Why is it forbidden to use mobile phones on the plane?

Many people are deeply skeptical about the rationality of the ban on "no cell phones on airplanes". While Stephanie's mobile phone photos of Endeavour penetrating the clouds were circulated on the Internet, many people also raised questions. Are mobile phones allowed on American planes? This is one of the most controversial issues in the field of civil aviation, not only for the public. In the aviation industry, the discussion on this issue has never stopped, and there is no satisfactory conclusion so far. Why is there such a ban? The rumor mill investigation has to start from 20 years ago.

199 1 year, the Federal Communications Commission (FCC) of the United States issued a regulation prohibiting passengers from using mobile phones on airplanes on the grounds that: 1, using mobile phones on airplanes will affect the ground base station system of mobile phones. We know that when you use a mobile phone, different base stations will serve you in different areas. When you move from one area to another, you need to reselect the base station and switch to the new base station. This process requires calculation. When using a mobile phone on an airplane, due to the high flight speed, switching will be very frequent, which will increase the workload of the base station; 2. Radio waves emitted by mobile phones may interfere with airborne electronic systems.

After the introduction of this regulation, the Federal Aviation Administration (FAA) of the United States also believes that mobile phones may indeed have substantial interference with flight systems, and this ban is imposed on all commercial airlines. In fact, this issue has attracted people's attention before the introduction of this regulation. In the early1960s, it was reported that an airplane deviated from its normal route due to radio interference. Although the speculation of this statement is very heavy, the problem is related to human life and cannot be taken lightly. The US government immediately launched an investigation, led by FAA and RTCA, and convened experts from government, industry and academia to conduct research for half a century.

Boeing expert Bruce? Dunham engaged in aircraft electromagnetic compatibility research 10 years. According to his memory, Boeing did receive several such accident reports. For example, during cruising, the autopilot system will occasionally turn off or yaw inexplicably. Some airlines report that passengers' use of mobile phones affects cabin pressure, magnetic orientation, navigation and ground-to-air communication systems [4]. What is even more frightening is an accident recorded in the "Flight Safety Reporting System" of the National Aeronautics and Space Administration (NASA), which is a platform for anonymous reporting of aviation accidents. When a Boeing 737 landed at night, the locator suddenly deviated greatly without any hint. When the captain noticed this serious incident, the plane had deviated from the route of 1 mile. At that time, the flying altitude was very low, so it was very dangerous to have such an accident. In the report, the captain complained that the tower didn't remind him to deviate from the course in time, and said with great certainty that there was a mobile phone or similar equipment in the cabin that interfered with the locator. Later, NASA also specially produced an accident set, which summarized all possible flight accidents related to mobile phones on the platform [6].

Dunham has conducted a large number of simulation experiments, and he called on some airlines to cooperate with the test. However, what puzzles Boeing engineers is that a large number of tests, whether in real flight or in the laboratory, have not reproduced the terrible situation mentioned in the above report.

For more data, this research has been delayed for decades and is still being studied. In this process, people also have some deeper understanding of this issue. In 1996, RTCA and FAA * * * jointly issued the guiding principle [8] on the use of mobile electronic devices in the air, pointing out that passengers should be allowed to use "some electronic devices" because no obvious interference has been observed, but in order to reduce the risk, when the flying altitude is lower than 10000 feet (about 3048 meters), especially in. Note that "some electronic devices" here do not include mobile phones-they are still required to be disabled all the time.

After accumulating some experimental data, RTCA believes that the electromagnetic interference factors in the actual situation are too complicated, and it is difficult to draw a clear conclusion in the experiment. Aircraft need to receive signals from ground launch towers and orbiting satellites through antennas for communication and navigation. Theoretically, once passengers use electronic devices, the radio waves emitted by these devices may interfere with this process in various ways. For example, these radio waves will escape from the gap between the glass window and the cabin door and be received by the airborne antenna, thus affecting its reception of normal signals. This is the so-called "front door interference".

The condition of front door interference is that the frequency of interference wave is exactly the same as that of normal carrier. Take the popular mobile phone in America as an example. When the mobile phone is used, it will emit working waves from 1850Mhz to 19 10Mhz, as well as some background clutter. The frequency range of background clutter can cover the frequency range used in ground-to-air communication. When the plane is far away from the tower, the signal of the tower is very weak, and the clutter generated by the mobile phone may interfere with it. Of course, there are other possible interference methods, which will not be described here.

Captain Richard of McDonnell Douglas MD-88? Ince may have encountered such a situation. He once reported that during a flight, there was a sudden strong noise in his headphones. He asked passengers to turn off all electronic equipment immediately through the radio, and the noise disappeared immediately. However, the factor that electronic equipment interferes with ship communication is only speculation. For electromagnetic phenomena, it is very difficult to prove causality conclusively, because there are too many factors to consider, and there are many factors that we don't know, such as how strong the interference will have an impact, and whether there are external factors, such as lightning or military radar. In a word, the influence of these mobile phones on airplanes mentioned above is either theoretical or based on speculation and cannot be proved by experiments.

In 200 1 year, NASA tested a Boeing 747 and a Boeing 737 for several weeks. They put an ultra-wideband radio transmitter in the passenger seat. The experimental results are very obvious, and the automatic collision avoidance system of the aircraft immediately went wrong, ignoring another aircraft nearby. Moreover, the instrument landing system also has obvious drift in the horizontal and vertical directions during the approach [9]. Although such a violent experiment is far from the daily situation, it at least proves the correctness of the previous theoretical results: once the clutter with the same working frequency as the aircraft components appears, it will indeed interfere with the flight system.

In 2005, the Federal Communications Commission intended to relax the ban. Under certain restrictions, passengers can use mobile phones on the plane. For example, cooperate with communication equipment manufacturers to limit the transmission power of mobile phones. They also consider developing a special airborne communication equipment for aircraft to meet the communication needs of passengers. However, this goodwill has attracted new controversy. Some people think that this move is forcing users to use only airborne communication equipment, which will obviously bring huge profits to airlines and violate commercial fairness. In 2006, the FAA once again announced that it would maintain its original opinion and prohibit the use of mobile phones on planes, which would be implemented by airlines themselves. In 2007, the FCC also maintained the original proposal [10]. "IEEE Spectrum" magazine (a periodical published by the Institute of Electrical and Electronic Engineers) questioned why this issue has been inconclusive for so many years, because FCC and FAA refused to spend money on experiments and always pushed the decision to airlines. .

This debate has lasted for half a century, and there is still no unanimous conclusion. From the perspective of scientific research, it is irresponsible to say that there is absolutely interference or there is absolutely no interference. But from the cost point of view, although the probability of such interference is small, the stakes are too high. Turning off the mobile phone is a low-cost measure for everyone. Therefore, it is wise to choose this conservative approach in the absence of a conclusion. What's more, while airlines have clear regulations, everyone should strictly abide by them and not cause other troubles.