How to Minimize Subsequent Effects of Cabin Decompression During Flight - Aviation Professional

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Saturday, January 9, 2021

How to Minimize Subsequent Effects of Cabin Decompression During Flight

       Cabin-Decompression,Types of Plane Cabin Decompression, Explosive Decompression,Slow Cabin Decompression


Many of air passengers did not know about what can occur during rapid decompression in aircraft. I am not making you feel that they are not knowledgeable enough, what I want is that they must have a safety awareness of the situation and understanding in few seconds they must be secured and doing oxygen mask and breath, otherwise they would not control their brains and bodies" No oxygen no life"!!

The fact, aviation is the safest mode of transport, by advance aviation engineering, ICAO Standards and Recommended Practices (SARPs), States civil aviation regulations, IATA safety Standards, airline safety policy. Furthermore, competency-based training of operational personnel, especially flight and cabin crew which cover abnormal and emergency procedures. All work together to safe you.

This article will help both passengers and flight attendants to review their knowledge regarding this subject. Safety culture has a significant influence on what passenger do about aircraft depressurization issue.

What happens when a plane loses cabin pressure?

Any failure of cabin pressurization above 10,000 feet required an emergency descent to 8,000 feet or the closest to that while maintaining the minimum safe altitude (MSA). Oxygen masks for each seat will drop down, the oxygen system have sufficient oxygen for all on board and give the pilot adequate time to descent to below 8,000 feet where no emergency oxygen required.

The problem is if passengers do not adhered to safety policy - being secured and doing their oxygen masks and breath - as fast as possible, they may suffer from Hypoxia which may lead them to lose their consciousness and a subsequent loss their lives.

Why a plane loses cabin pressure?

Cabin decompression can occur due to a pressurization system malfunction, small air leak, or damage to the plane that causes a breach in the plane structure, enabling cabin air to escape outside the plane, for example loss of a window, or a breach in the plane fuselage due to an explosion.

As a result of cabin decompression, the atmospheric pressure will change in the cabin to form a low concentration of oxygen, no enough oxygen at extreme altitude due to the atmospheric pressure in the cabin will going to equal the atmospheric pressure outside the plane.

The severity of the cabin decompression effects will depend on the type of cabin decompression and fast emergency response by flight and cabin crew.

Types of Plane Cabin Decompression

There are two types of plane cabin decompression

1- Explosive Decompression

It is also widely knowing as rapid decompression in aircraft (plane), uncontrolled cabin decompression, it is occurred as a result in a sudden loss in cabin pressure, and can be recognized by the following physical signs:

The sign

The cause

1-      A loud bang, thump or clap

As the result of the sudden contact between the internal and external masses of air.

2-       Cloud of fog or mist in the cabin

Due to the drop in temperature, and the change of humidity.

3-      A decrease in temperature

As the cabin temperature equalizes with the outside air temperature

4-      The release of the cabin oxygen masks

When the cabin altitude reaches 14 000 feet.

5-      Rush of air

As the air exits the cabin.

 

If a breach in the plane structure is the cause of the decompression, the following signs can be recognized:

• Unsecured items in the immediate area are ejected from the plane

• Debris may fly around the cabin

• Loose items may become projectiles

• Dust particles may limit visibility.

2- Slow Cabin Decompression

Slow cabin decompression can happen when there is gradual decrease in cabin pressure as the result of a faulty door seal, cracked window , or a malfunction in the pressurization system.

Slow decompression may not always be noticed for this reason flight attendants and passengers may not notice the changes in the cabin pressure, until the oxygen masks drop down from the Passenger Service Units (PSUs).

 

Therefore, the flight attendants and passengers must be aware of signs that could indicate a slow decompression. For example: an unusual noise, such as:

 

-  whistling

-   hissing sound around the door areas,

 

These unusual noises may be an indication of a slow decompression, therefore, if  Flight Attendants notice like these signs they must notify  the flight crew immediately.

 

Further signs, due to gas expansion, one of the first physiological indications of a slow decompression may be :

- Ear discomfort or ‘popping’,

-   Joint pain, or

-   Stomach pain

 

Hypoxia

The lower partial pressure of oxygen at altitude reduces the alveolar oxygen tension in the lungs and subsequently in the brain, leading to sluggish thinking, dimmed vision, loss of consciousness, and ultimately death. In some passengers, particularly those with heart or lung disease, symptoms may begin as low as 5000 feet, although most passengers can tolerate altitudes of 8000 feet without ill effects. At altitude there is about 25% less oxygen than there is at sea level.

Note : we will write about " Hypoxia"  in separate article in the future.

Time of Useful Consciousness

The time of useful consciousness refers to the time available to individuals to perform their tasks, after they have been deprived of oxygen, but are still aware of their environment and capable of controlling their actions.


TIME OF USEFUL CONSCIOUSNESS

 

Altitude

 

Moderate Activity

 

Sitting Quietly

 

22 000 feet

5 minutes

10 minutes

25 000 feet

2 minutes

3 minutes

28 000 feet

1 minute

1.5 minutes

30 000 feet

45 seconds

1.25 minutes

35 000 feet

30 seconds

45 seconds

40 000 feet

18 seconds

30 seconds


Conclusion

In the case of explosive cabin decompression, there may be a lot of confusion due to the high noise level and fog that makes it difficult to communicate in the cabin. In this case hand signs may work between Cabin Crew and Passengers.

Explosive decompression is more dangerous than slow cabin decompression. It is important for flight attendants and passengers to take fast actions by being secured and doing oxygen mask and breath immediately.

The first actions by Flight Attendants should be:

- Donning the nearest oxygen mask;

-  Sitting down and strapping in. secure self with seatbelt or harness

-  If flight attendant is unable to sit down, he should grasp the nearest fixed object or ask passengers to assist by holding on to avoid being ejected from the aircraft.

-  Hold on.  

Passengers also must do the same action as cabin crew, because, at the time of rapid decompression the cabin crew will be in a situation that can't help them the perform their safety duties , cabin crew must think about  their safety first to be able to help other passengers. Both cabin crew and passengers must help each other if they are able to do so.

It is important that the flight attendant who is seated closest to the cockpit, should immediately notify the flight crew of the oxygen mask deployment, and also to confirm that the flight crew have donned their oxygen masks.

Cooperation between flight attendants and passengers is highly required in like such emergency situation.

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