C 150 Engine failure
When I was a young commercial pilot I got an piece of excellent advice from a gentleman who had been flying since the 1930's. He told me to note the actual position of each engine gauge needle for each phase of flight. This is especially valuable if you normally fly the same airplane.
Any significant change in an engine gauge indication should be monitored and investigated. This advice saved me from a force landing as I was climbing out in a C150 on a routine instructional flight one day. I noticed that the oil pressure gauge was one full needle width below the the mid gauge white line. Every other flight the needle had had sat exactly over the white line mark. As we were only a few miles from the airport, I told the student to turn back.
Over the next 2 minutes the oil pressure slowly rolled back to zero. By this time we were on short final so I shut the engine down and we completed an uneventful landing. It turned out the oil pump drive gear had failed.
Had I not been monitoring the engine gauges the engine would have failed in a less than good area for a forced landing.