AOPA Turbine Pilot Magazine - March 2022 - 99

RUDDER & WRENCH
FLYING SMART /
Are we there yet?
AOA=12 deg
vY
AOA=15 deg
Back side of
power curve
AOA=1 deg
AOA=4 deg
Locating the region of reverse command
BY CATHERINE CAVAGNARO
Vertical speed vs. airspeed (power fixed)
AOA=7 deg
Front side of
power curve
Airspeed
(KCAS)
With a fixed throttle setting, the yoke position determines an elevator deflection that determines an angle of attack with which the wing flies,
which, in turn, results in a specific airspeed. The best rate of climb airspeed VY
(where increasing angle of attack increases vertical speed) and the back side of the power curve (where increasing angle of attack decreases
vertical speed).
I ALWAYS ENJOY hearing from readers and
it's especially nice to learn " Flying Smart "
topics resonate with them. Occasionally,
they pose questions about the science of
flight and I'm in my happy place when I get
to dive in, research, and present an answer.
Recently AOPA member Joel Neuman
wrote to share a conversation among flight
instructors regarding flight in the region of
reverse command when pitch controls airspeed
and power controls altitude.
Neuman took the position that " on
final approach, especially on short final,
most training airplanes are flying in the
region of reverse command. " Other flight
instructors, however, argued that " you
weren't quite there yet. " The question
Neuman posed to me is, " Where is there,
the transition from normal command to
reverse command? " In slowing from cruise
flight to approach and landing, I believe a
pilot is there well before entering the airport
traffic pattern and I'll explain.
The law of conservation of energy
implies that the total energy in a closed
system remains constant. For an airplane
those forms of energy are potential
(altitude), kinetic (proportional to the
square of velocity), chemical (fuel), and
that energy lost into the airmass (think
drag). While glider pilots make expert
use of an external energy source in the
form of updrafts from thermals, we'll
consider an aircraft that flies in still air
so that conservation of energy applies to
this system.
Figure 1. With a fixed throttle setting, the yoke position determines an elevator deflection that
determines an angle of attack with which the wing flies which, in turn, results in a specific
airspeed. The best rate of climb airspeed YY forms the dividing line between the front side of
the power curve (where increasing angle of attack increases vertical speed) and the back side
of the power curve (where increasing angle of attack decreases vertical speed).
forms the dividing line between the front side of the power curve
Throughout flight, the fuel supply consistently
decreases (assuming no in-flight
refueling) and the airmass energy increases
as drag opposes the aircraft motion. If the
aircraft gains one form of energy, such
as altitude or airspeed, conservation of
energy implies that another form must be
sacrificed. For example, flight at constant
altitude and airspeed requires that the rate
at which fuel is burned exactly compensates
for the rate at which energy is lost
because of drag. For this discussion, we'll
keep the flaps up, cowl flaps open, propeller
on a constant rpm setting, the ailerons neutral
and rudder deflections consistent with
coordinated flight. The remaining variables
will be throttle setting and elevator deflection
using the yoke. The pilot can use the
AOPA PILOT / March 2022
99
CATHERINE CAVAGNARO
Vertical speed (fpm)

AOPA Turbine Pilot Magazine - March 2022

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