Skygirl

The Queen Elizabeth II docked in San Francisco yesterday with apparently 300 people stricken with norovirus. http://www.sfgate.com/cgi-bin/articl...&sn=006&sc=405

These norovirus reports are taking a hit at the cruise industry, just as SARS took a hit on the airlines. Because of the publicity, I had a client this morning who wanted to cancel a cruise and fly to Europe instead. All of this publicity is kicking up fears once again in the traveling public. Of course this could indirectly some airline bookings as most have to fly somewhere to board a cruise ship. The man asked me if I would get on a cruise ship. I told him that of course I would, just as I hopped on a 747 and flew across the Pacific during the SARS outbreak.

I have a question for you pilots, and now is as good of a time as any to ask it. Often times clients and potential passengers will ask me about the air in airplanes. There is the belief out there that the air in the cabin is recirculated, and that no fresh air is introduced during the course of the flight. Can you folks set me straight on that issue and give me a good reply for your potential passengers?

tomgoodman

Some air is always leaving the cabin, through the outflow valve (which controls cabin pressure), cargo heat outflow, instrument cooling outflow, sink and toilet vents, etc. You used to be able to identify these areas from the outside by noting the nicotine stains! This air is replaced by outside air which has been compressed by the engines and fed into the A/C systems. Whatever air is in the cabin at any given moment is constantly being recirculated, which aids in maintaining a reasonable temperature in all parts of the cabin. So the bottom line is that cabin air is both fresh and recirculated. It's also quite dry, and you're typically at, say, 8000 feet presssure altitude and 74 degrees inside while it's 50 below zero outside!

Skygirl

Thanks Tom! I appreciate your answer and wisdom. Did I hear somewhere that in the newer aircraft that they were putting in more advanced air filtration systems that had a greater intake of fresh outside air? I realize that there is no getting around the dry air problem at altitude, unless someone can come up with some sort of efficient humidifying system. Now that could make an enterprising engineer a multimillionaire!

HSLD

The 787 will have electric pneumatic pumps for pressurization instead of using engine bleed air. On older airplanes cabin air is/was recirculated to save fuel (takes fuel to produce engine bleed air).

Because this plane has PLENTY of electrical generating capacity without significantly impacting fuel burn - it would reason that cabin air turnover wouldn't be the issue it was. I don't know what the air turn over rate will be on the 787, but based on the systems I'd guess it would be improved over the 777. The 787 will also have HEPA filters but I don't believe that the filtration affects cabin airflow rates.

The dry air problem is more of a challenge. Simply stated: it takes water to make humidity, water has weight, it takes fuel to carry weight. The engineer that can find a solution to the "gravity problem" would indeed do quite well.

Roll Inverted and Pull

Present day aircraft recirculate some of the cabin air. Cabin air is however, much fresher than air in say for instance, a big office building. There is always some fresh air coming into the cabin. BTW, cockpit air is all fresh air. We get our own supply.In the old days, before smoking was outlawed on passenger planes, the area aft of the outflow valves usually had a long trail of brown tar smeared along the fuselage. Sometimes the valves would get stuck due to tar buildup. Thankfully those days are over.