Re: Boeing 787 integer overflow

[robin.vowels@gmail.com]

On Monday, May 4, 2015 at 2:03:55 AM UTC+10, Peter Chapin wrote:
> 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,

That isn't the solution.
The solution is to have an appropriate error handler.

> but just adding an 
> item to the maintenance checklist might also be sufficient.

Things like that get overlooked.
Maybe not this year, but in 10 years, when everyone has forgotten about it.