Aircraft Pressurization Explained! And what happens when we lose it?
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- Опубликовано: 12 июн 2024
- Find out what is bleed air, how the air is conditioned and pressure controlled. What systems are there to warn the crew that something isn't right and what systems are in place when the pressure is lost.
I will be putting out more videos like this every month, let me know which ones you would like me to explain? 
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I will be regularly posting more videos about aircraft systems and different aviation concepts using motion graphics
- Petr
This is amazing. Will you do more like this for systems please? Its like a mini type rating knowledge refresher
THE MUSIC ON THIS VIDEO IS SO DISTRACTING SO UNNECESSARY
:0
I would not let. Anyone. Board aircraft with a watch on wrist watch two planes not a coincidence
I've read about packs and mix manifolds several times before, but this really helped me visualize how it all comes together, nice one, cheers.
I am glad that this helped!☺️
Honestly more information than I needed, but that's what makes this an incredible video. Thank you for the great work!
Ive been watching the standard instructional videos yet this one was the most enlightening
Searched around before finding this great video - clear, concise and the use of slides compliments your presentation style... this video has provided the answers I was looking for... very informative ... thumb up for you sir
Thank you for explaining this. We'll be looking forward for more technical issue of airplane .
I love that the duration of the video is 7 minutes and 38 seconds
Excellent RUclips Channel! The way of the full color animations it's the best!!! 💪🏾💪🏾💪🏾 Amazing job. Regards
Excellent! Thank You!
As always, very good content.
excellent fact to close out the video, i will now think about this every time i board a commercial airliner
Great explanation ! Thanks !
I was looking for this explanation. Thanks
Great job, thank you very much.
I learned something new today, thank you. ❤️❤️❤️
I am glad to hear that!
Great explanation many thanks.
Gnarly video!! Thanks!
Hi there, thanks for this video. Very informative!
What a great channel 🙌✈️ glad I found you
That was very helpful, thank you!!!
Well done video - cheers!
Outstanding explanation!!
Thanks a lot:)
This is what happened on the Helios Airways 522 flight... Normally the aircraft's internal pressure is managed automatically by the aircraft's two onboard pressurisation computers, but the pressurisation system can be swapped over to manual control.
On Helios 522 the pressurisation system was switched to manual to perform a ground test on one of the rear doors, but the maintenance staff forgot to put it back to auto once they were done. Since this system is so rarely ever adjusted, the flight crew never actually looked at it during any of the checklists, assuming it was in auto mode. If they had looked, they would have seen a Green "MANUAL" indicator illuminated where there should not have any indicators illuminated. At this point you're probably asking yourself "hold on. Why is the 'manual' indicator Green? Why isn't it Amber or Red?" Well, that's down to the fact that using the pressurisation system in manual mode can be a completely normal thing in the event of the pressurisation computers being non-functional for whatever reason. It's just a bit of extra work for the pilots to regulate the internal air pressure themselves. At the time at least, this wasn't considered a "non-normal" situation, it was categorized as a supplemental procedure. This may well have changed since.
Anyway, after the aircraft took off, with the pressurisation system in manual mode, the outflow valve was basically left open which meant that the differential pressure was below normal during the climb to cruising altitude, cabin altitude was above normal and the cabin climb rate was over double the normal rate. The flight crew had multiple opportunities to spot this problem but missed it every time, this was presumably due to the pilots "rhyming" parts of the checklists, which means they were just stating the settings were correct without properly looking and giving the correct responses from memory. This may have been laziness, complacency or due to a perceived time pressure... Or maybe just a genuine mistake. We'll never truly know.
When the Cabin altitude warning horn sounded, at the time there was no distinction between a "take-off config" warning and a "cabin altitude" warning, because the two use the same horn in the accident aircraft. So the flight crew mistook the alarm as an erroneous take-off configuration warning and attempts to clear the error by toggling the autopilot off and on again then doing the same with the auto-throttle. This was incorrect as a take-off configuration warning can only occur on the ground and the aircraft knows exactly how high it is at all times while powered up. So if that warning horn is ever heard in the air, it's a cabin altitude warning 99.99% of the time.
