It is difficult to comprehend just how little tolerance there is for failure in the maintenance of aircraft.
I have included an incident of an AH-47 that resulted in the loss of the crew and aircraft.
A/C crashed in a soybean field and burned at approx 1900 hrs 12 mi south of Clarksville off Gholson Rd during a routine night training flight. At approx 1848 hrs, flying 120 KIAS and 700′ AGL, A/C began to pitch up and roll left, followed shortly by M/R pitch housing and M/R blade separation from rotor head, T/B separation from fuselage and remaining M/R system separation from xmsn. Crash was caused by P/C link rod end bearing not being staked onto the #3 lower rod end.
What does all that mean? Components are small and forces are huge. The force of the aircraft far exceeds what can be expected. That is why we have a narrow window in which we can fly. Very specific rules and pressures and temperatures.
In this case, the aircraft lost the ability to control its movements. A problem with a bearing, a very small part, cause a catastrophic domino effect that shred to the point that the entire blade system, including the shaft that holds the blades and the aircraft together.