"Dee Flint" wrote ...
wrote ...

Depends on the size of the lot. On a lot that's , say, 100
feet wide, you can't put up a tower more than 50 feet high
and have its "fall circle" not go over the property line.

Yet is that actually the correct way to calculate it? That assumes that
the tower will break at the base and fall over from the base. This is not
the common failure mode (or so I've been told). From one of the experts
who was speaking to a city council meeting around here, the towers either
twist like a corkscrew or bend over somewhere between the middle and top.
The "corkscrew" is supposedly the most common failure mode as that is the
way the towers are designed to react if wind loads are exceeded. However
in neither case is there a "fall circle".

Does anyone have information on this? Although the speaker was supposed
to be an expert, I'd be interested in some independent information on
this.

The structure hight as a radius is the "worst-case" limit of
damage. Insurance underwriters, country commissioners,
et.al. likely don't want to expose themselves to the liability
of setting a more risky limit. Our anecdotal history of typical
tower failures may not seem as compelling to people with
actuarial risk at stake.