Using personal electronic devices during all phases of flight will be technically feasible in the future as modern aircraft are being designed to be tolerant to such devices, including transmitting PEDs.

However, airlines may continue to disallow the practice during takeoff and landing for operational reasons.

Guidance released last year by the US FAA described an acceptable means for designing and demonstrating aircraft tolerance to potential electro magnetic interference from PEDs. FAA advisory circular AC 20-164 identified RTCA document DO-307, which was borne out of a federal advisory committee and co-chaired by Boeing associate technical fellow Dave Carson.

Unlike a prior related RTCA document, which provided guidance on allowing T-PEDs on aircraft, DO-307 "stepped back a little bit and said, 'if you were to design an airplane and say you want it to be tolerant to these devices, how would you do that', said Carson.

DO-307 provides test methods to verify avionic system RF immunity for intentional transmitting PEDs and to verify interference path loss for PED spurious RF emissions. If the guidance is successfully completed then the aircraft is deemed tolerant in all phases of flight.

However, even if aircraft are deemed tolerant to PEDs through all phases of flight, there are "still other reasons to turn [PEDs] off" during takeoff and landing, said Carson, "such as [during] safety announcements and for passengers' physical safety".

"So you'd still probably tell people to turn [their PEDs] off and put them away."

Because many aircraft operating today have not been designed from the get-go for connectivity, some interference issues have arisen when airlines have moved to retrofit their aircraft with connectivity systems. In such instances, the parties can turn to AC 20-164 for guidance.

For example, Honeywell Phase 3 Display Units (DUs) were shown to be susceptible to blanking during electro magnetic testing for Gogo's in-flight Wi-Fi supplemental type certificate (STC) on Boeing 737NG aircraft.

Boeing and Honeywell determined that blanking may occur when the Phase 3 DU was subjected to testing procedures specified in AC 20-164 during Wi-Fi installations on the airplane. However, they concluded that actual electro magnetic interference levels experienced during normal operation of typical passenger Wi-Fi systems would not cause any blanking of the Phase 3 DU.

Nonetheless, Boeing deferred the activation of wireless systems that interface with passenger devices that could potentially interfere with the DU 3 displays, a move that impacted 777 customers which had ordered connectivity systems linefit to their aircraft.

Sources say that a forthcoming Boeing service bulletin will make the same condition as the STC for 737NG aircraft - that operators place placards in the flight deck saying that Wi-Fi and mobile devices are to be powered off if Honeywell Phase 3 DUs are present.

Emirates, whose 777 aircraft have Phase 3 DUs, already uses placards in its 777 cockpits. The carrier offers AeroMobile's mobile connectivity solution to passengers.

Boeing's Carson would not comment specifically on the service bulletin, or Boeing's plans for resuming connectivity linefits, but noted that it is "normal business" to conduct qual testing and to have some parts not pass.

He added: "Anytime we get a part that doesn't past he qual test, we work with the supplier to make sure it passes."

Source: Air Transport Intelligence news