Patrick Smith is not only a pilot but, author of the book Cockpit Confidential: Everything You Need To Know About Air Travel and owner of the website askthepilot.com.
Mr. Smith says he was shocked to find what most travellers believe to be cold, hard facts about flying. He’s ready to set the record straight.
Myth 1 – The air on a plane is mucky and filled with bacteria and viruses
Passengers and crew breathe a mixture of fresh and recirculated air. This combination, rather than using fresh air only, makes it easier to regulate temperature and helps maintain a bit of humidity.
The supply is bled from the compressor sections of the engines. Compressed air is very hot, but the compressors only compress; there is no contact with fuel, oil, or combustion glasses. From there, it is plumbed into air conditioning units, known to pilots as ‘packs’, for cooling, before being ducted into the cabin.
The air circulates until eventually it’s drawn into the lower fuselage, where about half of it is vented overboard. The remaining portion is run through filters, then remixed with a fresh supply from the engines, and the cycle begins again. People are known to describe jetliner cabins as ‘stagnant’.
It can seem this way at the gate or while taxiing, and during engine starts the air conditioning units will occasionally ingest exhaust fumes. But during flight the air is constantly in motion.
Those underfloor filters are described by manufacturers as being of ‘hospital quality’. Boeing says that between 94 and 99.9 per cent of airborne microbes are captured, and there’s a total changeover of air every two or three minutes – far more frequently than occurs in buildings.
You are no more likely to catch something from flying than you are from spending time in an office, classroom or movie theatre.
And of those who do get sick, usually it’s not through what they are breathing, but what they are touching. Lavatory door handles, contaminated trays and armrests etc. are the germ vectors of concern, not the air. A little hand sanitiser is a better safeguard than the masks I sometimes see travellers wearing.
If passengers have a legitimate gripe, it’s about dryness. Indeed cabin air is exceptionally dry and dehydrating – at around 12 per cent humidity it’s drier than you will find in most deserts. This is a byproduct of cruising at high-altitudes, where moisture content is somewhere between low and non-existent.
Humidifying a cabin would seem a simple and sensible solution, but it’s avoided for different reasons. First, to amply humidify a jetliner would take large quantities of water, which is heavy and expensive to carry around. Humidifying systems would need to recapture and recirculate as much water as possible, making them expensive and complicated.
They do exist: one sells for more than $100,000 per unit, and only increases humidity by a small margin. There’s also the important issue of corrosion. Dampness and condensation leeching into the guts of an airframe can be damaging.
The new Boeing 787 Dreamliner has the cleanest air of any commercial plane in existence, thanks to filters with an efficiency of 99.97 per cent. Humidity too will be substantially higher.
The plane’s all-composite structure is less susceptible to condensation, with a unique circulation system that pumps dry air through the lining between the cabin walls and exterior skin.
This is the one that really gets my pulse racing – partly because we hear it so often, and partly because it’s so outrageously, patently false.
My old comparison between flying and medicine is, I think, still the best one: modern technology helps a pilot fly a plane the way it helps a surgeon perform an operation. A jetliner can no more ‘fly itself’ any more than an operating room can remove a tumour or perform an organ transplant ‘by itself’.
We often hear of this proverbial ‘computer’ that flies the plane. There is no such thing. Rather, there is an autoflight system, made up of multiple sub-systems and components, each with a different function.
The ‘autopilot’ is just one of these components (the plane I fly has three autopilots). Loosely put, it’s the device that allows you to take your hand off the wheel. But you still need to tell it what to do, when to do it, and how to do it. There are, for example, no fewer than six different ways that I can program an automatic climb or descent on the 757, depending on preference and circumstances.
The automation is not flying the plane. The pilots are flying the plane through the automation. We are telling it which routes to follow, and how to follow them; which speeds and altitudes to fly, and when to fly them; and a hundred other things over the course of a flight.
You’d be surprised how busy a cockpit can become – to the point of task-saturation – with the autopilot on. Even the most routine flight is subject to countless contingencies and a tremendous amount of input from the crew.
That includes the takeoff and landing. In certain weather conditions, jetliners can and do perform automatic landings – autolands, we call them – as they’ve been doing for over 35 years (the first jet so certified was the British-built Trident, designed in the 1960s).
But in practice autolands are very rare. I see two or three each year, maybe. And the term is terribly misleading. The fine print of setting up and managing one of these landings is something I could talk about all day.
If it were as easy as pressing a button and folding my arms, I wouldn’t need to practice them twice a year in the simulator, or need to consistently review those tabbed, highlighted pages in my manuals.
It’s there if you need it – for that foggy arrival in Buenos Aires with the visibility sitting at zero – but it’s anything but simple. In a lot of ways, an automatic landing is more complicated, and more work-intensive, than a manual one
And there is no such thing as an automatic takeoff. Not in any Boeing or Airbus, anywhere, ever.
Myth 3 – In order to keep passengers calm and quiet during the flight, pilots will toy with the oxygen quantity. Minimizing airflow also helps to conserve fuel
The rate and volume of airflow is mostly automatic. On the Boeings that I fly, the switches are set to automatic mode prior to flight, and they stay there. The strength and volume of airflow remains consistent.
We only adjust the settings if there’s a malfunction (an overheat, a recirculation fan failure, or some other glitch in the plumbing). In over five years of flying 757s and 767s, this is something I have experienced only once or twice.
It’s similar on Airbus models. The airflow controls usually have three positions, labelled HI, NORM, and LO. The NORM position is standard. The HI position is used when a rapid change in cabin temperature is needed. The LO position does as the name implies.
While it provides a bit of fuel savings, it isn’t used very often. At most carriers, LO is used only when the passenger count is below a certain threshold. “In any case it’s not a big change,” says one Airbus captain. “Sitting in the cabin, it’s almost impossible to notice the difference.”
The idea that we cut back on oxygen is simply ridiculous. Oxygen levels are determined by pressurisation. Crews set up the pressurisation system (there’s a main and at least one backup) before departure, dialling in the intended cruising altitude and/or elevation of the destination airport. As with airflow, the rest happens pretty much automatically. We don’t mess with it unless something goes wrong.
Pressurisation, for those who don’t understand it, is what allows you to breathe normally while flying at high altitudes. Using air bled from the compressor sections of the engines, it effectively squeezes the rarefied, high-altitude air back into sea level air (or something reasonably close to it).
While en route, the cabin is held at the equivalent of anywhere from around 5000 to 8000 feet above sea level, depending on the aircraft type and cruising altitude. (Pressurizing all the way to sea level is unnecessary and would put undue stress on the airframe.)
In other words, you’re breathing as you would in Denver or Mexico City – minus the pollution.
Not only that, but subjecting passengers to an oxygen deficiency – a condition known as hypoxia – would have some rather undesirable effects. Although the symptoms of hypoxia can, at first, make a person feel giddy and relaxed, they also induce confusion, nausea, and migraine-strength headaches.
I remember the multi-day hypoxia headache I endured some years ago in Cuzco, Peru, an experience I wouldn’t wish on my worst enemy let alone a plane-load of customers.
And remember, pilots are breathing the same air as everybody else on a plane. An aircraft fuselage does not contain separate compartments with different pressure values in each.
The entire vessel is pressurized equally from the forward pressure bulkhead to the aft pressure bulkhead. This normally includes the cabin, cockpit, and lower-deck cargo holds.
Except that it’s not. In fact it’s cheaper now than ever before. A recent study shows how the average cost of an airline ticket has declined 50 per cent over the past three decades. And yes, that includes factoring in those ancillary add-on fees that have become so common.
Fares fell 21 per cent between 2001 and 2010 alone. Between 2005 and 2010, even with the airlines struggling and fuel prices soaring, the average economy class fare was the cheapest it had ever been.
And although fares have increased slightly over the past two or three years, they remain about 15 per cent lower than they were in 2000.
Perks and amenities aren’t what they used to be, but the trade-off is that far more people can afford to fly.
In years past, only a fraction of the population could afford to fly at all. In my parents’ generation, it cost several thousand dollars to travel between the US and Europe. Even coast-to-coast trips were something relatively few could afford.
The idea of flying as a form of mass transit, with college kids jetting home for a long weekend, is very new.
Myth 5 – Passenger Embellishment Factor (PEF)
That’s my term for people’s tendency to exaggerate the sensations of flight. The altitudes, speeds and angles you perceive often aren’t close to the real thing.
During turbulence, for example, many people believe that an aeroplane is dropping hundreds of feet at a time, when in reality, even in relatively heavy turbulence, the displacement is seldom more than 20 feet or so – the slightest twitch on the altimeter.
It’s similar with angles of bank and climb. A typical turn is around 15 degrees, and a steep one might be 25. A sharp climb is about 20 degrees nose-up, and even a rapid descent is no more severe than 10 degrees nose-down (usually it’s a lot less).
I can hear your letters already: you will tell me that I’m lying, and how your flight, was definitely climbing at 45 degrees and definitely banking at 60.
And you’re definitely wrong. I wish that I could take you into a cockpit and demonstrate. I’d show you what a 45-degree climb would actually look like, turning you green in the face. In a 60-degree turn, the G forces would be so strong that you’d hardly be able to lift your legs off the floor.
Distances between planes is another one. “While we were flying to LA,” somebody might recall excitedly. “Another plane passed so close to us, you could see the people inside!”
While landing on parallel runways or crossing perpendicularly at high altitudes, airliners often pass within close proximity. But close proximity, in the meticulously orchestrated doings of air traffic control, is measured in miles, or in thousands of feet. During cruise, vertical separation is never less than a thousand feet.
To an anxious flyer, his or her emotions revved by adrenalin, distances and sensations are distorted. Planes are big, and yes, a 747 zooming past you, a thousand feet above or below, appears to be very close. But trust me, you have never, ever been close enough to another plane to see faces through those small oval windows.