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Aircraft maintainers: Accelerations

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Aircraft maintainers: Accelerations

Postby Thorsten » Wed Nov 23, 2016 7:21 pm

Aircraft maintainers (especially JSBSim) - please read this!

(Partially a recap from other discussions)

While updating the blackout/redout simulation to something more
sophisticated, we noted several oddities of how accelerations are
referenced aircraft-side.

Problem 1:

/accelerations/pilot-gdamped

This property was previously only active if the user had opted to run
blackout/redout or head shake simulation. If used to drive an
accelerometer/fuel flow/... this would not have worked if the user did not
simulate blackout.

-> We are now updating it unconditionally which should restore
accelerometers etc. to always working condition

Problem 2:

/accelerations/pilot-g

This is a YaSim-generated property and it had a constant value for JSBSim
aircraft before our recent change, so using it in JSBSim never worked.

Again effects, accelerometers and fuel simulations of JSBSim craft using
it naively were broken up to now. Forensics on a couple of JSBSim aircraft
referencing it shows that some authors have been aware of this and have
hacked around it by writing it from the JSBSim systms section, other's
have conditionals in Nasal script on whether it exists,....

-> We are now updating it also unconditionally. What we don't know is
whether actually updating this property interferes with some of the hacks
that have been used.

My strong recommendation is that JSBSim aircraft reference
/fdm/jsbsim/accelerations/* for their needs as to my knowledge we do not
officially maintain a common set of acceleration-related properties and I
consider updating the property via property rules not a clean way to solve
the problem (we do hope it's the most likely thing to restore
functionality to everything, but given the mixture of broken functions and
hacks we found before the recent change, there is no obvious 'best way'
forward).

If you're using the property in a JSBSim aircraft, please check that
everything still works as intended and consider simply not using it in the
future.
Thorsten
 
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