Boeing's 787 airliners will soon have to be turned off and on again at least every 51 days to prevent 'several potentially catastrophic failure scenarios'.

A directive from the US government will force the planes to be shut down regularly to avoid glitches in the on-board computer systems.

If left for too long without being powered down, swathes of data can accumulate in the software and wreak havoc with the information displayed to pilots.

This could lead to incorrect data on airspeed, altitude and attitude being shown on primary displays, making it harder for pilots to maintain the safe flight and landing of the plane, according to the Federal Aviation Authority (FAA).

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Boeing's 787 airliners will soon have to be turned off and on again at least every 51 days to prevent 'several potentially catastrophic failure scenarios'. Clogged up software can provide false information to pilots in the cockpit if not turned off regularly (file photo)

WHAT HAPPENS IF THE 787S ARE NOT TURNED OFF AND ON AGAIN? According to a US airworthiness directive issued by the FAA, the planes must be cycled down every 51 days at the latest. This is because the operating system of the plane - dubbed common core system (CCS) - stops filtering out stale data from key flight control displays. It is unsure why this happens and the directive does not elaborate. However, if the data does accumulate in the systems, it can affect messages passed through the common data network (CDN) on the plane. The CDN handles all the flight-critical data (including airspeed, altitude, attitude, and engine operation). Several potentially catastrophic failure scenarios can result from this overloading of the CDN. Potential consequences include: • Display of misleading primary attitude data for both pilots. • Display of misleading altitude on both pilots' primary flight displays (PFDs). • Display of misleading airspeed data on both pilots' PFDs, without annunciation of failure, coupled with the loss of stall warning, or over-speed warning. • Display of misleading engine operating indications on both engines. Advertisement

According to the Register, planes are often left turned on for weeks at a time as crews change at airports or the planes are plugged in overnight during cleaning and maintenance.

The flaw with the software sees data clogging up the systems and feeding false information to pilots for various key metrics.

For example the Federal Aviation Authority (FAA) airworthiness directive, states airspeed, attitude and altitude figures given to both pilots could all be wrong.

The flaw also affects pilots' ability to monitor the condition of the engine and could prevent the stall warning horn and overspeed horn from working properly.

Software glitches mean the internal plane computer, called the common core system (CCS), doesn't filter out stale data.

This means the on-board ethernet-based network— dubbed the common data network (CDN) — is affected.

The CDN feeds data directly to the primary flight displays (PFDs) in the cockpit.

Backup monitors receive data from a different source and are therefore not affected, it is believed.

But the flaw with the primary screens occurs 'without annunciation of failure,' the document reveals.

A Boeing spokesperson told MailOnline: 'Boeing identified a potential scenario in which 787 data transmission could be delayed after many days of continuous airplane power on.

'On Jan. 16, 2020, Boeing recommended mitigating action to 787 customers to correct the issue. In addition, a permanent fix will be issued in the coming months.

'The FAA Immediate Adoptive Rule mandates the action to 787 operators that Boeing recommended.'

The aircraft manufacturer sold models to 59 airlines and there are around 200 Boeing 787s in use today in the US, according to the document.

Turning the planes off and on again in line with this new ruling is deemed an interim solution and the FAA is calling on Boeing to find a more comprehensive fix.

It will come into force on April 7 and the FAA has the power to force airlines to adhere to the rule because of the severity of the flaw.

The directive states: 'Given the significance of the risk presented by this unsafe condition, the unsafe condition must be immediately addressed.'

Performing the 'power down' requires no parts and only $85 of labour but will cost US operators of the plane $16,660 per cycle, the FAA estimates.

The flaw with the software sees data clogging up the systems of the 787 and feeding false information to pilots for various key metrics. For example the Federal Aviation Authority (FAA) directive states airspeed, attitude, altitude figures given to both pilots could all be wrong (file photo)

Boeing had a similar software issue in 2015 when it was mandated 787s must power down every 287 days.

This problem was found in simulations and stated that the aircraft may shut down 'regardless of flight phase' after 248 days, or eight months, of continuous use.

This FFA directive said: 'We have been advised by Boeing of an issue identified during laboratory testing.'

The laboratory testing that revealed the glitch was as series of simulations.

It would switch all engines into fail-safe mode and trigger a a loss of all AC electrical power.

Another plane in the Boeing fleet has also been beleaguered with technical issues, the 737 MAX.

The aircraft maker identified a flaw in an indicator light on the aircraft which is designed to warn of a malfunction in a system that helps raise and lower the plane's nose.

Boeing found this light was turning on when it shouldn't and reported it the the FAA in January.

This latest setback follows a string of problems with Boeing's best-selling plane.

The aircraft has been grounded since March following two fatal crashes that killed 346 people.

In October 2018, a 737 MAX nose-dived into the sea shortly after takeoff from Jakarta airport in Indonesia. All 189 people on board Lion Air flight 610 died.

Just five months later, the 157 passengers and crew of Ethiopian Airlines Flight 302 met the same fate, plunging into a field on a flight from Addis Ababa to Nairobi.

As with the Indonesian plane, the 737 experienced problems almost immediately after take off and hurtled out of the sky.

FAA Administrator Steve Dickson said in January the FAA is evaluating the issue.

Dickson told reporters that the FAA is working closely with the European Union Aviation Safety Agency and other regulators to tackle the 737 MAX issues so that the aircraft can get off the ground soon.

He added that the regulators will consult together on how plane makers can update their aircraft going forwards, after the fatal crashes led to calls for more thorough safety reviews.

Dickson refused to give a date for the 737 MAX getting back up in the skies.