As the search for aviator Steve Fossett continues, I've been thinking about the ways we try to track down missing people.
One of the leading independent experts on ELTs (emergency locator transmitters) is Doug Ritter, editor of the Equipped to Survive Web site. Ritter has written extensively about ELTs, which are installed on aircraft; EPIRBs, or emergency position-indicating radio beacons, which are carried on boats; and PLBs, or personal locator beacons, which are carried by individuals. If you have any interest in the subject, you should check out his Web site.
Ritter's most recent blog post, dated Thursday, concerns a recent memo from the chairman of the National Transportation Safety Board to the administrator of the Federal Aviation Administration. In the memo, he recommends that the new style of 406MHz ELT be mandated for use on all aircraft, replacing the existing mandate for 121.5MHz ELTs.
The issue is that the international COSPAS-SARSAT satellite system will stop processing 121.5MHz alerts in 2009, so the ELTs that are currently required will no longer serve their intended purpose. As the NTSB and Ritter point out, they don't work very well right now anyway.
I don't know whether Fossett's airplane had the new or old style of ELT, but that isn't actually what I want to talk about here.
It occurred to me that the whole idea of an ELT that transmits only in an emergency should be revisited.
Cell phones continuously announce themselves to the cell phone network as their owners move around. These announcements are very short and efficient, since there isn't much to say; they consume very little of the system's available bandwidth.
Similarly, I'm thinking that ELTs should periodically transmit their current position, direction and velocity. If these announcements happened every five minutes or so, a lost airplane could be located fairly quickly even after a sudden catastrophe, like running into the side of a mountain.
It's possible that these periodic transmissions would overload the existing COSPAS-SARSAT network, but perhaps these satellites can be replaced with more capable units over time. For example, beamforming techniques could be used to improve sensitivity in areas of heavy air traffic. Increasing the effectiveness of this system could save a lot of lives, which justifies some increase in cost.
The ELT should be self-contained, with its own UPS (uninterruptible power supply) and GPS receiver so that it can independently monitor the aircraft's motion. Once an aircraft departs from its normal flight envelope-- sudden descent, for example, or a roll maneuver in an airplane not designed for acrobatics--the ELT could begin transmitting more frequent updates.
This all comes to mind because I've been having similar thoughts about how the new 700 MHz public-service band should be used. This is the same band in which several companies, including Frontline Wireless, hope to create so-called Open Communication public wide-area networks. (On August 21, I blogged about about Frontline Wireless at the Hot Chips conference.)
I'd like to see ELT-like capabilities used in this new band, along with various other new operating modes...but that's a subject for a future post.