Dreaming of a more pleasant flight

Question: I just read your column regarding cabin pressurization and my question is about the new Boeing Dreamliner. I read somewhere that the extensive use of modern composites in the fuselage will allow for a larger maximum pressure differential from the added strength these new materials provide.

Do you have any idea how "low" the cabin might be able to fly if the aircraft is flying at 40,000 feet, or will that information not be available until the aircraft is certified?

—E.G. Morgan, Bainbridge Island, Wash.

Answer: As luck would have it, Boeing had just invited me to participate in a media summit regarding their new B-787 Dreamliner when I received your question. I was one of just nine media representatives from eight countries and the only American present.

After presentations by Boeing B-787 Chief Project Engineer Tom Cogan and several other representatives, our group was treated to a tour of a cabin mockup. I thought it was gorgeous, with beautiful colored lighting options available to the cabin crew. In addition, new composite materials used in the airframe permit windows that are larger than on any of today's current commercial aircraft. Many of the questions I've received through this column have to do with unhappiness about the small windows found in airliners, so I expect passengers will rave about the views from the new Dreamliner.

Window shades will also be a thing of the past. Instead, passengers will be able to lighten or darken their individual windows with the push of a button. In many instances, having the shade either up or down is the equivalent of having sometimes very harsh outside light either "on" or "off." Now passengers will be able to adjust their own windows to achieve the lighting they want.

One of my favorite touches of all is the addition of a window in the lavatories.

One of my favorite touches of all is the addition of a window in the lavatories. And when the plane is on the ground? Ground sensors in the landing gear send a signal to black out the windows in each lavatory, just in case someone is lurking about outside on a ladder.

The Dreamliner also has some new advances I never thought I'd see, and your question has to do with one of them. In my recent column about pressurization, I mentioned how a cabin altitude of 7,000 feet or slightly higher must be maintained when planes are at cruising altitudes, and that a lower cabin altitude wasn't possible due to the excessive pressure and stresses it would put on the airframe.

This is not true of the Dreamliner. The composite material used in the airframe is lighter, stronger and not as subject to fatigue as the material used in other aircraft. This is the first time in history a commercial airliner has been designed with the capability of maintaining a lower cabin altitude even at the highest cruise altitudes, and a real milestone in technological advances. The maximum cabin altitude in the Dreamliner will be just 6,000 feet.

It's interesting to note that although the airplane could be designed to be capable structurally of maintaining a sea level cabin, Boeing claims their testing revealed that a cabin altitude lower than 6,000 feet provided no meaningful improvement over a sea-level cabin, and since there is a cost to maintaining the cabin at sea level, they elected not to.

A cabin altitude of 6,000 feet may not sound like much of an improvement over a cabin at 7,000 to 8,000 feet that airplanes maintain now, but after a flight of more than a few hours, it can make all the difference in the world. The negative symptoms of soreness, dryness, fatigue, etc. are all markedly increased above 6,000 feet, especially after long flights. Those who suffer from ear pain should suffer less as well, with less of a pressurization change during flight than previously the case.

I am constantly answering emails from travelers who insist they get sick every time they fly, and ask why the air quality is so bad. The fact is, air on planes is already highly filtered. The Dreamliner, however, not only has an improved air filtration system, but this airplane is "smart" in that it will know how many people are on board. This is information the pilots will be able to enter from the cockpit. The reason it matters is that current filtration assumes the plane is full of people, but if it isn't, and the air conditioning systems can adjust for fewer people, less humidity is sucked out of the air. This new capability, along with some other factors, will ensure a cabin not nearly as dry as current cabins, a major factor in keeping passengers less susceptible to picking up airborne viruses and other maladies.

There are other major improvements as well. For instance, the actual source of air for the air conditioning and pressurization systems is radically different from previous airplanes, provided through electric air compressors. In my recent column about pressurization, I talked about the source of cabin pressurization being "bleed air" off the engines. Boeing uses significantly less bleed air (only for engine cowl anti-ice) on the Dreamliner, which in itself should be impressive to other pilots if not to passengers.

Here's why pilots will care: Any time bleed air is taken from the engines for systems such as air conditioning and pressurization, performance suffers somewhat. There is a penalty in how much thrust is produced by the engines any time bleed air is being tapped from the engines, and more fuel is burned. On hot summer days when the air is less dense, air conditioning systems are sometimes even turned off during takeoff on some planes to provide more thrust to the engines. The Dreamliner, however, doesn't divert air from the engines for most of the uses we see in today's airplanes, making it much more fuel efficient.

The information presented by Boeing was so interesting that for the first time, I've decided to write my column in two parts. I'll talk more about the improved fuel efficiency, new engine noise suppression improvements, size and other aspects of this fascinating new airplane next week.

In the meantime, I've put together a collection of photos from my trip. The first part consists of photos I took while the second part consists of photos provided by Boeing. You'll find the B-787 Dreamliner album in my online photo gallery (click on the B-787 photo to open the album). Be sure to note the jumbo-sized windows in both the cabin and lavatories.