Even though air travel is safer than ever and in many cases cheaper than 10 or 20 years ago, travelers love to complain about its agonies. Cramped and narrow seats, crying babies, chatty seat mates and armrest wars are common gripes. But other factors contribute much more to feelings of distress, especially on longer flights.
The silent killers are altitude sickness and dehydration. These come on you gradually, and most people don’t even know what hit them, blaming their discomfort on “jet lag.”
But help is on the way in the form of new commercial airliners constructed in large part of high-tech materials, including carbon-reinforced plastics.
The science behind air travel discomfort
In a study entitled “Effect of Aircraft-Cabin Altitude on Passenger Discomfort” in the New England Journal of Medicine, the authors write that people who “travel to terrestrial altitudes above 6,500 feet experience acute mountain sickness, a syndrome characterized by symptoms of headache, nausea, vomiting, anorexia, lassitude, and sleep disturbance.” The researchers call this “Acute Mountain Syndrome.” The ill effects are even more pronounced the older you are.
And no wonder. When you’re flying at 38,000 feet on a conventional aircraft, the cabin is pressurized at 8,000 feet, the equivalent altitude as Bogota, Colombia, or the Beaver Creek ski resort in Colorado’s Rocky Mountains.
But two newer airplane models, the Boeing 787 Dreamliner and the Airbus A350, are pressurized to 6,000 feet, which makes a huge difference in passenger comfort, as I discovered on some recent flights.
Not long ago I flew from San Jose, Calif., to London non-stop on a British Airways 787-9 (a larger version of the original 787-8) on a 10-hour flight. Soon after I had an opportunity to fly on an even longer leg from the Airbus factory in Toulouse, France, to Singapore, on a Singapore Airlines Airbus A350 delivery flight (it just happened to be Airbus’ 10,000 airframe). Breathing problems? No. Dry eyes and nasal passages? Didn’t happen. On both flights, after the meal service I fell into a deep sleep and only woke minutes before landing, feeling incredibly refreshed.
After returning from Singapore, I wanted a deeper understanding of the technology behind these new planes. Exactly how do these aircraft manage to create a more comfortable cabin environment, and why didn’t earlier models achieve these benefits? So I called Boeing to find out, and the company put me in touch with Blake Emery, Director, Differentiation Strategy, and Kent Craver, Regional Director, Cabin Experience and Revenue Analysis.
The answer? Plastics. More specifically, carbon-reinforced plastic composites.
‘Pressure drop oh pressure drop. You gonna feel it’
Flying at an “internal altitude” of 8,000 feet means your heart and lungs must work harder to supply oxygen to your vital organs than at sea level, causing fatigue and shortness of breath. It’s one reason why champion marathon runners hail from high-altitude locales: Their stronger lungs and hearts give them an advantage. Not just running, but even sleeping at higher altitude becomes more difficult (have you ever experienced, on a ski trip, waking up in the middle of the night gasping for breath?).
As your high school physics teacher may have explained, air flows from high pressure to low pressure, and atmospheric pressure goes down as altitude increases.
As a plane climbs to 35,000 feet and the pressure outside the plane goes down, the pressure inside the plane, set at a more comfortable lower altitude, becomes higher relative to the outside. So the higher cabin air pressure pushes out trying to equalize with the lower outside pressure.
When airplane designers further increase the interior pressure to achieve a lower and more comfortable cabin altitude, as with the 787, that puts even more stress on the plane’s structure. If that structure is made of metal, the continual bending and flexing of the metal weakens it. “Imagine bending a wire over and over until it breaks,” Craver explains. “It’s the same with aircraft metal.”
“Over time, that increased pressure difference adds stress to a metal airframe, which can shorten the life of the structure,” Craver explains. “While this is not a safety issue, it would certainly be an economic issue for an airline.” But plastic, and the way Boeing constructs its airplanes, means the airplane does not fatigue if you add pressure.
More humidity means more comfort, up to a point
Next, humidity. I had wondered how these new planes managed to maintain higher cabin humidity levels. (I even asked an airline engineer I was flying with to explain this but he couldn’t come up with an answer.) Are there humidifiers on board? No. It’s us. We passengers generate cabin humidity as we breathe and perspire. To reduce aridity, the 787 and A350 retain inside the cabin more of the humidity generated by passengers. They do this by regulating how much humidity is expelled outside the plane.
In fact, the crew can program the Boeing 787’s optimal humidity levels depending on the number of passengers onboard (the more passengers, the more cabin air is expelled). “The outside air at 35,000 feet has near zero humidity,” Emery explained, “But too much humidity inside the cabin is as bad as too little. Think how tired you feel when the humidity is at 100% on a hot day.”
Why don’t older planes keep more human-produced humidity inside the plane, you ask? According to Boeing’s Craver, “humidity can be detrimental. Metal corrodes,” eventually weakening aircraft structures and requiring repairs. “But carbon fiber doesn’t care if it gets wet.”
The 787 offers some other interesting features to increase passenger comfort. Larger windows, higher cabin ceilings, an advanced air filtration system, and software designed to suppress wind gusts to ensure a smoother ride. “It’s not just one item, it’s all of them together as a system,” Carver explained.
Eventually all planes will offer the same benefits, but it’ll take a couple of decades. There are 810 firm orders for the A350 (Singapore Airlines alone has 67 on order) and over 1,200 for the 787. Meanwhile, Singapore Airlines recently began non-stop 16-hour flights between San Francisco and Singapore using A350 jets and in 2018 will be flying 18 hours non-stop from L.A. and New York to Singapore using a longer-range A350 variant.
Although sitting in an airplane for 18 hours is not “fun” for most people (I know, I’ve done it), it’ll be a lot less taxing in one of these new jets.
Anyone wishing to arrive in better shape will do themselves a favor by doing a little research while booking airfares. To find out which routes the 787 and A350 fly, here are two useful websites: