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Density Altitude Calculator
Guys,
I just came across this - http://www.pilotoutlook.com/calculat...ude-calculator It may be useful for other students. They also have other flight planning tools at - http://www.pilotoutlook.com/flight_planning/calculators /r |
#2
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Density Altitude Calculator
On Jan 17, 5:39*am, Rajat Garg wrote:
Guys, I just came across this - http://www.pilotoutlook.com/calculat...ude-calculator It may be useful for other students. They also have other flight planning tools at -http://www.pilotoutlook.com/flight_planning/calculators Thanks Rajat. Its fun to play with but I dont know many pilots that actually worrry too much about the moisture effect on density. Its not that great except for very humid and hot days where it will be no more than 10%. Its best to calculate the density altitude when you are actually at the airfield ready to go, in which case you prollly wont have a computer. Easiest way is to just set the Kollsman window for 1013.2 ( or 29,92 if you are still behind the times :) ) . which of course gives you your pressure altitude then just correct for temp. Add or subtract 120 ft for each 1 deg C above or below the ISA temp for that pressure altitude. With a bit of practice you should be able to do it in your head in less than a minute eg set 1013.2 and say your altimeter reads 1500 ft that is your pressure altitude. ISA temp would be 15-2x1.5 or 12 deg C. if your actual temp read off the aircrafts outside temp gauge is say 20 deg C , then add 8 x120 or 960 ft to get 2460 ft density altitude. Terry PPL Downunder .. |
#3
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Density Altitude Calculator
"terry" wrote in message ... On Jan 17, 5:39 am, Rajat Garg wrote: Guys, I just came across this - http://www.pilotoutlook.com/calculat...ude-calculator It may be useful for other students. They also have other flight planning tools at -http://www.pilotoutlook.com/flight_planning/calculators Thanks Rajat. Its fun to play with but I dont know many pilots that actually worrry too much about the moisture effect on density. Its not that great except for very humid and hot days where it will be no more than 10%. Its best to calculate the density altitude when you are actually at the airfield ready to go, in which case you prollly wont have a computer. Easiest way is to just set the Kollsman window for 1013.2 ( or 29,92 if you are still behind the times :) ) . which of course gives you your pressure altitude then just correct for temp. Add or subtract 120 ft for each 1 deg C above or below the ISA temp for that pressure altitude. With a bit of practice you should be able to do it in your head in less than a minute eg set 1013.2 and say your altimeter reads 1500 ft that is your pressure altitude. ISA temp would be 15-2x1.5 or 12 deg C. if your actual temp read off the aircrafts outside temp gauge is say 20 deg C , then add 8 x120 or 960 ft to get 2460 ft density altitude. Terry PPL Downunder ---------------new post begins---------------- I agree that the effect of moisture is greatest at the highest temperatures, when the air can hold the mosture and that the effect of moisture on density altitude is admittedly small for aerodynamic purposes--notably lift. However, I have heard that the effect on power is much greater. For example, I would expect the same amount of moisture to cause a 1 percent drop in aerodynamic lift and approximately a 6 percent drop in power--at the same temperature and pressure. I do not have the real numbers available, and am not currently flying; but I believe that they are well worth the research for those who are! Peter .. |
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Density Altitude Calculator
On Jan 19, 10:34*am, "Peter Dohm" wrote:
"terry" wrote in message ... On Jan 17, 5:39 am, Rajat Garg wrote: Guys, I just came across this - http://www.pilotoutlook.com/calculat...ude-calculator It may be useful for other students. They also have other flight planning tools at -http://www.pilotoutlook.com/flight_planning/calculators Thanks Rajat. Its fun to play with but *I dont know many pilots that actually worrry too much about the moisture effect on density. Its not that great except for very humid and hot days where it will be no more than 10%. * *Its best to calculate the density altitude when you are actually at the airfield ready to go, in which case you prollly wont have a computer. *Easiest way is to just set the Kollsman window for 1013.2 ( or 29,92 if you are still behind the times :) *) . which of course gives you your pressure altitude then just correct for temp. *Add or subtract 120 ft for each 1 deg C above or below the ISA temp for that pressure altitude. With a bit of practice you should be able to do it in your head in less than a minute eg *set 1013.2 *and say your altimeter reads 1500 ft that is your pressure altitude. ISA temp would *be 15-2x1.5 or *12 deg C. *if your actual temp read off the aircrafts outside temp gauge *is say 20 deg C , then add 8 x120 or 960 ft to get 2460 ft density altitude. Terry PPL Downunder ---------------new post begins---------------- I agree that the effect of moisture is greatest at the highest temperatures, when the air can hold the mosture and that the effect of moisture on density altitude is admittedly small for aerodynamic purposes--notably lift. However, I have heard that the effect on power is much greater. *For example, I would expect the same amount of moisture to cause a 1 percent drop in aerodynamic lift and approximately a 6 percent drop in power--at the same temperature and pressure. I do not have the real numbers available, and am not currently flying; but I believe that they are well worth the research for those who are! Thats interesting Peter, Water does have a very high specific heat so perhaps it just absorbs a lot of the heat of combustion so there is less to convert into mechanical energy.? Surprising then that humidity isnt included in the take off charts, where power is critical. But then there are lots of anomalies with take off charts. Piper data shows take off distance to be a function of density altitude whereas Cessna tables show that take off is also a function of temperature, ie higher temperatures give better performance for the same density altitude. ( or you could also say higher pressures at the same density altitude are better) . the best explanation I had for the latter was that at higher pressures there is more driving force to get the air into the cylinder. Hope you get your wings back soon. Terry |
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