Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Loss Of Cabin Pressure, Why No Masks?  
User currently offlineBoston92 From United States of America, joined Aug 2006, 3390 posts, RR: 7
Posted (7 years 3 months 3 weeks 18 hours ago) and read 5761 times:

I am sorry if the title is misleading, but on a recent flight from JFK-PVD on Delta Connection while on the ground, we lost cabin pressure because the baggage people opened the hatch after we were all ready to go. Our ears sure did feel it. Why was there no masks? Do we have to be over 8000 feet for the masks to fall? Why were we even pressurized if we were not over FL 080?


"Why does a slight tax increase cost you $200 and a substantial tax cut save you 30 cents?"
51 replies: All unread, showing first 25:
 
User currently offlineShamrock350 From Ireland, joined Mar 2005, 6321 posts, RR: 14
Reply 1, posted (7 years 3 months 3 weeks 17 hours ago) and read 5731 times:

Aircraft pressurise when the door shuts but I dont think masks drop unless you are at altitude because there is no loss of oxygen.
I could be wrong on that but I do think aircraft pressurise when the door shuts, it's automatic.


User currently offlineRichardPrice From , joined Dec 1969, posts, RR:
Reply 2, posted (7 years 3 months 3 weeks 17 hours ago) and read 5709 times:

As Shamrock350 alluded to, theres no point in dropping an additional oxygen system if theres no requirement for it - all it would result in is additional cost to the airline to make the systems safe again and delay the aircraft while that was done.

User currently offlineAvt007 From Canada, joined Jul 2000, 2132 posts, RR: 5
Reply 3, posted (7 years 3 months 3 weeks 17 hours ago) and read 5710 times:

Typically, an aircraft will pressurize to 50 feet or so when the doors are closed, engines running, on the ground, to help the system maintain a nice smooth transition to flight. It's not a sudden change in pressure that drops the mask, it needs to be above a certain cabin altitude, somewhere around 10,000 feet. What type aircraft? If it was a CRJ, the o2 masks fall at 14,000 feet cabin altitude.

[Edited 2007-04-04 23:05:11]

User currently offlineAlias1024 From United States of America, joined Oct 2004, 2744 posts, RR: 2
Reply 4, posted (7 years 3 months 3 weeks 17 hours ago) and read 5696 times:

Dash 8s don't have oxygen masks for passengers. I'm guessing that is what you were on since that is what is shown when I search JFK-PVD on delta.com.


It is a mistake to think you can solve any major problems with just potatoes.
User currently offlineAvt007 From Canada, joined Jul 2000, 2132 posts, RR: 5
Reply 5, posted (7 years 3 months 3 weeks 17 hours ago) and read 5693 times:

Indeed, Alias is right. The Dash has a ceiling of 25,000 feet, and so doesn't require oxygen for the pax.

User currently offlineSkyexRamper From , joined Dec 1969, posts, RR:
Reply 6, posted (7 years 3 months 3 weeks 17 hours ago) and read 5660 times:

Quoting Boston92 (Thread starter):
while on the ground

Well thats your reason in any pressurized aircraft with overhead masks. Also the crews can elect to drop the masks but would not below 10,000 because the body will be fine with thinner air. And well passengers don't need to have O2 provided to them unless the cabin altitude is 14,000ft or higher. FAA doesn't care about passengers as long as they are a live and sleeping.  Wink Big grin


User currently offlineBoston92 From United States of America, joined Aug 2006, 3390 posts, RR: 7
Reply 7, posted (7 years 3 months 3 weeks 16 hours ago) and read 5504 times:

Quoting Alias1024 (Reply 4):
Dash 8s don't have oxygen masks for passengers.

Well that explains everything. But I doubt we were pressurized to 50 feet because I dont think I would have felt it that much. Plus, JFK is somewhere around 50 feet in elevation, right?



