Squeezing 'Black Box' Transmissions into Crowded Aviation Frequencies
Posted by: Keith Epstein on June 04, 2009
Since suggesting a way to end sole reliance on the relatively archaic (and sometimes irretrievable) flight data recorder as a way to understand causes of airplane tragedies such as Air France Flight 447(See Beyond the Black Box), we’ve heard from several aviation industry insiders and a regulator or two who note the underlying contentiousness over a crowded radio frequency might no longer be a stumbling block to any effort to expand the amount of operational data automatically transmitted from aircraft.
The concern focuses on increasingly crowded frequencies in the existing 1090 Mhz aviation band, which some say could reach capacity within five years. In September 2008, an FAA rulemaking committee, particularly concerned about high-density aviation corridors in areas such as the northeast U.S., requested an “urgent” study of congestion on 1090 MHz. The band is already used for air-to-ground communications, a network of ground-based transmitters that monitor locations of planes through transponders, and alarms meant to avert mid-air collisions. In July 2008, the government filed a petition with the FCC to add yet another set of equipment to the band: Devices designed to help pilots avoid collisions on the ground.
While that may sound like plenty, efforts at companies such a L3 are focusing on a way to cram still more data within the available space - perhaps as much as four times as much, which aviation communications specialists say could accommodate a scheme to transmit all the data an accident investigator (or airline cost efficiency personnel) might dream of.
Some of the technology is to be demonstrated to FAA officials in the months ahead. While company insiders naturally are wary of disclosing their proprietary methods, they have suggested multiple analogues to their approaches, comparing the data-compaction to the way cellphones send and receive signals in efficient spurts; to the addition of DSL to a phone line, permitting dramatic expansion of information flow without impeding voice traffic, and videoconferencing versus teleconferencing.
Thus additional messages can be sent over the 1090 Mhz band “without impacting the current messages using higher-order modulation schemes,” observes one avionics and communications specialist. “All of this would allow the 1090 band to send the types of aircraft state information on a continual basis that you were hypothesizing.”
And that, in turn, could mean that instead of spending tens of millions sending robotic submersibles in quest of an elusive black box beneath the ocean depths (while the world continues to wonder for years about the fate of the Air France Airbus 330) investigators would already be hard at work piecing together exactly what happened Sunday night over the waters of the Atlantic.
Instead of speculating without much evidence at all, they might even already have moved close to a conclusion.