Recently I mentioned Jay Rosen's complaint about Virgin America: the airline advertises normal 120 volt AC sockets at (most) seats, but Rosen said the power kept being cut off during his flight.

I wondered whether, as a technical matter, an airliner could actually produce enough power to keep a planeful of laptop users plugged in through a whole flight. Now I need wonder no more! Below and after the jump, two detailed replies by people in a position to know.

Short answer: No, you probably couldn't make this work. Short explanation: The necessary equipment is so heavy that, while it's fine for a train or bus, it's a real challenge for an airplane. For more, read ahead.

One reader says:

I ran some back-of the envelope calculations, and it turns out that providing guaranteed power to every seat in a large plane for the entire duration of a flight is quite a technical challenge.

Say you limited the power at each seat to 120V, 2A, a perfectly reasonable figure for charging a laptop - if everyone in a 500 seat plane drew 2 amps for the entire duration of an 8-hour flight, you would need the equivalent of ten or so Chevy Volt batteries, and an inverter the size of a large refrigerator (hopefully with some active power factor correction to prevent the "extreme sine waves" that Virgin references). Obviously, there would be less equipment for shorter flights/smaller planes, and everyone on the plane is not going to be drawing 2 amps for the entire duration of the flight, but if you want to guarantee power for everyone for the entire flight, it's what you need.

A simpler idea would be to have an alternator on the jet engine - but I have no idea if this is technically feasible, and it would have to be a fairly substantial alternator. Airline electronics typically run off of 400hz (rather than 50/60hz) because the transformers needed for 400hz power are much smaller and lighter than transformers needed for 50/60hz power (assuming the amount of power it can handle is equivalent), so you may need two separate alternators in this case.

Another idea is to have small inverters at each outlet, or row of seats, eliminating the need for a refrigerator sized inverter somewhere in the aircraft.

After the jump, a "translation" of the explanations from the Virgin American spokesman, to discuss the underlying technical realities. Now we know!