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The modern by design aircraft is protected against biological threats (COVID-19) better than you think

There are very few flights left, but they are still there. There are few of them because of COVID-19. Mainly due to the closure of passenger traffic and related quarantine measures. But I would like to talk about how terrible the threat of "catching" the virus, while inside the aircraft. Suddenly you for one reason or another need to fly? And inside there is a cramped closed space, and it seems that it is quite dangerous there.

I will describe the specifics of the Airbus 319/320/321 family, probably one of the most common narrow-body aircraft in the world that I have been flying for many years. I am not a specialist in Boeing and other types of aircraft, but I assume that the differences in the operation of the described systems are minimal. In addition, I am not a technical specialist serving these aircraft, so please be so kind as to forgive my possible minor flaws in the description of the technical part.

Most important:


Airbus A318 / 319/320/321 passenger compartment ventilation scheme

The passenger cabin of the aircraft is “cut” by the air conditioning system of the cabin into many, many layers, divided into rows and consisting of separate air flows. Visually, this is one space, but thanks to this system, it is extremely unlikely that you can become infected, except from your nearest neighbor. Plus, in flight, the air in the cabin is completely updated every 3 minutes and before being returned, it is passed through the cabin HEPA filters.

Now, let me tell you the details.

Past coronaviruses


So, during the previous spread of the MERS / SARS family of viruses, Airbus issued operational recommendations to all aircraft operators, and also answered in detail all the questions about the risks of transmitting the virus when passengers and crew are inside the aircraft. In March 2020, these guidelines were updated due to the proliferation of COVID-19 and sent out to all operators. We will consider some of them a little later.

In addition, all major regulators directly or indirectly related to civilian passenger transport issued detailed recommendations on actions that would help reduce risks for passengers / operators in connection with the COVID-19 pandemic. For instance:


Air in an airplane


Perhaps, now we will move on to our rams : any modern aircraft is equipped with air conditioning , boost and ventilation systems. Those who have worked on Soviet technology should be familiar with the abbreviations SLE and SARD(air conditioning system / automatic pressure control system). The main task of all these systems is to provide comfortable atmospheric parameters inside the aircraft cabin at all stages of flight, since people are gentle creatures and can comfortably exist only in a limited range of pressure and temperature. The cabin of the aircraft, if very simplistic, is a tin can with two openings (hereinafter, we will not use the godly word for any engineer: “ hole») - through one of them, air constantly flows out, and through the second it enters under a slight pressure. At the same time, the air flow from / to the openings is regulated using a special valve (s) so that the pressure difference inside and outside increases as you climb, the height in the cabin (in pressure) also increases, and the pressure in the cabin drops . With a decrease, the pressure difference inside and outside gradually decreases, the height in the cabin (in pressure) decreases, and the pressure in the cabin increases. The boost system is responsible for this process , by which we will go a little further. The temperature in the passenger cabin and the cockpit, as well as in heated luggage racks, is constantly maintained at approximately the same level - this is the work of the air conditioning system. Everything related to ventilation of the avionics compartment, toilets, kitchens, etc. - This is the operation of the ventilation system .

A small five-minute physics: I remind you that the percentage of gases in the air does not change with height, and only the partial pressure changes . For example, the partial pressure of oxygen in the air can be described as 21% of the pressure of a standard atmosphere ( ISA, International Standard Atmosphere) at 1013 hPa at sea level, which will be exactly 213 hPa. For example, when using the parameters of the standard atmosphere at an altitude of 11,000 meters, the temperature overboard will be -56.5 ° C and the air pressure 227 hPa. I propose to calculate the partial pressure of oxygen at a given height on your own as an exercise. At the same time, almost all civilian aircraft move at altitudes of 10-11 with a few thousand meters - this is near the border of the tropopause or slightly above it. If at this altitude an explosive (instantaneous) depressurization of the aircraft occurs, then the human body can be conscious from 15 seconds to 1 minute - such data are provided by the FAA (Federal Aviation Administration, a kind of Russian Federal Aviation Administration in the United States). It is for this reason that all planes,those flying above 3000 meters are required to be equipped with oxygen equipment for both pilots and passengers in accordance with airworthiness certification standards.

When depressurization occurs, pilots are obliged to drop to a height where passengers can breathe relatively freely without oxygen masks - this is usually a height of the order of 3000m or the minimum safe height in this sector, which can be more, but that's another story. The oxygen supply in gas generators (and for passengers oxygen is supplied to the masks using an individual chemical oxygen generator) is enough for at least 15 minutes, and an emergency decrease to a safe height takes about 4 minutes. And yes, I’m hurrying to upset you a little - the pilots' oxygen supply (and this is a separate oxygen cylinder) is designed for the same 15 minutes.

