I just reread a lot of this thread and will comment on one where Bill was made the Test Flight Pilot for his unit along with a couple others.
I worked in a General Support/Depot company in VN. After being there for six months I was assigned the job of going over aircraft after they came out of rebuild. We did a lot of rebuilds. What I would do is take the tech manual and spend hours going over every detail of the ship. Check all the nuts and bolts were safetied, check pitch settings for main and tail rotor blades, make sure all fluid levels were full, and in general that the AC was flight worthy. Then I would go get one of the test pilots, I think we had three as well, together we would run the AC up and check all voltages rotor blade tracking and such. That took several more hours. Once satisfied we would hover the AC for a while or until the test pilot was happy with it, and then test fly it. The company rule was that if I was not willing to fly in the left seat, the pilot wouldn't fly it either. I did a lot of that.
One day we had a ship that I deemed ready for test flight, but the pilot who I flew with a lot said I should get a hair cut, as I was getting scraggly, and he would take some mechanics on the flight with him. Worked for me. I came back from my hair cut to find a very angry test pilot. He asked me if I was sure the 45 degree gear box was full of lubricant. I replied I was. He then showed me the box and sight glass was devoid of any fluid. In a few more minutes of flight it could have failed causing severe problems. I assured him it had been full.
I had a mechanic fill it up again and we ran the AC up on the ground. In fifteen minutes the gear box was dry. The seals were bad and I was forgiven.
It's little things like this that kill people.
Another time I was test flying with a new pilot that I really didn't know. He was one of those that liked to get the most out of the AC. We were contouring a mountain which was very steep. In fact we were climbing almost vertical just a few feet from the trees. As we went over the top and he dropped the Collective to descend down the other side something went through the rotor blades with a clang, clang. Scared the bejeebers out of us and we returned to base immediately. I spent hours inspecting the rotor blades as well as the entire ship and never found any evidence of what caused the noise. I originally thought maybe a mechanic had left a tool someplace and when we went negative Gs it had flown up through the blades, or I was looking for bullet holes. Never found anything.