Once the flight crew started troubleshooting with this incorrect assumption, it is highly likely that confirmation bias starting factoring in. Once the cabin altitude passed 14,000ft. Four amber indications lit up within a short space of time, these were "MASTER CAUTION", meaning "Hey! Something's wrong!" "OVERHEAD" which means "Look up and see which warning is lit up", "PASS OXY ON" which means "The passenger oxygen masks have dropped. You've got 12 minutes to get the aircraft back below 14,000ft before the passengers are in danger of dying." and an "OFF" indication on the equipment cooling panel which means "There's not enough airflow to cool the electronics properly." both the passenger oxygen and equipment cooling warnings would trigger the Master Caution and if it wasn't reset before the second activation signal came in, it wouldn't come on a second time.
Once the aircraft reached 28,800ft. The FDR data shows that all attempts to communicate to the ground ceased along with all signs of activity within the flight deck, this is likely when the pilots and flight engineer lost consciousness due to Hypoxia. In the cabin the passengers and flight crew would have remained awake for at least 15 minutes since they had the EOGs (Emergency Oxygen Generators) to keep them conscious for 12 minutes and when those ran out the cabin altitude was at about 24,000ft. Which would have given a time of useful consciousness of about three minutes.
After that, the passengers and cabin crew would have started to pass out with the exception of a single flight attendant who utilised 3 of the 4 cylinders of therapeutic / medical oxygen aboard the aircraft to remain conscious until very end. During final minutes, this flight attendant, whole held a Commercial Pilot's License, gained entry to the flight deck and attempted to fly the aircraft themselves, however they had not received type rating certification so it would have been impossible for them to save the aircraft let alone fly it under ideal conditions, however they did their best and as the engines inevitably flamed out because the plane ran out of fuel (it had flown the full journey and six circuits of a holding pattern on autopilot as part of it's pre-programmed missed approach procedure) the flight attendant attempted to make a mayday call which unfortunately was not heard since the pilots had passed out before they could switch radio frequencies to ones used by controllers closer to their destination, additionally once the engines had flamed out and the aircraft was running on battery power and the Ram Air Turbine for hydraulics, the flight attendant attempted to level the aircraft out to reduce the impact forces. This final act actually caused the plane to narrowly avoid a residential area if I recall correctly, but unfortunately there were no survivors from the flight.
EDIT - Corrected the name of the airline.
Good overview😊👍🏻
Some pointers:
•The pressure is managed by one of the two CPCs, the other one is backup (they change role every flight).
•The takeoff config warning can come on inflight (not common tho)
•If that warning does comes on inflight is 99% takeoff warning due to flap sensor fault😉
•Cabin altitude warning comes on at 10000ft (just for info, not correcting)
•Autopilot and autothrottle is not connected to the takeoff config warn (doesnt make sense to disconnect due to t/s..)
•There isnt a flight engineer on any commercial jet anymore
•Equipment cooling came on before 14000ft, master caution stayed on so they didnt notice the pass oxy ON light (kind of what you said)
•Time of useful consciousness of 3 mins!?🤔🤷🏻♂️
•The flight attendant gets multiplied😆😉 (they)
•There is no RAT on the B737
This is great. Thanks
thank you, fantastic explanation and animations! :)
Amazing video
I am just your average passenger who finds planes fascinating, so yes, I learnt something new today. I knew something about cabin pressure but learnt so much more today :). Thank you. I am sure your channel is meant for Pilots and aviation experts, not average people like myself, but know that I enjoy your vidoes even if I don't understand a lot of it LOL!
Thank you it was very useful
Well-done!
thank you so much sir! helps me a lot!
A great video !
Great content 👍
Well explained
4:25 would you want to equalize the intake and out take once you are at cruise altitude?
good explanation. thumbs up👍👍
Thanks a lot!:)
I truly wish your Command Handbook was to the same quality as this and what I’ve seen your App........nice video....🙏🙏🙏
Maybe one day you might be on the bus.... I would look forward to seeing your app for that as well....
Good video. Thx
Wouldn't mind a video from you on how pressurization systems work on prop planes
Great video! What editing software did you use?
Loved it.
I think this is important to know, even if a passenger never experiences it. I've flown for millions of miles and never thought about this. Now I know.
