It's also worth remembering that phones don't use GPS
most of the time. They will look for cell towers and wifi access points first. Wifi access points can be looked up (via the 3G
/4G internet connection) against a database like skyhook - all these options use much less battery than turning on the GPS
radio and waiting for enough satellite locks.
As others have said, transmitting - particularly to satellites - requires much more power than your cell phone talking to the tower a block or two away.
One thing that might help in more densely travelled areas, is to establish a loosely connected grid network between aircraft. Send your position (and aircraft registration and date/time in UTC
) out every second or 5 seconds or whatever. Everyone who hears it records it, keeps it for 24-480 hours. This does not take up much space, even if one aircraft "hears" several dozen other aircraft. This way, if one aircraft goes quiet, it would be pretty easy to quickly determine its last location.
Speaking of storage, I find the amount of storage available for things like the CVR to be fantastically small. While I understand the need to have devices that are extremely robust, we also know that things like SD
cards are incredibly hardy, can survive tremendous shock and years in ocean water, and are available in fairly large sizes - up to 512GB last time I checked. Setting up the CVR to record to the super-durable crazy expensive storage, and rotating out older recordings to cheaper storage would only add a few grams. Quick back-of-the-envelope suggests that can accommodate nearly 900 hours of uncompressed CD
quality stereo audio.