On that oxygen in the toilets thing...
Apr. 4th, 2011 01:03 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
pecuniumNot quite a month ago I made a post about the FAA removing oxygen masks from passenger plane toilets. It was, and not just in my blog, but elsewhere when it was mentioned, poo-pooed as not a big deal. The number of sudden decompressions at high-altitude is too small to really worry about this.
This weekend a Southwest Airlines jet lost a chunk of fuselage (which is part of why one ought to keep one's seat beld fastened all the time. The plane was at 34,000 feet.
I'll pull a bit from my last post on that.
SKYbrary has a really nice set of pages on Hypoxia
There is a chart here of Times of useful consciousness At 35,000 feet, it's 30-60 seconds, if one is in good health and not engaged in physical activity, such as "moving about the cabin.
Southwest grounded a large part of the the Boeing 737-300s in the fleet, so they could inspect them for the fatigue damage which is presently the suspected cause of the 5'x 1' section of the plane that came off. In October an American Airlines plane also had a fuselage rip (I don't know the model). So far Southwest has checked about half the grounded planes (79 planes, the other 91 737-300s had their fuselage skin replaced recently, and so weren't seen as being at risk) and reports three have similar sorts of fatigue.
The cracks found in the three planes developed in two lines of riveted joints that run the length of the aircraft. The agency is focusing its probe on the area of the cracks but has not determined that the cracks caused the rupture.
NTSB board member Robert Sumwalt said Boeing was developing a "service bulletin" for all 737-300 models with comparable flight cycle time as the Arizona jet, which was 15 years old and had about 39,000 takeoff and landing cycles.
There are 931 such models in service worldwide, 288 of which in the U.S. fleet.
Boeing's bulletin would strongly suggest extensive checks of two lines of "lap joints" that run the length of the fuselage. The NTSB has not mandated the checks, but Sumwalt said the FAA is likely to make them mandatory.
The tear along a riveted "lap joint" near the roof of the stricken plane above the midsection shows evidence of extensive cracking that hadn't been discovered during routine maintenance before the flight – and probably wouldn't have been unless mechanics specifically looked for it – officials said.
"What we saw with Flight 812 was a new and unknown issue," Mike Van de Ven, Southwest executive vice president and chief operating officer, said. "Prior to the event regarding Flight 812, we were in compliance with the FAA-mandated and Boeing-recommended structural inspection requirements for that aircraft."
Sumwalt said that the rip was a foot wide, and that it started along a joint where two sections of the plane's skin are riveted together. An examination showed extensive pre-existing damage along the entire tear. Further inspection found more cracks in areas that had not torn open.
The riveted joints that run the length of the plane were previously not believed to be a fatigue problem and not normally subjected to extensive checks, Sumwalt said. (h/t HuffPo)
What I want to stress is the bolded portion, "a new and unknown issue." It's not that I think this problem is a really grave danger; to the fleet. It's that passenger planes are really complex systems, and there are lots of ways the structural integrity can fail. When that happens, the cabin will lose pressure. Odd are someone will be in the toilet, and that's a problem; if they have no access to oxygen.
This weekend a Southwest Airlines jet lost a chunk of fuselage (which is part of why one ought to keep one's seat beld fastened all the time. The plane was at 34,000 feet.
I'll pull a bit from my last post on that.
SKYbrary has a really nice set of pages on Hypoxia
There is a chart here of Times of useful consciousness At 35,000 feet, it's 30-60 seconds, if one is in good health and not engaged in physical activity, such as "moving about the cabin.
Southwest grounded a large part of the the Boeing 737-300s in the fleet, so they could inspect them for the fatigue damage which is presently the suspected cause of the 5'x 1' section of the plane that came off. In October an American Airlines plane also had a fuselage rip (I don't know the model). So far Southwest has checked about half the grounded planes (79 planes, the other 91 737-300s had their fuselage skin replaced recently, and so weren't seen as being at risk) and reports three have similar sorts of fatigue.
The cracks found in the three planes developed in two lines of riveted joints that run the length of the aircraft. The agency is focusing its probe on the area of the cracks but has not determined that the cracks caused the rupture.
NTSB board member Robert Sumwalt said Boeing was developing a "service bulletin" for all 737-300 models with comparable flight cycle time as the Arizona jet, which was 15 years old and had about 39,000 takeoff and landing cycles.
There are 931 such models in service worldwide, 288 of which in the U.S. fleet.
Boeing's bulletin would strongly suggest extensive checks of two lines of "lap joints" that run the length of the fuselage. The NTSB has not mandated the checks, but Sumwalt said the FAA is likely to make them mandatory.
The tear along a riveted "lap joint" near the roof of the stricken plane above the midsection shows evidence of extensive cracking that hadn't been discovered during routine maintenance before the flight – and probably wouldn't have been unless mechanics specifically looked for it – officials said.
"What we saw with Flight 812 was a new and unknown issue," Mike Van de Ven, Southwest executive vice president and chief operating officer, said. "Prior to the event regarding Flight 812, we were in compliance with the FAA-mandated and Boeing-recommended structural inspection requirements for that aircraft."
Sumwalt said that the rip was a foot wide, and that it started along a joint where two sections of the plane's skin are riveted together. An examination showed extensive pre-existing damage along the entire tear. Further inspection found more cracks in areas that had not torn open.
The riveted joints that run the length of the plane were previously not believed to be a fatigue problem and not normally subjected to extensive checks, Sumwalt said. (h/t HuffPo)
What I want to stress is the bolded portion, "a new and unknown issue." It's not that I think this problem is a really grave danger; to the fleet. It's that passenger planes are really complex systems, and there are lots of ways the structural integrity can fail. When that happens, the cabin will lose pressure. Odd are someone will be in the toilet, and that's a problem; if they have no access to oxygen.
