Screaming on flight

If you understood the problems with sustaining sea level pressures in a cabin at 40,000 ft where the pressure differential is off the chart, you would understand why the cabin altitude is only at 5000 ft. The engineering is extremely stretched as it is to do what it does. To keep all the pressure in a vessel as large as the fuselage of a jet airliner is a monstrous task when you have to allow the outflow of contaminated air and the inflow of fresh and heated air every three minutes to keep you comfortable. The airframe isn't the problem anymore. That child's eustachian tubes are the problem.

 

At least among Boeings, I know that the 787 keeps its pressure closer to sea level than all the rest; I assume the Airbus A350 is similar.

 

I might be in error but I seem to remember a 16PSI structural limit on the fuselage. Multiply that by all the square inches of surface inside a fuselage and you can see why it is difficult to contain a bomb in waiting. The air-conditioning packs do marvelous work to keep 5000 ft. level in the cabin.

 

Listed in the AFM as 9.9 PSI max. Keeps a cabin altitude of 6000 in normal operation, rising up to 8000 in certain degraded modes.

 

Andrew- Next time show the girl how to do a Valsalva. Pinch nostrils closed and blow gently against it. Have helped several passengers with ears plugging and that usually clears it. If they have a blocked sinus, they are screwed, however.

 

Be very careful doing that maneuver too vigorously as it can blow out the round window vestibular membrane within the inner ear leading to inner ear fluid leak and vertigo. Better to take some Afrin 10-15 mins before taking off and 45 mins before landing (just at the start of the initial descent). Sudafed can be added to further open the nasal mucosa and make eustachian tube opening a bit easier. Chewing gum, drinking water or giving kids juice all help.

 

As mentioned, 787 has the best comfort in that regard.
Among private jets, G650 has internal pressure closest to sea level.

 

Cabin altitude at FL450 is ~4000ft.
Having a submarine builder for a father helps

 

My tips for clearing ears......Avoid dairy for days before the flight to help avoid the thickening of your mucous. As divers know, tipping the head back and looking upward can make clearing the ears a breeze, given the mucosa and congestion arent in bad shape. Pulling upward on the top of the air also helps me a little. Adding in a yawn even more. Pressurizing the ears is my last resort as it can force bacteria laden mucous into the eustachian tube, from what I understand.

 

I've always been in awe of a fat man being sucked out a small window. That gives you an idea as to what forces engendering is up against.
Image Unavailable, Please Login

 

Thanks, it has been a while since I was around that stuff but I still remember something higher than 9.9 but don't have a manual. I was in an airplane next to an airplane, a B-50, that was being pressure tested and all of the nose glass blew out. The resounding boom and glass shrapnel hitting us was no different than a bomb. I was also near a 707-320 center section that blew up while it was being tested and the force and sound is all the same. A faulty test bench couldn't read the over pressure and allowed full flow of the plant air source to go until it blew. Powerful stuff.

 

Stresses can be quite high, especially around cutouts and at splices. Airplanes also have damage tolerance criteria, which can require carrying limit flight loads plus operational pressure with a crack extending one or more frame bays (>20 inches).

AFM value is the normal operating limit. The relief valve setting would be a few tenths higher.

Hi-blo testing at the factory would be 1.33 times max relief valve setting (considered as limit load). Structure ultimate is 1.5 times limit, or 1.33*1.5=2.0 times max relief value setting (generally never tested).

 

Thanks, Mr.Curry. One item that stunned me was the explosive decompression of the Comet that emptied the cabin in 1/6th of a second and the crucial evidence of what had happened was the discovery of paint from the fuselage window belt on the upper surface of the wing near the wing tip.

 

Nobody pack Afrin anymore? Some guys swear it's saved them a lot of potential problems as a get me down. I don't think I have ever used it but I carry a bottle with me every flight, of course we have a few more ups and downs. We recently established that the max VVI that the aircraft will display is 9,999, beyond that you are on your own

 

Not sure what you mean by 'engendering'.

That pic looks fake. Is it?
If not, have a description?

Who/what took the pic?

 

Good Lord, that's like 25 - 26 individual panes of glass... the whole nose of the B-50 / B-29 is glass.

Was the B-29 the first pressurized bomber?

 

Yes, the B-29 was the first pressurized bomber. That pressure test blew the nose dome skyward and it hit the control tower window about 50 yards away. This was on the east side of Boeing Field in the winter of 1950-1951. We spent many long hours repairing the dents in the airplanes that were hit with the glass shrapnel. Luckily, everyone was INSIDE the airplanes when the burst took place, so no one was injured. Subsequently, the airplanes were covered with cargo nets when they were pressure tested.

 

Rod- Affirmative, that is why I said blow gently. As a second generation fighter jock, I can clear my ears directly, too fast for docs to see, and only have to Valsalva rarely.

 

I've always used a different technique...

Pinch nose and hold it.
Open mouth wide.
Swallow, while mouth is open.

Always works.
Has the advantage of not 'pushing' on the eardrum.

 

They also found paint on the horizontal stab. The fuselage apparently peeled open like a banana. Boeing made sure that that could not happen with the 707.

 

Yawning usually works pretty well, also.

 

Since they've gotten rid of smoking and non-smoking sections on aircraft, I've advocated subdividing the passengers in a different way:

WITH SMALL CHILDREN

or

WITH NO SMALL CHILDREN

Otherwise, I'd try and persuade parents of children less than age 5 not to fly. In my case, I did not fly until age 7.

 

I think the pic is from an air crash investigation television recreation of the actual event.

[ame]http://www.youtube.com/watch?v=PNTHm2pvZTQ[/ame]

This is the event:
https://en.wikipedia.org/wiki/British_Airways_Flight_5390