 |
Photo | Relatives of passengers who were traveling on Malaysia Airlines Flight 370 watched a news conference at a hotel in Beijing on Monday. Credit Feng Li/Getty Images |
Questions Over Absence of Cellphone Calls From Missing Flight’s Passengers
SEPANG,
Malaysia — When hijackers took control of four airplanes on Sept. 11,
2001, and sent them hurtling low across the countryside toward New York
and Washington, frantic passengers and flight attendants turned on
cellphones and air phones and began making calls to loved ones, airline
managers and the authorities.
But
when Malaysia Airlines Flight 370 did a wide U-turn in the middle of
the night over the Gulf of Thailand and then spent nearly half an hour
swooping over two large Malaysian cities and various towns and villages,
there was apparently silence. As far as investigators have been able to
determine, there have been no phone calls, Twitter or Weibo postings,
Instagram photos or any other communication from anyone aboard the
aircraft since it was diverted.
There
has been no evidence “of any number they’re trying to contact, but
anyway they are still checking and there are millions of records for
them to process,” said Ahmad Jauhari Yahya, the chief executive of
Malaysia Airlines, at a news conference on Monday.
Reconstructing the Plane’s Path
The main communications systems of the Malaysia Airlines
plane were turned off about 40 minutes into the flight, forcing
investigators to try to piece together the plane’s location from other
systems.
Transponder
Secondary Radar and Text Updates
Air traffic controllers typically know a
plane’s location based on what is called secondary radar, which requests
information from the plane’s transponder. A plane also uses radio or
satellite signals to send regular updates through Acars, the Aircraft
Communications Addressing and Reporting System. Both of those systems
were turned off.
Primary Radar
Two Malaysian military radar stations tracked a
plane using primary radar, which sends out radio signals and listens
for echoes that bounce off objects in the sky. Primary radar does not
require a plane to have a working transponder.
SATELLITE
Satellite Communications
If Acars updates are turned off, the plane
still sends a “keep-alive” signal, that can be received by satellites.
The signal does not indicate location, but it can help to narrow down
the plane’s position. A satellite picked up four or five signals from
the airliner, about one per hour, after it left the range of military
radar.
The
apparent absence of any word from the aircraft in an era of nearly
ubiquitous mobile communications has prompted considerable debate among
pilots, telecommunications specialists and others. Most of the people
aboard the plane were from Malaysia or China, two countries where mobile
phone use is extremely prevalent, especially among affluent citizens
who take international flights.
Some
theorize the silence signifies that the plane was flying too high for
personal electronic devices to be used. Others wonder whether people
aboard the flight even tried to make calls or send messages.
According
to military radar, the aircraft was flying extremely high shortly after
its turn — as much as 45,000 feet, above the certified maximum altitude
of 43,100 feet for the Boeing 777-200. It then descended as it crossed
Peninsular Malaysia, flying as low as 23,000 feet before moving up to 29,500 feet and cruising there.
Vincent Lau, an electronics professor specializing in wireless communications at Hong Kong University of Science and Technology,
said that the altitude might have prevented passengers’ cellphones from
connecting to base stations on the ground even if the phones were
turned on during the flight or had been left on since departure.
The
hijacked planes on Sept. 11 were flying very low toward urban targets
when passengers and flight attendants made calls from those aircraft, he
said.
Base
station signals spread out considerably over distance. So cellphones in
a plane a few miles up, like Flight 370, would receive little if any
signal, he said.
Base
station design has improved since the Sept. 11 attacks to provide
better, more focused coverage of specific areas on the ground. But that
also means somewhat less signal intensity is wasted in directions where
callers are unlikely to be located, such as directly overhead, Mr. Lau
added.
Lam Wong-hing, a wireless communications specialist at the University of Hong Kong, said
that cellphones transmit at one watt or less, while base stations
typically transmit at 20 watts and sometimes much more. So even if a
cellphone showed that it was receiving a signal while aloft, it might
not be able to transmit a signal that was strong enough to make a
connection, he said.
The
metal in an aircraft reduces cellphone signals somewhat. If a passenger
had pressed a cellphone against a plastic window with a line of sight
to a cellphone tower then it is possible a connection might have been
made even at a fairly high altitude, because plastic barely blocks a
cellphone signal at all, Dr. Lam said.
Estimated range of plane with its remaining fuel if it was flying at the plane’s maximum speed ....
Many
aircraft carry air phones using radio or satellite technology, and the
Malaysia Airlines jet was equipped with them in business class. The
plane continued to send satellite pings for nearly seven hours after it
was apparently diverted.
But
air phones these days tend to be part of an aircraft’s in-flight
entertainment system. If someone deliberately diverted a plane and
turned off its transponder and other communications equipment, that
person is likely to have disabled the in-flight entertainment system so
that passengers could not figure out from the map that they were flying
in the wrong direction, said a telecommunications expert who insisted on
anonymity because he was not authorized to talk to the news media.
If the entertainment system was turned off, the air phones also would not work, the expert said.
The
Chinese news media have reported that there have been some instances of
people calling cellphones of passengers of the missing flight and
hearing ring tones, sometimes days after the plane disappeared. Telecom
experts have dismissed that as evidence that the cellphones are still in
use, saying that a ring tone may be heard while the international phone
system is searching for a phone and trying to connect a call.
There have been no reports of anyone answering calls to the cellphones of passengers or flight attendants aboard the plane.
Investigators
do not know if anyone aboard the plane even tried to make a call.
Passengers would have quickly become unconscious if the plane
depressurized as it soared to an unusually high altitude right after the
turnaround, pilots said. Whoever diverted the plane could have disabled
the release of oxygen masks.
Dr.
James Ho, an associate professor of medicine at Hong Kong University,
said that death could come within minutes if someone were the equivalent
of outdoors at 45,000 feet. But without information on the speed of
depressurization, it is hard to predict the medical consequences, he
said.
A
table used by pilots for “time of useful consciousness” without an
oxygen supplement at various altitudes shows only nine to 15 seconds at
45,000 feet, compared with five to 10 minutes at 22,000 feet.
Mobile
phone service is widely available in sizable areas of western China and
eastern Kazakhstan, raising the question of why nobody from the plane
has tried to make a call if it did fly north and land safely, instead of
flying out into the Indian Ocean until it ran out of fuel.
If
the flight did land safely with the passengers and flight crew still
healthy, whoever was in charge of the aircraft would also face a
formidable task in any attempt to provide food, water and shelter for
more than 200 people.
Chris Buckley contributed reporting from Sepang, and Nicola Clark from Paris.
A version of this article appears in print on March 18, 2014, on page A10 of the New York edition with the headline: Questions Over Absence of Cellphone Calls From Missing Flight’s Passengers.
Hank Paulson, 9-1-1. The World Stage and How Does the Future Look According to the WHOLE Real Truth?
ReplyDeleteWorld Reacted in 2001, September 11, and here we go again? Reenactment of how does a Coup d'etat and Coup d'grace virtually appear in our minds via ?
ReplyDeleteWe've got lots of FALSE FLAGS and nowadays the actors aren't starving, not at all. Where are the Chinese and the Americans and of course the Russians, Et Al, taking the game of virtual digital power?
ReplyDelete