On 9 Mar 2010, at 09:18, James Turner wrote:
>> Could someone take a look and commit please ?
>
> I'm testing these now, and will commit in a couple of moments.
Committed now, with some changes:
- I've switched the pressure-alt source to be configurable, instead of
hard-coded; it defaults to /instruments/altimeter/pressure-alt-ft
- the ias and mach limits are read each frame, so they could (potentially) be
updated from Nasal
- I've removed the default values for alt-threshold / ias-limit / mach-limit,
on the assumption that anyone enabling the barber-pole will supply appropriate
values. If people disagree with that, adding back the B1900 values (or similar)
as default is easy.
My biggest concern is that the code references /velocities/mach to compute the
mach-limit, which seems undesirable - instruments should read/compute values
based on physical properties if possible - that's certainly the philosophy of
the basic instruments.
Ideally, we would extend the airspeed indicator to compute Mach as described
here:
http://williams.best.vwh.net/avform.htm#Mach
I know OAT is available trivially, which lets us compute CS (speed of sound)
easily, but computing TAS from IAS is more complex, as the formulae show. If
someone can explain the formuale in detail to me, I'd be happy to add a
'indicated-mach' property to the airspeed indicator code (effectively allowing
it to be used as a mach-meter too), and then use that mach value for the
mach-limit computation.
Comments? I guess all the formulae required already exist elsewhere in the code.
Regards,
James
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