54

I did high altitude training about three months ago, up to 30,000 feet simulated altitude. Here's the timeline: Within 30 seconds (oximeter 100-95): noticed physical symptoms beginning. I could tell that something was wrong, but felt functional. Within 60 seconds (oximeter ~90): mild headache. Still able to write my name. Not feeling good, but ...


50

Aircraft design has not changed that much in the last 10 years. In fact, most aircraft in production 10 years ago are still in production. The cargo holds in typical airliners are indeed pressurized. Take a look at a cross section of an airliner (A380 here): The round shape of the fuselage outline is very efficient at withstanding pressure. Because of that,...


34

Short answer The purpose of pre-pressurization is to avoid discomfort for passengers and crews during takeoff and landing. By storing air in the cabin before the aircraft rotation or landing, the pressurization controller is able to smooth out: The variations of bleed air supply when the engines deliver the highest thrust and need all available air. The ...


34

Yes, it's real. Here's the official accident report on BA5390, which says: The commander had been partially sucked out of his windscreen aperture And: The two men tried to pull the commander back within the aircraft [but] the effect of the slipstream frustrated their efforts There's also Aloha 243 where one cabin crew member was ejected, although ...


31

Here is the text extracted from Boeing's 777 Flight Crew Operations Manual: In cabin altitude controller cruise mode, maximum cabin altitude is 8,000 feet. When the takeoff field elevation is higher than 8,000 feet, the cabin descends to the cabin cruise altitude while the airplane is climbing. When the destination airport elevation is greater than 8,...


31

What part aft of the bulkhead would leak pressure? That's a partial misunderstanding of what a bulkhead is there for. You could build the aft cone section to keep the pressure, but it would be a much heavier solution. The shape of the final aft section is not well suited to resist pressurization stresses: the best shape is a sphere; the cylinder (with ...


28

The pressure in the cabin does not remain the same. It decreases, but much more slowly, in such a manner that when the aircraft is at 37000 feet the pressure in the cockpit is the equivalent of 7000 or 8000 feet. Keeping the cabin pressure at sea level would pose incredible stress on the fuselage, due to huge difference in pressure between the inside and the ...


28

Not likely. Consider how food products normally make it to you. Any competent US maker of soda or chips will design their product to be shipped on Interstate 70 or 80, via Sherman Summit (8650') or the Eisenhower Tunnel (11,158') or more likely by rail, via again Sherman Summit (8015') or Moffat Tunnel (9239').* Aircraft are pressurized to a pressure ...


26

A lot of consideration is placed on the airframe (which has to hold for 20+ years) rather than the passengers. One of the primary reasons is to slow corrosion of the aluminium airframe. This is also why the Boeing 787 is a lot more humid - corrosion is no longer an issue in a composite fuselage (or a lot less at least). Boeing and the Economist sum it ...


25

Aircraft windows are multiple layers thick. The side facing the passengers is just a plastic sheet, since they wouldn't want the passengers scratching up the actual expensive glass window. Beyond the inner pane there are two actual structural window panes. The outer one is normally the one bearing the load, while the inner one serves as a backup. However, ...


25

Even the unmanned RQ-4 Global Hawk has a pressurized compartment. The low air density at altitude would not be sufficient to cool the electronics, so a pressurized electronics compartment had to be added. I am not sure, but I expect the same reason required pressurization in the U-2 and the SR-71. The electronics were, besides the pilots, also an occupant ...


23

Once the airplane is closed up, all doors and windows secure, pressurization comes down to the following: how much air is being pumped into the cabin? how much air is being let out of the cabin? Air enters the cabin (on a jet powered airplane) through bleed air taps in the high pressure compressor of the engines. This air is routed through air cycle ...


23

Typically, the pressurization system is run by engine bleed air. Using that bleed air means you have less engine power available than is maximally available with the bleeds off. If you're on a runway that requires all your power, you do a no-bleeds takeoff, which means you have no pressurization. Shortly after takeoff you would turn the bleeds on.


23

If you are asking about all or some of the masks as your title suggests, it has happened before. One such example from 2008 is Qantas Flight 30. After the accident, numerous passengers said that some oxygen masks did not deploy, whilst others had deteriorated elastic. Consequently, it was reported that one passenger smashed a panel of the ceiling to ...


22

According to this document by Boeing: Altitude: How High Is Just Right? Today's airplanes are pressurized to a typical cabin altitude of 6,500 to 7,000 feet (1,981 – 2,133 m), with a maximum certification altitude of 8,000 feet (2,438 m). Because the advanced composite materials that make up the 787’s fuselage do not fatigue, the 787 can be ...


