Questions tagged [cabin-pressure]

Airplane cabins are pressurized so that the air inside remains breathable at high altitudes.

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31 votes
6 answers
36k views

How thick is the skin of an aircraft like the Airbus A350 or Boeing B777?

We can evaluate how thick walls are by looking at door or window frames, however that isn't representative of an aircraft fuselage, which appears to be very thin: Airbus A350 XWB forward fuselage, ...
7 votes
2 answers
1k views

Have any commercial airline passengers ever been injured from hypoxia due to a depressurization event?

This question is inspired by the question "What can I do to save my life if oxygen masks fail to drop down? Is it possible?" One of my first thoughts upon seeing that question was: do you need to do ...
13 votes
1 answer
5k views

Passenger window insert pops out mid-flight

I was on a domestic flight from DCA to ORD in December on an Airbus A319. I was in row 31 and two rows ahead of me on the left side of the plane, I noticed while deplaning at ORD the passenger window ...
0 votes
0 answers
73 views

Do aircraft depressurise when taking off from a high elevation airport? [duplicate]

A jet aircraft generally maintains a cabin pressure of 7000-8000 ft during cruise. If the aircraft departs from a high elevation airfield, such as Quito (approx. 10,000ft), will the aircraft ...
1 vote
2 answers
328 views

In an F-16, at what altitude is supplemental oxygen considered essential life support?

Combat aircraft like the F-16 employs hypobaric pressurisation with supplemental oxygen from a regulator. However, at what point does the manual call for the pilot to start using the regulator, what ...
5 votes
1 answer
202 views

Is there good information available on maximum operating altitudes whilst maintaining a sea level cabin?

I am in the process of reviewing the aircraft we regularly commission for air ambulance transfers. Although the majority of transfers are undertaken with a standard cabin altitude ( 4 - 8,000 ft) some ...
22 votes
3 answers
4k views

Why is a dedicated compressor more efficient than using bleed air to pressurize the cabin?

Bleed air is air "stolen" from the compressor of the jet engine and has traditionally been used to pressurize the cabin. The alternative is to use a separate compressor just to provide cabin ...
2 votes
1 answer
217 views

How was the Douglas DC-6 pressurized?

It's my understanding that modern airliners are pressurized using bleed air from the compressor stage. But how did piston-engined aircraft like the DC-6 get pressurized? I couldn't find any answers ...
11 votes
4 answers
7k views

Why aren't aircraft cabins pressurized to sea level pressure?

From an article on WHO's website: Although aircraft cabins are pressurized, cabin air pressure at cruising altitude is lower than air pressure at sea level. At typical cruising altitudes in the ...
9 votes
2 answers
5k views

Is the Diamond DA62 pressurized?

In a recent conversation about the Diamond DA62 I was speaking with someone who thought the aircraft was pressurized. I was shocked considering the door design. Shocked to the point of disbelief. A ...
4 votes
1 answer
267 views

How to escape from a pressurized airplane?

Saudia Flight 163 was an airplane where all passengers and crew onboard died following a cargo fire. The plane managed to land safely, and the passengers had moved to the front of the cabin. However, ...
24 votes
5 answers
8k views

Is the cabin pressure "worse" at the back of the cabin than in front?

My mother has a bad hearing problem and wears 2 hearing aids. She tells me the air pressure is worse for her in the back of the plane than the front. I would like to know if this is true - is there a ...
4 votes
1 answer
2k views

How is the 737 NG/MAX able to operate at a pressure differential greater than that at which the cabin-pressure relief valve operates?

So I was reading about the 737's cabin-pressurization system, and then I came across these two bits of information: Limitations Max differential pressure: Series Max Diff 1/200's [sic] 7.5psi ...
26 votes
1 answer
4k views

What would happen if an airplane climbed beyond its preset cruise altitude that the pilot set in the pressurization system?

What would happen? Would the cabin pressure increase too much and cause damage?
2 votes
1 answer
2k views

Can Airbus A320 doors be opened mid-flight?

Today I learned how airliner doors are typically an outward facing plug and cabin pressure would make them nearly impossible to open mid-flight. It's easy enough to see that for the shape of Boeing ...
9 votes
1 answer
935 views

Was the safe landing of Southwest flight 1380 extraordinary or expected?

I've been reading with great interest and concern about the recent Southwest flight that resulted in the first fatality in that airline's history. There's one question I haven't seen answered, though:...
22 votes
3 answers
10k views

Why do paratroopers not get sucked out of their aircraft when the bay door opens?

