Flight Training - August 2024 - 15

PERSPECTIVES FLIGHT LESSON
PREFLIGHT HOW IT WORKS
BY DENNIS K JOHNSON
BY IAN J. TWOMBLY
LEADING-EDGE SLOT
GO WITH THE FLOW
SOMETIMES AIRCRAFT DESIGNERS GET IT
right and their creation ends up with clean
wings, simple flaps, and no gimmicks.
And sometimes it looks like the Beverly
Hillbillies rolling down the taxiway with
stuff hanging off every surface.
Many of these appendages are meant
to solve problems that crop up during
flight testing, although sometimes they
appear in the design stage as a way to eke
out extra performance in the form of lowspeed
handling, faster cruise speeds, or
increased stability.
Leading-edge slots have been known
to be an original design feature, although
in most traditional general aviation
airplanes they solve problems. Slots are
lengthwise holes behind the leading edge
of the wing that lower the stall speed.
If you consider how a wing works, the
principle is simple. As a wing moves
closer to the critical angle of attack the
airflow across the top begins to separate,
usually starting from the back and moving
forward. Slots act like a built-in jet of air
that provides more energy across the top
of the wing, allowing it to adhere at higher
angles of attack. The reason we don't find
slots on every wing is because there's a
drag penalty. On short takeoff and landing
airplanes, the primary goal of great
runway performance is more important
than the drag penalty, so you're more
likely to find them there.
The most famous example of slots on
a standard GA airplane is probably the tail
of the Cessna Cardinal. Soon after it was
introduced, owners complained that the
airplane was sensitive in pitch and that it
was easy to both strike the tail and land
hard on the nose. Engineers discovered
the tail was stalling too early during
landings, a symptom of having moved the
leading edge of the wings back to improve
visibility. A program began to retrofit the
tails with slots installed upside down (the
tail provides lift in a direction opposite the
wings), which turned out to be successful
and fixed the problem.
Slots are different from slats, which
are essentially flaps on the front of the
wing. Slats are moveable and change the
chord of the wing, whereas slots are fixed
and solve an issue with stalling at too low
an angle of attack.
ian.twombly@aopa.org
Leading-edge slots
Stabilator
15
FLIGHT TRAINING APRIL 2017
FLIGHT TRAINING AUGUST 2024
15
STEVE KARP

Flight Training - August 2024

Table of Contents for the Digital Edition of Flight Training - August 2024

Contents
Flight Training - August 2024 - Intro
Flight Training - August 2024 - Cover1
Flight Training - August 2024 - Cover2
Flight Training - August 2024 - Contents
Flight Training - August 2024 - 2
Flight Training - August 2024 - 3
Flight Training - August 2024 - 4
Flight Training - August 2024 - 5
Flight Training - August 2024 - 6
Flight Training - August 2024 - 7
Flight Training - August 2024 - 8
Flight Training - August 2024 - 9
Flight Training - August 2024 - 10
Flight Training - August 2024 - 11
Flight Training - August 2024 - 12
Flight Training - August 2024 - 13
Flight Training - August 2024 - 14
Flight Training - August 2024 - 15
Flight Training - August 2024 - 16
Flight Training - August 2024 - 17
Flight Training - August 2024 - 18
Flight Training - August 2024 - 19
Flight Training - August 2024 - 20
Flight Training - August 2024 - 21
Flight Training - August 2024 - 22
Flight Training - August 2024 - 23
Flight Training - August 2024 - 24
Flight Training - August 2024 - 25
Flight Training - August 2024 - 26
Flight Training - August 2024 - 27
Flight Training - August 2024 - 28
Flight Training - August 2024 - 29
Flight Training - August 2024 - 30
Flight Training - August 2024 - 31
Flight Training - August 2024 - 32
Flight Training - August 2024 - 33
Flight Training - August 2024 - 34
Flight Training - August 2024 - 35
Flight Training - August 2024 - 36
Flight Training - August 2024 - 37
Flight Training - August 2024 - 38
Flight Training - August 2024 - 39
Flight Training - August 2024 - 40
Flight Training - August 2024 - 41
Flight Training - August 2024 - 42
Flight Training - August 2024 - 43
Flight Training - August 2024 - 44
Flight Training - August 2024 - 45
Flight Training - August 2024 - 46
Flight Training - August 2024 - 47
Flight Training - August 2024 - 48
Flight Training - August 2024 - 49
Flight Training - August 2024 - 50
Flight Training - August 2024 - 51
Flight Training - August 2024 - 52
Flight Training - August 2024 - 53
Flight Training - August 2024 - 54
Flight Training - August 2024 - 55
Flight Training - August 2024 - 56
Flight Training - August 2024 - Cover3
Flight Training - August 2024 - Cover4
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