Hi Rousseau,
tiptanks cannot be jettisonned in flight, that's clear, question was just, if
the can easily be removed on the ground, and for some types, this seems to
be possible, by replacing them with standard wingtips. Ok, there's still the
question, what means "easily" ! In this case I would think of some hours, as the
wingtips usually houses navigation lights, so it would be necessary to work on
the wiring (Some of the argentine Morane MS.760, for example, seem to have been
flown without tiptanks sometimes).
About the Seahawk, I have found no pictures showing it with tiptanks, just with
underwing tanks on pylons ...
