Airliners, Ebola, Myths and Facts


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Airliners, Ebola, Myths and Facts

The most recent communicable disease being linked with air travel as a possible factor in its spread is Ebola, which joins a long line of other contagions, such as SARS, H1N1, Hepatitis and even the basic flu, in the screaming air travel headlines.

There are two ways in which air travel could actually be a factor in the spread of such infections. First is the simple reality of transporting those infected to an uninfected area, and second is the propagation of infectious elements among people near the disease carrier.

This last consideration is medical and comes with contingencies well beyond my level of expertise. But what is absolutely common knowledge is that countermeasures in any public place–which an airliner is–are rudimentary. Your airline seat–like your theater seat, your seat at a dinner table, a taxi cab, a bus, a classroom, or any public area–is not sanitized before your use, no matter who sat there before you. That’s the public health standard in the modern world.

Yet the media rushes to the airport to show file footage of an airliner, then grab man on the street interviews with deplaned passengers, asking if they’re concerned about being exposed to [fill in contagion du jour] from other passengers who have visited [fill in global contagion hotspot] from possible proximity to an infected person.

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It’s a short leap from there to certain urban myths about air travel. First, and most persistent yet absurd, is “passengers are in a sealed tube, breathing the same air.”

The reality of an airliner is yes, the hull is pressurized, but no, it is not sealed. In fact, the fundamental link between pressurization and air conditioning on a passenger airliner at all altitudes is a constant outflow from the jet in flight, into the atmosphere. The controlled outflow is key to moving volumes of air through the cabin in a deliberately designed pattern for many vital functions beyond passenger comfort.

In a Boeing 737-800, that carefully crafted flow pattern drives air from two air conditioning systems through the cabin and cockpit, down through the forward electronic equipment bay below the cockpit where it picks up residual heat from electronic systems to keep that vital equipment at optimum operating temp, then the airflow proceeds back around the cargo compartment, keeping that compartment from getting too cold, then overboard through an automatically modulated outflow valve.

Key to that process is flow. The plane is not sealed, so constant airflow is mandatory–and here’s where another urban myth surfaces: airlines are limiting airflow to save money.

The fact is, airlines are increasing airflow to save money: in our Boeing, we have two large, powerful recirculating fans driving airflow which in basic Venturi logic, draws air from the air conditioning systems and eases the workload ultimately on the engines from which the bleed air is tapped and thereby increasing fuel mileage.

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The urban myth about decreased aircraft airflow to save money probably originated in the early seventies when the OPEC oil embargo drastically spiked fuel prices. Airline engine technology was simpler and less efficient before today’s high-bypass fan engines were developed. But even then, less bleed air really never improved airline fuel burn and regardless, an jetliner was never a sealed tube and always required metered outflow balanced with input to maintain pressurization.

“Raising the altitude in the cabin to save money” is the third urban myth with no basis in fact. First, in the Boeing, pilots have control of the rate of change only–the cabin altitude is set at a constant differential between inside and outside the hull based on maintaining the strength of the fuselage. Hollywood may have inspired the myth that pilot can “raise the cabin altitude,” but the only thing we can actually do is climb or descend and when we do, the pressurization systems maintain a constant differential and a constant airflow in order to maintain structural integrity of the fuselage.

So back to my original point: yes, airliners are the hardware of mobility that now mixes populations experiencing regional outbreaks with others a world way, but only in the modern sense of scale: all continents are now linked by air travel in hours rather than days or months of travel. But travel itself is the fundamental reality of the twenty-first century, period.

And that mode of travel, “air travel,” is neither conducive to propagation any more than any other public place, nor is any airline adding any infectious risk to “save money.” The most glaring stupidity in that persistent myth is the vital contingency the the flight crew must blindly increase their own health risks to do anything of the kind.

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In the passenger airline flight crew world, we often refer to an airliner as “the flying Petri dish,” because people with every communicable disease board, fly, sneeze, hack and cough just as they do in any public place. But that’s no different than the environment endured by the first grade teacher, the restaurant waiter, or pediatric nurse.

