"Peter R." wrote in message
...
Today I spotted two four inch and one six inch vertical cracks in the side
window at the seat directly behind the pilot seat. The cracks are almost
perfectly straight and originate at the top frame more or less in the
middle
of the window. The aircraft is a 1973 V35B and I would imagine that this
window is that old.

Do they originate from the area around the hinges?


How does this happen? Old age? Cold to hot? Some other force that decided
that one month since my last aviation maintenance expenditure was too
long?

If they migrate to/from the hinge, I'd guess an inordinate sideload (stress
fracture).