22

How do they prevent pressurized air to leak from the doors? They don't. The seal does not have to be perfectly airtight. The requirement is that it will create enough impediment to the air that wants to gush out, where "enough" is defined by the capability of the conditioning system to input new air into the cabin. In other words, everything is fine as ...


22

The main reason is that it's simpler than having everyone wear supplemental oxygen masks. There is no specific requirement for pressurizing an airplane but there are requirements for supplemental oxygen as per FAR 91.211 (a) General. No person may operate a civil aircraft of U.S. registry-- (1) At cabin pressure altitudes above 12,500 feet (MSL) up ...


22

The valves will not be able to maintain cabin pressure until the plane descends to 10,000 feet at best glide speed. The oxygen masks will deploy before then. At least that was the case for Air Transat Flight 236, an A332 that ran out of fuel over the Atlantic and glided to a deadstick landing. The occurrence report on page 96 (see the table) estimates that ...


21

The answer depends on what kind of aircraft you're talking about, and how much control the crew has over the pressurization systems. For example, in theory you could very well reduce or completely shut off the air to the cabin on a 777. This could also be done by a single crew member alone. The pilots have full control of this system should say the one of ...


21

From whats written here f100 skin is 1.0 - 1.4mm b747 skin is 1.8 - 2.2mm a320 skin is about 1.1mm According this article on the 757 ...Although Boeing specified that the skin in that area of the fuselage must be 0.039in (0.99mm) thick... Some interesting info here as well.


19

In short Bypass bleed air is a fraction of the bleed air coming from the core compressor. It's named like this because it doesn't cross the air cycle machine of the packs as does the regular bleed air. On the following picture this bypass bleed air is identified as trim air. Its purpose is to be mixed with cooler bleed air from the packs to modulate the ...


19

Just a couple of mm thick, about 2-3 is enough. The fuselage barrel gets its strength from the large diameter: bending moments of the fuselage (and wing) get translated into tension and compression loads in the skin. The aircraft skin is the main load bearing structure. It's the same principle as that for I-beams:they are that shape because the top and ...


18

Here is a plot of cabin pressure on one flight. You can see a small increase in pressure right before takeoff. The decrease and increase in pressure is fairly constant during climb and descent. The pressure will change based on the aircraft's altitude, and will not reach a minimum limit until closer to the aircraft's service ceiling. This keeps pressure ...


17

The question you're asking roughly translates to What is the time of useful consciousness at 39,000 feet?. The answer is "About 15-20 seconds, once the pressure bleeds off." The FAA has a handy table for this: From Chapter 16 of the Pilot Handbook of Aeronautical Knowledge. You can get a PDF of Chapter 16 here, or you can grab the whole thing from the FAA ...


17

I assume the hole has been properly deburred, otherwise you could suffer cuts on the sharp edges of the hole. What happens else depends on altitude and flight speed. At low level, the outside temperature should be tolerable and the pressure difference between inside and outside should be small, so your hand will be fine. At higher altitude, outside air ...


17

You almost have the answer in your question; bleed air is hot, compressed air taken from the engine compressors. Bypass bleed air here refers to some of that air which is bled off the engine, but not routed through the air cycle machine (pack). When the air comes out of the pack, its really cold. The pilot has a knob which blends the cold air from the ...


17

If all ACM failed, an alarm would sound in the cockpit. And two messages would appear on the ECAM/EICAS¹. One indicating that the ACMs failed and the other indicating that cabin altitude² is rising above desired level. Pilots would execute corresponding checklist, and the one for rising cabin altitude calls for rapid descent to 10,000 ft. That is the ...


16

There are a couple of things that contribute to the dryness of cabin air: Cabin air is drawn from engine bleed taps in the high pressure compressor. This is ambient air, which at the flight levels is normally quite dry and then heated and compressed, which will lower the relative humidity, making it seem even drier. The air cycle machine subsequently ...


16

No, the are not even nearly airtight, and leak air quickly on their own. Air pressure is maintained with bleed air or a powered pump. FAA has a thorough, well-illustrated guide to the systems involved. As for why they're not built completely airtight, aircraft are mostly riveted and glued, not welded, so their structure is inherently not solid. You'd need ...


15

Pressurization is controlled by two processes: air in and air out. Air is constantly being let out of the cabin through (at least) 2 outflow valves, typically located at the aft limit of the pressure vessel. Air is let into the cabin through the air cycle machines (a.k.a the "packs") which are provided with very hot and high pressure air from the ...


Only top voted, non community-wiki answers of a minimum length are eligible