Was the aircraft victim of an accident or was its disappearance a result of terrorism? Was it shot down, hijacked by intruders or the crew, did it ditch and sink rapidly as a consequence, or did it land successfully at one of the 634 runways on its theoretical pathways suitable for a B777 to be stowed away and held for ransom? We might not know the answer to these disturbing questions for months and years to come. However, the travelling public is astonished to learn that the B777 of flight MH370 was not under active surveillance. How can it be that in times where anybody can be located homing on a cell phone a commercial airliner just gets lost?
Since the end of World War II, air traffic has been surveyed by radar. Primary radars pick up the reflection of an electronic beam from an aircraft to determine its position. This technology has its limitations given a range of only 70 nautical miles. Aircraft have therefore been equipped with transponders that respond to radar inquiry. These secondary radar systems typically range up to 250 nautical miles. If an aircraft flies outside of the range of a radar station, such as over the open sea or remote areas, so called procedural air traffic control, which involves position reports and estimates, is used to control air traffic. Nevertheless, unknown to the travelling public, most of the commercial air traffic is not under active control for a large amount of a given flight.
The industry has developed the Aircraft Communication Addressing and Reporting System (ACARS), on which operators can transmit via satellite aircraft data from anywhere in the world on a privately operated network. Typically, only engine data are regularly sent for analysis during a flight to a carrier’s base and to the engine manufacturer, and some company communications (text messages) are done. However, given that this private sector communication solution is expensive, airlines limit the usage of these services and don’t send other data, such as position reports, over these networks.
Over 10 years ago, a new technology called Automatic Dependent Surveillance – Broadcast (ADS-B) has been developed in the United States. With ADS-B, each aircraft will be equipped with a digital transmitter reporting its position and other parameters every second to a simple ground based receiver. The new system costs less than 10 percent of traditional radar systems, and it allows following any aircraft continuously. Trials in Alaska have been so successful that the American Federal Aviation Administration (FAA) has made the system mandatory on all aircraft in the United States by 2020. Today, about 60 percent of commercial airlines are equipped with ADS-B, but only a few countries (e.g. USA, Australia) have ground installations to receive the signals. To address the lack of surveillance over remote areas where no ground installations are possible, private operators are currently developing satellite systems that could pick-up and rebroadcast ADS-B at reasonable cost. Would flight MH370 have been equipped with ADS-B, the search would have been a question of hours, as the reference point would have been the point of its last transmission seconds before disappearance.