Re: Ada / Boeing 777

[digitig@cix.compulink.co.uk ("Tim Rowe")]

ron thompson <thompsor@admin.tc.faa.gov>

> The only "bugs", "problems", "burps", "hiccups", whatever
> you wish to call them that matter in an airplane are
> the ones that keep it on the ground.

This is patently wrong, and dangerously so. "bugs", "problems", "burps", 
"hiccups" that keep an aircraft on the ground are intrinsically pretty 
safe. The ones that *do* matter are the ones that are likely to encourage 
the aircraft to *return* to the ground in an untimely and inadequately 
controlled manner. Commonly called a crash.

As an example, there was a known fault on one of the Airbus range (which 
has been flying total fly-by-wire for *many* years before the 777!) that 
meant that when flying a heading of 00 degrees, if the pilot commanded 
the aircraft to turn a bit one way, the aircraft could actually turn the 
other way. It was turning to the correct heading, but it was going the 
359 degree route, not the 1 degree route. Now, there are not many runways 
in the world that are close to north-south, but there are a few, and when 
that bug showed itself on a final approach I bet the pilots pants turned 
brown. The pilot recovered it safely, but it was the subject of an 
accident investigation, and I read about it in the published results. It 
turned up in comp.risks, too, as you might expect. Presumably JAA is 
satisfied that it's safe, but sorry, the fact that it is flying is not 
any such proof.

AIUI the Airbus range has triplicated *diverse* systems for critical 
functions. The 777 has triplicated *identical* systems (I'm trusting the 
press for this, so it may not be gospel).

digiTig
(Tim Rowe)