Flight Training - September/October 2022 - 17

HOW IT WORKS
BY DAVE HIRSCHMAN
AUTOPILOT
BETTER THAN A MERE HUMAN
AUTOPILOTS HAVE GROWN DRAMATICALLY IN THEIR CAPAbilities
and shrunk in size since Lawrence Sperry invented
the first way back in 1912. The original idea was akin to
cruise control in a car: Relieve the pilot of boring, mundane,
repetitive, and fatiguing chores such as keeping an airplane
on heading and altitude for hours at a time. Now, expanded
computer power, miniature microprocessors, and sophisticated
software allow autopilots to do much more than
Sperry ever dreamed.
On a corporate jet, airliner, or military transport, for
example, the crew often engages the autopilot shortly
after takeoff and disengages it on final approach before
landing. The autopilot (or automated flight control
system) guides the airplane throughout the climb, cruise,
descent, and approach phases of flight, and it does so
smoothly and reliably with greater fidelity than any
mere human.
Autopilot systems include mechanical servos that connect
to aircraft flight controls in one, two, and sometimes
three axes. Those servos attach to aileron linkages for roll,
elevator for altitude, and trim for yaw.
DID YOU KNOW?
Modern autopilots can follow GPS, VOR, localizer, and glideslope
signals. They can climb or descend to pilot-selected altitudes, and
they can do that at the rate or indicated airspeed of the pilot's
choosing. Autopilots must be able to be disconnected by pressing
a disengage button (usually on the yoke or control stick), turning
the unit itself off, or pulling a circuit breaker.
GPS HDG
145
HDG/TRK
push sync
HDG
APR
NAV
TRK
Directional
mode selector
UP
AP
FD
YD
LVL
DN
IAS
VNAV
VS
ALT SEL
120
110
100
Y
push sync
ALT
Climb/descent
mode selector
E
T
G5
110
90
80
5
G
4900 10
29.92
4
5100
10
5
5000
AP
155
ALT 5000
161165
GP
5000
Autopilot settings
displayed on
PFD: Heading and
altitude modes,
5,000 feet
Many modern, digital autopilots are equipped with
" envelope protection " that prevents pilots from inadvertently
flying too fast or too slow or rolling too steeply,
whether pilots actively engage their autopilots or not.
These features are essentially operating in the background
and monitoring the airplane at all times.
Autopilots also can be programmed by the flight crew
to fly instrument approaches, and they do so with uncanny
precision by constantly accounting for crosswinds and upand
downdrafts.
Autopilots are at the core of new safety technology
such as Garmin's pioneering autoland system that enables
airplanes to land safely at the airport of its own choosing if
the pilot is incapacitated.
Autopilots are sure to have an even more central role in
aviation's future.
They enable autonomous drone flight as well as the
next generation of advanced air mobility vehicles now
in development.
dave.hirschman@aopa.org
Autopilot disconnect switch
Roll servo
Pitch servo
FLIGHT TRAINING SEPTEMBER/OCTOBER 2022
17
10
10
10
10
STEVE KARP
Flight Training - September/October 2022

Table of Contents for the Digital Edition of Flight Training - September/October 2022
