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Flaps, Slats, Spoilers and Tabs: Secondary Flight Control Surfaces
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Dec 7, 2024
Discover the essential role of Secondary Flight Control Surfaces in modern aviation!—the unsung heroes that enhance an aircraft’s performance and efficiency. Unlike primary controls like ailerons, elevators, and rudders, secondary flight controls are designed to fine-tune an aircraft’s aerodynamics, making operations safer and more efficient during critical flight phases. Here’s what you’ll learn: ✈️ What are Secondary Flight Control Surfaces? A clear explanation of their purpose and importance in aviation. ✈️ Types of Secondary Controls: Flaps: How they increase lift for takeoff and reduce speed for landing. Slats: Their role in maintaining lift at lower speeds. Spoilers: How they assist in descent, braking, and roll control. Trim Systems: Adjusting control forces for stability and pilot comfort. ✈️ Where they’re located on the aircraft: A visual guide to their positions on large commercial and smaller general aviation aircraft. ✈️ Real-world applications: Examples of how pilots use these controls during takeoff, landing, and in-flight adjustments. This video is perfect for aviation enthusiasts, students, technicians, engineers, and pilots who want to deepen their understanding of these critical systems.
View Video Transcript
0:05
in this video we're taking a closer look
0:08
at secondary flight control surfaces The
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crucial yet often overlooked systems
0:12
that fine-tune an aircraft's performance
0:15
ensuring safe and efficient flight
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operations unlike primary controls which
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handle basic movements like pitch yaw
0:22
and roll secondary flight controls focus
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on fine-tuning the aircraft's behavior
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from enhancing lift during takeoff to
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minimizing drag and helping with
0:31
smoother more controlled Landings these
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systems make all the difference come
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along as we break down the various types
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of secondary flight controls explore
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their unique roles and discover how they
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enhance the aircraft's overall
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aerodynamic performance there are
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several secondary or auxiliary flight
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control surfaces here's a breakdown of
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their names locations and functions as
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seen on most large
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aircraft flaps are found on most
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aircraft they are usually inboard on the
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wings trailing edges adjacent to the
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fuselage Leading Edge flaps are also
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common they extend forward and down from
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the inboard Wing Leading Edge the flaps
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are lowered to increase the camber of
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the Wings and provide greater lift and
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control at slow speeds they enable
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landing at slower speeds and shorten the
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amount of Runway required for takeoff
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and Landing the amount that the flaps
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extend and the angle they form with the
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wing can be selected from the flight
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deck typically flaps can extend up to 45
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to 50° there are various kinds of flaps
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plain flaps form the trailing edge of
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the wing when the flap is in the
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retracted position the air flow over the
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wing continues over the upper and lower
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surfaces of the flap making the trailing
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edge of the flap essentially the
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trailing edge of the wing the plain flap
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is hinged so that the trailing Edge can
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be lowered this increases Wing camber
1:54
and provides greater lift a split flap
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is normally housed under the triling
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edge of the wing it is usually just a
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braced flat metal plate hinged at
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several places along its Leading Edge
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the upper surface of the wing extends to
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the trailing edge of the flap when
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deployed the split flap trailing Edge
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lowers away from the trailing edge of
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the wing air flow over the top of the
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wing Remains the Same air flow under the
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wing now follows the camber created by
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the lowered split flap increasing lift
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fer flaps not only lower the trailing
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edge of the wing when deployed but also
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slide a effectively increasing the area
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of the wing this creates more lift via
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the increased surface area as well as
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the wing camber when stowed the Fowler
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flap typically retracts up under the
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wing trailing Edge similar to a split
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flap an enhanced version of the Fowler
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flap is a set of flaps that actually
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contains more than one aerodynamic
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surface in this configuration the flap
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consists of a four flap a mid flap and
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an aft flap when deployed each flap flap
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section slides afon tracks as it lowers
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the flap sections also separate leaving
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an open slot between the wing and the
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four flap as well as between each of the
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flap sections air from the underside of
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the wing flows through these slots the
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result is that the laminer flow on the
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upper surfaces is enhanced the greater
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camber and effective Wing area increase
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overall
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lift heavy aircraft often have Leading
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Edge flaps that are used in conjunction
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with the trailing Edge flaps while while
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they are not installed or operate
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independently their use with trailing
3:33
Edge flaps can greatly increase Wing
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camber and lift when stowed Leading Edge
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flaps retract into the Leading Edge of
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the wing activation of the trailing Edge
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flaps automatically deploys the Leading
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Edge flaps which are driven out of the
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Leading Edge and downward extending the
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camber of the wing another Leading Edge
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device which extends Wing camber is a
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slat slats can be operated independently
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of the flaps with their own switch in
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the Flight Deck slats not only extend
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out of the Leading Edge of the wing
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increasing camber and lift but most
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often when fully deployed leave a slot
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between their trailing edges and the
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Leading Edge of the wing this increases
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the angle of attack at which the wing
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will maintain its laminer air flow
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resulting in the ability to fly the
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aircraft slower with a reduced stall
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speed and still maintain
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control a spoiler is a device found on
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the upper surface of many heavy and high
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performance aircraft it is stowed FL
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flush to the Wing's upper surface when
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deployed it raises up into the Airstream
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and disrupts the laminer air flow of the
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wing thus reducing lift spoilers are
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unique in that they may also be fully
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deployed on both Wings to act as speed
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brakes the reduced lift and increased
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drag can quickly reduce the speed of the
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aircraft in Flight dedicated speed brake
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panels similar to flight spoilers in
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construction can also be found on the
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upper surface of the wings of heavy and
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high performance aircraft they are
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designed specific speically to increase
