If our technology breaks we have learnt to turn it off and back on again. Well, from next week this is now a mandatory requirement every 51 days for Boeing 787 operators!

3 April, 2020

Control-Alt-Delete, the famous three-finger salute that allows us to force shutdown, reboot or restart our personal computers when they run into operating problems. Most of us have used the three-key combination, some us probably fairly frequently, which was especially designed to be impossible to execute with one hand in order to avoid the potential for accidental reboots.

The shortcut was actually designed only to be used internally by developers to overcome issues without the need to follow a time consuming process of powering down of the system and booting it back up. The latter is another solution we have all heard from IT support. These highly-paid experts who we rely on for protecting our work and systems simply ask: “Have you tried turning it off and back on again?”

It may seem a simple solution, but it works. When you reboot a computer, every single programme and process ends as the power leaves the computer during the restart process. Once it starts back up, you have a clean slate of sorts again and, more often than not, a faster, better working computer – and more often than not, the issue you were facing has resolved itself.

This same logic applies to many other electronic devices such as televisions, smartphones, internet routers, DVDs, digital cameras. While they are not computers, they all have operating systems and software that run into the same issues as desktop and laptops computers. The same can be said about a Boeing 787 or for that matter any modern generation airliner.

Not so long ago, the author actually sat on a poorly Embraer E-Jet on the apron at John Paul II Kraków-Balice International Airport while the flight crew identified the systems problem that was delaying the aircraft’s departure. After a couple of polite messages from the pilot apologising for the delay, the increasingly frustrated passengers – which included many airline and airport executives returning from a conference – burst out in nervous laughter when the pilot’s third message was that he was about to turn the aircraft off and back on again to try and fix the problem.

It seems a rather simple solution for a USD300 million aircraft like a 787, but its flight management system and other cockpit technology is effectively a computer system, albeit a very specialised and complex one. If it works for our Dell laptops it should be the same for our Boeing widebody.

Well, in the past couple of weeks operators of the 787 have been told by the US Federal Aviation Administration (FAA) that they now have to power-cycle their aircraft (including all -8, -9 and -10 variants of the aircraft) every 51 days. Yes, that means switch the aircraft off and back on again. It is the kind of story you would have expected to read earlier this week on April Fool’s Day, only this is a real issue and directive from the regulator that if not completed could lead to "several potentially catastrophic failure scenarios," it warns.

In an airworthiness directive (AD) issued on 26-Mar-2020 and effective 07-Apr-2020, the US regulator requires “repetitive cycling of the airplane electrical power”. Just like we can be prone to leaving our computers in standby mode, aircraft, especially widebodies used on long-haul networks can be flying most of the day and night. Even on the ground they can remain powered-on while cleaned or maintained. This means it could actually be weeks before their systems are shutdown.

The FAA says the AD has been prompted by a report that the stale-data monitoring function of the aircraft’s common core system (CCS) may be lost when continuously powered on for 51 days. This, it says, could lead to “undetected or unannunciated loss of common data network (CDN) message age validation, combined with a switch failure.

For most of us that are unaware, the CDN is an Ethernet-based bi-directional copper and fibre optic network that manages the data flowing between the 787's onboard systems and handles all the flight-critical data (including airspeed, altitude, attitude, and engine operation).

The FAA warns that failure to complete the 51 day power-cycle could result in the display of misleading primary attitude data, airspeed data or engine operating indications for both pilots. This erroneous flight-critical data being displayed as valid data “could reduce the ability of the flightcrew to maintain the safe flight and landing of the airplane,” explains the regulator.

An investigation of safety dockets shows that this latest requirement is not the first time such a requirement has been directed for operators of the 787. A previous software bug identified in 2015 required airlines to power down their 787s every 248 days for fear that electrical generators could shut down in flight.

It is a similar story with the Airbus A350, operators of early versions of the -900 variant, having to complete power cycles every 149 hours to avoid "partial or total loss of some avionics systems or functions," according to an EU Aviation Safety Agency (EASA) directive.

Even against the guidelines of our IT teams we have all left our laptops on sleep mode for long periods of time. Having now heard how failures to shutdown equipment could effect the safety of multi-hundred million dollar aircraft, my computer will certainly be shutdown tonight!