Missing Flight MH370: Are there really unmonitored black spots? Your questions answered

A navigational radar on Indonesia's National Search and Rescue boat shows details during a search in the Andaman sea (AFP/Getty)

10 days after Malaysia Airlines flight MH370 from Kuala Lumpur to Beijing was lost, the range of possibilities to explain its disappearance is still extremely wide. We invited readers to pose questions about the lost Boeing 777- and the wider implications of the biggest mystery in 21st-century aviation.

Given the level of satellite coverage, are there really unmonitored black spots?

Sarah Johns

Many travellers have reacted with dismay or astonishment to the revelation that it is apparently so difficult to track the movements of a 250-ton aircraft with 239 people aboard. To understand why it is tricky, first look at the needs of individual nations. Governments are interested in knowing about aircraft flying overhead or approaching their airspace. In the US, Europe and some other parts of the world, control is maintained at all times. At the other extreme, parts of sub-Saharan Africa have extremely patchy coverage. South East Asia is busy in aviation terms, but air-traffic management is not as effective as in Europe. The main way to detect an aircraft whose transponder (which normally transmits identification details) is turned off is through “primary radar”. This is Second World War technology that sweeps the sky with a high-energy electromagnetic beam and registers any reflections. An unexplained radar “blip” in the early hours of the morning may go unnoticed, especially if it goes away quickly, or at least may not prompt a reaction.

From the airlines’ perspective, a relatively primitive reporting system has worked remarkably well over the decades: duty rooms note the departure time, estimate the arrival time, and ask the crew to report their position by radio at regular intervals. This could be replaced by a much more effective satellite reporting system, though it would prove expensive to retro-fit existing aircraft.

There is effectively saturation coverage by satellite of the surface of the earth, albeit with some weakness around the poles (not relevant in this case). Satellites fitted with cameras are routinely able to see aircraft in flight – to see some snapped serendipitously, just search for “Google Earth planes flying”. But in the hours of darkness, this would be virtually impossible.

I don't understand from the "pings" why the aircraft can be in two possible corridors in relation to the satellite?

James Taylor

After the main communication systems were turned off aboard MH370, one channel remained open: a periodic “handshake” between the aircraft and an Inmarsat communications satellite in geostationary orbit 22,250 miles above the Indian Ocean. The last was at 8.11am, local time. From the time that it took the responding “ping” to reach the satellite, it is possible to compute the distance from the satellite. Then, elementary geometry comes into play: draw a circle on the surface of the earth showing all the points that match that distance. The circle has a circumference of about 18,000 miles, but most of it can be disregarded because the limited range of the plane from its last known point. In addition, the Malaysian authorities chose to rule out a 1,200-mile segment between the two arcs, though the logic for doing so seems flawed: they say it takes into account the minimum flying speed of the jet, though this interpretation appears to ignore the possibility that the aircraft could zig-zag or fly around in circles.

The aircraft is unlikely to be exactly on one or other arc, since in the time since that “handshake” was registered it could have flown 250 miles in any direction.

Do cabin crew have no way to signal an “incident”? Perhaps they should after this

Michael Choo

Cabin crew have access to emergency locator transmitters, but these are electronic distress beacons designed to be used in the event of a ditching at sea or forced landing rather than in flight. There is no publicly available evidence that one was activated aboard MH370.

What will the impact be on airline security?

Gina

The long-term effects will depend upon what more we learn about the fate of MH370. But already the aviation community is looking at two possible areas of intensified security, one affecting passengers and the other pilot.

The revelation that two passengers were travelling on stolen passports may lead to a requirement that details of travel documents are compared against a central database of missing passports. And if it is found that either an intruder to the flight deck or one of the pilots was responsible for the disappearance, there may be calls for an air marshal to be seated on the cockpit to deter unwanted intrusions – and to keep an eye on the captain and first officer.

Either move would prove expensive, and the latter would be strongly resisted by many pilots.

Weren't there reports of passengers’ mobiles still ringing? Stories dismissed but now credible.

Paul

Early on in the hunt for the aircraft, some reports suggested that passengers’ mobiles were ringing out rather than going straight to voicemail – but it appears that this was simply due to the phone networks' configuration. Indeed, one of the most troubling aspects of this case is the absence of reliable evidence of contact between people on the plane and their relatives on the ground. If and when the passengers became aware of a threat, a natural response would be to attempt to contact family using mobile phones. Although voice calls from a plane at 30,000 feet do not usually work, SMS messages sometimes do. In their absence, it is difficult to conclude other than the passengers were prevented from using them, or that the plane was flying over the sea well out of range of mobile-phone masts.

A friend bought a Malaysian Airlines ticket before this happened. Now she's very worried indeed. Is there need to be?

John Brady

No. Flying on commercial jets remains an astonishingly safe form of transport. The accident-free record of Britain’s airlines over the past 25 years is the envy of the world, but other major carriers – including Malaysia Airlines – are also extremely safe. The most significant risk of any trip to South East Asia is a road accident.