A military plane with 38 passengers on board has gone missing on its way to Antarctica, after losing radio contact with Chile's air force on Monday evening.
In a world of GPRS networks and sophisticated air traffic control systems, how can a plane disappear like this?
Typically, the first indication that a plane has gone missing will be when it vanishes from the radar, or fails to communicate with air traffic control. How soon after its actual disappearance this might be depends on where it is flying.
On a busy flight path, a disappearance might be spotted in moments. On other routes, it might take 10 to 15 minutes for it to be noticed. When a plane is flying over water it must make regular contact with air traffic controllers on the ground.
As soon as it drops off the radar, the first thing the air traffic controller will do is contact the next radar facility on the plane's flight path, and then others in the area, to see if they can detect it. If not, they will notify the destination airport where the plane is heading to – as well as all other radar facilities.
There are international search protocols which become effective once the disappearance has been announced – everyone is obliged to start looking for the plane. The military forces in most countries will be informed, so they can lend assistance.
The search will involve military aircraft and naval vessels in the area, as well as passenger planes and civilian boats. The missing plane will be searched for on radar and also with the naked eye. Some will go out of their way to scout the area where it is believed the aircraft has disappeared.
Naval vessels will send people on deck to look for debris in the water. The pilots of passenger planes flying over the area will make a point of literally looking out the window – presuming the weather is clear – in search of the missing plane. From 30,000 feet you're probably not going to see much, but it's almost a kinship among aviators as well as a requirement to offer whatever help one can.
The airport where the plane is heading will usually become a focal point immediately after the disappearance. This is usually when members of the press and families are informed. This is also important because eye witnesses need somewhere to feed their information and relatives need a point of contact. In the instance of the missing Chile plane, the Chilean air force is controlling communications.
Flights will rarely be grounded or diverted, unless – as in the case of Malaysia Airlines flight MH17, which was shot down over the Ukraine in 2014 – there is a clear indication that the area is unsafe. The airport of departure will, however, check its runways to look for parts or debris. If there is nothing untoward, then flights will continue.
The investigation will normally be led by the country where the aircraft is registered or the country it is flying to. However, help will be available from many quarters, not least because passenger planes typically carry travellers of many nationalities.
Each member of an investigating team will focus on a different potential cause. One will focus on weather – what the conditions were like in the area, whether other aircraft reported problems such as turbulence. Another will focus on the aircraft itself – when it was last serviced, previous problems with the model and so on. Security, of course, will be another line of enquiry. And another team will look at the human factor, which was the cause of the Germanwings Flight 9525 crash – has the pilot had disciplinary action before? How are things at home? It's all about eliminating the least likely causes.
The investigation will last as long as it takes. In the case of the 2009 crash of Air France 447, for example, it lasted for quite some time as it took two years just to find the plane. Then they had to go to the bottom of the Atlantic Ocean to find the black boxes so they could start trying to figure out what happened.
There are two black boxes, which are actually orange in colour. One carries the cockpit voice recordings for the last 30 minutes of flight, which includes conversations between the pilots, and conversations with air traffic controllers. The other box records the data, things like air speed, altitude, and how all of the systems in the aircraft – electrical, hydraulic and so on –were functioning at the time of the incident. Between the two boxes, if the data can be fully recovered, it provides a very comprehensive forensic analysis of what was happening on the aircraft.
A black box recorder. Photo: iStock
Occasionally the investigation won't get anywhere. The cause of the Malaysia 370 crash remains a mystery and there are a couple of flights in aviation history for which there is still not a probable cause. In the first instance, it is of great help to investigators when debris is found. Debris, along with the cockpit and data recorders, often provides enough information alone to establish the probable cause or causes of the incident.
The Telegraph, London