Ron,
Take a look at this and see if you think this would be a good route to go with
this.
The time and subjective part of course is the number of landings needed to dial
in the aircraft model.
Mfg reports that I am aware of seem to publish landing distances on both dry
and wet surfaces using a std FAR approach (50' ht over threshold, 3 degree
slope, published weight, and a Vapp=1.3Vso)
- Once I have flown enough landings to determine "bp" (braking power) and "wbp"
(wet braking power) percentages of the FG base "1" value that closely matches
the published figures, put that in a formula including metar rain and snow. I
don't know how to code it yet, but this is the formula in laymen terms. (built
on a single weight basis) These are the parameters from a yasim fdm.
gear/gear[1]/gear-friction-factor='x'(float), where as: x = BP-((BP-WBP) *
(greater value, rain-norm or snow-norm or snow-cover))
gear/gear[2]/gear-friction-factor='x'(float), where as: x = BP-((BP-WBP) *
(greater value, rain-norm or snow-norm or snow-cover))
/environment/metar/snow-cover='false'(bool) (assuming
snow-cover=True to have value of 1, or no braking ability)
/environment/metar/rain-norm='0'(double)
/environment/metar/snow-norm='0'(double)
Example :
If :
Test results for dry surface = .750
Test results for dry surface = .500
Metar Rain-norm value = .675
Metar Snow-norm value = .110
Metar Snow-cover value = false
Then:
/gear-friction-factor= .750-((.750-.500)*.675)
So braking power applied to model:
/gear-friction-factor=.58125
If it works then the file could be used for any model, once the wet-to-dry
braking range is found, which as mentioned would be the most time consuming and
somewhat subjective part.
Peter
On Dec 19, 2009, at 12:57 PM, Ron Jensen wrote:
>> Simulating braking coefficients by limiting /controls/gear/brake-* isn't
> the best way to go. For JSBSim aircraft static friction coefficients for
> each gear can be adjusted on the fly by changing
> fdm/jsbsim/gear/unit[*]/static_friction_coeff. I'm pretty sure yasim
> has something similar...
>
>
Peter Brown
FG "Farmboy"
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