Re: Boeing 737 and 737 MAX software

[tranngocduong@gmail.com]

On Thursday, April 18, 2019 at 12:27:44 AM UTC+7, Maciej Sobczak wrote:
> > I know nothing about the software.
> 
> Me neither, so we are in a perfect condition to discuss it!
> 
> > But I don't think it is written in Ada. If it was, programmers must have chosen a wrong subtype.
> > 
> > In the crashed Ethiopian 302 aircraft, ~30 seconds before impact, the nose points 40 deg. toward ground, and the AoA indicates 75 deg. As 40 + 75 = 115 > 90 deg., this would imply negative airspeed.
> 
> So how would Ada help in this situation?
> What if the above addition is never performed? Because, you know, the result of this addition indicates a flight parameter that either nobody cares about or that is already obtained by other (presumably more reliable) means?
> 
> In which case Ada would be a perfectly valid language there.
> 
> -- 
> Maciej Sobczak * http://www.inspirel.com

The addition computes airspeed. More specifically it computes the elevation angle, one of the 3 components of the airspeed (as a vector in 3-dimensional space), quite a critical flight parameter.

True, airspeed needs not be computed this way. But it must be somehow computed. All flight parameters must be somehow computed. If not for flying, then at least for monitoring. The software is supposed to run on multiple (redundant) computers, takes input from multiple (redundant) sensors, computes flight parameters using multiple (redundant) algorithms.

True, it is possible that the software was written in Ada. But then, the fact that it didn't raise an exception (or even worse, programmers managed to find a proof that it can never raise one), indicating a failure to detect/handle so "exceptional" situations as AoA implying negative [horizontal] airspeed, is simply unbelievable.