A few instances of injury/death were reported when passengers/pilots got partially sucked out of the airplane due to cabin depressurisation in a commercial aircraft. Paratroopers, on the other hand, ...
3 votes
2 answers
1k views

How exactly does the cabin pressure of an airliner change during ascent and descent?

At cruise altitude, airliners' cabin altitudes are usually at 6000-8000 ft, but how and when does it get there respectively how does it behave from ground until cruise altitude? Is the cabin ...
-6 votes
1 answer
267 views

How can an aircraft door be modified to open in flight at cruising altitudes?

Just do a Google search for opening an airliner door in midair will spring up a dozen sites of why this is nearly impossible, if not possible. And the difference between the inside of the plane and ...
21 votes
3 answers
38k views

Does the B787 (Dreamliner) operate with higher cabin pressure?

The Boeing 787 Dreamliner's fuselage is almost completely made of composite carbon fibre material, which is not susceptible to metal fatigue. The main reason why the cabin pressure in a pressurized ...
1 vote
1 answer
304 views

What would be the lowest possible cabin altitude (respectively, highest possible pressure on board) of an airliner in 1155 Pa exterior pressure? [closed]

How well does an airliner's pressurization work at extremely high altitudes (extremely low atmospheric pressure)? Does the system provide an absolute pressure differential, or is the differential a ...
3 votes
3 answers
18k views

What's the difference between positive and negative pressure relief valves?

In cabin pressurisation systems, I thought that the negative relief valve is automatically opened if outside pressure becomes greater than inside pressure.
3 votes
0 answers
469 views

Did Helios Flight 522 take off with its pressurisation mode selector in manual? [closed]

I'm currently doing a write up on the Helios Flight 522 disaster. Full disclosure, this is a journalistic piece, and I'm not an aviation expert. I'm many hours in at this point and most of it so far ...
20 votes
5 answers
6k views

Can airliners take off, cruise and land while unpressurized?

I'm wondering if the pressurization of the cabin has a part to play in the structural integrity of the fuselage, the same way an unopened soda bottle is stiffer compared to one that's open.
0 votes
3 answers
1k views

How did the unpressurized Cessna Grand Caravan fly at 43,000 ft? [closed]

Recently I've seen a Cessna 208 Grand Caravan flying as high as 43,000 ft MSL on flightradar24. Perhaps it's still in the air if you look over eastern Canada (the Grand Caravan has a unique shape from ...
2 votes
0 answers
53 views

How is airliner pressurization being coped with at high altitude airports? [duplicate]

Cabin altitude in a passenger airliner must not become more than 8,000 ft, but what if an airliner flies to or from an airport at a higher elevation, such as Quito and La Paz? How is onboard pressure ...
2 votes
2 answers
730 views

With supplemental oxygen, what altitude can a pilot safely operate at?

Will there be operating limitations regarding ascent or descent speed to avoid decompression sickness? What altitude will require a pressure suit?
12 votes
3 answers
8k views

How hot would pressurized air get if the air conditioning failed?

I understand that aircraft are pressurized by pushing air into the cabin using the engines, and using a valve to let the air escape at a controllable rate thus achieving the desired pressure ...
0 votes
1 answer
153 views

Who make the fuel system, cabin pressurization system, and firefighting system?

Who makes the fuel, cabin pressurization, and engine firefighting system for an aircraft with engines on, or in, the wings? Fuel tanks and fuel pipes, pressurized air pipes and heat exchanger, and ...
3 votes
2 answers
345 views

How would tiltwing aircraft pressurize their cabins?

For fix-wing aircraft, the pressurized air can travel from the engine through the wing and into the cabin. However, a tilt-wing aircraft, such as the CL-84 Dynavert (shown below), will have its wings &...
5 votes
1 answer
2k views

What happens if the crew do not set a FLT ALT in the cabin pressurization panel and leave it at zero but AUTO is still selected?

On the 737NG, will the cabin maintain a lower altitude than the plane or will cabin altitude equal aircraft altitude? Will there be ANY cabin pressurization or none at all? When will the HORN sound? I ...
0 votes
2 answers
1k views

How are cabin pressure and oxygen level maintained inside the airplane? [duplicate]

How are cabin pressure and oxygen level maintained inside the airplane?
33 votes
1 answer
29k views

Why is there a hole in one of the layer of an airplane's windows?

