AOPA Pilot Magazine - February 2023 - 92

RUDDER & WRENCH
child's play. A robust rule of thumb is that
every 10 percent weight decrease means
maneuvering speed goes down by 5 percent.
So, when I'm flying my Beechcraft
Bonanza at 2,650 pounds (roughly 20 percent
down from its 3,300-pound maximum
gross weight) and I hit the bumps, I shave
10 percent off the maneuvering speed of 134
knots and hold 120 knots to stay safe.
Unfortunately, for every good rule of
thumb I hear a few bad ones. Best glide airspeed
seems to provide ample fodder for
them to sprout, and, with the help of the
internet, to grow. Upon engine failure, it's
important to target best glide airspeed to
increase the likelihood that we'll be able to
reach terrain favorable enough for a positive
ending to the flight. Flying too slow or too
fast means the aircraft won't travel as far.
Such a scenario is arguably more stressful
than public math, so rules of thumb abound.
I'm sure they are well-meaning, but some
are misguided and even dangerous. Here
are some of the rules to avoid:
Avoid: " Dial the trim wheel all the
way back to full nose-up trim. "
The idea is that doing so will result in
approximately the best glide airspeed, but
this is completely unfounded. I can find no
regulation for aircraft certification that full
nose-up trim is associated with the gliding
characteristics of the aircraft. In my
Cessna 152, trimming full nose up gave me
a value slower than best glide airspeed,
although not too far off, but doing so in
my Beechcraft Bonanza gave me way too
slow an airspeed. This advice is especially
dangerous for engine failure after takeoff
when we might be holding an airspeed
below best glide airspeed, and it's important
to push forward on the control column
to avoid a stall. Reaching first for the trim
wheel could be disastrous. We should use
trim to relieve control pressures, not as a
primary form of aircraft control.
Avoid: " Look out the side and make
the wing level with the horizon. "
There is no reason why, on any given
aircraft, a wing that is parallel to the horizon
in an engine-out situation will give rise
to best glide airspeed. Furthermore, if you
can remember to stare out the side window
long enough to achieve and maintain
this attitude, you have the wherewithal to
look at the airspeed indicator, pitch for best
92
AOPA PILOT / February 2023
glide airspeed, and trim to reduce the pressure
needed to sustain that condition.
Avoid: " Average V
X
and V for best
Y
glide airspeed. "
The FAA publication Best Glide Speed
and Distance says best glide airspeed provides
the most distance per unit of altitude
lost and, " on most airplanes, it will be
roughly halfway between V
X
Y
(best angle
of climb speed) and V (best rate of climb
speed). " These airspeeds are computed
from a drag polar constructed by the manufacturer
during flight testing (a graph of
climb rate vs. airspeed for a given power setting),
the curve corresponding to V
and V
X
Y
involves an operational powerplant, and this
is not the case for gliding flight. The three
airspeeds V
X
, V , and V for my Bonanza are
Y
X
BG
76 knots, 96 knots, and 105 knots respectively.
Averaging V
and V would give me
Y
about 86 knots, or almost 20 knots slower
than the aircraft's actual best glide speed.
If you don't remember your best glide
airspeed, locate it in your pilot's operating
handbook, memorize it, and put it on your
checklist for backup. If you have the time to
fine-tune your response during an enginefailure
scenario, understand that best glide
airspeed changes with factors such as aircraft
weight and atmospheric conditions.
Factors that improve aircraft performance
(reduced weight, tailwinds, updrafts) mean
we can afford to fly a little slower than the
published speed, and those that hurt performance
(headwinds, downdrafts) mean we
should fly faster to maximize the glide. (See
" Coming Up Short: Your Best Glide Probably
Isn't, " September 2018 AOPA Pilot.)
Rules of thumb are meant to simplify
complex procedures and provide dependable
results. Not only are the rules above
unfounded, but none makes addressing an
engine failure scenario any simpler than setting
an appropriate airspeed and using the
elevator trim to relieve control pressures.
A good rule of thumb can help during
a stressful situation. But when we hear
of a new rule, it's important to evaluate it
with a critical eye to ensure it's both effective
and helpful. Catherine Cavagnaro
owns Ace Aerobatic School in Sewanee,
Tennessee and is the Gaston Swindell Bruton
Professor of Mathematics and Computer
Science at Sewanee: The University of
the South.
http://efirc.com/pilot

