Loss of cabin presure?

Question

Last week, I was on a flight that depressurised (fun and games). We were told was there was a problem with the air conditioner, next thing you know we’ve got oxygen masks. So, 3 questions:

1) What does the air conditioner breaking have to do with cabin pressure?

2) What are the risks involved with decompression? (Slow depressurisation, not explosive.)

3) What are the actual statistics about planes’ depressurising? (How often does it happen?)

Ta :-)

Answer 1

1) any breach of the pressurized, contained cabin can lead to a depressurization.....the air conditioning 'packs' are run off of bleed air from the engines, so a breach in any joint or connection between the bleed air ducts and the ducting to the cabin could cause depressurization.....most of the ducting is run through the wings and it is an unpressurized area, so it is entirely possible.......

2) hypoxia is the immediate effect of a depressurization at altitude, but since you are still here to ask the question, the effects obviously were minimal, or none if you got the mask on quickly

3) depressurizations are rare, especially gradual ones....more common are the rapid, or 'explosive' decompressions, and these usually hit the news pretty quickly....only one gradual decompression i can think of made the news in the last 10 years or so....a professional golfer whose plane gradually lost pressurization due to a faulty valve and it killed them all and the plane ran out of fuel and crashed......usually when this type of decompression happens, the onset of hypoxia is gradual and unnoticed and ends in death

Answer 2

#1 Bossman has it.

All I'd add is that for aircraft air conditioning means heating, cooling and pressurization. So if the A/C fails then you lose the pressurization too.

Other effects are cold, when you decompress the aircraft at 30,000 feet you end up with much colder air. Oxygen won't cure that, but getting down will.

I know you didn't ask but rapid decompression can give you the bends because it's the percentage change that makes the difference. During development the B777 had two explosive decompressions, one when an a/c duct blew off at a joint and the other when a flap valve blew through its seat in an a/c pack failure test.

Answer 3

2. A lack of sufficient oxygen will bring on hypoxia by reducing the alveolar oxygen tension. In some individuals, particularly those with heart or lung disease, symptoms may begin as low as 1500 m (5000 ft) above sea level, although most passengers can tolerate altitudes of 2500 m (8,000 ft) without ill effect. At this altitude, there is about 25% less oxygen than there is at sea level.

Passengers may also develop fatigue or headaches as the plane flies higher. As the operational altitude increases, reactions become sluggish and unconsciousness will eventually result. Sustained flight operations above 3,000 m (10,000 ft) generally require supplemental oxygen (oxygen mask) or a pressure suit.

It is always an emergency if a pressurized aircraft suffers a pressurization failure above 3000 m (10,000 ft). If this occurs, the pilot must immediately place the plane in an emergency descent and activate oxygen masks for everyone aboard.

3. BOAC Flight 781 in-flight metal fatigue failure caused an explosive decompression, a form of cabin depressurization, in 1954, which killed 35 people. This was the first of a series of de Havilland Comet accidents that would cease the production of the aircraft.

Turkish Airlines Flight 981 which involved a DC-10 losing its rear cargo door. The severity of the depressurization damaged hydraulic controls causing the flight crew to lose control. All 346 on board were killed.

Japan Airlines Flight 123 was a Boeing 747 that had its rear pressure bulkhead fail, resulting in a decompression. The damage to the aircraft would sever the hydraulics of their aircraft, and the flight crew were unable to maintain control. 520 Passengers died with only 4 survivors.

Aloha Airlines Flight 243, a Boeing 737, suffered from explosive decompression, resulting in the loss of one flight attendant's life.
United Airlines Flight 811 which had a United Airlines Boeing 747-122 lose its forward cargo hold door, resulting in the loss of several seats in Business Class and the deaths of 9 passengers.
Golfer Payne Stewart and five others died in a Learjet accident as a result of loss of cabin pressure.

Helios Airways Flight 522, a Cypriot Boeing 737, crashed in Greece on August 14, 2005, killing all 121 people on board. It is currently believed that the plane depressurized and the pilots fell unconscious.

China Airlines Flight 611, a Boeing 747, disintegrated while climbing to cruising altitude on May 25, 2002, killing all 225 passengers on board. It was brought down by metal fatigue (caused by faulty repair some 22 years earlier) leading to the cabin's decompression.

Answer 4

Its not really an aicoonditior, even though it is reffered to as one. It is actually called an Air Cycle Machine, ACM. This machine runs off the hot compressed air from the N2 section of the turbines. (Second stage of compression). This air is extremly compressed, and around 350 degrees. Because it is under pressure, it is used to pressurize the aircraft, and being hot, air can be blown across the pressure lines to heat the aircraft, (This gas is also feed through the fuel tanks to keep the fuel from freezing at high atlitudes). The air in the lines can also be expanded, and with expansion of gas, the temp drops. (gas laws of temp proportional with pressure, as pressure increases, temp incerases, vice versa). thus being used as an airconditior.

Answer 5

The higher the altitude the less oxygen... when your brain lacks oxygen you get ga ga dizzy and finaly unconciousness
takes over when you black out....therefore the little oxy masks
come down....I have flown many times, even across the ocean and have not had the need for oxy masks...