastic bag if I shouldn't be worried that it may not inflate?
Going back SFO-CLE tomorrow, scheduled as Ship 416... I may actually use the IFE this time.
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MarkHKG From United States of America, joined Dec 2005, 960 posts, RR: 2
Reply 1, posted (5 years 6 months 2 weeks 4 days 11 hours ago) and read 1931 times:
Quoting Lincoln (Thread starter): What's the purpose of the plastic bag if I shouldn't be worried that it may not inflate?
The bag is an oxygen "concentrator". It fills up with oxygen so you can get a higher-than-normal percent of oxygen from the bag (versus from the atmosphere) when you breath it in. A one-way valve for the bag opens when you take in a breath, so you get the oxygen from the bag - but closes when you exhale. This prevent exhaled CO2 from entering the oxygen bag. There is a safety check valve that allows you to breath atmospheric air if nothing is flowing to the bag though so you'll never suffocate.
The oxygen bag does indeed inflate, albeit it is situation dependent. On some aircrafts that use a manifold system (i.e. big oxygen tanks in the hold), the flow rate to the mask is altitude controlled. (You get more flow rate at higher altitudes). But if the cabin altitude is at 14,000 feet, the flow setting on this mask is on the low end so you may not notice any inflation whatsoever. (0.5-1 lpm to the mask at 14,000 feet versus 3lpm at 35,000 feet)
On other aircraft, chemical oxygen generators are designed to generate a higher flow rate at the initial reaction, then slowly reduce the flow rate over time. This design assumes that a lot of oxygen is needed initially, but then as the aircraft descends the flow rate can be lowered. This system is not altitude controlled, it is purely a chemical reaction. So while you might see the mask inflate initially, you would notice it inflating slower or not at all as time went on. But oxygen is still flowing for the duration of the chemical reaction, which is about 12-16 minutes depending on the model.
Also when people take a breath - or breath very rapidly (which is commonplace when people are panicing from the mask drop) - they deplete the oxygen filled in bag faster than normal. So the bag may be pretty flat if they don't slow down their breathing.
The best way to see if there is oxygen flow is to look for an "in line indicator", seen on some designs of masks. On some masks this is a green bar on the bag which inflates if there is flow. On others it is a green "pop out" tag that shows oxygen is flowing.
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