LATAM 787-9 sudden drop in cruise
https://www.aviationtoday.com/2015/0...-software-fix/
Avionics Today 05-05-2015] Boeing will provide a software update later this year to address an issue that causes the 787 Dreamliner’s Generator Control Units (GCUs) to simultaneously go into failsafe mode after being powered continuously for 248 days. The FAA has issued an Airworthiness Directive (AD) calling for 787 operators to address the glitch, which is caused by a software counter internal to the GCUs that will overflow after 248 days of continuous power, the AD states.
Boeing 787-9 Dreamliner. Photo: Boeing
According to the FAA’s directive, when a 787 has been powered continuously for 248 days, it can lose all Alternating Current (AC) electrical power due to the GCU software anomaly. The directive requires a repetitive maintenance task for electrical power deactivation on 787s.
“This condition is caused by a software counter internal to the GCUs that will overflow after 248 days of continuous power. We are issuing this AD to prevent loss of all AC electrical power, which could result in loss of control of the airplane,” the FAA’s directive states.
Boeing plans on issuing a software update for the 787 by the fourth quarter of 2015 to address the issue.
Originally, Boeing observed this GCU software issue during lab testing after eight months of continuous power. After discovering the issue, Boeing recommended the AD’s mandated actions to operators on April 19, 2015.
“It is important to note this issue was observed in the lab only after eight months of continuous power, which would be highly unusual. All operators have already completed the cycle off-cycle on fix, and they know how often they need to do it in the future until the software update arrives later this year,” a spokesman for Boeing told Avionics Magazine.
Most importantly, the AD addresses an anomaly that would only occur under extremely rare conditions within normal airline fleet schedules. By performing a power-off/power-on cycle, operators eliminate the risk that all six generators aboard the aircraft would lose power at the same time.
In the directive, the FAA indicates that in the occurrence that the four main GCUs associated with the engine mounted generators were powered up at the same time, the four GCUs would all fail at the same time. This would result in a “loss of all AC electrical power regardless of flight phase,” the AD states.
Boeing 787 fleet maintenance records indicate that all in-service airplanes have already performed a power-off/power-on cycle within their ongoing maintenance schedules. Operators that have a definitive record of a power cycle within the last 120 days do not need to take any immediate action, Boeing has confirmed. A total of 28 aircraft in the U.S. registry are affected by the AD, which has also determined that the cost of the electrical power deactivation is one work hour at $85 per deactivation cycle.
Since it first entered service in 2011, Boeing has delivered 258 total 787s, and has a backlog of 847 undelivered Dreamliners.
Avionics Today 05-05-2015] Boeing will provide a software update later this year to address an issue that causes the 787 Dreamliner’s Generator Control Units (GCUs) to simultaneously go into failsafe mode after being powered continuously for 248 days. The FAA has issued an Airworthiness Directive (AD) calling for 787 operators to address the glitch, which is caused by a software counter internal to the GCUs that will overflow after 248 days of continuous power, the AD states.
Boeing 787-9 Dreamliner. Photo: Boeing
According to the FAA’s directive, when a 787 has been powered continuously for 248 days, it can lose all Alternating Current (AC) electrical power due to the GCU software anomaly. The directive requires a repetitive maintenance task for electrical power deactivation on 787s.
“This condition is caused by a software counter internal to the GCUs that will overflow after 248 days of continuous power. We are issuing this AD to prevent loss of all AC electrical power, which could result in loss of control of the airplane,” the FAA’s directive states.
Boeing plans on issuing a software update for the 787 by the fourth quarter of 2015 to address the issue.
Originally, Boeing observed this GCU software issue during lab testing after eight months of continuous power. After discovering the issue, Boeing recommended the AD’s mandated actions to operators on April 19, 2015.
“It is important to note this issue was observed in the lab only after eight months of continuous power, which would be highly unusual. All operators have already completed the cycle off-cycle on fix, and they know how often they need to do it in the future until the software update arrives later this year,” a spokesman for Boeing told Avionics Magazine.
Most importantly, the AD addresses an anomaly that would only occur under extremely rare conditions within normal airline fleet schedules. By performing a power-off/power-on cycle, operators eliminate the risk that all six generators aboard the aircraft would lose power at the same time.
In the directive, the FAA indicates that in the occurrence that the four main GCUs associated with the engine mounted generators were powered up at the same time, the four GCUs would all fail at the same time. This would result in a “loss of all AC electrical power regardless of flight phase,” the AD states.
Boeing 787 fleet maintenance records indicate that all in-service airplanes have already performed a power-off/power-on cycle within their ongoing maintenance schedules. Operators that have a definitive record of a power cycle within the last 120 days do not need to take any immediate action, Boeing has confirmed. A total of 28 aircraft in the U.S. registry are affected by the AD, which has also determined that the cost of the electrical power deactivation is one work hour at $85 per deactivation cycle.
