4 ms·
> The root cause was determined to be an undue triggering of the rudder order COM/MON monitoring concomitantly in the 3 FCPC. At the time of the aircraft latera
by fnord77 5y ago
> The root cause was determined to be an undue triggering of the rudder order COM/MON monitoring concomitantly in the 3 FCPC. At the time of the aircraft lateral control flight law switching to lateral ground law at touch down, the combination of a high COM/MON channels asynchronism and the pilot pedal inputs resulted in the rudder order difference between the two channels to exceed the monitoring threshold. The FCPC1 failed first.
In lay-programmers terms, this sounds like a race condition. Is that correct?
- zaarn 5y agoNot quite. The computers disagreed, they didn't race. Likely cause might be that the sensors responsible for detecting touchdown might have been rusty or failed. The computers aren't racing towards ground law here, they switched to ground law at different times sufficiently apart that the monitoring watchdog turned them all off for commanding the aircraft to do three different things. Imagine it more like website and it's hosted by three servers with a replicated database. A monitoring tool checks that the number of entries in each server's database is the same. If one server has a different number, the tool turns it off, it now requires a human to bootstrap the database again. If two servers disagree the website goes offline, because it's no longer possible to tell which server has correct data and not operating is cheaper than the man hours required to puzzle the data back together. In this case, a likely cause might be that suddenly the network latency between the three servers got suddenly very large (cable damage maybe?) and now all three no longer agree on the dataset. The servers are shutdown.