Plane down on the Capital golf course near Moorabbin
Join Date: Jan 2008
Location: turn L @ Taupo, just past the Niagra Falls...
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golfbananajam is completely correct. Carb icing is far more likely to develop during low power operations when the throttle butterfly is presenting a large surface-area to the mass-flow leading to an induction icing event. As he states, usually easily detected and rectified prior to trying for takeoff power. At high power settings (as during a takeoff) the likelihood of induction icing becoming an issue is vastly reduced, as a consequence of the wide-open throttle butterfly presenting (as close as possible) a knife-edge to the induction mass-flow, as much as the sheer volume of the mass-flow itself clearing ice buildup by virtue of Itself.
Another very persistent icing myth is that icing is more likely an issue in the colder months/locations than in summer... sorta makes sense, yah? Nah. A basic principle of air’s ability to retain moisture is that: warm air can hold and retain more moisture than cold air. Met 101. To get induction icing, you need... moisture. So the reality is that you are far less likely to get induction icing issues in the winter months or the colder locations. It’s the warmer spots you need to pay more attention to.
When I was flying the old BN2A a wee while ago now, it was SOP to select carb air HOT immediately after engine-start, with selecting COLD the very last action before shoving the throttles up for departure. Climb and even cruise usually flown at full throttle -the only power reduction being to bring the props back below 2750 and mixture leaned viciously. Never had any problem with induction icing or engine health operating that way for close to 8 years. Admittedly, the BN2A with the normally aspirated O-540’s was well known to be particularly susceptible to induction icing, particularly during low power ground operations, requiring a little more care and attention than other common types.
Last edited by RadioSaigon; 19th Jun 2019 at 14:22. Reason: Grammar/clarity
Join Date: Sep 2018
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Sorry? What???
golfbananajam is completely correct. Carb icing is far more likely to develop during low power operations when the throttle butterfly is presenting a large surface-area to the mass-flow leading to an induction icing event. As he states, usually easily detected and rectified prior to trying for takeoff power. At high power settings (as during a takeoff) the likelihood of induction icing becoming an issue is vastly reduced, as a consequence of the wide-open throttle butterfly presenting (as close as possible) a knife-edge to the induction mass-flow, as much as the mass-flow itself clears ice buildup by sheer virtue of the mass-flow.
Another very persistent icing myth is that icing is more likely an issue in the colder months than in summer... sorta makes sense, yah? Nah. A basic principle of air’s ability to retain moisture is that: warm air can hold and retain more moisture than cold air. Met 101. To get induction icing, you need... moisture. So the reality is that you are far less likely to get induction icing issues in the winter months.
When I was flying the old BN2A a wee while ago now, it was SOP to select carb air HOT immediately after engine-start, with selecting COLD the very last action before shoving the throttles up for departure. Climb and even cruise usually flown at full throttle -the only power reduction being to bring the props back below 2750 and mixture leaned viciously. Never had any problem with induction icing or engine health operating that way for close to 8 years. Admittedly, the BN2A with the normally aspirated O-540’s was well known to be particularly susceptible to induction icing, particularly during low power ground operations, requiring a little more care and attention than other common types.
well said -
Amazing the incorrect info out there & old wives tales, carby icing is just one subject!Note that the post I responded to said that carby ice would be noticed in the run-up bay. Over 1,000 hours in Jabs with a carby temp probe tell me that.