Since it first entered service in 2011, Boeing has delivered 258 total 787s, and has a backlog of 847 undelivered Dreamliners.
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It isn't, obviously, but (a) the risk event probability of all four GCUs shutting down generators simultaneously will certainly have been calculated as vanishingly low and (b) no one anticipated that any GCU would shut down because the firmware had a glitch like this baked in.
Edit: Also, if this is what occurred on the subject LATAM flight, surely it will have been the first time ever to have occurred in the wild (the sky). And it seems to me that would be vanishingly unlikely. The maintainers would have had to fail to perform the firmware/software update and the aircraft would have to have been powered up for 248 days. I don't gamble but I'd bet against that.
Edit: Also, if this is what occurred on the subject LATAM flight, surely it will have been the first time ever to have occurred in the wild (the sky). And it seems to me that would be vanishingly unlikely. The maintainers would have had to fail to perform the firmware/software update and the aircraft would have to have been powered up for 248 days. I don't gamble but I'd bet against that.
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There's a much more informative thread on this subject in Australia, New Zealand & the Pacific.
Maaaate! Got ya good!
Check your atlas: Flights to New Zealand usually head EAST over water from Australia, and not lumps of magnetic ore that make the compass spin wildly like in the Bermuda Triangle.
You will also note the aircraft was significantly closer to New Zealand than SunnyOz, and the New Zealanders also have a somewhat warped sense of humor and a streak of larrikanism as well.,
Here's a deviant suggestion: We are nearing the peak of the 10 year sunspot cycle. Unless you can pinpoint sunspot activity as directly affecting the aircraft at that particular time and date, I strongly suspect whatever the problem was, it was NOT external and NOT location based,and was confined to that one aircraft. Conspirators in this thread are welcome to prove me wrong.
Don't be too hasty in saying that it is a long way from WA and ore deposits.
Doesn't anyone shut down the aircraft, lock it up and take the keys home anymore?
Ironsand occurs extensively on the west coast of New Zealand's North Island. The sand makes up a large portion of the black-sand beaches on the North Island, as well as the surrounding sea floor. The magnetite in the sand contains fairly large quantities of titanium, and is sometimes referred to as titanomagnetite.
powered up for 248 days
The bug has been addressed by the new software, but it requires the operator to install the new software. This is a Chilean aircraft, so it's up to them to keep up, and they have had 5-6 years to do so. This time interval wasn't something for the pilots to manage but for the maintainers.
I suspect that the report into this event is going to be uncomfortable reading for someone or other.
One thing does occur though. If the fix has been available for 5, 6 years and hadn't been installed, there's been enough time for this behaviour to have occured 7 or 8 times by now if the aircraft hadn't been routinely de-powered in all that time.
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It isn't, obviously, but (a) the risk event probability of all four GCUs shutting down generators simultaneously will certainly have been calculated as vanishingly low and (b) no one anticipated that any GCU would shut down because the firmware had a glitch like this baked in.
Edit: Also, if this is what occurred on the subject LATAM flight, surely it will have been the first time ever to have occurred in the wild (the sky). And it seems to me that would be vanishingly unlikely. The maintainers would have had to fail to perform the firmware/software update and the aircraft would have to have been powered up for 248 days. I don't gamble but I'd bet against that.
Edit: Also, if this is what occurred on the subject LATAM flight, surely it will have been the first time ever to have occurred in the wild (the sky). And it seems to me that would be vanishingly unlikely. The maintainers would have had to fail to perform the firmware/software update and the aircraft would have to have been powered up for 248 days. I don't gamble but I'd bet against that.
248 days. This reminded me of something I came across in the late 1990s. A particular piece of networking equipment that we had deployed on various customer sites died periodically. From memory it was not 248 days, but memory plays tricks.
The problem occurred at 2^31 hundredths of a second after power up. Well guess what?
2^31 hundredths of a second is indeed 248 days. The time was stored in a 32 bit signed integer, one bit used for the sign and the other 31 bits for the value. After about 248 days there is a risk of an arithmetic overflow and unpredictable software behaviour.
Looks like pretty poor testing for an aviation product.
The problem occurred at 2^31 hundredths of a second after power up. Well guess what?
2^31 hundredths of a second is indeed 248 days. The time was stored in a 32 bit signed integer, one bit used for the sign and the other 31 bits for the value. After about 248 days there is a risk of an arithmetic overflow and unpredictable software behaviour.
Looks like pretty poor testing for an aviation product.
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Chief Bottle Washer
Discussion here with many duplicate posts, so this thread is now closed 👍
