I was looking for propeller data and stumbled on a very interesting article from 1941 about the merits and demerits of the various materials used. Here's a link to the article.
1941 | 2165 | Flight Archive
There are a load of adverts in the middle that are as much fun as the article. For those that may not want to wade through the entire thing here is a quote relevant to balloon cable strikes.
"From the point of view of reliability
and wearing properties, solid duralumin
has the most enviable reputation.
Out of all the many thousands of dural
blades which have been used in De
Havilland variable-pitch airscrews,
not a single, shank or tip failure has
been reported in service, apart from
such obviously accidental damage as
that caused, by flying into balloon
cables. Even if a balloon cable does
hit a dural blade, the cable will
usually be cut and the damage to the
blade will only be such as can be
comparatively easily repaired by resmoothing
the surface ; and even in the
comparatively rare cases where a part
of the blade has actually been removed,
machines have successfully
reached their bases.
Under conditions of normal civil
operation, the life of a dural blade is
extremely long, and there are already
many De Havilland blades which have
well exceeded 4,000 hours."
Cheers
Steve