Originally Posted by
Bbtengineer
I will stop after this but I’m not having it.
Requirements always come from somewhere else. That’s not special.
You don’t take a stupid requirement.
I see this problem as related to computer architecture, how the computers are connected, and the lack of an EICAS display unit.
The problem is that the B737 was designed at a time when there was no computers in the aircraft.
Problems was indicated by lamps. if you want to indicate a new issue, you need to install a new lamp, and hard-wire it into the master caution.
The instruments and autopilot for left and right side was intentionally separated.
The fault insulation is manual, you disconnect whatever is needed to be disconnected (AP, AT, Trim switches) and then compare instruments to locate the problem.
If you start comparing values in software, you run into the problem of how to display the fault information.
The PFD can display some information, but it will newer be a real EICAS, it will be difficult to indicate multiple issues at the same time.
If the software performs fault insulation, then you need to be able to se from what side it is using data from, and you might need to be able to override this.
You can mount a lamps to indicate this, but how many indicators do you need?
And what if the software for this is upgraded, do you then need to drill new holes for new indicators ?
In the current architecture air data is only connected to one flight control computer, if one flight control computer fails, then the remaining one also looses air data from that side (As I understand it, please correct me if I'm wrong).
With all those issues, it might be tempting to keep tings as is, in order not to wake up the type certification goods, by changing something.
'As is' is to document that the faults is manageable by the pilots.