Tip 5: What’s the Cause?Okay, so we have a bunch of terms. How do we use them to determine cause of the accident? We first must define an accident. That's spelled out in Part 830 of Title 49 of the U.S. Code of Federal Regulations. Then the investigator must establish what factors led to the accident. Here's an example.Our pilot, Mr. Zero, decides to do touch and go's in his airworthy single engine plane at the local sea level airport with a 5000-foot runway. After about ten successful landings and take-offs, Mr. Zero is downwind and suddenly the engine quits! He radios that he just ran out of fuel and is going to land (that's a given). On the turn from base to final, witnesses see the aircraft's nose pitch up then suddenly the left wing dips and the plane semi spins into the ground short of the runway. Poor Mr. Zero is killed and the plane is junk. An investigation reveals that the plane is (was) airworthy, Mr. Zero suffered no medical issues and was qualified to fly, but alas there is no gas in the plane. Once filled with gas, the engine runs. There is no evidence of fuel starvation due to systems failure. This is a case of fuel exhaustion. Records indicate the plane was never fueled before take-off and Mr. Zero was seen getting into the plane without doing a preflight. When did the accident become an accident? Well, once positive control of the aircraft was lost and it became junk with a fatality then it became an accident. So, the primary cause of the accident was the failure of the pilot to maintain positive control of the aircraft. Contributing factors were the lack of gas and preflight. After all, had Mr. Zero successfully landed without fuel, there would have been no accident. Understandably there is latitude in determining cause. Let's change the scenario. Mr. Zero did a preflight; the aircraft was airworthy and had plenty of fuel. Instead of being at the local airport, Mr. Zero is flying at night over the mountains. Suddenly the engine quits because of a fuel system failure that results in a long glide into darkness and rocks. Though Mr. Zero is just as dead and the plane just as crunched, the probable cause might be different. After the investigation, we might determine there was a catastrophic fuel pump failure for whatever reasons (not pilot-induced) that caused an in-flight engine failure over hostile terrain void of safety zones, at night, which resulted in the fatal crash. There is a difference between fuel starvation and fuel exhaustion.