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Why Do Airline Transponders Even Have an "Off" Switch?



Ever since Malaysia Airlines Flight 370 disappeared, a fascinated public has asked: Why can somebody in the cockpit shut off the transponder?

 

John Gadzinski, a Boeing 737 captain, said that among fellow pilots "there is a raised eyebrow like Spock on `Star Trek' - you just sit there and go, `why would anybody do that?
 
It turns out there are several legitimate reasons why a pilot might want to shut off this key form of communication that allows air traffic controllers to identify and track airplanes.

Authorities believe that Flight 370's transponder was intentionally shut off, delaying search and rescue efforts and helping to conceal the plane's location - a mystery unsolved more than 10 days after the Boeing 777 vanished.
 

It's rare for a pilot to turn off a transponder during flight, but occasionally there is cause.

  •  Sometimes a transponder malfunctions, giving out incorrect readings.
  •  The device could have an electrical short or catch on fire. Pilots would want to shut it down rather than risk a fire spreading to the rest of the cockpit or airplane.
  •  Pilots used to routinely turn off transponders on the ground at airports so as not to overwhelm air traffic controllers with so many signals in one location. That is increasingly less the case as pilots now use "moving map" displays that take the transponder data and show them the location of other planes on the ground, helping guide them around airports without mishaps.

"As long as there are pilots, they'll be able to switch off systems," said Andrew Thomas, editor-in-chief of the Journal of Transportation Security.

Airplanes have two transponders. There are two knobs in the cockpit - one on the right, the other on the left - that control one or the other. When one transponder is on, the other is normally in standby mode.

To turn off a transponder, a pilot turns a knob with multiple positions and selects the "off" setting. The second transponder doesn't automatically activate if the first one is shut down - a knob would also have to be turned. In this case, it appears one transponder was turned off, and the second not activated.

Ross Aimer, a retired United Airlines pilot and former 777 instructor, said it is possible that one pilot could reach up and turn off the transponder without the other pilot seeing it, say if one was looking away or distracted.
 

If the plane was in contact with an air traffic controller, the controller would alert the pilots that the transponder signal had been lost. But, Aimer - now head of Aero Consulting Experts - said, if they were not in contact with an air traffic controller, a pilot might miss it if the other shut down the transponder.

In the case of the missing Malaysian plane, even pilots are a bit puzzled by somebody turning off the transponder.

John Gadzinski, a Boeing 737 captain, said that among fellow pilots "there is a raised eyebrow like Spock on `Star Trek' - you just sit there and go, `why would anybody do that?'" 
 
 

(AP)  Finding the missing Malaysian jetliner would be a coup for any of the more than two dozen countries out there looking. But for China and the United States, it's a lot more than that - it has been a chance for the two rival powers in the Pacific to show off what they can do in a real-life humanitarian mission across one of the world's most hotly contested regions.

The Navy ship that has been helping search for the missing Malaysian airliner is dropping out of the hunt, U.S. military officials said Monday.

The Navy's 7th Fleet determined that long-range naval aircraft are a more efficient means of looking for the plane or its debris, now that the search area has broadened into the southern Indian Ocean.

Long-range Navy P-3 and P-8 surveillance aircraft remain involved in the search, Cmdr. William Marks, a spokesman for the 7th Fleet, said in an emailed statement.

The USS Kidd, an Arleigh Burke-class destroyer that has been searching in the Indian Ocean, will return to its normal duties.

The Malaysian Airlines plane has been missing for more than a week. No debris or wreckage associated with the aircraft has been found.

The P-8 Poseidon and the P-3 Orion can cover up to 15,000 square miles in one nine-hour flight. The aircraft also are equipped with advanced surface search radars and electro-optical sensors and can fly at low altitudes if visual identification is needed.

The decision was made in consultation with the government of Malaysia. A Pentagon spokesman said Defense Secretary Chuck Hagel told Malaysian Minister of Defense Hishammuddin Tun Hussein on Monday evening that the United States is fully committed to working with Malaysia to locate the plane.

 

The hunt has major ramifications for Beijing, which has been rapidly improving its military while aggressively challenging neighbors over territorial disputes. Washington is looking to prove it's still the top dog to allies worried about how seriously it takes the threat China poses to the Pacific status quo.

So far, neither country has come up with anything significant. But they have been vigorously waving their flags.

China has the most at stake and has been taking an unusually high-profile role. Almost immediately after Malaysia Airlines Flight 370 disappeared March 8, China dispatched its largest-ever rescue flotilla to the initial search area in the South China Sea, which Beijing considers its own backyard.

