Jim Wilson writes: > My boss files IFR most of the time but rarely starts a flight in > anything but VFR conditions. He has many thousands of hours and a > great aircraft, but has been known to drive or take commercial when > he absolutely has to be somewhere on a day with questionable > weather in the forecast (days when most instrument rated pilots > fly). It seems a little bit excessive, but he's been flying 40 > years without getting into a single dangerous weather situation.
Actual IMC affects different people in different ways -- some pilots absolutely hate it (the way people hate hornets or fingernails on a chalkboard), some don't mind it in small doses, some will fly a whole trip IMC as long as they have an autopilot, and some don't see any big deal in hand-flying IMC. I'll see which category I fall into when I have more real (non-training) experience, but so far, I feel very comfortable in actual. > > When I came inside (wet) for the debrief, he chewed me out for > > not putting on carb heat every 15 minutes or so in IMC (not part > > of the > > What happens if you do or don't turn on that carb heat? When the fuel vaporizes, it has to draw heat out to do it (the same way water draws heat from your skin when it evaporates), so the carb venturi can become very cold even on a hot day -- if it is humid or your are flying in cloud, the moist air can form ice inside the carb until eventually the air supply to the engine is choked off. As a result, all carbureted engines are required to have an alternate air source that can heat the air (usually unfiltered) -- when you pull carb heat, air heated by a shroud around the exhaust flows into the carb instead of the colder outside air. Of course, if you let enough ice form that the engine stops, there is no hot exhaust, and therefore, no way to melt the ice. The 140 hp, six-cylinder Continental O300 engine used in the Cessna 172 up until 1967 was notorious for carb ice, as was the smaller Continental engine used in the Cessna 150 (I don't know about the 152). When Cessna switched a four-cylinder Lycoming engine for the 172 in the late 1960's, the carb ice problem became much less serious, since the Lycoming carb draws its air past part of the (hot) oil system. The Cherokee is even less likely to develop carb ice, since its Lycoming engine is more tightly cowled and tends to run hotter. Because of the early problems with the Continental engine, the 172 POH had all kinds of warnings about carb heat, including a requirement to turn on carb heat for landing and any procedure (such as descent) where RPM fell out of the green arc. Cessna left those in when it switched to the Lycoming until it switched to the fuel-injected IO360 in the 172R, and generations of students and teachers in 172 have had the carb-heat rule pounded into their heads. That's never been the case for the Cherokee -- the POH does not recommend carb heat for descent, landing, or other low-power maneuvers, and suggests putting it on only if carb heat is actually suspected. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
