Harold wrote:

If a small single engine plane can out-climb its engine-out glide ratio from
take off through the top of climb point, wouldn't it follow that it can
always theoretically make it back to the departure airport in the event of
engine failure ?

Sure, except that you have to get turned around first. There is always some
altitude below which you will not be able to return to the airport. This tends
to be between 600 and 900' AGL in a typical powered aircraft.

George Patterson
To a pilot, altitude is like money - it is possible that having too much
could prove embarassing, but having too little is always fatal.