Blackout Bug: Boeing 737 cockpit screens go blank if pilots land on
specific runways
Odd thing haunts Next Generation airliner
family (not the infamous Max)
A Boeing 737-800 (file photo)
Boeing's
737 Next Generation airliners have been struck by a peculiar software flaw that
blanks the airliners' cockpit screens if pilots dare attempt a westwards landing
at specific airports.
Amid the various well-reported woes facing
America's largest airframe maker, yet another one has emerged from the US
Federal Aviation Administration; a bug that causes all pilots' display screens
in the 737-NG airliner family to simply go blank.
That bug kicks in when
airliner crews try to program the autopilot to follow what the FAA described as
"a selected instrument approach to a specific runway".
Seven runways, of
which five are in the US, and two in South America - in Colombia and Guyana
respectively - trigger the bug. Instrument approach procedures guide pilots to
safe landings in all weather conditions regardless of visibility.
"All
six display units (DUs) blanked with a selected instrument approach to a runway
with a 270-degree true heading, and all six DUs stayed blank until a different
runway was selected," noted the FAA's airworthiness directive, summarising three
incidents that occurred on scheduled 737 flights to Barrow, Alaska, in
2019.
The controls in the 737 cockpit
The DUs are the five main
screens in front of the pilots plus the sixth in the lower middle position of
the instrument panel. When they go offline, pilots rely on analogue
backups
Although full technical details were not given in the
airworthiness directive, the FAA said that the seven runways had "latitude and
longitude values" that "triggered the blanking behaviour", suggesting some kind
of memory interaction between onboard computers causing the screens to stop
displaying any information until a different runway was selected in the flight
plan.
The bug affects 737-600, -700, -700C, -800, -900 and -900ER model
aircraft, which are running Common Display System Block Point 15 (CDS BP 15)
software for their display electronic units (DEUs) together with flight
management computer (FMC) software version U12 or later.
FMCs hold the
flight plan, thus navigating the aeroplane from waypoint to waypoint. DUs are
the main screens displaying aircraft information to the pilots and are powered
by two DEUs, each of which serves three of the DUs. The system arrangement is
described in more detail on this website under the heading "NG Flight
Instruments."
In the airworthiness directive the FAA said it had
"confirmed that the faulty version of DEU software has already been removed from
all airplanes conducting scheduled airline service into the affected airports"
in the US.
Runways where Boeing 737 Next Generation aircraft
are not supposed to land. Source: US FAA
Commercial jet airliners
are far from immune to software bugs. Infamously, Boeing's 787 Dreamliner needed
power cycling every 248 days to prevent the aircraft's electronics from powering
down in flight, while Airbus' A350 was struck by a similar bug requiring a power
cycle every 149 hours to prevent avionics systems from partially or even totally
failing to work.
Human error with electronics can also cause problems for
commercial aviation: a typo in GPS co-ordinates left an Air Asia Airbus A330's
navigational system thinking it was 11,000km away from its true position, while
the captain of another airline's A330 found out the hard way that hot coffee and
electronic hardware really do not mix.
Boeing has not responded to The
Reg's request for comment.
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