"Why does a slight tax increase cost you $200 and a substantial tax cut save you 30 cents?"
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 24
Reply 8, posted (7 years 3 months 3 weeks 14 hours ago) and read 5452 times:

Most modern aircraft will automatically pre-pressurise to 50-100 feet below field elevation on the ground. So if the field is 50 feet above sea level, the cabin altitude will be at around sea level or slightly lower. On some types this doesn't happen until the throttles are advanced for takeoff for just this kind of reason. However, even with the outflow valves fully open, with packs on and doors closed a small pressure differential can exist.

Suddenly releasing even a small cabin differential pressure could be noticeable as your ears are very sensitive. If the pressure difference was released slowly you wouldn't feel it.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineBoston92 From United States of America, joined Aug 2006, 3390 posts, RR: 7
Reply 9, posted (7 years 3 months 3 weeks 14 hours ago) and read 5442 times:

Quoting Jetlagged (Reply 8):

All right thanks. BTW, did somebody steal somebody elses signature or is just a very rare coincidence?????



"Why does a slight tax increase cost you $200 and a substantial tax cut save you 30 cents?"
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 24
Reply 10, posted (7 years 3 months 3 weeks 13 hours ago) and read 5429 times:

Quoting Boston92 (Reply 9):
BTW, did somebody steal somebody elses signature or is just a very rare coincidence?????

Coincidence, I hope  Smile



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineANITIX87 From United States of America, joined Mar 2005, 3299 posts, RR: 13
Reply 11, posted (7 years 3 months 3 weeks 11 hours ago) and read 5380 times:
Support Airliners.net - become a First Class Member!

Quoting RichardPrice (Reply 2):
all it would result in is additional cost to the airline to make the systems safe again

What does this consist of? One time we landed in ATH so hard (TWA800, 742) that the masks came out of their housings. What would the crew have had to do? I don't know if the return flight left on time or not, but it was quite a weird landing.

TIS



www.stellaryear.com: Canon EOS 50D, Canon EOS 5DMkII, Sigma 50mm 1.4, Canon 24-70 2.8L II, Canon 100mm 2.8L, Canon 100-4
User currently offlineBoston92 From United States of America, joined Aug 2006, 3390 posts, RR: 7
Reply 12, posted (7 years 3 months 3 weeks 11 hours ago) and read 5370 times:

Quoting ANITIX87 (Reply 11):

It is like when airbags deploy on your car, if they do, you need to take it tnto the mechanic, you can not just 'put it back in'.



"Why does a slight tax increase cost you $200 and a substantial tax cut save you 30 cents?"
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 24
Reply 13, posted (7 years 3 months 3 weeks 10 hours ago) and read 5360 times:

Quoting Boston92 (Reply 12):
It is like when airbags deploy on your car, if they do, you need to take it tnto the mechanic, you can not just 'put it back in'.

Not quite the same. Airbags aren't reusable and must be replaced whereas oxygen masks simply need to be restowed. Time consuming nevertheless, especially on something the size of a 747-200.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineMarkHKG From United States of America, joined Dec 2005, 960 posts, RR: 2
Reply 14, posted (7 years 3 months 3 weeks 9 hours ago) and read 5343 times:

Quoting Jetlagged (Reply 13):
whereas oxygen masks simply need to be restowed.

Unless the oxygen mask is a chemical oxygen generator system, which requires each individual generator that was fired to be replaced.

Quoting Boston92 (Thread starter):
Do we have to be over 8000 feet for the masks to fall?



Quoting Avt007 (Reply 3):
If it was a CRJ, the o2 masks fall at 14,000 feet cabin altitude.

As noted, most commercial aircraft only have drop-down masks activate at around 14,000 feet. The decompression announcement starts (if installed) and cabin lights go to to bright (if selected as an option) as well.

"DON MASK, FASTEN SEAT BELT!"  Smile



Release your seat-belts and get out! Leave everything!
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 24
Reply 15, posted (7 years 3 months 3 weeks 2 hours ago) and read 5260 times:

Quoting MarkHKG (Reply 14):
Unless the oxygen mask is a chemical oxygen generator system, which requires each individual generator that was fired to be replaced

Of course, but I was think of the case mentioned where the masks deployed in a hard landing, so presumably no oxygen flow occurred (the system would not be armed).



