Flight Training - November 2013 - 15
HOW IT WORKS
Flight controls
The drive behind the ailerons, rudder, and elevator
BY IAN J. TWOMBLY
PLUS See how control systems move.
TURN LEFT OR right on the yoke and the
ailerons move. Pull back on the stick and
the elevator deflects up. But how? Roll,
pitch, and yaw are easily understood, but
how those control surfaces move isn’t.
Different airplanes have different solutions, but almost all of them fall into three
categories—cable and pulley, pushrod, or
electronic.
Cessna’s 152 and 172 use a cable and
pulley system for all three control surfaces.
Both yokes are attached to a “Y” column
behind the panel. When the pilot rotates
the yoke, a sprocket rotates, setting off
a series of movements down the length
of the steel or stainless steel cable. Each
time a bend in the system is required, it’s
routed through a pulley—a grooved disc
that rotates on a shaft often bolted directly
to the airframe. Just short of the aileron or
rudder is a bellcrank, which converts the
movement from a cable to the metal rod
that articulates the aileron. The rudder and
elevator trim are also cable-driven. These systems are light;
the cables can take some punishment without failing; and
they are thin, so they can squeeze through tight spaces.
They do stretch over time and thus require inspection and
maintenance.
Pushrods are metal tubes that create a direct mechanical linkage between the control column and the control
surfaces. As a result they provide a direct-response feel on
the controls, which many pilots prefer. They are also more
complicated, and come with lower mechanical tolerances.
Electronic or fly-by-wire systems have grown in acceptance in higher-end business and commercial aviation but
remain outside the scope of most recreational flying. These
systems transmit pilot control movement into an electric
signal that is sent to a control servo, which then moves the
control surface. There are numerous benefits to such a system. The biggest is envelope protection, which limits stalls,
overspeeds, and other unsafe conditions.
STEVE KARP
CONTROL PREFLIGHT
A number of the rituals we perform before flying are to check for various control system problems. The preflight inspection
calls for manipulating all controls and checking for free cable or pushrod movement, proper linkage to the yokes or sticks, and
in many cases, ensuring both the control mechanism and the control surfaces themselves are properly attached. Similarly, the
run-up control check is to ensure free and correct movement from the cockpit. Any problems you discover should be addressed
by a mechanic.
NOVEMBER 2013 FLIGHT TRAINING
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Flight Training - November 2013
Table of Contents for the Digital Edition of Flight Training - November 2013
Flight Training - November 2013
Contents
Member Benefits
Right Seat
Centerline
Letters
A Small Contribution
Success Story
How it Works
News
Training Products
ASI News
Final Exam
Tech Tip
Flight Lesson
Flying Carpet
ONE WHEEL DOWN
AVIATION ETIQUETTE
NO BIG DEAL
TECHNIQUE
Weather
Checkride
ATP Me
Career Advisor
Tech Talk
Aviation Badges of Honor
Let Me Make This Perfectly Clear
Advertiser Index
Debrief
Flight Training - November 2013 - Flight Training - November 2013
Flight Training - November 2013 - Cover2
Flight Training - November 2013 - Contents
Flight Training - November 2013 - 2
Flight Training - November 2013 - 3
Flight Training - November 2013 - Member Benefits
Flight Training - November 2013 - 5
Flight Training - November 2013 - Right Seat
Flight Training - November 2013 - 7
Flight Training - November 2013 - Centerline
Flight Training - November 2013 - 9
Flight Training - November 2013 - Letters
Flight Training - November 2013 - 11
Flight Training - November 2013 - A Small Contribution
Flight Training - November 2013 - 13
Flight Training - November 2013 - Success Story
Flight Training - November 2013 - How it Works
Flight Training - November 2013 - News
Flight Training - November 2013 - 17
Flight Training - November 2013 - Training Products
Flight Training - November 2013 - ASI News
Flight Training - November 2013 - Final Exam
Flight Training - November 2013 - Tech Tip
Flight Training - November 2013 - Flight Lesson
Flight Training - November 2013 - 23
Flight Training - November 2013 - Flying Carpet
Flight Training - November 2013 - 25
Flight Training - November 2013 - ONE WHEEL DOWN
Flight Training - November 2013 - 27
Flight Training - November 2013 - 28
Flight Training - November 2013 - 29
Flight Training - November 2013 - 30
Flight Training - November 2013 - 31
Flight Training - November 2013 - AVIATION ETIQUETTE
Flight Training - November 2013 - 33
Flight Training - November 2013 - 34
Flight Training - November 2013 - 35
Flight Training - November 2013 - NO BIG DEAL
Flight Training - November 2013 - 37
Flight Training - November 2013 - 38
Flight Training - November 2013 - 39
Flight Training - November 2013 - TECHNIQUE
Flight Training - November 2013 - 41
Flight Training - November 2013 - Weather
Flight Training - November 2013 - 43
Flight Training - November 2013 - Checkride
Flight Training - November 2013 - ATP Me
Flight Training - November 2013 - Career Advisor
Flight Training - November 2013 - 47
Flight Training - November 2013 - Tech Talk
Flight Training - November 2013 - Aviation Badges of Honor
Flight Training - November 2013 - 50
Flight Training - November 2013 - Let Me Make This Perfectly Clear
Flight Training - November 2013 - Advertiser Index
Flight Training - November 2013 - 53
Flight Training - November 2013 - 54
Flight Training - November 2013 - 55
Flight Training - November 2013 - Debrief
Flight Training - November 2013 - Cover3
Flight Training - November 2013 - Cover4
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