And the airline seats are about as “sanitized” as the movie seat you sat in, the tray table as “clean” as the restaurant tabletop the busboy just wiped with a wet rag dipped in tepid, hours-old water from a well-used bucket.

In other words, as far as infectious disease exposure risk, an airliner is just like any other public area–we just move faster and more frequently from place to place. It’s not a sealed tube, no one is reducing airflow or raising the cabin altitude to save money.

So use common sense about flying, recognize the airliner cabin as a public place and behave accordingly (thanks for mopping the lav floor with your socks, BTW), and breathe easy when you do, knowing the truth about these unfounded flying myths.

More insider info? Step into the cockpit:

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These 25 short essays in the best tradition of JetHead put YOU in the cockpit and at the controls of the jet.

Some you’ve read here, many have yet to appear and the last essay, unpublished and several years in the writing,  I consider to be my best writing effort yet.

Priced at the printing production cost, this collection is not for profit–it’s for YOU to keep.

Own a piece of JetHead, from Amazon Books and also on Kindle.

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12 Responses to “Airliners, Ebola, Myths and Facts”

  1. Well said, still laughing at the socks in the lav comment.

    It’s sad but in the main, the people that will read your words are the ones that already know most lines put out by the media are myths and hyperbole and shout at the tv as they perpetuate them..

  2. Randy Sohn Says:

    Wish that I had Glenn Beck’s E-mail address so I could sent this to him!

    • Good idea:

      Glenn Beck | me@glennbeck.com

      “Stu” | stu@glennbeck.com
      Stu is the Executive Producer and Head Writer for the Glenn Beck Program.

      I didn’t get into it in the article, but you know how the switching of bleeds on the 727 and 707 could lead to the incorrect perception back in the day that bleed air was being limited. But not really!

      • “the pressurization systems maintain a constant differential and a constant airflow in order to maintain structural integrity of the fuselage”. Indeed. I recall an Aero Lab course where the professor demonstrated the relative strength of pressurized and unpressurized thin-walled aluminum structures by crushing full and empty beer cans. Shame about the wasted beer, but it was for science…

  3. Chris, the latest version of the Tumbleweeds is now in my webshop… Could you mention it as well? Next to just Amazon… Regards, martin

    JetHead’s Blog schreef op 2-10-2014 16:57: > WordPress.com > Chris Manno posted: ” Airliners, Ebola, Myths and Facts The most > recent communicable disease being linked with air travel as a possible > factor in it’s spread is Ebola, which joins a long line of other > contagions, such as SARS, H1N1, Hepatitis and even the basic flu, in ” >

  4. […] public place, the life of an airline pilot. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own […]

  5. Christine Von Allwoerden Says:

    Thank you ! I was wondering if you pick up the recent headlines. I do love the socks in the lav (-:

  6. peggywillenberg Says:

    Socks in the lav? Ew.

  7. And Ebola is actually much less contagious than SARS or avian flu which was airborne.

  8. Michael A. Says:

    Chris-
    The Pilot in theory can control the pressurization of a Boeing 737NG (I’m not familiar with the classic 737 controls, but I assume this is applicable to them as well). If both auto and altn modes of the cabin pressure control system fail or the dc motor that controls the outflow fails there is manual control. Manual control uses a seperate dc motor to control the outflow valves. Using manual control you can change the pressurization in the cabin depending on how you control the outflow valves. All that being said, I have never heard of a pilot switching to manual, except for preflight checks. It is the third backup to a system that if a pilot found something wrong with would land the plane before even needing to go to that backup.

    • “In theory” anything is possible. I’m talking about practical and real life. Being typed in the 737-800 and flying it PIC 90+ hours a month I’m familiar with the manual pressurization valve (yes, I know the study guide answers about DC motors, etc, thanks anyway) so “in theory” a pilot could use it exactly against it’s design, which is to keep the cabin at the designed pressure differential. In fact, most systems can be defeated and used improperly as you are suggesting. But that’s more Clancy-novel fodder than anything anyone would do.

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