DevX
I thought that 'squat' switches were now used on the undercarriage which prevents reverse thrust being operative whilst airborne, irrespective of where the levers are.
If only they all work 100% of the time.
If one depends on a switch and circuit that is quietly not doing it's job every now and then. Then you better have a backup system that does it's job more reliably.
And if you never test these circuits or devices before each flight just what are the combine probabilities that two or more will fail at the same time?
Lauda is just one of many incidents that pointed at unknown probabilities combining together, thus the 3rd lock is now mandatory.(and even that is not 100%)