By Chris Zombolas October 10, 2008 12:00am
But of much more serious concern is the threat of interference to aviation safety.
Could a laptop computer or mobile phone have caused Qantas QF72 to plunge near Exmouth in Western Australia this week? The answer is yes.
It is well-known in the electrical engineering community that electronics systems, including air navigation systems, may be adversely affected by electromagnetic interference, or EMI.
EMI is generated by the operation of virtually all electronic equipment but the highest levels (hence the highest risks) are generated by portable transmitters including those in mobile phones and laptop computers. Mobile phones, laptop computers and other consumer devices often have a range of inbuilt radio transmitters including Wi-fi, WiMax, Wii, IEEE802.11a,b,g,n and Bluetooth.
The use of portable wireless transmitters in consumer devices is rapidly proliferating. The spread of transmitter technology appears to be happening faster than the refinement of EMI standards used to ensure aircraft safety. While newer aircraft are tested for electromagnetic compatibility with current transmitter types, the interference potential on older aircraft may not be known.
It follows that if these devices are used by large numbers of passengers in flight, the risk of EMI, albeit small, will increase.
Chris Althaus, CEO of the Australian Mobile Telecommunications Association, declared recently that mobile phones "are absolutely safe". That's drawing a very long bow indeed.
EMI experts disagree. In a poll conducted by US publication Interference Technology, which services the EMI engineering community, readers were asked to give their views on in-flight mobile phone use and potential interference problems. Of the respondents, 56 per cent foresaw problems with allowing in-flight mobile phone calls – 28 per cent predicting some glitches and the other 28 per cent opposing the idea as dangerous.
A more scientific study published by the Carnegie Mellon University in 2006 involved the monitoring of mobile phone and portable electronic devices on 37 US commercial flights. The study indicated that the risk of interference to a plane's navigation system is indeed real.
Alarmingly, one of the researchers, Bill Strauss – an expert in Aircraft EMI in the US Naval Air Warfare Centre – concluded that: "The risk posed by these portable devices is higher than previously believed. These devices can disrupt normal operation of key cockpit instruments, especially Global Positioning System receivers, which are increasingly vital for safe landings".
The study also found that one to four mobile phone calls were made during each flight, despite rules prohibiting them.
The Qantas plan for an on-board picocell (essentially a miniature base station) to "safely monitor and manage the transmission levels of mobile devices, ensuring non-interference with both aircraft systems and ground-based mobile communications systems" may find a workable solution.
But it does not appear to take into account the human factors such as passengers defying the rules, and the ever-changing and proliferating wireless technologies in consumer devices.
When a phone is switched on, it transmits a signal at full power. Can Qantas guarantee that all passengers will switch on the mobile phone only on the ground, or that they will only be used in Flight Mode? Laptop computers and personal digital assistants can have six or more different transmitters and the number is growing. The laptop/PDA transmitters are mostly set to automatically transmit when they are powered up. Can Qantas guarantee that transmitters not controlled or managed by the Telstra picocell will not cause EMI?
In the US, the Federal Aviation Administration and the Federal Communications Commission are the regulators responsible for aircraft safety and communications respectively. The FAA has documented cases of EMI to aircraft systems. It is yet to be convinced that safety and effective communications will not be compromised, and are awaiting the results of further research before they consider lifting restrictions on using these devices in flight.
Electromagnetic interference is insidious and relaxing the restrictions will send the wrong message to passengers – that the use of electronic devices on board aircraft does not concern safety. If air safety is indeed of paramount importance, why should Qantas and other airlines take the risk?
Chris Zombolas is technical director of EMC Technologies Pty Ltd, a company specialising in testing and consulting in the field of electromagnetic compatibility and interference (EMC/EMI) and electromagnetic radiation.