"Peter Duniho" wrote

If the air is bumpy, it always potentially could exceed the design
limits of the airplane. For that matter, you could be flying along in
completely smooth air and experience sudden and severe turbulence.
I haven't read Machado's book, so I don't know what he says and what
he doesn't. I would disagree that there's never any turbulence
outside of a thunderstorm that you need to worry about, or that
there's never any moderate turbulence in which newer planes might have
a concern. Those kinds of absolutes seem troublesome to me.

Quoted from Aerodynamics for Naval Aviators:

"The loads imposed on an aircraft in flight are the result of
maneuvers and gusts."
"As a general requirement, all airplanes must be capable of
withstanding an approximate effective +/- 30 foot per second
gust when at maximum level flight speed for normal rated power.
Such a gust intensity has relatively low frequency of occurrence
in ordinary flying operations."

BTW, the aircraft must withstand the 30 fps gust at Vno (top of
the green arc) even if the aircraft cannot attain Vno at maximum
power.
Weather induced gust loading establishes Vno, pilot induced
maneuver loads establishes Va.

Bob Moore