In this age of GPS how do you lose a plane?
28 Dec 2014 Jason 1
The world is in shock again as another civilian airliner goes missing, and the families of those on board are struggling to come to terms with the gut-wrenching agony of not knowing what has become of them.
It’s the pain of not knowing that is causing many to question why authorities are able to just “lose” a plane.
Many wonder why in this modern age of GPS, with everything from pets to cranes being tracked down to the meter, why something as large as a jet isn’t being traced every step of the way. Simply put, how do you lose a plane?
In the hours following the recent AirAsia Flight QZ8501 disappearance, search and rescue have what has been described as a very broad search area, divided into sections approximately 30,000 square miles in size. The search has also been hampered by treacherous weather, reducing the possibility of locating survivors or even the plane for that matter.
The good news is that it is over the relatively shallow Java Sea, a congested airspace and popular shipping route.
Even still why don’t we have a GPS location (latitude & longitude) to pinpoint the location of the aircraft? In the case of MH370 that would have saved the ongoing delays and millions of dollars spent in a search that is still continuing today.
To understand the answer to that question we first need to know how planes are currently tracked.
How planes are tracked
While we commonly use GPS to track terrestrial (earth-based) objects likes cars, planes are tracked using radar. Radar, which stands for RAdio Detecting And Ranging, was developed in the 1930s and, as the name suggests, uses radio waves to detect solid objects. A radar station transmits bursts of high-powered radio frequencies, which collide with objects and bounce (or echo) back so it can be determined how far away it is, and how quickly it is moving (using the Doppler shift).
In addition to this rather rudimentary location technology, most modern planes are equipped with Mode-S transponders which transmit back to the radar station helpful information including altitude. These transponders regularly ‘ping’ air traffic control, allowing them to track the path of individual planes.
For all its versatility and ubiquity, radar has its limitations. Too far from land, low altitude or failure of the plane’s transponder can cause radar to become ineffective. Unfortunately, one, or all, of these events are generally associated with an aircraft in difficulty. In these situations, ground control rely solely on radio communication from the plane’s personnel.
ADS-B – GPS for planesWhile pilots have used GPS for some time to identify their location, this was never shared with air traffic control. ADS-B intends to change that.
ADS-B is on-board technology that uses GPS to determine its location, instead of radar, and then transmits this information to ground stations. You can see this technology in action on freely-available websites.
While ADS-B is becoming the new standard for air traffic control to track planes, it too has limitations, particularly when an aircraft is too far from a ground station (such as over the ocean). The coverage area is improving but there are still a lot of blind spots.
In these situations, aircraft can use ACARS to send data to satellites, like a type of online black box flight recorder. Data limitations normally mean it is only used in very remote areas, and often limited to basic pings that don’t provide investigators enough information to pinpoint a plane’s crash site.
Plane tracking – It’s just not that simple
The challenges of effective and accurate plane tracking are big: current technology is unreliable at times, the globe is much bigger than we often realize and the most effective systems rely on cooperation from the both the plane and personnel on board – something that simply can’t be guaranteed in the event of an accident, whether intentional or not.
Proactive tracking systems (i.e. not reliant on the aircraft responding) are possible but we’re not there yet. Perhaps satellites equipped with radar and photographic identification can map individual aircraft along their route?
Until then disappearances such as AirAsia Flight QZ8501 will continue to confound the public, and result in massive search and rescue efforts and hopefully relatively quick closure for loved ones grieving for those missing.