AOPA Pilot Magazine - August 2023 - 98

RUDDER & WRENCH
NEVER AGAIN /
Tip vortex?
What is that?
Wake turbulence could kill you
BY JIM GARDNER
IT WAS SEP T EMBER of 1970, and I was
only seven months from getting out of the
U.S. Air Force at Randolph Air Force Base
(RND) in San Antonio. I was a 1,000-plus
hour instructor pilot in the T-37 squadron at
RND and an experienced platform instructor
teaching aerodynamics, instrument
procedures, and systems in both the T-37
and T-38 aircraft. On the side I had begun
giving flight instruction as a CFI at SAT, flying
Cessna 172s and Piper Cherokee 180s.
In the previous three or four months the
FAA and the Air Force had issued a flight
98
AOPA PILOT / August 2023
advisory about clear air turbulence (CAT)
following behind and descending from
" large aircraft, " whatever that meant. But
with close to 1,500 total hours, I believed
I could handle anything the weather and
other aircraft could throw at me, and I
scoffed at tip vortex issues. I was about to
find out how serious this phenomenon is.
U.S. Air Force information implied that
vortex forces were strong, especially when
a small light aircraft might encounter a
much larger heavy aircraft at high angles
of attack. These vortices follow the jumbo
jet and descend some undetermined
amount. Word was to stay clear. Like most
instructors in the squadron, I read and disregarded
this safety advice.
I had begun flying at San Antonio
International with John, who happened to
be the weather instructor in our squadron,
and was scheduled to begin his commercial
training in the Cherokee 180. I really
don't recall the first part of this flight
which took place almost 25 years ago,
but I will never forget the last 10 minutes.
We were in the pattern on downwind for
Runway 12L when I instructed John to
perform a spot landing on the numbers,
and he acknowledged. It was not his first
spot landing, so I was observing his aircraft
control and not deeply involved in
instructing. My right elbow was on the
armrest, right hand on the top canopy
bow; my left arm was behind John to
allow more room in the cockpit. My feet
were flat on the floor. John had both feet
on the rudder pedals, the yoke in his left
hand and throttle in his right hand.
It was a fair weather day with quartering
winds less than 10 knots from the
right, and we were about to turn left base
when we heard tower clear an American
Airlines DC-8 (the original jumbo jet) for
takeoff on 12R. These two parallel runways
are fairly close, and the threshold
for 12L is displaced about 1,500 feet. That
meant that as we turned the Cherokee to
base we were looking straight at the DC-8
as the aircraft on the surface added power
and turned from the taxiway to 12R with
jet blast barreling from four engines.
John was concentrating on his pattern
and spot landing as I watched the
American Airlines flight accelerate in
front of us, to the right. As we descended,
the DC-8 accelerated away from us, lifted
the nose, and got airborne. We made our
spot landing and John added power to
accelerate. It took a few seconds to accelerate
to flying speed and John made a
good takeoff.
Immediately following liftoff, at
maybe 10 feet of altitude with about 70
knots-nose high and accelerating-the
Cherokee began an abrupt and strong
roll to the left. Without making a control
input, John looked at me and yelled,
" What are you doing? "
SARAH HANSON
AOPA Pilot Magazine - August 2023

Table of Contents for the Digital Edition of AOPA Pilot Magazine - August 2023
