Differences Between Ailerons, Flaps, and Spoilers

If you have ever glanced out the window of a commercial aircraft, you may have noticed several moving parts on the wings. While those shifting panels, known respectively as ailerons, flaps, and spoilers, may appear similar in form, their placement and deployment are unique. In this blog, we will explore the core differences between these control surfaces and their specialized roles in controlling flight dynamics.

What Are Ailerons?

Ailerons are located on the outer trailing edges of each wing, their purpose being to control an aircraft’s side-to-side tilt or roll. They deflect asymmetrically, with the downward-deflected aileron increasing lift on one wing, while the upwards aileron reduces lift on the opposite wing. These surfaces usually come into play during turning maneuvers, and they are reverted to a neutral position to level the aircraft when turning is no longer required.

What Are Flaps?

Flaps are mounted on the wing’s trailing edge, located closer to the fuselage. Serving to increase lift and drag at lower speeds, these surfaces are extended downward to increase the camber, or curvature, of the wing. As a result, this enables the aircraft to generate more lift without needing higher speed for shorter takeoff rolls and slower, safer landing approaches. Once the aircraft is in cruising flight, the flaps are retracted to reduce drag once more.

Types of Flaps

• Plain Flaps: The most basic flap type, plain flaps are easy to manufacture and maintain, but generate relatively modest lift improvements and significant drag. These are commonly found on light general aviation aircraft.
• Split Flaps: Split flaps deflect only the lower portion of the wing surface, producing significant drag in addition to increased lift. This type was historically used on older aircraft designs such as the Douglas DC-3 and World War II-era bombers, but other designs have largely replaced them.
• Slotted Flaps: Widely used on modern general aviation and turboprop commuter aircraft, slotted flaps include a gap between the wing and flap so high-pressure air can flow from below the wing over the upper surface of the flap. This energizes the boundary layer, delaying flow separation and greatly improving lift efficiency.
• Fowler Flaps: Fowler flaps slide rearward before deflecting downward, increasing both the wing area and camber. The resulting large increase in lift serves large commercial airliners well, along with some business jets and military transports. Moreover, these flaps can be multi-slotted to further boost their performance.

What Are Spoilers?

Placed on the upper surface of the wing, spoilers are deployed to interrupt smooth airflow across the wing, resulting in a rapid reduction in lift and an increase in drag. Rather than helping the aircraft generate lift or maintain directional control, spoilers are used deliberately to degrade lift and modify aerodynamic performance during specific phases of flight.

Spoilers can be deflected in two primary ways:

• Symmetrical deployment is typically used during descent and after landing. This method uniformly disrupts lift across the wings, allowing for increased rate of descent without accelerating and ensuring better ground contact for braking once the aircraft has landed.
• Asymmetrical deployment (on one wing only) is used for roll control in place of or in addition to ailerons, which is particularly useful at high speeds where excessive aileron deflection could cause structural stress or adverse yaw.

While common on jet-powered commercial airliners, military transports, and many business jets, spoilers are not present on most small general aviation, as their aerodynamic and performance needs are usually met with ailerons and flaps alone.

Types of Spoilers

• Speed Brakes: These variants are designed to raise symmetrically, increasing drag and reducing airspeed. During descent or in-flight deceleration, this action empowers pilots to reduce airspeed without altering the aircraft’s pitch or configuration. Dedicated speed brakes can be found on some aircraft, but often, sections of the main spoiler system double as speed brakes.
• Ground Spoilers: Ground spoilers deploy symmetrically upon landing to remove lift and keep the aircraft firmly on the runway for braking. In many planes, deployment is automatic upon main gear compression and throttle reduction, though they can be manually activated before landing.
• Roll Spoilers (Spoilerons): Used in conjunction with or in place of ailerons to provide roll control, roll spoilers extended asymmetrically to reduce lift on one side. During high-speed flight or on wide-body aircraft, the use of large ailerons could induce undesirable yaw or excessive torsional loads. As such, some aircraft rely on them for redundant and more effective roll authority.

Secure Flight Control Components on ASAP Supply Chain

As we have laid out, each of these panels on aircraft wings has a clearly defined role in controlling roll, adjusting lift, or managing drag. Because they are so vital for adjusting an aircraft’s course and behavior, they must be maintained to the highest standards. ASAP Semiconductor is ready to help professionals secure high-quality aileron, flap, and spoiler parts for countless types of aircraft through our website, ASAP Supply Chain.

In addition to a wide-spanning inventory of top-notch parts, this platform presents convenient browsing options and quotation services intended to be quick, easy, and accommodating to each customer’s unique specifications. With our curated procurement options, we always strive to present fast lead times and competitive pricing. To see how ASAP Supply Chain can deliver reliable procurement solutions for even the most urgent or unique operational requirements, connect with our team at any time.