Critical equipment used by the air carriers, general aviation and controllers cannot be evaluated until there is no impact on the air traffic system. To make flying safe for commercial carriers and the flying public, there must be redundant critical equipment. Equipment can only be evaluated or repaired in the wee hours of the morning when most technical support people are operating at their lowest physical and mental capacity. Solid-state technology has influenced FAA to purchase single channel systems. The design and installation of most equipment does not support a system that is failure-proof.
Static electricity can and does cause component failures.
In places where dual channels do exist, power supplies are common to both channels. This does not allow complete evaluation of defective equipment or intermittent problems without the risk of shutting the total system down. The high volume of air traffic and talk of increasing the arrival and departure speeds of aircraft will mean the MTTR will need to be less than the present time allowed to restore service.