needs to be robust enough to ensure that all potential problems are resolved before the aircraft gains certification
The certification process cannot uncover all the issues that may arise once the aircraft is put into the rigours of commercial use. A couple of examples.
About to enter downwind at home base following an offshore flight in a 212, when a high freq manifested itself, lasted about ten seconds, and terminated with a bang. Everything normal in the cockpit, and normal landing and shutdown followed. Big puddle of oil underneath on the pad coming from the hell hole. Oil in transmission sight glass zilch. Rotor brake disc was found lying on the deck and the bevel gear had dropped into the trans and flung about taking chunks out of gear wheels various. Ultimate cause I don't know, but I'm not about to suggest it signified a great problem for the 212 type. Stuff happens, though I'm mutchly glad it didn't happen offshore and having to ditch in mega seas in the middle of winter.
One of our pilots landed a 205 on fixed floats in the ocean to pick up the survivors from the above Wessex. Aircraft was returning home at low altitude and slow speed with a high freq, when it suddenly rolled inverted and crashed. Two pilots survived, crewman and pax perished. Cause? Gearbox spat a wheel out through the case, which in turn removed one of the jacks. Only ever flew the H-34 version, but once again I'm not about to suggest the aircraft had a history of main G/B issues. Stuff happens.