AOPA Pilot Magazine - August 2014 - 20

PROFICIENT PILOT

Something for nothing

BY BARRY SCHIFF

Creating your own tailwind

BARRY SCHIFF

writes for
AOPA Pilot
from Southern
California.

20 | AOPA PILOT August 2014

ONE OF THE MOST POPULAR cross-country flights from
the Los Angeles Basin is, not surprisingly, across the
Mojave Desert to Las Vegas. Convective turbulence,
though, can make it a rough flight. It was during such
a flight with my mentor, Paul Blackman, in his North
American Navion, that he taught me in the summer of
1956 a useful technique that I have used in turbulence
ever since.
The roughness during this flight began in earnest as
we passed over Barstow, California. During the updrafts,
I would lower the nose so as to maintain altitude and
reduce power to prevent an excessive increase in airspeed. Upon entering a downdraft, I would add power
and raise the nose to continue maintaining altitude. This
is the most common method of coping with convective
turbulence. As I fought through the thermals, Paul just
sat there in the right seat, his arms folded across his
chest and a knowing smile on his face. He slowly shook
his head in a disapproving manner.
"What's the matter?" I asked. "Am I doing something wrong?"
"There's a better way to do this," he said. "Something
we learned crossing the deserts of North Africa during the war."
I was all ears. Paul had been a command bomber
pilot in B-24 Liberators and was a marvelous instructor. When he spoke, it was wise to listen.
"When you hit an updraft," he began, "use it to your
advantage. Allow the airplane to gain altitude. Don't
fight it. For just as night follows day, downdrafts follow
updrafts." The idea, he explained, is to have surplus altitude available to sacrifice when transitioning from an
updraft to a downdraft.
"When you enter the downdraft," he continued,
"simply allow the airplane go down with it. Don't fight
that, either.
"In terms of aircraft performance," he yelled over
the air and engine noise, "thermals can be beneficial.
They give you something for nothing. So don't fight it.
Go with it. When in the surging updraft, just hold a constant attitude [not altitude], leave the power alone, and
allow the airplane to rise."
He explained that lowering the nose to maintain
altitude is counterproductive. It results in increased
airspeed and less time spent in the rising air to take
advantage of the free lift.
Sounds simple enough, I thought.

Paul then added, "Raising the nose in a downdraft
is similarly counterproductive. The reduced airspeed
causes you to remain longer in the sinking air. When
you hit a downdraft, apply the same technique that you
used in the updraft. Hold a constant attitude, leave the
power alone, and allow the airplane to descend, sacrificing the altitude gained in the thermal. Increasing power
at reduced airspeed to attempt maintaining altitude in a
downdraft-especially in the heat of the summer-can
result in an overheated engine."
None of this is earthshaking to sailplane pilots.
They are adept at maximizing en route performance
by decreasing airspeed and climbing in rising air. They
allow their aircraft to lose altitude and increase airspeed
in sinking air, which lessens their exposure to it. The
idea in both airplanes and sailplanes is to spend more
time in updrafts and as little time as possible in downdrafts. This technique is suitable only when flying VFR.
This technique also is good practice in severe or
extreme turbulence, occasions when maintaining
a more-or-less constant attitude is strongly recommended. This is structurally safer than imposing the
damaging G loads that could result from attempting to
maintain altitude during such turbulence (when IFR or
VFR). It goes without saying, of course, that airspeed
should kept at or below the minimum maneuvering
speed (VA) when the degree of turbulence calls for it.
Another method of improving en route performance
involves envisioning the wind as it flows over mountainous or hilly terrain, and then altering course so as to fly
within rising air as much of the time as possible. For
example, when the wind is blowing across a valley, fly
along the downwind side to take advantage of the rising air usually found there. Depending on the nature of
the terrain, such a ride is often smooth. At such a time,
simply lower the nose to prevent climbing and enjoy
picking some extra knots in the process. It's like creating your own tailwind.
Cruising on the other side of the valley would be in
sinking air that might not even be noticeable except that
you might begin wondering why your airplane doesn't
seem to be performing as well as it should.
It's all a matter of knowing the direction of the wind
and using it to advantage. The difference in flight time
can be significant.
AOPA
WEB

www.barryschiff.com

http://www.barryschiff.com

AOPA Pilot Magazine - August 2014

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