On a commercial airliner, there is a hole in one of the layer of the passenger windows. See here: and here: Or in more detail: Can you explain the physical reasons for this design choice?
14 votes
6 answers
5k views

Should depressurization be considered in the event of an inflight cabin fire?

Uncontrolled cabin fires only need a few minutes to spread throughout the cabin of an aircraft, killing everyone onboard and destroying the airframe. Now, we all know that depressurization and fire ...
0 votes
6 answers
796 views

Why don’t airports use jetways as an airlock to avoid having to repressurize the plane for every flight?

Seems like it could save money perhaps. Has this been considered in the past?
8 votes
3 answers
2k views

Is it possible for a pressure loss in the cockpit to not extend to the cabin?

I have done research into the question of pressure differences between the cabin and cockpit and the theoretical answer I receive the most is that the pressure difference would equalize almost ...
0 votes
3 answers
341 views

Was there ever a supersonic flight in a non-pressurized plane, and what is/would it be like for the pilot?

If you went supersonic in a plane that has no pressurized cockpit, would you be completely deaf (because of flying faster-than-sound)? Would it be dangerous to the pilot even if he/she was in an ...
4 votes
1 answer
377 views

How often is the cabin air replaced in A320?

One of the A320 pilots told me that there is an icao rule that air should be replaced every 90 seconds? Is this true ? can someone give me a supporting article for the same
5 votes
3 answers
726 views

Is the increased humidity on modern jets artificial?

Aircraft manufacturer’s including Boeing and Airbus have emphasised on greater passenger comfort owing to an increase in humidity on newer jets such as the 787 and A350 artificial? Or is it a direct ...
9 votes
3 answers
25k views

Are there any pressurized piston-engine aircraft?

Are there any pressurized piston engine-powered aircraft? Or does pressurization require a turboprop or jet?
0 votes
2 answers
1k views

How does outflow valve work?

As we know that outflow valve normally closes during climb and cabin altitude also increase but why does outflow valve open if we have selected manual pressurisation and increasing cabin altitude !
12 votes
3 answers
9k views

What's the relation between cabin pressure and altitude?

Usually, cabin pressure of an airliner is kept at a value corresponding to an altitude of not more than about 2000m. Now, I heard that before takeoff, the pressure is already increased a little for ...
20 votes
6 answers
15k views

Why is air mixed with bypass air on the A/C of an aircraft?

Air is taken from the compressors, then it is cooled by the air that comes from the ram air inlet. After that, it is compressed and cooled again by an expansion turbine. When finally air is condensed, ...
1 vote
1 answer
496 views

Does ELMS inhibit cabin pressure alarms on the 777, and would the MEC Override Vent be stuck open following an electrical failure?

I found this article rather interesting, but like most things on the internet, they can be wrong. I couldn't think of a better site to address this question. This user says: when ELMS takes over ...
-5 votes
3 answers
333 views

How can I communicate an emergency de-pressurization descent to the cabin as a passenger?

Hypothetical scenario. I'm on a commercial airliner (A320) as a passenger, sitting by the wings. We are cruising at 32,000. The oxygen masks suddenly drop down and the nose pitches down heavily, ...
-2 votes
3 answers
473 views

Why does a decompression occur when a hole appears on the fuselage of an aircraft? [closed]

I've never understood the mechanics behind explosive decompression and what is has to do with the difference of pressure. I know the pressure in the cabin is set to a certain point, but don't ...
1 vote
0 answers
123 views

Why does the 737-300 outflow valve indicator give different readings?

The 737-300 outflow valve opens and closes in manual mode under AC or DC side. While in DC, the indicator is accurate, but when it's in AC mode it reads open when closed. Does the outflow valve have ...
2 votes
3 answers
10k views

How does the outflow valve work on a cabin pressurization system?

When you fill up a cabin with warm air the pressure of the cabin will rise. An outflow valve controls the desired pressure. But with pressure rising doesn't the temperature rise because you're ...
4 votes
2 answers
3k views

Do pilots breathe the same air as passengers?

Do pilots breathe the same quality of air as passengers ? (i.e. identical parameters: same O2, CO2 and O3 levels, same temperature, same humidity, etc.) Do pilots breath the same air as passengers (...
10 votes
4 answers
10k views

How are turboprops and other propeller planes pressurized?

I know how most turbofan jets are pressurized: But it can't be the same with turboprops, as I don't understand how propellers can take in the air. Yet, planes like Q400s can fly above 8000', all the ...