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drag and reduce the speed of the
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aircraft when deployed the speed brake
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control in the flight deck can deploy
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all spoiler and speed brake surfaces
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fully when
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operated the force of the air against a
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control surface during the high speed of
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flight can make it difficult to move and
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hold that control surface in the
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deflected position a control surface
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might also be too sensitive for similar
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reasons several different tabs are used
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to Aid with these types of problems
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let's take a closer look at the various
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tabs and their uses while in Flight it
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is desirable for the pilot to be able to
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take their hands and feet off of the
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controls and have the aircraft maintain
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its flight condition trims Tabs are
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designed to allow this most trim tabs
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are small movable surfaces located on
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the trailing edge of a primary flight
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control surface the most common
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installation on small aircraft is a
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single trim tab attached to the trailing
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edge of the elevator most trim tabs are
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manually operated by a small vertically
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mounted control wheel however a trim
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crank may be found in some aircraft the
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flight deck control includes a trim tab
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position
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indicator placing the trim control in
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the full nose down position moves the
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trim tab to its full up position with
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the trim tab up and into the Airstream
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the air flow over the horizontal tail
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surface tends to force the trailing edge
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of the elevator down this causes the
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tail of the aircraft to move up and the
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nose to move down if the trim tab is set
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to the full nose up position the tab
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moves to its full down position in this
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case the air flowing under the
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horizontal tail surface hits the tab and
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forces the trailing edge of the elevator
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up reducing the elevator's angle of
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attack this causes the tail of the
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aircraft to move down and the nose to
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move
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up the aerodynamic phenomenon of moving
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a trim tab in one direction to cause the
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control surface to experience a force
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moving in the opposite direction is
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exact ly what occurs with the use of
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balance tabs often it is difficult to
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move a primary control surface due to
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its surface area and the speed of the
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air rushing over it deflecting a balance
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tab hinged at the trailing edge of the
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control surface in the opposite
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direction of the desired control surface
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movement causes a force to position the
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surface in the proper Direction with
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reduced Force to do so balance Tabs are
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usually linked directly to the control
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surface linkage so that they move
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automatically when there is an input for
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control surface movement
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they also can double as trim tabs if
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adjustable in the flight
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deck Servo Tabs are very similar in
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operation and appearance to the trim
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tabs a Servo tab is a small portion of a
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flight control surface that deploys in
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such a way that it helps to move the
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entire flight control surface in the
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direction that the pilot wishes it to go
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a Servo tab is a dynamic device that
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deploys to decrease the Pilot's workload
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and destabilize the aircraft Servo Tabs
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are sometimes referred to as flight tabs
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and are used primarily on large aircraft
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they aid the pilot in moving the control
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surface and in holding it in the desired
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position only the servo tab moves in
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response to movement of the Pilot's
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flight control and the force of the air
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flow on the servo tab then moves the
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primary control surface another device
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for aiding the pilot of high-speed
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aircraft is the spring tab the control
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horn is free to Pivot on the hinge axis
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of the surface but it is restrained by a
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spring for normal operation when control
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forces are light the spring is not
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compressed the horn acts as though it
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were rigidly attached to the surface at
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high a speeds when the control forces
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are too high for the pilot to operate
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properly the spring collapses and the
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control horn deflects the tab in the
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direction to produce an aerodynamic
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force that aids the pilot in moving the
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surface anti- Servo tabs work in the
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same manner as balance tabs except
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instead of moving in the opposite
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direction they move in the same
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direction as the trail faing edge of the
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stabilator in addition to decreasing the
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sensitivity of the stabilator an antis
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Servo tab also functions as a trim
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device to relieve control pressure and
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maintain the stabilator in the desired
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position the fixed end of the linkage is
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on the opposite side of the surface from
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the horn on the tab when the trailing
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edge of the stabilator moves up the
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linkage forces the trailing edge of the
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tab up when the stabilator moves down
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the tab also moves down conversely trim
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tabs on elevators move opposite of the
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control
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surface many small aircraft have a
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non-movable metal trim tab on the rudder
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this tab is bent in One Direction or the
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other while on the ground to apply a
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trim Force to the rudder the correct
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displacement is determined by trial and
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error usually small adjustments are
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necessary until the aircraft no longer
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skids left or right during normal
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cruising
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flight these secondary flight control
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surfaces all work together together to
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make flying more efficient safer and
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more comfortable whether it's improving
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lift during low speed flight or
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increasing drag for a quick descent each
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of these surfaces has a specific purpose
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thanks for watching
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[Music]
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