Re: Spark length dependence on air pressure.

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Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Jim,

Another thought.  Instead of using a look up table (probably the most 
accurate) one could use the following exponential equation using 18000 feet 
as the half pressure point.  Note, I use "2^" cause this is the half 
pressure point and this equation would predict that at 36000 ft the 
pressure would be 1/4 of sea level and I dont know if this is true.  Im 
being somewhat lazy here cause I dont want to look it up.

Gerry R.

Pabsolute = Psealevel_STP *  2 ^ (-density_altitude/18000)

> Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
>
> Except that density altitude isn't what he wanted.  He needs actual 
> density ratio. You'd still need to know what altitude corresponds to what 
> density (numerically).