3 ms·
So that depends on if you mean a power source temporarily goes down or if a box experiences a power blip. So in the first case each box usually has 3 different
by sbradford26 8y ago
So that depends on if you mean a power source temporarily goes down or if a box experiences a power blip. So in the first case each box usually has 3 different sources of power, something like the generators on the engines, then backup on the 24 volt bus, then finally a backup battery.
In the second scenario it depends on how long the blip is. Usually there are holdup requirements that a box will not reset if power is lost for x amount of time. If power is lost for longer it will save state and leave itself in a state that will come back up quickly.
What I am thinking is happening in this case is that some value is getting messed up in NVM and it must be reset by the maintenance crew, so the "reset" they are talking about isn't just rebooting after the error occurs. But if you reboot before the error happens the NVM doesn't get messed up and the value is just updated with the correct number.
- cm2187 8y agoSo you think the one hour quoted by the article isn't the time it takes for the system to boot but rather the time it takes for the maintenance to access the device, reset it, and close everything?
- pjc50 8y agoSounds plausible - it takes 1h to follow the "reboot checklist", of which only a few seconds is actually the reboot.
- sbradford26 8y agoThat seems much more reasonable to me. Mostly because planes are rebooted for maintenance every so often between flights and customers(Airlines) would be not be okay with a 1 hour reboot time. There are also usually maintenance tests that can be ran to reset a box on the plane. So the technician would have to put the plane in maintenance mode and run through the test to get the box reset or something.
- paulie_a 8y agoYes they might not be okay with that but airlines apparently can hold the passengers for 8 hours because of delays. To the point of toilets overflowing. I think if you run an airline, you are legally required to go out of your way to to provide terrible service.
- bronco21016 8y agoHard to say what the actual procedure is. Might need a cold dark airplane for an hour for the GCU to clear memory or you might have to open panels and go back there and physically disconnect power to GCUs to get it done. It seems to me opening panels would probably take more than an hour.
- bdonlan 8y agoRealigning the IMUs would take something like 20 minutes alone (though it depends on the plane's current latitude).
- bronco21016 8y agoI’m currently working on an aircraft that has IMUs rather than AHRS/RNAV/GPS. I cannot recall ever seeing them take more than 5 minutes on first start up in the morning. Manuals specify 2.5-10 minutes. This is on a 1980s model. I’m sure newer designs are quicker.