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In-Flight Web Access Coming Soon?
tewl wrote to us with news that in-flight Internet and e-mail may soon be available on commercial airline flights, but that U.S. airlines are still wary of it. It sounds pretty interesting, but it also sounds like the earliest it's going to roll out is next year. Honestly, I'd like them to work on power adaptors first, but, hey.
The plane has three identical generators - two driven off the main engines, and one driven by a small turbine in the tail (the APU).
The generators are connected to the engines by a CSD (Constant speed drive) that...well, runs the gennies at a constant speed. The CSD is basically just a mechanical transmission. They generate 120 volts at 400Hz. (Incidentally, that's what that 'whine' is on the audio channels that you can hear - it's the 400Hz bleeding over). DC power for the stuff that runs on DC is 28vdc. It is either provided by the battery, or by the T/R (transformer/rectifier) units from the 120VAC supply.
Normally, in flight, the APU gets shut down, and power is provided by the engine-driven generators. This energy isn't free of course - if everyone turned their laptops on, the Captain would have to push the thrust levers a little bit more forward. I don't remember what the ratings of the generators are (but if you're really interested, email, and I'll look it up).
The generators cannot supply the same bus at the same time (there's a left and right bus) because if they are out of phase, all hell breaks loose. (The B727, so I am told, can run more than one generator on a single bus, but the B727 has a flight engineer to make sure everything is in phase)
Other aircraft services, such as pressurization and airconditioning are NOT electrical (although they are controlled electrically!). The air you breathe in a plane comes out of the engines off some of the high-pressure compressor stages (the compressor is *before* the combustion chambers). This extremely hot air goes through the PACKs (pressurization and airconditioning kit) so that it reaches you at the right temperature. Incidentally this is why you sometimes get smoke in the cabin when that engine all the way out there on the wing croaks.
Have you ever wondered why the lights flicker just after engine start? Well, on the B737 at least, Boeing employs "break before make" switches when the two power buses are switched from the APU's generator to the engine driven generators, hence there's a brief power outage when one of the pilots reaches up to the overhead panel and throws the switch.
Also...the engines on the B737 are not started by electricity! They are started by compressed air. To get the engines going, first you have to crank up the APU and use its compressor bleed air to start the engines. Smaller jets have electrically started engines though (bizjets like Lears, Citations etc.)
Oolite: Elite-like game. For Mac, Linux and Windows
Anyway, I work at Tenzing, and here's some info to clear up some of the confusion. You may think some of Tenzing's ideas suck, but hey.
Email: You'll be able to use your current email account, you won't need a special tenzing account. There's some software that basically "dials up" to the onboard server; your laptop thinks it's connected to your ISP. It's pretty transparent, except you gotta use our SpecialNiftySoftware to start the whole process. Then the server just acts as a proxy between you and your ISPs actual mail servers. Mail gets collected, and every x minutes (set by the airline) all the mail is bundled, sent to the ground, and new mail for you gets sent up to the plane. So there is a delay.
Web: As noted, there's cached web content. However, it's not all just static crap. Partnerships with various places and search engines will allow searches, online orders, etc, in flight. Selected stuff will be updated during the flight, like stock quotes and maybe weather and whatever else our marketing dorks decide is necessary, but most updates will happen between flight legs.
Actual connectivity: None, yet. Some companies are working on actual broadband access during flights, but it's still experimental. We hope to get partnerships with these folx later. :)
Electronic device usage: Well, standard airline rules apply. The connection is thru the plane's phone lines to the seats, so there's no special new concerns. We've asked about using wireless, but the gov doesn't like that idea at the moment.
Quake games: Probably possible, but remember that, at least at first, you're limited to phone dialup speeds (since you connect thru the modem). Whether the games are doable or not depends on how the engineers setup the onboard boxes.
A piece of trivia: The servers are all running some OS that happens to be pretty popular around here. Muahah.