Mobile phones still pose a real risk to the safety of planes even when in the supposedly flight-safe ‘airplane mode’.
The feature found on most handsets disables all external signals from a phone but the device can still use WiFi, which interferes with some faulty screens still in use.
A vulnerability was discovered in 2014 that caused cockpit screens in Boeing 737 Next Generation and 777 airliners to suffer with interference from WiFi signals.
In 2014 the US Government promptly issued a deadline for all operators to replace or fix the fault by November 2019, but some are still believed to still be in use.
An exact number is not known as some may have been fitted to now retired aircraft or flight simulators but it could be as high as 70.
United Airlines and American Airlines both have outstanding screens to replace – with 17 and 14 aircraft respectively needing updates before the November deadline.
Discount airline Ryanair reportedly told the FAA in 2014 that its fleet contained 707 of the affected Honeywell units, arguing that the requirement to replace all of them was ‘imposing a high, and unnecessary, financial burden on operators.’
Ryanair told MailOnline it has completed the inspections and ‘any affected DUs have been replaced, in compliance with the FAA’s recommendations.’
Manufacturers of the faulty screens, Honeywell Aerospace, originally refuted the ruling but provided the figure of 70 in a statement in an attempt to push back against the ‘potentially hundreds’ claim of BNN Bloomberg who first reported the story.
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Leading global air carriers American and United Airlines must replace and upgrade cockpit flight displays before November or risk them being declared non-airworthy (file photo)
The directive to replace the potentially vulnerable display units was issued by the US Federal Aviation Administration (FAA) in the November of 2014.
‘We are proposing this airworthiness directive to prevent loss of flight-critical information displayed to the flightcrew during a critical phase of flight, such as an approach or takeoff,’ the agency announced at the time.
Such issues, it continued, ‘could result in loss of airplane control at an altitude insufficient for recovery, or controlled flight into terrain or obstacles.’
At this time, the agency gave airline operators five-years to upgrade to meet airworthiness standards.
‘A 60-month compliance time frame means the risk is low, and does not need to be addressed right away,’ an FAA spokesperson told BNN Bloomberg.
Display unit manufacturer Honeywell Aerospace had originally told the FAA that 10,000 units — equivalent to almost 1,700 aircraft — were likely affected by the issue across the world, including 1,300 airliners registered in the United States.
A spokesperson for Honeywell told BNN Bloomberg this week that 8,000 of the suspect components had been replaced, while less that 400 remained to be upgraded.
While these numbers are lower than the original estimate, the discrepancy can be accounted for by older planes being withdrawn from service, replacements being made outside of Honeywell’s facilities and other regulators not imposing a recall.
Delta Airlines and Southwest Airlines both reported having fully completed the mandatory upgrades ahead of schedule.
Since then, the airline has not upgraded all 707 such screens, but a Ryanair spokesperson told BNN Bloomberg that all had been inspected and ‘any affected display units have been replaced.’
The US Government issued the directive to upgrade all display units in Boeing 737 Next Generation and 777 cockpits after detecting a potential safety issue in 2014
Honeywell International spokesperson Nina Krauss told BNN Bloomberg that the firm was unaware of any incidents of mobile phone or other radio frequencies interfering with display screen outputs during flight.
She added that one case was known where all six display units in a 737 cockpit went blank, but that the issue had been traced to a software bug which has been fixed.
‘Even if a blanking incident were to occur,’ Ms Krauss added, the units are backed up by multiple redundancies.
Aviation Safety Reporting System — which is administered by NASA — has reportedly received more than a dozen accounts of ‘critical’ incidents aboard Boeing 737 Next Generation or 777 airliners in which flight information has disappeared while airborne.
Although none of the incidents reported led to disaster — and the reports constitute anonymised crew summaries rather than the results of technical investigations — the glitches all apparently caused concern for the respective flight crews.
A 737 out of Costa Rica in the January of 2017 reportedly had all map displays and flight-management computers go dark ‘during a critical phase of flight in mountainous terrain’, the crew reported.
Fortunately, the incident occurred in the daytime and in fair weather conditions.
Under less favourable circumstances, they noted, ‘it could have been a potentially disastrous outcome.’
Officials determined that sufficiently strong radio signals — such as from mobiles, Wi-Fi and outside sources like weather radar — could disrupt cockpit flight displays (stock image)
In the same year, a 737-800 lodged a safety report noting that key flight data flickered off whilst the jet was climbing through a turbulent patch of air — and that the same phenomenon was observed, but to a greater extent, during descent.
Ground-based maintenance crews, however, were unable to find any issues that would have accounted for the glitches after the craft had safely touched down
‘Due to no known cause for a known recurring problem, I refused the aircraft for the next leg,’ the pilot wrote in his aviation safety reporting.
A similar issue struck a 737-700 in September 2018, with the pilots reporting that flight information flashed on and off displays and showed varying figures for the craft’s air speed and altitude before the primary display unit went completely black.
‘At that time, we decided it was best to get the aircraft on the ground,’ the pilots wrote in their account of the incident.
Display unit manufacturer Honeywell Aerospace had originally told the FAA that 10,000 display units — equivalent to almost 1,700 aircraft — were likely affected by the issue across the world, including 1,300 airliners registered in the United States (file photo)
Frequent flyers may be saddened to hear that, even once all the affected planes have either been upgraded or taken out of service, mobile phone usage will still be restricted mid-flight.
Engineer Tim Wilson of the Embry-Riddle Aeronautical University told BNN Bloomberg that having too many fully-active mobile phones still ‘could be a real problem’ while in the air.
The more devices emitting radio signals, he reportedly added, the higher the risk of interference in the operation of the craft’s flight systems.
It is not clear exactly what amount of radio interference would be required to trigger the problems in the faulty Honeywell display units.
However, the FAA did describe such as being susceptible ‘to radio frequency emissions in WiFi frequency bands at radiated power levels below the levels that the displays are required to tolerate for certification of WiFi system installations.’
No US airline permits the use of mobile phones to make calls while their craft are in the air — a rule reinforced by a US Congress prohibition legislated in 2018.
In contrast, Wi-Fi transmissions made during so-called ‘Airplane Mode’ are permitted because they operate at lower, less impactful, power levels.
MailOnline has approached the airlines for comment.