Re: Boeing 787 integer overflow

[Peter Chapin <PChapin@vtc.vsc.edu>]

On Sun, 3 May 2015, Maciej Sobczak wrote:

>> Can anyone comment on what language Boeing used for this?
>
> It does not matter. The ability to run continuously for 8 months was 
> most likely not in the requirements (planes have to be switched off for 
> maintenance more frequently than that anyway), so there was no need to 
> implement a solution for this.

I guess it depends on if there is a *requirement* to reboot the system 
periodically (less than 8 months) in the maintenance plan. The matter 
should be handled somewhere and it seems like it wasn't. In other words it 
was just "luck" that these systems have been getting restarted frequently 
enough.

Planes obviously don't fly for 8 months straight and I'm sure they get 
maintained, in general, more regularly than that as well. I don't know 
precisely which system this issue is connected with, but it seems possible 
to me that, in some cases at least, some systems would be left up and 
running while others are being maintained. In other words a daily 
maintenance schedule may not imply that the counter in question is getting 
reset daily.

A software fix might be nice, such as increasing the counter to 64 bits to 
push the overflow time out to something ridiculous, but just adding an 
item to the maintenance checklist might also be sufficient.

Peter