Beijing sent four warships and five coast guard and civilian patrol service vessels, along with helicopters and fixed-wing surveillance aircraft. Among the warships are two of China's largest and most advanced amphibious docking ships. The 20,000-ton vessels are equipped with helicopters and a range of small boats, including up to four hovercrafts.

"On the one hand, China is simply doing its duty in orchestration with other countries," said Ni Lexiong, a military expert at Shanghai's University of Political Science and Law. "On the other hand, this operation offers an opportunity to assess the Chinese navy's willpower, efficiency and ability to carry out operations far from home, especially in comparison with the U.S."

Fresh off a massive relief effort after Typhoon Haiyan devastated the Philippines - which China barely got involved in - the U.S. was once again quick to respond. Within days, the Navy had two destroyers in the South China Sea participating in the search, the USS Kidd and the USS Pinckney. Both are both based in San Diego but were training in the area when the jet disappeared.

Since the flight was bound for Beijing and two-thirds of the passengers were Chinese, the public expects the government and military to pull out all the stops. With more Chinese traveling abroad than ever - 100 million last year, more than double the figure for 2009 - they are increasingly reliant on their government to assist and protect them when overseas, and they are looking for proof that it can fulfill that role.

National prestige is also a huge factor.

Though the U.S. remains the dominant power in the Pacific, China deeply craves that role. Sizable chunks of its defense spending, which has grown significantly over the past two decades to $131 billion, have been devoted to boosting its ability to project force for both military and humanitarian missions.

China's Achilles' heel is its relative lack of experience, not having fought in a major conflict since the end of the Korean War in 1953. Its leaders have been trying to compensate with more realistic training scenarios, including joint maritime search and rescue exercises with other nations.

"Everyone understands, without anything being said, that the U.S. has unmatched search and rescue capabilities that reflect the size and sophistication of its air and naval forces," said Avery Goldstein, a China security expert at the University of Pennsylvania. "China's capabilities in this regard are improving but not yet in the same league, especially for operations at great distance from the Chinese mainland."

Given new clues from radar and satellite data that the missing Boeing 777 turned west and flew on for several more hours, the search has shifted to a vast swath of land and sea stretching from the southern Indian Ocean up to Kazakhstan. That's an area that neither China nor the U.S. has traditionally put much emphasis on, and has forced both to rethink their strategies.

The U.S. Navy decided that long-range naval aircraft were a more efficient way to search such a vast area, so will be relying on P-3 and P-8 planes, while the two destroyers go back to normal duties.

The mission is one of the first on the international stage for the P-8 Poseidon, one of the newest additions to the Navy's air capabilities. The Navy touts the aircraft as the world's most advanced anti-submarine and anti-surface ship reconnaissance plane and says it can cover 15,000 square miles (38,850 square kilometers) in a nine-hour flight.

China, meanwhile, has sent most of its ships involved in the search toward Singapore, where they will split into two groups, one traveling north and the other south. They will be searching two huge blocks of ocean off the coast of Sumatra and near the Andaman Islands - a total area of 300,000 square kilometers (186,000 square miles), or roughly three times the area they searched in the South China Sea.

A big problem for China is its bad blood with virtually all of its neighbors, many of whom are key players in the search. China has territorial disputes with India, Japan, the Philippines and Vietnam, and many other countries in the region are wary of its efforts to exert more control over Pacific shipping lanes that could impact their freedom of trade.

"China is strong in terms of hardware, but it lacks experience and good security ties with regional states," said China expert Li Mingjiang at Singapore Nanyang Technological University. "The U.S. sailors have far better networking with their regional counterparts, making it more possible for the U.S. to play a leading role in the search and rescue effort."

Chinese officials haven't done themselves any favors by criticizing Malaysia's leadership in the search effort. Some saw that as an attempt to shift public attention away from its own shortcomings, and Beijing's weak military-to-military relationship with Malaysia probably exacerbated the issue.

Japan, which is Washington's staunchest ally in Asia and is locked in a tense dispute with China over several small islands, has been watching Beijing's response especially closely. Experts in Tokyo say that while they remain skeptical, there is hope that by coming together with other countries to pursue a common goal, China may learn to work more amiably with its neighbors.

"Some people say China is trying to use the mission as a way to show off its presence, but that also means they are stepping up their efforts and capabilities in disaster relief," said Kyouji Yanagisawa, a former Japanese Cabinet adviser on national security. "This is a search operation and I think it could be an opportunity to cultivate trust among participating countries, rather than conflict."

 


 

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