i use a mix of visability and animation tags
I sometimes use this
<PartInfo>
<Name>parked_pilot</Name>
<AnimLength>50</AnimLength>
<Animation>
<Parameter>
<Code>
(A:GENERAL ENG RPM:1,RPM) 100 < (A:SIM on GROUND, bool) + (A:BRAKE PARKING POSITION, bool) + 3 ==
</Code>
</Parameter>
</Animation>
</PartInfo>
you will notice this uses ANIMATION tags. Using this, you start with your Pilot in the normal position. Then at Frame 1, move him somewhere hidden, like in the fuselage. This only works if you have a fuselage big enough to hide him tho
This code will remove the crew, when the aircraft is ON THE GROUND, the PARKING BRAKE IS ON, and the engine Number 1 is below 1 RPM.
as i said, you can use visability, also. I use the same code, but in that mode, to show ground equipment, which comes on in the same conditions
<PartInfo>
<Name>parked_part</Name>
<Visibility>
<Parameter>
<Code>
(A:GENERAL ENG RPM:1,RPM) 100 < (A:SIM on GROUND, bool) + (A:BRAKE PARKING POSITION, bool) + 3 ==
</Code>
</Parameter>
</Visibility>
</PartInfo>