Can Cell Phones Really Interfere With Aircraft?

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It’s an issue that is constantly being questioned: whether or not cell phones will actually interfere with aircraft. Well, according to Bloomberg, the answer is yes. In 2014, U.S. government officials revealed that passenger cellphones and other types of radio signals could interfere with the display units on certain models of Boeing 737 and 777 aircraft.

Display units on some 737 models are affected. Photo: Wikimedia Commons

The report was from the U.S. Federal Aviation Administration (FAA) and notes that certain display units (DUs – cockpit screens) made by Honeywell International are vulnerable to interference.

The report says that interference can come from “Wi-Fi, mobile phones and even outside frequencies such as weather radar.” Apparently, over 1,300 aircraft registered in the U.S. were affected. The FAA has given airlines until November 2019 to replace the units.

This is what the FAA gave as a reason for the issuance of their 2014 airworthiness directive (AD):

“We are issuing this AD to prevent loss of flight-critical information displayed to the flightcrew during a critical phase of flight, such as an approach or takeoff, which could result in loss of airplane control at an altitude insufficient for recovery, or controlled flight into terrain.”

Affected aircraft

According to the FAA, the AD applies to all “Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes, and Model 777 airplanes.”

Air France
Back in April 2013, Air France stated that both it and KLM have operated Boeing 777 airplanes equipped with WiFi and have had no problems with their display units. Photo: Air France

A Boeing spokesperson said that they found the interference in a laboratory test in 2012 but hasn’t seen similar issues on other aircraft. Furthermore, Honeywell is aware of only one instance where all six display units in a 737 cockpit went blank. However, the cause of that issue was a software problem. It has since been fixed and is currently being flight-tested, a Honeywell spokesperson said.

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Through Bloomberg’s reporting, an FAA spokesperson said on Thursday that the FAA decides on compliance time for its directives by assessing the level of risk:

“A 60-month compliance time frame means the risk is low, and does not need to be addressed right away,”

In testing, Virgin Australia found that “DU blanking occurred only when the WiFi radiated power source (set-up in the flight deck) was increased to a high level”. However, it reported that under normal operating conditions there was no blanking of the DU, but interference was present.

The spokesperson at Honeywell says that “even if a blanking incident were to occur,” the units are backed up by multiple redundancies.

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The issue reportedly affects Boeing 737 Next Generation models. Photo: Wikipedia

The extent of the problem

Honeywell initially reported that 10,100 display units (approximately 1,700 aircraft) were in question worldwide. Bloomberg checked in with Honeywell, who said 8,000 components have been replaced and less than 400 need upgrading.

There are several reasons the number could be lower:

  • Some airlines might have had the work performed at non-Honeywell facilities.
  • Regulators in other regions of the world might not have ordered the units replaced.
  • Some planes might have been taken out of service due to age.

Airline response

For airlines in the U.S., Delta and Southwest have completed their overhauls. However, American Airlines has 14 more jets that need refurbished units. United still needs to refurbish units on 17 aircraft.

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Ryanair CO2
An all 737 fleet, Ryanair is the world’s largest operator of the 737. Photo: Ryanair

A Ryanair spokeswoman said it hasn’t upgraded all of its 707 screens. In the original FAA report, it says the following about Ryanair:

Ryanair asserted that requiring the [Notice of Proposed Rulemaking] actions on all airplanes, irrespective of the installation or operation of WiFi systems in the cockpit, is imposing a high, and unnecessary, financial burden on operators.

The 2014 FAA report estimates the cost at more than $2,000 per DU. Ryanair’s response was to inspect all of its display units and replace any affected DUs.

Real-world situations

Outside of controlled testing, there have been a number of reports of display unit issues. Found by Bloomberg using the Aviation Safety Reporting System (ASRS) this is what some pilots have been experiencing:

  1. September 2018. Pilots of a 737-700 noticed various flight information flashing on and off, showing different airspeeds and altitudes. Then a primary display unit went blank.
  2. January 2017. Pilots of a 737 flying lost all of their map displays and the flight-management computers on both sides of the plane. This was “during a critical phase of flight in mountainous terrain,”
  3. Late 2017. A 737-800 caption reported that key flight data intermittently disappeared as the jet was climbing through turbulence and the screens blanked even more during the descent. After the plane landed, maintenance crews couldn’t find any reason for the blanking display units.
  4. Mid-Late 2017. The pilot of a 737-800 reported multiple episodes of important flight information “blanking or simply not functioning”. The plane flew into a wind shear due to lack of data.

It should be noted that these reported incidents have not been definitively ruled as caused by radio signal interference. Furthermore, the issues are not exclusive to the Boeing aircraft mentioned. In fact, a similar search for A320 aircraft shows reports of pilots having issues with their Multi-Function Control and Display Units (MCDUs). With aircraft being the complicated machines that they are, one issue may be a symptom of any number of problems.

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Delta 777
Delta reports that its overhaul of display units is complete. Photo: Delta

Conclusion

Whether or not you’re in a 737 or 777 with the affected equipment, experts say that your phone can cause interference. Professor Tim Wilson at Embry-Riddle Aeronautical University says the problem is cumulative. Apparently, “the greater the number of phones emitting radio signals, the greater the potential for interference with a plane’s flight system.” Wilson is department chair for electrical, computer, software and systems engineering at Embry-Riddle.

So maybe your phone by itself isn’t going to be a problem. But if enough people are also using the signal-emitting functions of their devices, there could be some serious consequences…

 

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