“guinea pigs” in a test aircraft,
a machine that “was unsafe
and their child had communicated that to them.”
McCorkle was in a good mood when
he returned to the Pentagon press briefing room next, on May 9. He was there to
confirm, as CNN had reported five days
earlier, that the crash investigators had
found nothing wrong with the Osprey.
Using charts on an easel, McCorkle
described how the accident had unfolded.
He didn’t name
any of the pilots,
but he explained
that those flying the
first Osprey into Marana, Wright
and Bianca, had missed their
3,000-foot checkpoint and begun
their approach into the airfield
late. Rather than wave off and go
around, they had come down “high and
hot,” forcing Brow and Gruber to follow
in what none of the pilots seemed to sense
was a pell mell descent. McCorkle’s third
chart traced Brow’s speed and altitude
over the last seconds of the flight, as
reconstructed from his Osprey’s Crash
Survivable Memory Unit, a device that
records airspeed, altitude, and other data.
“In summary, the data shows that the mishap aircraft was in a high rate of descent
at a relatively low forward airspeed,”
McCorkle said. “These characteristics can
lead to a condition known as power settling, or vortex ring state.”
Here Be Dragons
With that, McCorkle introduced a new,
and for many people occult-sounding term
into the debate over the Osprey. “Vortex
ring state” was esoteric not only to the
general public but in the aviation world as
well. It was a term from fluid mechanics,
an expression even an aeronautical engi-
neer could go a career without
hearing very often. Vortex ring
state described a condition a
rotor could get into as a result of
what Navy and Marine Corps pilots
called “power settling” and Army and
Air Force pilots knew as “settling with
power.” What it all amounted to was a
way to describe a rotor that was no lon-
ger creating thrust and lifting as it should
because it was descending into its own
downwash too quickly.
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APRIL 2010 | ROTOR & WING MAGAZINE
