Range Report Density Altitude from Temp and Station Pressure?

[LoneWolfUSMC]

Before I try to reinvent the wheel and give myself an anneurism in the process, does anyone have a formula to calculate Density Altitude from Station Pressure (inHg) and temp (*F)?

I have the charts and all the numbers and apps, but I need a simpler way to do it with nothing more than my noggin and a stick in the dirt.

I am sure I can eventually distill the long formulas into
Something useful, but the margin of error will be there.

 

[Lowlight]

Re: Density Altitude from Temp and Station Pressure?

Lindy to rescue

Manual DA

 

[LoneWolfUSMC]

Re: Density Altitude from Temp and Station Pressure?

I have read through that a couple times before posting but I did not see anything that would allow me to bypass the charts and do the straight math. Maybe I am just missing it. I do get a little fuzzy at the end of the shift.

 

[Lowlight]

Re: Density Altitude from Temp and Station Pressure?

You need Baro, Temp and Humidity to do it...

I would stick with what he has, or just carry a Kestrel.

 

[Lowlight]

Re: Density Altitude from Temp and Station Pressure?

Not sure if this has it...

http://wahiduddin.net/calc/density_altitude.htm

 

[LoneWolfUSMC]

Re: Density Altitude from Temp and Station Pressure?

I carry the Kestrel I was just hoping to come up with a "lite" way to do it with just the data off my Pathfinder.

I am going to laminate Lindy's tables and throw them in the databook, but sometimes I like to pick the gnat shit out of the pepper.

 

[GasLight]

Re: Density Altitude from Temp and Station Pressure?

There really isn't an easy way without using a chart. But the shortest way there may be to find Pressure Altitude:

29.92-current baro.=x then take x*1000+Current field elevation=pressure altitude

And then find Density Altitude using Pressure Altitude, but need a chart to find Standard Temperature at the level of Pressure Altitude.

DA = PA + (120 Vt)

where
DA = density altitude
PA = pressure altitude at the level you desire density altitude
120 = a temperature constant (120 feet per 1°C)
Vt = actual temperature minus standard temperature at the level of the pressure altitude.

 

[LoneWolfUSMC]

Re: Density Altitude from Temp and Station Pressure?

Dave, I am thinking the laminated chart is the way to go. If that isn't available then it's a SWAG and correct off of the splash!

 

[Pat M]

Re: Density Altitude from Temp and Station Pressure?

John did you check these out (i picked up 2 + think there very good)

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2022604&page=1

 

[LoneWolfUSMC]

Re: Density Altitude from Temp and Station Pressure?

Pat, yes I have one and I am working on a writeup on it.

 

[Unsichtbar]

Re: Density Altitude from Temp and Station Pressure?

Lindy would be the source of a simplifed formula and have an idea of what you need.

You might find the below useful. Two links below this might serve to check your math online caculator. Hope it helps you out

http://en.wikipedia.org/wiki/Density_altitude

"Not all this copied"
"Density altitude can be calculated from atmospheric pressure and temperature (assuming dry air).


where

DA = density altitude in feet
P0 = atmospheric (static) pressure
PSL = standard sea level atmospheric pressure (1013.25 hPa)
T = true (static) air temperature in kelvins (K) [add 273.15 to the Celsius (°C)] figure
TSL = standard sea level air temperature (288.15 K)
b = 0.235
Easy formula to calculate density altitude from pressure altitude

This is an easier formula to calculate (with great approximation) density altitude from pressure altitude ..and International Standard Atmosphere temperature deviation

Density altitude in feet = pressure altitude in feet + (120 x (OAT - ISA_temperature))
Where:

OAT = Outside air temperature in °C
ISA_temperature = 15 °C - (1.98 °C/1000 ft × actual altitude in feet)

http://wahiduddin.net/calc/density_altitude.htm

http://wahiduddin.net/calc/calc_da.htm