Interesting Facts:


  1. It is widely believed that pilots should not wear a beard or mustache, as "Oxygen masks cannot be worn / used." This is not so: the design of the mask is such that a very tight fit to the face is ensured, regardless of the presence of vegetation on the pilot's face.
  2. The chemical oxygen generator in the cabin during operation is heated to fairly high temperatures (above 100 ° C), so after removing the mask from the face, do not be surprised by the smell of burning plastic and possibly even light smoke in the cabin. This is normal.

And now, smoothly move on to all three aircraft systems:

  • (Air Conditioning): , , ( Airbus COCKPIT, FWD CABIN, AFT CABIN – , ) . . – , :

    1. lx-photos

    (PNEUMATIC) APU (Auxiliary Power Unit, — – , ). , PRECOOLER (). , – :

    CFM56 PRECOOLER’

    PRECOOLER 200 . ( 1). PACK 1 PACK 2 ( ), MIXER UNIT (), , HEPA , . 1. TRIM AIR VALVE, – . , – PRECOOLER’, PACK’, .

    , PACK. , 200 40 PSI ( 2,7 ). PACK’ – , . AIR CYCLE MACHINE (“”) – , . PACK :

    lx-photos PACK’

    — – MIXER UNIT, , PACK 1 PACK 2 , HEPA . , MIXER UNIT – LP GROUND CONNECTION (Low Pressure Ground Connection – ), EMERGENCY RAM AIR (, MIXER UNIT ). , , PACK’ :

    – , – HEPA , – MIXER UNIT. lx-photos

    MIXER UNIT – . «» – HEPA . lx-photos

    « » — , Airbus , 3 . – , , PRECOOLER’ PACK’ ( ), , HEPA . , , , , USA (, Airbus — ):

    1. Donaldson Filtration Solutions
    2. Pall Aerospace

    , Pall Aerospace Pall Medical , HEPA , . 0.01-0.2 , , :


    HEPA

    Airbus , , ( — ):
    « , HEPA , MERS ( ) COVID-19 ».
    99,99% – , , HEPA .

    - ?

    1: MIXER UNIT’a, TRIM AIR VALVE . , . . , , :


    Airbus A318/319/320/321



    . , .

    «» – , . HEPA . , WHO (World Health Organization) , — ( , ). , , , , , . , ( , ):



    , . :



    , – , , , . Airbus . , EASA 2020-02R4 07.04.2020, Airbus:
    « HEPA , ».

    ? :

    , Airbus , , COVID-19 ( – ):
    « . , , , MIXER UNIT’, . , , . , HEPA , MIXER UNIT. , HEPA , COVID-19, ».
    , – , .. ( 200 PRECOOLER’a, -), .

    ( , – Airbus, ) – , .


    1. Airbus , – FAP (Flight Attendant Panel), . – .
    2. – -60 , – . – , . – ( «» ..) .
    3. , - PACK’. , PACK .
    4. PACK’, , EMERGENCY RAM AIR – , . MIXER UNIT.
    5. APU , , LP GROUND CONNECTION. MIXER UNIT, , , .
    6. – APU. PACK’ MIXER UNIT , .
    7. PACK’ – . « » () – .

  • (Pressurization): , . – . – , – .

    CPC (Cabin Pressure Controllers, ), outflow valve ( ) safety valves ( ). , – , CPC outflow valve .

    , – . , . , – safety valves — , , () ( 8,6 PSI) .


    1. 14000ft (4300 ). , , . – 8000ft (2500 ) .
    2. , ( ) DITCHING. (!) , .
    3. , : / . FMGS (Flight Management Guidance System) , . ( – ), ( ) , .

  • (Ventilation): , . — ( ), ( 2) . – , , .


    1. () , .
    2. / , , ( ). - , ( ). , 1 – .
    3. . ? .
    4. , CABIN FANS – , HEPA . — .


Probably, I would like to end with this about aircraft systems that help you to feel good both in flight and after it and say a few words about what the airlines are doing to minimize the risks of infection and infection of employees:

  • Masks / gloves (yes, do not laugh!) For the cockpit / flight crew.
  • Detergents / disinfectants with increased concentration in accordance with the recommendations of the Federal Service for Supervision of Consumer Rights Protection and Human Welfare - employees who process the interior are fully dressed in disposable protective suits with gloves and masks.
  • Processing folding tables, armrests of chairs, handles and luggage racks - the places that passengers come into contact with most often.
  • The aircraft used to return our compatriots go through an additional stage of complete disinfection of the passenger cabin.
  • Airing (not in the sense of “let's open the window”) of the aircraft cabin using air sampling from the APU and the standard air conditioning system of the cabin before and after cleaning. It takes literally 5 minutes on the ground to completely replace the air in the cabin.

Well, that seems to be all. Perhaps the presentation was somewhat messy, but there are always comments where you can ask a question. Write, I will try to answer.

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