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#11
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"private" wrote in message
news:3Q6ve.1795956$6l.1699114@pd7tw2no... [snip] None of what you wrote suggests that atmospheric subsidence would have any significant effect on the aerodynamics or engine of an airplane. It is true that there are variety of atmospheric effects related to nightfall. But they don't change the way the airplane flies, not in a way that requires even knowing about atmospheric subsidence, never mind understanding it. Pete |
#12
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"Peter Duniho" wrote in message ... "private" wrote in message news:3Q6ve.1795956$6l.1699114@pd7tw2no... [snip] None of what you wrote suggests that atmospheric subsidence would have any significant effect on the aerodynamics or engine of an airplane. It is true that there are variety of atmospheric effects related to nightfall. But they don't change the way the airplane flies, not in a way that requires even knowing about atmospheric subsidence, never mind understanding it. Pete Hello Pete, I agree that subsidence does not change aircraft aerodynamics, and does not have a significant effect on engine power. What it does do is change the way an aircraft performs. Rising air adds to an aircraft's climb rate, sinking air subtracts from it. There will be small changes in maximum level cruise speed and aircraft attitude with respect to horizon when flying in descending air. IMHO it is better to have unrequired knowledge than to be in ignorance when that knowledge is needed. My main instructor always maintained that you can never have too much weather knowledge. There is some discussion of subsidence and katabatic and glacier fed downslope winds in this excellent BC weather manual from Navcan. There is also discussion of coastal diurnal and wintertime outflows. http://www.navcanada.ca/ContentDefin...k/bc/BC31E-V.P DF Note chapter 2 Aviation Weather Hazards, page 28 provides discussion of glacier winds and notes local wind speeds to 80 knots and notes that these winds may be magnified by terrain funneling and comments that they may be pulsing in a kind of reverse thermal. I would submit that this subsidence is substantial and hardly "irrelevant from a practical standpoint." This subsidence can add to the reduction of performance due to density altitude and is often a factor in failure to climb after takeoff or inability to out climb rising terrain and has contributed to lots of crumpled aluminum in the mountains. Just my .02 |
#13
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Not to beat this dead horse any deader, but folks who learn to fly where
this knowledge is important, such as Canada, Alaska, New Zealand, etc, get it as part of their training. I'm chauvinist enough to think that the majority of participants in this ng do not fly in those areas, and thus a general question to the group won't get many enlightened responses. I learned to fly in Southeast Alaska, and never heard the word subsidence mentioned. Bob Gardner "private" wrote in message news:5kgve.1798330$6l.939730@pd7tw2no... "Peter Duniho" wrote in message ... "private" wrote in message news:3Q6ve.1795956$6l.1699114@pd7tw2no... [snip] None of what you wrote suggests that atmospheric subsidence would have any significant effect on the aerodynamics or engine of an airplane. It is true that there are variety of atmospheric effects related to nightfall. But they don't change the way the airplane flies, not in a way that requires even knowing about atmospheric subsidence, never mind understanding it. Pete Hello Pete, I agree that subsidence does not change aircraft aerodynamics, and does not have a significant effect on engine power. What it does do is change the way an aircraft performs. Rising air adds to an aircraft's climb rate, sinking air subtracts from it. There will be small changes in maximum level cruise speed and aircraft attitude with respect to horizon when flying in descending air. IMHO it is better to have unrequired knowledge than to be in ignorance when that knowledge is needed. My main instructor always maintained that you can never have too much weather knowledge. There is some discussion of subsidence and katabatic and glacier fed downslope winds in this excellent BC weather manual from Navcan. There is also discussion of coastal diurnal and wintertime outflows. http://www.navcanada.ca/ContentDefin...k/bc/BC31E-V.P DF Note chapter 2 Aviation Weather Hazards, page 28 provides discussion of glacier winds and notes local wind speeds to 80 knots and notes that these winds may be magnified by terrain funneling and comments that they may be pulsing in a kind of reverse thermal. I would submit that this subsidence is substantial and hardly "irrelevant from a practical standpoint." This subsidence can add to the reduction of performance due to density altitude and is often a factor in failure to climb after takeoff or inability to out climb rising terrain and has contributed to lots of crumpled aluminum in the mountains. Just my .02 |
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