"George Patterson" wrote

Roofs in this area of NJ are designed for a snow load of around 30 pounds
per
square foot. I expect they're stronger in Iowa, but they're still not
designed
to hold a typical small plane.

George Patterson

That is a bit of a missunderstanding. If you had snow, level on the roof,
up to where there was 30 lbs/sq. ft, that would load the roof to a point
that it would do no damage to the roof, and even more significant, it would
not sag more than a certain amount that is determined by a formula, with
span heavily considered. Add on to this, that the design safety margin is
about a factor of two, so you could load the roof to 60 lbs, and the roof
might be close to failing.

This small plane on the roof would have more weight per square foot than the
30 pounds, but would be way less than the amount of weight of the snow in
that span/area.

If the material the deck is made of would be strong enough to spread the
load without failing, it would not be an issue. This is most likely the
case, since the roof deck is made of steel, dense foam, and rubber membrane.
The foam has no strength, but would deform and absorb much of the force of
the impact.

Another thing that was unsaid is that the roof and the plane would need
repair; perhaps considerable repair. It would still beat landing on a
house, or a full parking lot with poles all over, or a street full of cars
and poles and wires. A field would beat the h*ll out of the roof or all of
those other places.

That said, I don't want to be put in the situation of any of the choices,
but the roof landing done under control should not involve any fatalities.
--
Jim in NC