Re: [Jsbsim-devel] C-172 Performance

[Gregory P. <gpi...@so...>]

Hi Jon



I found the biggest difference between 172's I flew as a CFI was the type of
prop they had (climb or cruise). Cessna 152's could vary even more. The
difference in level flight at the same rpm could be up to 15 mph. For
pattern work you wanted the climb prop since it accelerated and climbed
faster. I found aircraft with a constant speed prop to have less differences
between aircraft and closer to their book values.



Also remember, a lot of POH's have passed through a marketing department.
And during this translation the numbers can become embellished some. When a
customer is looking to buy an aircraft, they compare POH's, so marketing may
fudge things to make the aircraft look better.



gregoryp







----- Original Message ----- 
From: "Jon Berndt" <js...@ha...>
To: <jsb...@li...>
Sent: Wednesday, October 13, 2004 5:01 AM
Subject: RE: [Jsbsim-devel] C-172 Performance


> Here's something to try. First off, I'm not sure which C-172 is leading to
concerns, the P
> or R version.
>
> Here are some things to try for testing:
>
> Make sure the pilot and a passenger are present (using the POINTMASS
descriptor). Add 120
> pounds of baggage (at the CG). Make sure a full fuel load is carried, and
that the base
> aircraft weight is correct.
>
> Try using this prop for testing:
>
> <AC_THRUSTER FILE="prop_generic2f">
>
> NOTE: This prop isn't set up at this time to feather or provide drag
correctly.
>
> Like I said, I have tested the C-172x (essentially the R model) and so far
have found that
> with the above mods the aircraft performs fairly well compared to the
published figures -
> within 10% and sometimes as close as 1%.
>
> Sea level speed seems good, too - my tests show it less than 1% off.
>
> However, this is not a rigorous set of tests I have done. I'll try and
formalize the
> testing and publish the results as well as the comparison data. That ought
to be
> productive.
>
> Jon
>
>
>
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