In this month’s system design column, Walter Shawlee 2 reminds us of a safety issue that many may have forgotten–electromagnetic interference (EMI) caused by personal electronic devices (PEDs). Walter reports that the British Civil Aviation Authority (CAA) has been conducting research on the effects of one PED, the mobile phone, on cockpit systems and has made some sobering findings. During tests under laboratory conditions CAA researchers discovered the following anomalies:
Compass froze or overshot magnetic bearing;
Indicators became unstable;
Digital VOR navigation bearing errors of up to 5 degrees occurred;
VOR navigation To/From indicator reversal occurred;
VOR and ILS course deviation indicator errors were noted with and without failure flags;
Sensitivity of the ILS localizer receiver was reduced; and
Background noise was detected on audio outputs.
The results have been questioned by some persons in the industry because the testing for the research was not conducted under real-world conditions. For example, no aircraft were used for the testing and the mobile phone transmissions were simulated.
However, the CAA supported its research by sifting through the UK Mandatory Occurence Reporting submissions between 1996 and 2002. The agency found 35 reports that cite mobile phones as a factor in safety-related incidents. The reported anomalies include mobile phones activating smoke alarms in the baggage compartment and phone conversations entering flight crew head sets, interrupting flight deck communications. The study also mentioned the fact that mobile phone use during aircraft operations distracted the flight and cabin crews and increased their workloads.
CAA officials also say they have not concluded their research; the study is ongoing. The latest findings are from the agency’s second study; the first study determined that mobile phones cause EMI, and the second attempted to determine how they interfere and what systems they affect.
Why so much research into mobile phone use on aircraft? "We had a lot of questioning by the public and [mobile phone] manufacturers of why a ban on mobile phone use is in place," a CAA official explains. "Some thought it was just so the airlines can charge high fees for their satellite phones.
"We felt there was a requirement to prove there is a case," the official adds. The civil authorities in Australia also are "campaigning against mobile phone use" in aircraft, says the official, and are using CAA research on the topic to bolster their campaign.
To further back up their resolute view, UK authorities bring to court a person who violates the ban on mobile phone use "about once every three or four months," says the official. "People have been sent to prison [for such a violation]," he adds. The official quickly clarifies the remark: "We are, of course, talking about people who refuse to obey the rule and perhaps becomes abusive."
Like the CAA, the U.S. Federal Aviation Administration (FAA) bans mobile phone use in operating aircraft, as does the Federal Communications Commission. The FCC established a ban because phone use on operating aircraft can cause problems to the mobile phone service.
So, with rules in effect, people in prison, and proof that a safety issue exists, why would anyone risk using a mobile phone in an aircraft? Two reasons. The law of averages plays a part. The Cellular Telecommunications & Internet Association estimates that there are 150 million mobile phone subscribers in the United States, and 1.2 billion worldwide. We have all seen people in cars, restaurants and other public places who appear unable to give their mobile phones a rest. Not surprisingly, that attitude persists in airline cabins.
In addition, as Walter points out in his column, airline passengers have received "mixed messages" regarding mobile phone use on aircraft. An FAA official points out that while most airlines forbid mobile phone use until the aircraft is at the gate and the cabin door is open, at least one airline announces that phones can be used after the aircraft turns off the runway. Also, while some airline crewmen sternly note that mobile phone use is a punishable offense, many make placid, routine-sounding requests to turn off the phones.
The aviation industry can do nothing to stem the proliferation of mobile phones, but until we ensure that all aircraft electronics are completely immune to EMI, we should insist on a strong, consistent message regarding the use of mobile phones and other PEDS.