Points for Pilots

Oil temperature of the plane's engine plays a much more important role than often assumed. The manufacturer typically gives a range of acceptable values. As long as oil temperature is within that range, the pilot assumes that all is well. So did we, until recently. The Rotax manual specifies a normal oil temperature range of 190-230 deg F. For short periods, the temperature may go as high as 285 deg F with synthetic oil. Let's evaluate these numbers. Oil oxidation doubles for every 18 deg F temperature increase, and oil life decreases by 50% for every 15 deg F above 140 deg F. So the rate of oxidation approximately increases by a factor of 4 over the range 190-230 deg F. At the same time, oil life is reduced to less than 20%. Over the range 190-285 deg F, the oxidation rate increases approximately by a factor of 32, and oil life is reduced to less than 2%. These are substantial factors and reductions.  In the past we wondered why the oil drained during an oil change...

The Digitrak autopilot by TruTrak keeps the plane level and on the selected true course. We have used that autopilot for several months and are impressed by its performance. Two situations have come up where the autopilot took a strange action. In both cases, we had caused the problem. Below, we describe the two problems and appropriate remedial action. Case 1 The autopilot is engaged in flight, holding a specified true course. My passenger asks for something in the baggage compartment. Turning around, I grab the item and give it to the passenger. He suddenly says, “Look, we are turning.” Indeed, we are in a gentle left turn. I disengage the autopilot and go back to the original course. Engaging the autopilot again, it immediately begins a left turn again. Once more, I disengage the autopilot. Something must be wrong with the autopilot, right? Just then I look down and see that the ball is out of center. Apparently, when I turned around to grab the item in ...