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 16991 posts, RR: 67
Reply 16, posted (7 years 3 months 3 weeks 1 hour ago) and read 5253 times:

Quoting Jetlagged (Reply 13):
Airbags aren't reusable and must be replaced whereas oxygen masks simply need to be restowed.

You mean I could be wearing a used mask? Not that it isn't better than passing out, but eeeeww.  Wink

[Edited 2007-04-05 15:16:36]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineKdm From New Zealand, joined Feb 2006, 115 posts, RR: 0
Reply 17, posted (7 years 3 months 3 weeks 1 hour ago) and read 5243 times:

I have this theory about face masks which it would be nice to know if it rings true.

At 30,000 feet if the plane has a huge problem and takes a sudden dive (like a bit of the fuselage falls off) we have complete loss in cabin pressure I have two choice. 1. take oxygen 2. don't bother.

Theory 1) If the plane depressurises and I need a mask there is a serious problem. I take the mask breath nice chemically produced air, Pilot drops the plane to 10,000 feet. I have now used up my 2 minutes of oxygen but no problem I can now breath. Plane either lands safely so fine, or crashes and a die living and breathing the last 10,000 feet wishing I had passed out.

Theory 2) Plane depressurises, I don't bother taking oxygen. I pass out. either the plane crashes, I don't care as I have passed out or once the plane gets to 10,000 feet I now have enough oxygen to breath so I regain consciousness the pilot has got the plane under control so all is OK.

I prefer option 2. Have I got this wrong.


User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 18, posted (7 years 3 months 3 weeks 1 hour ago) and read 5243 times:

Quoting Boston92 (Thread starter):
Do we have to be over 8000 feet for the masks to fall? Why were we even pressurized if we were not over FL 080

Most Aircraft for eg the B737 have an Air - Grd selector sw on the CPC panel that is moved to Flt after all doors are closed to prepressurise the Aircraft.This could be 150-200ft below runway elevation.Hence when the cargo door was opened the Pressure loss was felt.
However for the O2 masks to drop.Cabin Alt needs to reach 14,000ft or manually deployed by crew.

regds
MEL



Think of the brighter side!
User currently offlineTristarsteve From Sweden, joined Nov 2005, 3976 posts, RR: 34
Reply 19, posted (7 years 3 months 3 weeks 1 hour ago) and read 5235 times:

Quoting MarkHKG (Reply 14):
Unless the oxygen mask is a chemical oxygen generator system, which requires each individual generator that was fired to be replaced.

When the masks drop down, the chemical generators do not start to produce oxygen until you pull on the mask. If you look you can see a string that goes from the plastic hoses up to the generator. Pulling on the mask pulls the pin out of the generator and starts the generator.

If masks fall down, they need to be repacked. It takes time, and is very fiddly rolling up three or four masks and getting them all nice and neat into a box which is two sizes too small, then closing the door before they fall down again.

Quoting Jetlagged (Reply 15):
Of course, but I was think of the case mentioned where the masks deployed in a hard landing, so presumably no oxygen flow occurred (the system would not be armed).

The system is armed, but there would be no flow unless a pax pulled the mask down and put it on.

Quoting Avt007 (Reply 5):
Indeed, Alias is right. The Dash has a ceiling of 25,000 feet, and so doesn't require oxygen for the pax

The regulations state that you must be able to descend to 10000ft in a given amount of time. It used to be TWO minutes. At 25000ft you need oxygen if you can't descend fast.

The good old DH Trident 2 had no oxygen system and flew over 30000ft. It could descend fast enough to get down ib time with its air deployable thrust reversers.


User currently offlineThrottleHold From South Africa, joined Jul 2006, 655 posts, RR: 1
Reply 20, posted (7 years 3 months 2 weeks 6 days 21 hours ago) and read 5190 times:

Quoting Kdm (Reply 17):
Theory 2) Plane depressurises, I don't bother taking oxygen. I pass out. either the plane crashes, I don't care as I have passed out or once the plane gets to 10,000 feet I now have enough oxygen to breath so I regain consciousness the pilot has got the plane under control so all is OK.

