Paul Phelan/CAIRNS

A programme to buy passenger-owned electronic devices identified as interfering with navigation or flight management systems on its customers' flights has been launched by Boeing.

Airlines suspecting radio frequency interference from the devices are being asked to record the type of equipment, including serial and model numbers, and passenger contact details. Boeing then contacts the passenger with an offer to purchase the equipment to try to isolate the source and nature of the interference.

Efforts by manufacturers and airlines to pin down specific devices have been frustrated by the random nature and inconsistency of recorded events. Some now believe that radiation from terrestrial installations such as those of telecommunications systems may play a part.

One airline says: "There is no hard evidence that onboard devices are causing problems. The engineers refute it as rubbish, saying that the amount of energy required to produce some of these events is far greater than the devices' maximum possible output. Marketing don't want to get involved, because they don't want to tell passengers they cannot do something. The safety position is that, because we don't know, we treat it cautiously, so we don't allow the items to be operated in climb and descent."

Boeing is believed to have purchased a passenger's laptop computer in Europe when the airline found the problem kept returning as it was switched on and off. "Boeing then tried to reproduce the problem on their own aircraft and couldn't. They leased the actual aircraft from the airline and, using the same computer, they still couldn't reproduce the problem. That's consistent with our experience - we track each report on an aircraft seating plan, and these events are totally random in respect to location on the aircraft and to the items of equipment. We're starting to think we might have to look more closely at ground-based equipment such as telecommunication towers or FM transmitters," says the airline.

Electromagnetic interference is well known to the military, particularly at low level, where there is heavy interference in areas such as Europe. The problem is believed to have resulted in several accidents.

The carrier reports two events in its Boeing 747-400s, a year apart, but in the same location, at the same time of day and producing an identical 40° turn off track on both occasions. Anomalies have also been reported over a large radio telescope. Events have included porpoising oscillations, substantial course deviations and "map shift" on navigation displays.

Source: Flight International