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Himayeti

Himayeti

Pre-takeoff checklist
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Mar 23, 2022
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Himayeti
That was the fake pilot's name, made up by a KTVU news intern regarding the Asiana accident at SFO back in 2013.

He's back!

https://www.nytimes.com/2023/05/26/world/asia/plane-door-open-asiana.html

I have always wondered about this ever since I sat in front of a deranged person who tried to open an emergency exit over the Bering Strait at 35K ft.

Luckily he didn't try it at 700 ft!
 
Kenny Phillips said:
Here's a link without a paywall: https://www.usatoday.com/story/trav...nes-door-opened-mid-flight-video/70259869007/
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Sends me to:
a2c3f14b6aa249da8c29a5ef1846e1f0.jpg
 
I just disabled the scripts on the NYT page which allowed me to read it without paying. Evil Piracy, I know.
 
farmrjohn said:
Also available free on the BBC website https://www.bbc.com/news/av/world-asia-65722391 I thought the plug type doors would not open while the plane was pressurized. Do Airbus planes depressurize prior to landing?
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According to the evening news they were at 700 feet, just before landing, when he opened the door. Explanation was that pressurization wouldn't prevent opening the door at that point.
 
My understanding is that the cabin pressure is held at 8000' or so, so presumably it could open anywhere below that point?
 
farmrjohn said:
Also available free on the BBC website https://www.bbc.com/news/av/world-asia-65722391 I thought the plug type doors would not open while the plane was pressurized. Do Airbus planes depressurize prior to landing?
Click to expand...

All planes depressurize by the time they land. Generally if you have manually controlled pressurization you set it to 500 feet above field elevation at some point prior to landing, while automatic systems may put less tolerance in.

In any case, at 700 AGL the pressure differential would not be enough to prevent opening the door. Pressure diff at that point is probably at or under 0.3 psid.

Dana said:
My understanding is that the cabin pressure is held at 8000' or so, so presumably it could open anywhere below that point?
Click to expand...

That's generally where it'll be on an airliner in cruise. However, as they descend, the pressure will be increased (aka the cabin will descend too) unless it's a manual system and they leave it set to a cabin altitude of 8000 which would be very unusual.
 
Probably should’ve sat him in back. I had a passenger jam his knee against the controls mildly upsetting the airplane. He immediately turned to me and said “what are you doing?” I said “ me? , nothing, but if you don’t get your knee off that control quickly we are going to start having a big problem.” He moved his knee and said sorry.
 
flyingcheesehead said:
In any case, at 700 AGL the pressure differential would not be enough to prevent opening the door. Pressure diff at that point is probably at or under 0.3 psid.
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Let's see, how big is the emergency window? FAA says minimum of 19 x 26? If so, that is 494 square inches. At 0.3 PSID, that is a mere 148 pounds of pressure. :)
 
Pinecone said:
Let's see, how big is the emergency window? FAA says minimum of 19 x 26? If so, that is 494 square inches. At 0.3 PSID, that is a mere 148 pounds of pressure. :)
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Schmancy arithmetic aside, ;) Kent is right - it’s differential that controls if a plug-door can be opened and at 700’, I bet that force was minimal.
Let’s hope this factoid doesn’t get out to the crazies.

A better link?
https://www.newswest9.com/article/n...orea/507-364bb3ee-4759-4da5-a1aa-92ab5547f845
 
flyingcheesehead said:
All planes depressurize by the time they land. Generally if you have manually controlled pressurization you set it to 500 feet above field elevation at some point prior to landing, while automatic systems may put less tolerance in.

In any case, at 700 AGL the pressure differential would not be enough to prevent opening the door. Pressure diff at that point is probably at or under 0.3 psid.



That's generally where it'll be on an airliner in cruise. However, as they descend, the pressure will be increased (aka the cabin will descend too) unless it's a manual system and they leave it set to a cabin altitude of 8000 which would be very unusual.
Click to expand...
I know that on certain airplanes the pressure differential is only allowed to be greater than or equal to the ambient.
 
Kenny Phillips said:
I know that on certain airplanes the pressure differential is only allowed to be greater than or equal to the ambient.
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Most. They are not stressed to have more pressure on the outside.
 
Judging from the photo of the plane on the ground, if it was over water while on final, someone got a nice big beach float.

ap23146259827054-ca95591860aea98cec78c3de5456fc7fcc5969ed-s1100-c50.jpg
 
I read that to mean the pressure inside the fuselage would always be greater than or equal to the outside pressure.

And this is a very good thing. Think of a water bottle. Partly full. Take off and climb, no big deal. Open it at altitude and come back down, it crumples and collapses.
 
Kenny Phillips said:
I know that on certain airplanes the pressure differential is only allowed to be greater than or equal to the ambient.
Click to expand...
Let'sgoflying! said:
I don't understand 'pressure differential...being greater than or equal to ambient'.
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Salty said:
I thought it was just me.
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Um, yeah. There's no such thing as "ambient pressure differential"... The pressure differential is the difference between the cabin pressure and the ambient pressure.

I suppose he could have meant a positive pressure differential, but I don't know of a single airplane whose pressurization system could possibly create a negative differential. Air is pumped into the cabin, and the differential is regulated by an outflow valve.

But, a pressure "equal to the ambient", or a pressure differential of zero, means that pressurization is not contributing any force towards keeping the door closed, and it'll just open right up.
 
mentourpilot’s descript of the event & factors allowing a door to be opened.
Did not realize Airbus doors have a nitrogen bottle that assists opening.

 
upload_2023-6-12_17-42-23.png
The pressure differential is the thing, and the fuselage has to be able to handle it. 8000' cabin altitude is usual, so that older or unhealthy folks can still get enough oxygen. The slope of the cabin altitude rise or descent, its feet per minute, has to also be somewhat gentler than the aircraft rate of climb or descent so that people aren't screaming in pain as their inner ear pressures can't adjust fast enough.
 
Let'sgoflying! said:
I think Petter was saying the cabin is pressurized to an altitude below field, before takeoff.
Click to expand...
Now, why would they do that? They're just going to have to let the pressure decrease again.
 
flyingcheesehead said:
... but I don't know of a single airplane whose pressurization system could possibly create a negative differential...
Click to expand...

I suppose you could manually close the outflow valves, turn off bleed air and descend. Not that anyone would ever do that. It would blow the safety reliefs at one point though.
 
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