What if the aircraft is flying over mountainous terrain with an MSA way in excess of 10,000ft? It has to stay up to clear the terrain.
A descent to 10,000ft may take anything up to 8 or 9 mins. Do you really want to risk starving your brain of oxygen for this length of time?

Best choice is to don the mask.


User currently offlineAvt007 From Canada, joined Jul 2000, 2132 posts, RR: 5
Reply 21, posted (7 years 3 months 2 weeks 6 days 21 hours ago) and read 5178 times:

Quoting ANITIX87 (Reply 11):
What would the crew have had to do?

All the crew has to do is write it in the logbook, and walk away. Maintenance (as usual) has to clean up their mess.

Quoting MarkHKG (Reply 14):
The decompression announcement starts (if installed) and cabin lights go to to bright (if selected as an option) as well.

I've also seen IFE and inseat power systems tied into this as well. Both are shut off in case of mask deployment.

Quoting Tristarsteve (Reply 19):
very fiddly rolling up three or four masks and getting them all nice and neat into a box which is two sizes too small, then closing the door before they fall down again.

I once opened a mask panel to get at something behind it. When the masks were stowed, the string mentioned earlier had wrapped it self around the door, and as soon as I opened it, SNAP, and the O2 starts to flow. I had to wait over an hour for the generator to cool enough to remove. What a PITA.


User currently offlineMarkHKG From United States of America, joined Dec 2005, 960 posts, RR: 2
Reply 22, posted (7 years 3 months 2 weeks 6 days 20 hours ago) and read 5163 times:

Quoting Kdm (Reply 17):
If the plane depressurises and I need a mask there is a serious problem.

There are many cases where the masks drop due to a decompression, and it turns out it was NOT a serious problem with the airframe/aircraft itself. (Just wrong configuration settings that are rapidly corrected.) It's not like in the movies where the masks drop right before the plane crashes.



Release your seat-belts and get out! Leave everything!
User currently offlineBoston92 From United States of America, joined Aug 2006, 3390 posts, RR: 7
Reply 23, posted (7 years 3 months 2 weeks 6 days 17 hours ago) and read 5111 times:

Quoting ThrottleHold (Reply 20):
A descent to 10,000ft may take anything up to 8 or 9 mins. Do you really want to risk starving your brain of oxygen for this length of time?

There is only a supply for 2 min of air, and when the plane loses oxygen, I doubt the pilot will perform a normal 2000 fpm descent to FL140. It will be a most UNcomfortable rapid descent down.



"Why does a slight tax increase cost you $200 and a substantial tax cut save you 30 cents?"
User currently offlineMarkHKG From United States of America, joined Dec 2005, 960 posts, RR: 2
Reply 24, posted (7 years 3 months 2 weeks 6 days 16 hours ago) and read 5109 times:

Quoting Boston92 (Reply 23):
There is only a supply for 2 min of air,

Passenger oxygen systems typically produce oxygen for 10-15 minutes.



