AOPA Pilot Magazine - May 2013 - 22

LICENSE TO LEARN

The dark night rises

BY ROD MACHADO

Give your eyes time to adapt
I REMEMBER the time I spent an entire day at a nearby
airport filming video segments for an online aviation
magazine. It was the perfect confluence of airplanes,
sunlight, and even more sunlight. That’s right. For
eight hours, the cameraman kept a large light reflector pointed at my face. You know you’ve been out in the
sun too long when you hear the sound of bacon frying
and there isn’t any bacon. Yeah, that was my face. At
the end of the day I was camera crispy, but that wasn’t
the worst of it.
Toward the end of the session, we filmed a few
landings from inside my Bonanza A36. Everything
went well, except for the landings. For a reason that
I’ll reveal soon, my depth perception was off, rendering me unable to properly estimate the height for the
landing flare. Thump! OK, we all have bad days but
few of us have them on video. With daylight waning,
we packed up and I flew off into the sunset. Literally.
The sun was setting as I approached my home airport.
That’s when I went blind—or nearly so.

My depth perception was off, rendering me
unable to properly estimate the height for
the landing flare.

ROD MACHADO

is an aviation
humorist, active
CFI, and a member
of the Aviation
Speakers Bureau.

22 | AOPA PILOT May 2013

While on a left base to Runway 19L, I glanced
toward the runway. It was gone. So was the airport
and coastline. Bermuda Triangle? Not this time.
Unbeknownst to me, I was staring in my own reality
show titled, When Night Blindness Strikes. Believe me
when I say that a two-lane airport with a high-volume
mix of airliner and GA traffic is the last place you want
to lose sight of your sight. My instinct had me climbing
away from the airport, returning 20 minutes later once
my eyes had begun acclimating to the dark.
I was the victim of extreme photobleaching. It
turns out that the cells in your retina that are responsible for night vision, known as rods, contain a
light-sensitive chemical called rhodopsin. I’m very
fond of chemicals, especially this one, because it’s
responsible for our sight. When sunlight strikes the
rods, the chemical rhodopsin splits apart (a process
known as photobleaching) and initially forms two
other chemicals, opsin and trans-retinal. As this split
occurs, a small amount of electrical energy is released
and sent to the brain via the optic nerve. This is what
forms an image inside your noggin. Eventually these

chemicals recombine to form rhodopsin (they become
unbleached), which once again becomes useful for
converting light into sight.
The problem occurred because I spent way too
much time in direct (and directed) sunlight. Since
rhodopsin can only be replenished at a certain rate,
I managed to photobleach a substantial amount of
my eyes’ available supply. My subsequent exposure to
darkening conditions rendered me night blind.
As a general rule, it takes about 30 minutes for the
eyes to replenish their supply of rhodopsin and adapt
to the dark. You can, however, achieve a moderate
degree of adaptation to the dark after 20 minutes if
you’re using dim-red cockpit lighting.
Since then, I’ve learned to wear sunglasses when
shooting videos in direct and intense sunlight. I’m even
prepared to slip on an arc-welding helmet if the cameraman treats me like an ant under a magnifying glass
(the Darth Vader look should eliminate any chance of
being ramp checked, too).
Over the years my fondness for unsplit rhodopsin
has grown even stronger, especially since it regenerates at a slower rate as we get older. Age also tends
to diminish the amount of light entering the eye. The
retina of a 60-year-old person receives only one-third
of the light it did at 20 (even during the daytime). You
don’t have to be a rhodopsin scholar to realize what
this means in terms of your eyes’ ability (or lack of it)
to adapt to night time conditions with age.
If that weren’t enough, your color sensitivity
declines with age, making it more difficult to discern
what lies beyond your airplane’s windscreen at night.
Blues (taxiway lights) and greens (threshold lights
and right-wing position light) are more affected than
other colors and become less detectable. Of course,
FAA inspectors wearing blue or green jumpsuits are
harder to see at night, too. One might easily nab you
for a ramp check—unless you were wearing your arcwelding helmet, of course.
Considering the eye’s limitations, a part of me
wishes I were a bat, or at least carried one in my pocket
during sunset flights. Echolocation has never looked
so good; at least, that’s what I hear. So give your eyes
time to adapt before the dark night rises, especially if
you’ve spent a bright day in the sunlight.
AOPA
WEB

www.rodmachado.com

http://www.rodmachado.com

AOPA Pilot Magazine - May 2013

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