Sporty's E6B density altitude disparity

My trusty Sporty's Electronic E6B does not agree with the Density Altitude
Chart. My instructor is at a loss to explain the difference. Can anybody
tell me what's going on?

Here's a sample problem:
Field Elevation: 1165
Altimeter Setting: 30.10
Temperatu 21°C
___________________

Using the standard chart:
http://pacificrimprinting.com/densalt.pdf

30.1 in. Hg Pressure Altitude Conversion Factor: -165
Pressure Altitude: 1000
Density Altitude: 2000
___________________

Sporty's E6B calculation:
Pressure Altitude: 985
Density Altitude: 1894

The Sporty's pressure altitude is off by -15 feet and the density altitude
is off by -106 feet. I can't imagine Sporty's marketing a flawed
E6B, which one is inaccurate?

--
Dallas

I entered the same numbers in my Sporty's E6B and got
PA: 998
DA: 1910

Which is about the same as on the chart.
Your reading of 2000 DA for 1000 PA is slightly off. You need at least
22 deg C for that.

- Tom

On Sun, 29 Apr 2007 17:20:43 GMT, "Dallas"
wrote:

My trusty Sporty's Electronic E6B does not agree with the Density Altitude
Chart. My instructor is at a loss to explain the difference. Can anybody
tell me what's going on?

Here's a sample problem:
Field Elevation: 1165
Altimeter Setting: 30.10
Temperatu 21°C
___________________

Using the standard chart:
http://pacificrimprinting.com/densalt.pdf

30.1 in. Hg Pressure Altitude Conversion Factor: -165
Pressure Altitude: 1000
Density Altitude: 2000
___________________

Sporty's E6B calculation:
Pressure Altitude: 985
Density Altitude: 1894

The Sporty's pressure altitude is off by -15 feet and the density altitude
is off by -106 feet. I can't imagine Sporty's marketing a flawed
E6B, which one is inaccurate?

On Sun, 29 Apr 2007 17:59:35 GMT, Tom L. wrote:

I entered the same numbers in my Sporty's E6B and got
PA: 998
DA: 1910

You entered the *same* numbers into your Sporty's E6B and got different
numbers than my Sporty's E6B?

What's going on here?

--
Dallas

On Sun, 29 Apr 2007 17:59:35 GMT, Tom L. wrote:

I entered the same numbers in my Sporty's E6B and got
PA: 998
DA: 1910

Field Elev : 1165
Pressure Alt: 1000
Temp : 21 C

DSSCalc - DA = 1931
CoPilot 1931
Garmin GPS 1930

If you want me to dig out the software I wrote based on "Flight Theory
for Pilots", it's around here someplace...

On Apr 29, 4:16 pm, Blanche wrote:
On Sun, 29 Apr 2007 17:59:35 GMT, Tom L. wrote:

I entered the same numbers in my Sporty's E6B and got
PA: 998
DA: 1910

Field Elev : 1165
Pressure Alt: 1000
Temp : 21 C

DSSCalc - DA = 1931
CoPilot 1931
Garmin GPS 1930

If you want me to dig out the software I wrote based on "Flight Theory
for Pilots", it's around here someplace...

Blanche, my flight planning software AirPlan comes up with 1931 as
well...

Dean

Blanche wrote in
:

On Sun, 29 Apr 2007 17:59:35 GMT, Tom L. wrote:

I entered the same numbers in my Sporty's E6B and got
PA: 998
DA: 1910

Field Elev : 1165
Pressure Alt: 1000
Temp : 21 C

DSSCalc - DA = 1931
CoPilot 1931
Garmin GPS 1930

If you want me to dig out the software I wrote based on "Flight Theory
for Pilots", it's around here someplace...


FWIW - My 13 year old Jeppesen TechStar for PA = 1000 and Temp = 21C also
gives DA of 1931'. Worked just fine on my instrument written.

--
Marty Shapiro
Silicon Rallye Inc.

(remove SPAMNOT to email me)

Dallas wrote:
On Sun, 29 Apr 2007 17:59:35 GMT, Tom L. wrote:

I entered the same numbers in my Sporty's E6B and got
PA: 998
DA: 1910

You entered the *same* numbers into your Sporty's E6B and got different
numbers than my Sporty's E6B?

What's going on here?


It is called tolerance. An E6B is a mechanical device. The
registration of the embossing on the various rings can be a little off.
The rivet may not be exactly centered on all of the disks, etc. It
doesn't take much to be off by a fair bit given the meager resolution of
the scales on the E6B. When I took my commercial written last year, I
could never get exactly the numbers in the study guide for the
computation problems, but I was close enough to know which answer was
correct.

Matt

On Sun, 29 Apr 2007 17:59:35 GMT, Tom L. wrote:

I entered the same numbers in my Sporty's E6B and got
PA: 998
DA: 1910

Here's photo evidence of our discrepancy:
http://img.photobucket.com/albums/v1...SportysE6B.jpg

BTW, mine is fresh from Sporty's a month ago.


--
Dallas

Right he

http://www.flickr.com/photos/8058120@N06/477406074/

Feel free to use the picture if you decide to call Sporty's.

BTW, mine is two or three years old. Yours must have the new and
improved algorithms.

On Sun, 29 Apr 2007 19:58:04 GMT, Dallas
wrote:

On Sun, 29 Apr 2007 17:59:35 GMT, Tom L. wrote:

I entered the same numbers in my Sporty's E6B and got
PA: 998
DA: 1910

Here's photo evidence of our discrepancy:
http://img.photobucket.com/albums/v1...SportysE6B.jpg

BTW, mine is fresh from Sporty's a month ago.

On Sun, 29 Apr 2007 22:22:56 GMT, Tom L. wrote:

BTW, mine is two or three years old. Yours must have the new and
improved algorithms.

Indeed. :-)


--
Dallas