Release your seat-belts and get out! Leave everything!
25 ThrottleHold : A chemical generator will supply 15-20 mins of O2, depending on the type fitted. On the Airbus, an emrgency descent is performed at thrust idle and s
26 Jetlagged : In a bottled O2 type system, as on the 747-200, pulling the mask will not release oxygen unless the main oxygen valves have been opened, either autom
27 Andz : I'd like to see the scientific odds on the same aircraft having more than one depressurisation requiring passenger oxygen.
28 Post contains images Starlionblue : Hehe. Very good point. Besides, if the choice is cooties or dying, I'll take the cooties.
29 EMBQA : Not true..!! It depends on the interior configuration. Most if not all of Mesa's Dash-8's have drop masks which are supplied by a bottle, not chem ge
30 Boston92 : Damn, I am having a blank, what do they call the emergency exits? It is an old war term. It'll come to be later. I keep coming back to Storkie Exits,
31 474218 : The cabin was not pressurized, if it had the cargo door could not have been opened. Aircraft doors are forced against their stops and seals when they
32 Avt007 : If it was indeed a Dash, you are correct, the outlfow valves should have been open, I don't think they close until the power levers are above a certai
33 Boston92 : It was a Dash, and because of my window seat, I could see the baggage handlers say the number "4" to our captain, meaning four more bags. They re open
34 HAWK21M : Considering the cabin pressure while on ground.Opening the door would not take effort.Was the Anticoll lights on at that time. regds MEL
35 474218 : If the Dash main cabin door is 2' X 5' (I presume it is actually larger) there would be between 600 lbs and 1200 lbs pushing the door against the sto
36 Avt007 : I was doing a pressurization run outside the hangar when a guy came out with the logbook and opened the door. It has a lever outside the aircraft whic
37 Boston92 : I never said there was "damage" to our ears, or that it hurt, I just said you could feel it. More like a discomfort.
38 HAWK21M : Wasn't the Anticolls on during the Pressurisation Check. regds MEL
39 Avt007 : Yes the red lights were on, but here is a classic case of night shifts screwing you up, and why I don't like pressurization runs near other people. Th
40 Post contains images HAWK21M : Fatigue Induced error regds MEL
41 VHXLR8 : As already mentioned, not true. Absolutely!! A couple of examples; 737/767 have 12 minutes; A330s have 15 mintues; 767s can also have a high terrain
42 MarkHKG : I watched an old TWA training video for the older variant of the 747, and when the masks drop, the decompression announcement starts, in perfect Brit
43 Alias1024 : I think you are looking for sortie. It is just French for exit. Freedom picked up Dash 8s that uesd to fly in Canada, hence the English and French.
44 Boston92 : I just had my return trip this morning and I noticed that. My friend who was with me said it was an old war term, but this morning he just noticed it
45 Post contains images VHXLR8 : "There is no cause for alarm, but please put on your oxygen maks, or else you may die within the next few minutes. Also, our duty free sales will be
46 Jetlagged : The word sortie is still used in the military to mean a raid. You are leaving your base to do this, hence sortie. It's from the French verb sortir (t
47 Starlionblue : I don't want to talk to you no more, you empty headed animal food trough wiper. I fart in your general direction. Your mother was a hamster and your
48 Post contains images Jetlagged :
49 Yellowstone : What sort of chemicals do they use in the O2 generators? If I'm remembering my chemistry right, the two possibilities that come to mind are potassium
50 MarkHKG : I was under the impression it was a sodium chlorate (NaClO3) core at the heart of the system. Makes a nasty burning smell once the oxygen generation c
51 474218 : Chemical Oxygen Generators two main ingredients are Sodium Chlorate and Iron Power, several other chemicals are used the most prevalent being Barium P
Top Of Page
Forum Index

Reply To This Topic Loss Of Cabin Pressure, Why No Masks?
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Why No Wing-mounted Engines Small Jets posted Wed Feb 21 2007 20:08:02 by Redcordes
Why No RR Powered A300 posted Sat Dec 30 2006 04:43:25 by 747400sp
Cooling Of Cabin Air In Engine posted Wed Dec 13 2006 03:34:25 by Jawed
Why No Further A330 Stretch? posted Fri Nov 10 2006 03:50:51 by MarkC
A340-600 Why No Body Gear Steering? posted Fri Nov 3 2006 18:16:18 by BALandorLivery
Why No Retractable Gear On Aerobatics Planes? posted Thu Nov 2 2006 20:54:17 by QFA380
Why No Papi On W/B Rwys At LAX? posted Wed Oct 18 2006 06:58:06 by Adipasqu
Why No Douglas Competitor To The Boeing 727? posted Mon Jul 31 2006 21:51:50 by 747400sp
Why No Short Haul Versions? posted Fri Jul 28 2006 14:34:18 by Tobi3334
Why No Auto-Land? posted Thu Jul 27 2006 16:38:03 by Marklaw

Sponsor Message:
Printer friendly format