Will this same pressurization system work for water and space? How menuverable are the "pressure packs?"
i would like you to talk about negative relief valves. thank you
There was an incident w/ American Airlines flight 329 from Miami to New Orleans on May 17, 2023 with loss of Aircraft Pressurization.
Stole from the Engine part got me cracking 🤣 ( bleed air )
Thank you 💓
You are welcome:))
I like the background music.
I DID learn something new. I learned that we, the passengers, only get about 12 minutes of oxygen~! I thank the heavens for conscientious pilots~!! I've always had a good experience flying.
What safety margins are you referring to?
Fantastic! very well done! Continua così!
So I’m deducting that the B737 MEL limitation of not flying over FL250 with one pack inoperative comes from the fact that if the other pack would fail in flight at a higher level the time of useful conscious would be to short, or is it because with only one pack you couldn’t pressurize the cabin enough to fly at a higher level? Please correct me if I’m wrong, or if there are any other factors involved in this limitation. Ps. Awesome video, keep it up!
The one pack is capable of providing the normal pressure in the cabin all the way up to FL410 in B737. The MEL restriction is for dispatch because you are already dispatching with one PACK, there is higher risk of loss of pressurization. If you lose one pack after dispatch then no such restriction exists and you can complete the flight. After landing, the defect would have to be fixed or aircraft dispatched with the MEL and max cruise altitude of 25.000ft
Thanks for the info! Great stuff
What airliner cruises at 41,000’?
Pressure demand system. This system supplies oxygen under pressure slightly over-inflating the lungs and allows flight above 40,000ft. The overpressure lowers the lung in altitude so gas exchange occurs in the lung alveoli. Above 40,000ft 100% oxygen without pressurization would be insufficient!
I think the speaker should clear his throat a little bit LOL
Now I can solve my AGK questions thank you !
I heard from a 737 pilot that if the plane loses pressure they have to put the plane in a controlled nose dive if they are at cruising altitude.
Yeah I think all pilots in all airliners do that
It’s called an emergency descent and pretty much all pilots learn it when they get to the commercial license stage of their flight training
What happens if for some reason, a window breaks or a door is opened at 41000ft? Do they have to descend below 10000ft to keep the pressure in the control?
Yes. FAA Regulation 14 CFR FAR 25.841 Pressurized Cabins requires emergency descent within 17 seconds to prevent passengers and flight crews from hypoxia which is catastrophic leading to loss of consciousness, serious brain injury, even death.
You mentioned an app that can be downloaded. What is the app name?
The 737 Handbook www.737handbook.com
How does the higher pressure inside the plane than outside not cause the plane to explode?
How does a submarine not implode at high pressure? It is the strength of the aircraft material that can withstand that kind of pressure difference.
Airbus aeroplane is safer than other? or not?
12 minutes,… to descende 41,000 ft, thats a really fast change in altitude!!! 😮
Me a Cessna pilot who was told by my instructor to learn about pressurization has learned about a 737 system hell yeah 😂😂 😂
Question why not just hold your breathe ? Many people can go minutes without breathing
Absolutely 😂 right
Trying to hold your breath during a depressurization may damage your lungs
yes yes yes yes YES!
Hey my friend, can you send this to Boeing? Make sure there’s lots of pictures
Scary
Because I’m not flying from London to Madrid
Ask Lockheed what happens when a plane cabin depressurizes mid flight.
Edit: Sorry, McDonnell Douglas.
"We have to pressurize the cabin"
"That's easy. We'll use high pressure exhaust gases from the engines"
"No, it has to be air"
"Exhaust is air"
" _Breathable_ air"
"Now it has to be _breathable?_ You said 'pressurize the cabin', now there's breathing involved? Geez. Nothing's ever good enough for you"
Why is the music so loud
41k seriously. Never been above 36. I have been on 20 flights
some flights can go up to 50,000ft it depends on the plane weight
Who knows a lawyer that I can call for sueing my university for mal practice and the infringement of turture laws.
I’m more confused now
If it's a Boeing, then the CEO has to step down.
3D printed medical interfaces for astronauts...where is that education?
Check your staff. Please. Get FB I. CIA. Two planes. Not. Good check. Everyone. Who works on these aircraft. Urgent. Urgent immediately
Greedy pilots always want to hog all the oxygen 😡