Points for Pilots

Most small airplanes use a heat muff around the muffler for heat in the cockpit. Fresh air is piped into the heat muff. The heated air is ducted into the cockpit as needed. This system works well, provided exhaust gases do not become part of the heated air. If that happens, carbon monoxide (CO) enters the cockpit. Even small concentrations of that deadly gas can incapacitate pilots and passengers. Thus, great care must be taken to prevent this disaster. There are other ways CO may enter the cockpit: for example, due to a flawed design of the exhaust system where in a certain attitude CO may enter a fresh-air intake. We had this problem originally in our plane during steep angles of attack. A redesign of the exhaust system solved the problem. The publication Detection and Prevention of Carbon Monoxide Exposure in General Aviation Aircraft by the Federal Aviation Administration has an in-depth discussion of the CO hazard. Here, we shall not repeat that material, but summarize some...

We have had seven major causes for rough running of our Rotax 912 engine.  Four of them are covered in this post. They are: fouled plugs, faulty ignition cable, improper grounding of ignition module, and broken exhaust baffle. The remaining three causes are discussed in separate posts:  carburetors not synchronized ,  imprecise propeller pitch , and  worn Belleville washers in the gearbox . Fouled Plugs During most years, we fly almost exclusively using 100 octane low-lead avgas (100LL). Our use of 100LL avgas is not a choice but forced on us: Almost all airports that used to offer automotive gasoline (autogas) have stopped that service.   The term low-lead  for 100LL is an industry ploy to make us feel good. One gallon of fuel contains about 2 grams of lead. That is a large amount compared with the quantity in the leaded automotive gasolines of the 1960s.  The lead problem stems from the fact that in recent decades Continental and Lycoming, t...

O n low-level VFR flights, we typically enter the next destination airport into the GPS unit and deal with deviations forced by high towers, controlled airports, TFRs, restricted areas, and so on, with temporary deviations from the direct course.   This approach forces us to track the course on the sectional chart — a good thing. If the navigation equipment ever fails, we will be well prepared for appropriate action.  For the same reasons, we never let the autopilot execute the flight plan in the GPS unit. Instead, we input the GPS bearing to the destination into the autopilot, and adjust that setting manually as needed. Suppose we are approaching an obstacle forcing a course change. If we detour close to the obstacle, we add some distance — a bad thing. We avoid that through a course correction for the autopilot while we are relatively far from the obstacle. In the past, we carried out estimation of the course correction 30-60miles out as follows.  We w...

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 ...