Airlines have been ordered to replace or modify the cockpit display units fitted to hundreds of Boeing aircraft.
The US Federal Aviation Administration said tests had indicated that mobile phone and computer signals could cause the screens to go blank.
The affected aircraft are typically fitted with several screens, each of which costs thousands of pounds.
The displays’ manufacturer Honeywell has stressed that the problem has not been experienced in-flight.
“The only known occurrence was during a developmental test conducted on the ground,” a spokesman told the BBC.
“We worked with Boeing and addressed any concerns in 2012 with new display hardware.”
Boeing had previously issued an alert in November 2012 after All Nippon Airways and wi-fi vendor noticed interference caused by the installation of an in-flight internet system on Boeing 777s and 737s.
The ‘phase 3’ display units were found to be susceptible to the same radio frequencies used to transmit data via wi-fi.
The FAA also said it was concerned that the screens could be disrupted by mobile satellite communications, cellular signals from phones, and air surveillance and weather radar.
The regulator noted that the displays were required to provide pilots with information about airspeed, altitude, heading and pitch and roll, and added that the fault could cause a crash.
”We are issuing this airworthiness directive to prevent loss of flight-critical information displayed to the flight crew during a critical phase of flight, such as an approach or take off, which could result in loss of airplane control at an altitude insufficient for recovery, or controlled flight into terrain,” the regulator said.
Boeing said that it had recommended that carriers implement the changes in 2012.
However, the FAA said that it had estimated that a total of 1,326 Boeing 737s and 777s still needed to make the change.
The replacement programme is estimated to cost about $13.8 million to implement.
Ryanair had complained that requiring action on all aircraft, irrespective of the installation or operation of wi-fi systems in the cockpit, was imposing a “high and unnecessary” financial burden on carriers, the FAA said.
Honeywell had suggested that airlines should be forced to install new screens only if wi-fi enabled tablets or other such equipment were used in the cockpit.
However, the FAA rejected these complaints saying it wanted to “eliminate” any risk of interference.
“We do not agree that no problems have occurred on in-service airplanes, since the wi-fi… testing that disclosed this susceptibility was conducted on an in-service airplane fitted with phase 3 display units,” it said.
The FAA has given the airlines involved five years to swap or modify the components.
Sourced from Travel Weekly