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Spoiler (aeronautics)

technology Maturity 11-13 Next article →

In aeronautics, a spoiler is a specialized device used to manipulate airflow over an aircraft's wing. These devices are typically hinged plates located on the upper surface of an airfoil.

Boeing 767-323ER spoilers on descent to POS, AAL 1167, 11-29-12
Boeing 767-323ER spoilers on descent to POS, AAL 1167, 11-29-12

By extending upward into the rushing air, spoilers disrupt the smooth, streamline flow of air. This disruption serves two primary purposes: increasing drag and decreasing lift. While pilots and manufacturers often refer to them as "speed brakes," there is a technical distinction between spoilers and true airbrakes. Airbrakes are designed to increase drag without disrupting the lift distribution across the wing span. In contrast, spoilers intentionally disrupt lift distribution while also increasing drag.

The mechanism of a spoiler relies on creating a controlled stall. When a spoiler plate rises, it blocks the air from flowing smoothly over the wing. This causes a controlled stall over the specific portion of the wing located behind the plate. As a result, the lift produced by that section of the wing is greatly reduced.

Lift dumperinnerworkingsa320
Lift dumperinnerworkingsa320

This process allows pilots to manage the aircraft's descent rate and speed with high precision. By changing the lift and drag, the pilot can alter the glide angle during an approach without necessarily changing the aircraft's speed.

Spoilers are categorized into different types based on their specific functions during flight. Flight spoilers are deployed at controlled angles to increase the rate of descent or to assist with roll control. When used for roll, these are called "spoilerons."

Air Jamaica A321 landing spoilers opened
Air Jamaica A321 landing spoilers opened

These work by raising on only one wing, which decreases lift on that side and causes the plane to roll. Ground spoilers, also known informally as lift dumpers, serve a different purpose. These have only two positions: fully deployed or fully retracted. In modern fly-by-wire aircraft, a single set of surfaces can act as "multifunction spoilers," performing both flight and ground duties.

The history of these devices shows a shift in how different aircraft manage descent. Until the 1960s, most gliders, or sailplanes, used spoilers to control their descent for landing. Since then, gliders have mostly replaced spoilers with Schempp-Hirth type airbrakes. A significant milestone occurred in 1948 when Martin Aircraft developed spoilers that could assist in roll control.

Qantas Boeing 737-800 spoiler deployed for descent
Qantas Boeing 737-800 spoiler deployed for descent

This innovation led to the development of the spoileron. Using spoilerons can help reduce adverse yaw when rudder input is limited at higher speeds. It also allows flaps to occupy more of the wing's trailing edge by eliminating the need for dedicated ailerons.

Ground spoilers are critical for safety during the landing phase of a flight. They typically deploy automatically upon touchdown to perform three main tasks. First, they increase form drag to help slow the aircraft down. Second, they prevent the aircraft from "bouncing" on the runway. Third, they cause a significant loss of lift, which places more weight on the landing gear.

Lift dumperinnerworkingsa320
Lift dumperinnerworkingsa320

This increased weight allows the wheel brakes to work more effectively without the tires skidding. Some aircraft, like the British Aerospace 146, use exceptionally wide-span spoilers to generate enough drag to make reverse thrust unnecessary.

In certain specialized cases, spoilers serve to protect the aircraft's mechanical systems. In air-cooled piston engine aircraft, spoilers can prevent "shock cooling" of the engines during a descent. Without spoilers, an aircraft might descend too quickly, causing the engine to cool more rapidly than normal. This rapid cooling can lead to serious mechanical issues like cracked cylinders or stuck valves. By using spoilers, the pilot can maintain a desired descent rate while keeping the engine at a power setting that generates enough heat to stay safe. This is especially important for turbocharged piston engines, which operate at higher temperatures.

Despite their utility, the improper use of spoilers can lead to serious aviation accidents. Many incidents have been caused by pilots forgetting to deactivate ground spoilers or deploying them prematurely. For example, Air Canada Flight 621 crashed in 1970 due to premature deployment at low altitude. In 2007, TAM Airlines Flight 3054 experienced a major disaster in Brazil where the plane slid off the runway. On that occasion, the plane's spoilers may have been the only available method for braking at high speed. Even as recently as August 2023, a Beechcraft 390 crashed in Malaysia due to the inadvertent deployment of spoilers while attempting to arm them.

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🖼️ Images & Media (4)
File:Lift dumperinnerworkingsa320.jpg
Lift dumperinnerworkingsa320.jpg
File:Air Jamaica A321 landing spoilers opened.jpg
Air Jamaica A321 landing spoilers opened.jpg
File:Boeing 767-323ER spoilers on descent to POS, AAL 1167, 11-29-12.jpg
Boeing 767-323ER spoilers on descent to...
File:Qantas Boeing 737-800 spoiler deployed for descent.jpg
Qantas Boeing 737-800 spoiler deployed...
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