Ham radio enthusiasts could be partly responsible for landing U.S. airlines with an $8 million bill to fix faulty equipment on Boeing 787 Dreamliner airplanes after it was discovered that simple radio signals can knock out a faulty transponder on the popular widebody plane used by American, United, and Alaska Airlines.
The issue came to light after the Federal Aviation Administration (FAA) reported “multiple instances of loss of transponder for airplanes entering airspace in the presence of CW interference.”
CW interference refers to continuous-wave radio signals like Morse code, military transmitters, and even amateur ham radio signals, which have been found to interfere with the transponder on some Boeing 787s.
When Dreamliners fitted with this faulty transponder fly through areas where continuous-wave radio signals are present, there is a risk that the Mode S transponder function doesn’t ‘reply’ to radar interrogations.
Without this electronic ‘reply,’ air traffic controllers might not be able to see where the aircraft is, and the emergency Traffic Collision Avoidance System (TCAS), often described by aviation safety experts as the ”last defense against mid-air collisions,” might not generate life-saving alerts properly.
In a worst case scenario, the FAA warned that a mid-air collision could occur.
When the FAA tested the faulty transponder in areas of CW interference, they discovered it didn’t send a reply to at least 90% of ‘interrogations,’ so the agency went about ordering a fix.
To do so, the FAA was required to issue an Airworthiness Directive, although this first required the agency to request feedback from stakeholders and other interested parties.
Boeing had no objection to the draft airworthiness directive, while the Air Line Pilots Association also supported the FAA’s intervention.
Several airlines did, however, raise some concerns. Kenya Airways, for example, asked whether the suggested fix could be delayed until the root cause of the problem could be identified.
Meanwhile, United Airlines and KLM Royal Dutch Airlines raised concerns about the availability of spare parts from the transponder’s manufacturer, Collins Aerospace.
One commentator also suggested that the suggested compliance time to fix the transponder should be shortened over fears that it could be connected to 5G cell phone signals. The FAA rejected that request, explaining that the issue was not connected to 5G signals.
Although the fix applies to any Boeing 787 anywhere in the world that is fitted with the faulty transponder, the FAA only works out the cost that the airworthiness directive might have on U.S.-based carriers.
The total cost estimated by the FAA came to $7.95 million.
The final rule for this airworthiness directive was published this week, and airlines have up to four years to ensure that all of their Boeing 787s are fixed.
