No Bite From Bluetooth

Premium passengers with Air Canada can beam the latest information on flight schedules and other items directly into their Bluefish Wireless palm pilots while visiting the carrier's Maple Leaf lounges, according to a March 11 announcement. The development illustrates the proliferation of portable electronic devices (PEDs) using Bluetooth and 802.11 "intentional emitter" technology (see ASW, Feb. 10). It's one thing to have unintentional emitters aboard airplanes, such as laptop computers and hand- held games, but what about these low-power intentional emitters? A December 2000 Intel report discounts the potential for interference with aircraft systems:

"[The] worst-case interference from Bluetooth devices to the VHF [very high frequency] communications and navigation systems used by all aircraft ... is some 20 to 40 dB below the interference threshold for these systems. For the high sensitivity UHF [ultra high frequency] systems, TCAS [traffic alert collision avoidance system], GPS [global positioning system] and Satcom [satellite communications], the Bluetooth signal is just below the interference threshold; but, considering the signal design of Bluetooth and the signal processing of these systems, the effective safety margin is more than adequate to prevent any disturbance to those systems."

To really test aircraft vulnerability, the Bluetooth signal was boosted to 1 watt and placed "in close proximity to the aircraft systems and cables." Again, no problem. Nonetheless, the study recommended that the Federal Aviation Administration consider these policies for PEDs incorporating Bluetooth devices:

"a. The use of any PED, with or without Bluetooth, is prohibited in aircraft during any critical phase of flight. (The intent is that the same prohibition that applies to any PED during all critical phases of flight also applies to Bluetooth, an intentional emitter, but would allow the use of PEDs with or without Bluetooth during non-critical phases of flight.)

"b. The use of any PED which has the capability to intentionally transmit electromagnetic energy other than that emitted by Bluetooth is prohibited in aircraft at all times unless testing has been conducted to ascertain its safe use."

(Report: http://www.bluetooth.org/foundry/sitecontent/document/Aircraft_Safety_Report_for_B luetooth. Note especially Figure 8-2 on page 26, showing that the worst-case safety margins for Bluetooth are greater than for PEDs, where in many cases the interference exceeds the level permitted for proper functioning of the aircraft system.)