The bewildering search for MH370 continues

It is possible for a plane to 'disappear' by turning off the identification transponder. Photo: ITV News/Dan Rivers

There is very little concrete information about the disappearance of flight MH370.

We know it was flying perhaps as high as 45,000 feet before rapidly descending to approximately 5000 feet.

We don’t know what prompted the precipitous descent, but it may have been to avoid local radar, by “terrain masking”; effectively hiding behind mountain ranges or using the curvature of the earth to dodge Malaysian radar, as it flew across the Indian ocean.

Malaysian investigators now think the plane flew at 5,000 ft over three unnamed countries, but we don’t know which they are.

I asked former Tornado pilot and now commercial passenger jet officer Jake Waterson how feasible it would be for an experienced aviator to work out how to “vanish” from radar screens.

He suggested it would be relatively easy once the plane’s transponder has been switched off.

A simply trigonometry calculation would enable any pilot to work out how low he’d need to fly to shield himself from radar stations, providing the pilot knew where the radar stations were and their elevation above sea level.

Waterson said fuel consumption would be significantly greater at low altitude, where the air is denser, meaning the range of the aircraft would be dramatically reduced. He explained:

If you were heading towards mountainous areas you obviously wouldn’t want to stay at that height.

But he said a brief period of "tactical low level flight would enable the jet to "escape" from Malaysian radar before it was able to climb back to normal cruising height once it was out of “view”, several hundred miles away from Malaysia.

Of course this is all predicated on first turning off the plane’s identification transponder, the small device carried by every aerial vehicle which can be programmed to broadcast a unique 4 digit identifying code, along with critical metadata, like altitude.

To find out what happens when you turn off the transponder, I took to the sky in a light aircraft with a helpful pilot, Robin Durie.

In a pre-arranged demonstration he turned off his plane’s transponder, literally with the touch of a button. A few seconds later air traffic control at a nearby RAF base acknowledged that our signature code, 2651, was no longer showing on their screens.

We were then just an anonymous “blip”, and had Robin combined deactivating the transponder with a rapid descend, we too could have “vanished”.

MH370 did continue to leave the faintest of electronic trails though. An “electronic handshake” continued with the Inmarsat Indian Ocean Satellite for several hours.

Experts were able to establish the distance from the satellite of the last handshake, giving a huge search “arc” which they are now scouring for evidence of a crash.

It is a bewildering search so far without any conclusion.

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