"Mark Hansen" wrote in message
...

Well, you get your clearance from Ground/Clearance Delivery, but then
there may be any number of delays between that time, and when you're
ready to take off.

You need to let the tower know when you're ready (by telling them that
you're holding for IFR release). The tower then begins negotiating for
a slot in the 'system' for your flight. Once they have a slot ready,
they clear you to take off.


Why is it necessary to tell the tower you're holding for an IFR release?
Whether or not an IFR release is necessary is an internal ATC matter. If
the tower must call for IFR release it should do so right after taxi
clearance is issued to an aircraft that previously was issued an IFR
clearance.



I was told this 'holding for release' should never take more than a
few minutes, but then I fly out of a not-so-busy tower-controlled
airport (Sacramento Executive, KSAC).

I was taught never to assume that I would be able to just tell the
tower that I was ready to go.


Were you taught why you should never assume that?



This step of finding a slot in the
system for me can't begin until I let the tower know that I'm ready.


That's ridiculous.