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Priority to aviate, not communicate

March 11: A Vietnamese military helicopter yesterday flew over the Gulf of Thailand. Planes and copters from nine nations are scouring the waters near a Malaysia Airlines flight’s last reported location. Answers to some basic questions:

How could a Boeing 777 simply vanish? Aren’t they always tracked by radar or satellites?

Radar coverage is not universal, especially over water. In areas without radar, pilots are generally required to radio in their positions at fixed intervals, mostly to assure that air traffic controllers can keep aircraft out of one another’s way. Between intervals, something could go wrong.

Planes like the 777 also have automatic systems that send out data on engine performance and other technical functions. Those signals go to a maintenance base, not to air traffic control.

Air France used those signals to help determine what happened when its Flight 447 disappeared over the equatorial Atlantic. Investigators may be doing something similar in Kuala Lumpur.

Plane crashes most often happen on landing or takeoff, but this flight vanished almost an hour after takeoff when it was cruising. What could cause a plane to crash at that point in a flight?

In three crashes at sea in the last few years, the aircraft’s speed-sensing systems have malfunctioned. In two of those cases, crews failed to diagnose and cope with the problem. (In the third, there was probably nothing they could have done.) A deliberate act by a pilot, terrorism or an attack in the cockpit could be other causes.

Shouldn’t the signals from transponders or “black boxes” have pinpointed the aircraft by now?

If the black boxes are in water, “pingers”, which emit a tone, are activated. But these are audible only in a limited area. And the plane may not be in the water.

Why would the authorities not have found debris after so many hours of searching?

They may not be looking in the right place. The plane flies at 16km a minute, and no one knows exactly when it crashed, or whether it departed its assigned track before doing so.

How far from its last known location could the aircraft have strayed?

While we know where the last radio contact was, we do not know how long after that the air plane crashed, so it is hard to say. A jetliner cruising at 10,668 metres could glide as far as 129 or 145km after losing engine power if the pilots still had control.

Are there any signs that terrorism might have been involved?

No group is known to have claimed to have destroyed the plane. Beyond that, not enough is known to spe- culate.

If the plane had a major malfunction, wouldn’t the pilots have called for help and sent distress signals?

Pilots have a mantra for setting priorities in an emergency: aviate, navigate, communicate.

The first priority is to fly the plane. Telling air traffic controllers on the ground what is going on comes third, since doing so is unlikely to instantly yield any help with the crisis in the cockpit, whatever it may be. If the pilots are fighting to keep the plane aloft, they may not have time to use the radio.

Could one of the pilots have crashed the plane deliberately?

It’s been known to happen: The crashes of an EgyptAir flight from Kennedy International Airport in 1999 and a SilkAir flight in Indonesia in 1997 were attributed to intentional acts by cockpit crew members.

But nothing is yet known publicly to suggest that that happened on the Malaysia Airlines flight.

Have other planes disappeared in this way in recent years?

There is no record of big planes simply disappearing, though they may take some time to find.

A few pieces of debris from Air France Flight 447 were spotted floating in the Atlantic the day after the plane crashed in June 2009, but it took five days to find most of the wreckage.

Small aircraft may be missing for much longer if they go down in remote areas. Steve Fossett, the daredevil adventurer who flew around the world solo in a plane and set records in a balloon, took off in his private plane in Nevada on September 3, 2007, and his remains were found in October 2008.

 
 
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