Flight Training - June 2015 - 30

CALCULATING CENTER
OF GRAVITY
Finally, a reason you studied math
If only your third-grade teacher were a pilot,
she would have easily answered the "why do we
have to learn this" question. Absent an app, a
little bit of algebra is required to calculate the
total weight and center of gravity. The formula
goes like this: weight x arm = moment.
Do that for each station-meaning empty
weight of the airplane, luggage, fuel, people,
and so on. The total weight is simply addition.
The center of gravity is the sum of the moments
divided by the total weight. Check that against
the manufacturer's data to make sure you're
within limits.

30 /

FLIGHTRAINING.AOPA.ORG

Does it make any difference where the
various items of cargo are placed in the
airplane?
While it might take some imagination
to picture yourself flying bush cargo in a
DC-3, it doesn't take much imagination
to picture what would happen if the baby
elephant were the last cargo loaded-in
the tail of the airplane.
And while it's clear that where cargo
is placed in a big airplane matters, many
general aviation pilots simply don't think
this matters with the type of airplanes
we fly. But I promise you that it's possible
to load a four-seat Cessna 182 just as
disastrously as our fictitious DC-3 with
the baby elephant in the tail. For proof,
just look to NTBS accident reports, which
show more than 100 weight-and-balancerelated crashes in the past decade. So
what's the problem here?
I think it's a combination of several
factors. Weight and balance has always
been a bit of a snoozer in ground school,
and the concepts are not easily grasped.
Those crazy weight-and-balance graphs
with their grids, intersecting lines, and
envelope markings are hardly intuitive.
And to make matters worse, the flood
of apps for weight and balance over the
last few years haven't helped GA pilots to
better understand the science behind the
glass screen.
A recent encounter with a student pilot
only strengthened this suspicion. I was
filling out my logbook in an FBO's hangar
after returning a rental airplane from an
early morning flight. A CFI and his student were next up, and they were doing a
preflight briefing on the airplane I'd just
returned. The student was showing his
instructor an iPhone app on which he'd
run the weight and balance. The instructor was very careful to double-check the
student's entries and then nodded his
approval: "Well done."
The student showed me his app, demonstrating how to enter the data, and then
proudly said, "And so long as you're inside
the yellow frame lines, your weight and
balance is good to go!"
"And if you're outside them?"
"Then you can't fly," said the student.
"Oh, right, I got that," I replied, "but


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Flight Training - June 2015

Table of Contents for the Digital Edition of Flight Training - June 2015

Contents
Flight Training - June 2015 - Cover1
Flight Training - June 2015 - Cover2
Flight Training - June 2015 - Contents
Flight Training - June 2015 - 2
Flight Training - June 2015 - 3
Flight Training - June 2015 - 4
Flight Training - June 2015 - 5
Flight Training - June 2015 - 6
Flight Training - June 2015 - 7
Flight Training - June 2015 - 8
Flight Training - June 2015 - 9
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Flight Training - June 2015 - Cover3
Flight Training - June 2015 - Cover4
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