AOPA Pilot Magazine - February 2023

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

Contents
AOPA Pilot Magazine - February 2023 - Intro
AOPA Pilot Magazine - February 2023 - Cover1
AOPA Pilot Magazine - February 2023 - Cover2
AOPA Pilot Magazine - February 2023 - Contents
AOPA Pilot Magazine - February 2023 - 2
AOPA Pilot Magazine - February 2023 - 3
AOPA Pilot Magazine - February 2023 - 4
AOPA Pilot Magazine - February 2023 - 5
AOPA Pilot Magazine - February 2023 - 6
AOPA Pilot Magazine - February 2023 - 7
AOPA Pilot Magazine - February 2023 - 8
AOPA Pilot Magazine - February 2023 - 9
AOPA Pilot Magazine - February 2023 - 10
AOPA Pilot Magazine - February 2023 - 11
AOPA Pilot Magazine - February 2023 - 12
AOPA Pilot Magazine - February 2023 - 13
AOPA Pilot Magazine - February 2023 - 14
AOPA Pilot Magazine - February 2023 - 15
AOPA Pilot Magazine - February 2023 - 16
AOPA Pilot Magazine - February 2023 - 17
AOPA Pilot Magazine - February 2023 - 18
AOPA Pilot Magazine - February 2023 - 19
AOPA Pilot Magazine - February 2023 - 20
AOPA Pilot Magazine - February 2023 - 21
AOPA Pilot Magazine - February 2023 - 22
AOPA Pilot Magazine - February 2023 - 23
AOPA Pilot Magazine - February 2023 - 24
AOPA Pilot Magazine - February 2023 - 25
AOPA Pilot Magazine - February 2023 - 26
AOPA Pilot Magazine - February 2023 - 27
AOPA Pilot Magazine - February 2023 - 28
AOPA Pilot Magazine - February 2023 - 29
AOPA Pilot Magazine - February 2023 - 30
AOPA Pilot Magazine - February 2023 - 31
AOPA Pilot Magazine - February 2023 - 32
AOPA Pilot Magazine - February 2023 - 33
AOPA Pilot Magazine - February 2023 - 34
AOPA Pilot Magazine - February 2023 - 35
AOPA Pilot Magazine - February 2023 - 36
AOPA Pilot Magazine - February 2023 - 37
AOPA Pilot Magazine - February 2023 - 38
AOPA Pilot Magazine - February 2023 - 39
AOPA Pilot Magazine - February 2023 - 40
AOPA Pilot Magazine - February 2023 - 41
AOPA Pilot Magazine - February 2023 - 42
AOPA Pilot Magazine - February 2023 - 43
AOPA Pilot Magazine - February 2023 - 44
AOPA Pilot Magazine - February 2023 - 45
AOPA Pilot Magazine - February 2023 - 46
AOPA Pilot Magazine - February 2023 - 47
AOPA Pilot Magazine - February 2023 - 48
AOPA Pilot Magazine - February 2023 - R1
AOPA Pilot Magazine - February 2023 - R2
AOPA Pilot Magazine - February 2023 - R3
AOPA Pilot Magazine - February 2023 - R4
AOPA Pilot Magazine - February 2023 - 49
AOPA Pilot Magazine - February 2023 - 50
AOPA Pilot Magazine - February 2023 - 51
AOPA Pilot Magazine - February 2023 - 52
AOPA Pilot Magazine - February 2023 - 53
AOPA Pilot Magazine - February 2023 - 54
AOPA Pilot Magazine - February 2023 - 55
AOPA Pilot Magazine - February 2023 - 56
AOPA Pilot Magazine - February 2023 - 57
AOPA Pilot Magazine - February 2023 - 58
AOPA Pilot Magazine - February 2023 - 59
AOPA Pilot Magazine - February 2023 - 60
AOPA Pilot Magazine - February 2023 - 61
AOPA Pilot Magazine - February 2023 - 62
AOPA Pilot Magazine - February 2023 - 63
AOPA Pilot Magazine - February 2023 - 64
AOPA Pilot Magazine - February 2023 - 65
AOPA Pilot Magazine - February 2023 - 66
AOPA Pilot Magazine - February 2023 - 67
AOPA Pilot Magazine - February 2023 - 68
AOPA Pilot Magazine - February 2023 - 69
AOPA Pilot Magazine - February 2023 - 70
AOPA Pilot Magazine - February 2023 - 71
AOPA Pilot Magazine - February 2023 - 72
AOPA Pilot Magazine - February 2023 - 73
AOPA Pilot Magazine - February 2023 - 74
AOPA Pilot Magazine - February 2023 - 75
AOPA Pilot Magazine - February 2023 - 76
AOPA Pilot Magazine - February 2023 - 77
AOPA Pilot Magazine - February 2023 - 78
AOPA Pilot Magazine - February 2023 - 79
AOPA Pilot Magazine - February 2023 - 80
AOPA Pilot Magazine - February 2023 - 81
AOPA Pilot Magazine - February 2023 - 82
AOPA Pilot Magazine - February 2023 - 83
AOPA Pilot Magazine - February 2023 - 84
AOPA Pilot Magazine - February 2023 - 85
AOPA Pilot Magazine - February 2023 - 86
AOPA Pilot Magazine - February 2023 - 87
AOPA Pilot Magazine - February 2023 - 88
AOPA Pilot Magazine - February 2023 - 89
AOPA Pilot Magazine - February 2023 - 90
AOPA Pilot Magazine - February 2023 - 91
AOPA Pilot Magazine - February 2023 - 92
AOPA Pilot Magazine - February 2023 - 93
AOPA Pilot Magazine - February 2023 - 94
AOPA Pilot Magazine - February 2023 - 95
AOPA Pilot Magazine - February 2023 - 96
AOPA Pilot Magazine - February 2023 - 97
AOPA Pilot Magazine - February 2023 - 98
AOPA Pilot Magazine - February 2023 - 99
AOPA Pilot Magazine - February 2023 - 100
AOPA Pilot Magazine - February 2023 - 101
AOPA Pilot Magazine - February 2023 - 102
AOPA Pilot Magazine - February 2023 - 103
AOPA Pilot Magazine - February 2023 - 104
AOPA Pilot Magazine - February 2023 - 105
AOPA Pilot Magazine - February 2023 - 106
AOPA Pilot Magazine - February 2023 - 107
AOPA Pilot Magazine - February 2023 - 108
AOPA Pilot Magazine - February 2023 - 109
AOPA Pilot Magazine - February 2023 - 110
AOPA Pilot Magazine - February 2023 - 111
AOPA Pilot Magazine - February 2023 - 112
AOPA Pilot Magazine - February 2023 - Cover3
AOPA Pilot Magazine - February 2023 - Cover4
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