Sporty's E6B density altitude disparity

Scott Skylane wrote
Haha, remember all those old Boeing performance charts, Bob? No two
people could ever get the same answer, and no one person could ever get
the same answer twice!

That just meant that you always had a correct solution. :-)

Bob Moore

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...

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 29 Apr 2007 20:43:21 GMT, Bob Moore wrote:

My reading of the chart shows about 1800' density altitude.

I noticed that too... I took the problem out of the Jeppesen Private Pilot
Manual and they came to the 2000' conclusion that I was using. 1800'
would make my Sporty's the most accurate.

*grumble*

But, that doesn't explain why none of the electronic calculators agree with
the 1000' pressure altitude on the chart.

--
Dallas

On 29 Apr 2007 14:11:56 -0700, Kev wrote:

So it's no surprise how different they can be.

That makes me feel a little better. My concern is that I'm taking this E6B
into the written and I'd hate to find out it's little brain is retarded -
after the test.

--
Dallas

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

On Sun, 29 Apr 2007 22:36:55 GMT, Dallas
wrote:



But, that doesn't explain why none of the electronic calculators agree with
the 1000' pressure altitude on the chart.

Since moisture content of the air has a significant effect on the
calculation and I have never seen a specification for relative
humidity as part of the "standard day" it would seem that everyone is
free to pick their own value which would cause different results.

On Sun, 29 Apr 2007 22:41:12 GMT, Dallas
wrote:

That makes me feel a little better. My concern is that I'm taking this E6B
into the written and I'd hate to find out it's little brain is retarded -
after the test.

Be afraid. The test is multiple choice so if only one answer is close
to the one you got with your E6B pick it. If your only alternative is
the wiz wheel stick with the E6B. However if they give you a chart you
are supposed to read then I would use the chart. Remember you are not
expected to give the "right" answer, you are expected to give the
answer they are looking for.

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

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.



Ignore my last reply as I thought you had a real mechanical E6B, not
these fake electronic devices. It does appear that you got a bum unit.

Matt