Ailerons are essential flight control surfaces mounted on the trailing edges of an airplane’s wings. Their primary function is to control the aircraft’s movement along the roll axis, which allows the aircraft to bank left or right. Whether flying a Cessna Skyhawk here at Epic or a Boeing 737 for the airlines, understanding how they work is fundamental to aircraft operation and maintenance.
Quick Navigation to Ailerons
Basic Functions
Types and Designs
Training Issues
General Information
What do ailerons do?
The function of ailerons is to manage roll control by creating differential lift on each wing. When the right aileron deflects downward and the left aileron upward, the airplane rolls to the left, and vice versa. This movement is coordinated through cables or other mechanical linkages in the flight control system.
How do ailerons work?
Ailerons work by changing the camber (curvature) of the wing to increase or decrease lift. The deflection, known to pilots as ‘aileron deflection’, alters the wing’s aerodynamic characteristics. Most dual control aircraft link them so that both the pilot and co-pilot can manage them simultaneously. How they work becomes clear in this context as they are roll-controlling surfaces that influence aircraft stability and maneuverability.
Hinge and Balance
The hinge and hinge mechanism are crucial for smooth, safe, and controlled movement. Engineers use balance techniques, such as mass balancing and aerodynamic shaping, to prevent flutter at high velocity. Balanced ailerons ensure responsiveness and safety, especially on high-performance or large aircraft.
Types and Designs of Ailerons
Design Considerations
There are several types of ailerons, each with unique design considerations and meaning:
- Frise-type: Designed to reduce adverse yaw by projecting the leading edge of the raised aileron into the airflow.
- Differential: These reduce drag by allowing the upward-deflecting aileron to move more than the downward one.
- Coupled ailerons and rudders: Improve turn coordination by automatically linking yaw and roll.
- Flaperons: Combine the function of flaps and ailerons, used for both elevation and roll control.
- Spoilerons: Alternative devices that assist or replace ailerons in controlling roll, particularly in large jets like the 737.
Some modern aircraft, including certain carbon fiber composite airframes, incorporate advanced aileron design for weight reduction and improved responsiveness.
Inboard and Outboard Ailerons
Larger planes like the Boeing 737 often feature both inboard ailerons (used at lower speeds) and outboard ailerons (used at higher speeds), depending on the flight phase. These work in conjunction with other control surfaces to provide optimal handling.
Reversible Controls and Trim Tabs
Older aircraft may have reversible controls, where pilot input directly moves control surfaces. Modern aircraft rely on boosted systems, but some still include a trim tab on the aileron to reduce pilot workload and maintain level flight.
Ailerons in Practice
In training aircraft such as Epic’s Cessna Skyhawks, pilots learn to master aileron input for standard turns, steep turns, and roll axis coordination. Effective use of ailerons is vital for all aspects of flight, from crosswind landings to precision aerobatics.
“In Epic’s pilot training as well as our aircraft mechanic classes, we spend a lot of time covering design, function, and ‘what if’ scenarios. This includes reviewing accident data and trouble-shooting. Fun fact: “Aileron” means “fin” or “little wing” in French.” –Josh Rawlins, Chief Operating Officer and Aircraft Mechanic Program Director
Emphasis on Safety
Aileron failures and control issues have been contributing factors in several serious aviation accidents. These often involved misrigged controls, cable failures, or icing-induced reversals. Such malfunctions can result in a loss of control and, in some cases, catastrophic crashes. At Epic, we emphasize the critical need for proper maintenance and thorough preflight inspections in our flight schools and aircraft mechanic schools.
Below are a few recent examples of incidents in which ailerons played a central role:
- ATR 72-212 (1994): American Eagle Flight 4184 crashed after an aileron hinge moment reversal caused by ice accumulation led to an uncontrollable roll into an inverted dive. This resulted in the deaths of all 68 people onboard.
- Piper Arrow (2017): A pilot narrowly survived a crash after the ailerons were connected in reverse, causing the aircraft to roll in the opposite direction of control input.
- Embraer ERJ 190 (2018): An Air Astana ferry flight in Portugal encountered an aileron reversal due to rigging errors. This prompted a Mayday call and an extreme flight with severe wing oscillations and temporary loss of control.
- Piper PA-22 (2020): An aircraft mechanic incorrectly rigged the aileron cables, resulting in reversed control and a subsequent crash. The pilot and mechanic were both on the flight and survived.
These are just a few examples we share in Epic’s pilot ground school classes and in our aircraft mechanic classes. We cannot overemphasize the role ailerons play in safe flight.
History and Timeline
This unique aircraft part has a surprisingly rich and contested history. Its evolution reflects a broader journey of experimentation, legal battles, and technological innovation in aviation. Here’s a quick overview of its development and historical significance:
Early Years
- Early Vision of Matthew Piers Watt Boulton (1868): Believe it or not, the concept predates the Wright brothers. In 1868, British inventor Matthew Piers Watt Boulton patented a system of lateral control using moveable surfaces on an aircraft’s wings. His design provided the groundwork for what would later become known as ailerons. Though Boulton never built a working aircraft, his foresight in understanding the need for roll control was a crucial theoretical leap.
- Pioneers of Flight and the Rise of Wing Warping: In the late 19th century, Otto Lilienthal experimented with body movement and wing warping to control gliders. Then in 1903, the Wright brothers made the first powered flight using a complex system of wing warping, not ailerons. Their successful patent for lateral control led to years of litigation against competitors using similar control methods.
Early 20th Century
- Independent Development: In 1904, French engineer Robert Esnault-Pelterie constructed gliders and powered aircraft with rigid, hinged control surfaces, the first true ailerons, that offered better reliability and less structural stress than wing warping.
- Legal Disputes and Innovation: Glenn Curtiss, an American aviation pioneer, began using ailerons in 1908, which led to a legal battle with the Wrights. Despite significant mechanical differences, U.S. courts sided with the Wrights due to the broad language in their patent. These lawsuits slowed innovation until 1917, when the Wrights’ patent expired.
Modern Era
- Wartime Adoption and Refinement: By World War I, they were the standard method for roll control in most aircraft. Designers refined them to improve performance and reduce adverse yaw. This led to differential, frise-type, and coupled ailerons.
- Postwar Advancements: With the advent of jets and high-speed flight, engineers introduced systems like spoilerons, flaperons, and inboard and outboard ailerons.
- Modern Design and Materials: In the late 20th century, innovations in carbon fiber, fly-by-wire systems, and trim tab technology led to lighter, stronger, and more responsive ailerons. Today, they are integrated into sophisticated flight control systems, which often operate in tandem with spoilers and elevons for fine-tuned maneuverability.
From Boulton’s 1868 patent to today’s high-tech jets, this story highlights the balance between vision, invention, and practical engineering. Although initially overlooked, Boulton’s work represents a visionary starting point in the long journey of mastering roll control.
Check Out Our Video on Ailerons!
Their Importance and Future
Ailerons play a crucial role in roll control, allowing an aircraft to rotate around its longitudinal axis. From their complex design and hinge mechanisms to their role in advanced aircraft like the 737, these control surfaces are a marvel of aerodynamic engineering. Whether you’re exploring differential ailerons, flaperons, or spoilerons, understanding the use of ailerons enhances every pilot’s knowledge of how airplanes work. This includes why wings don’t just lift, but roll too.
Their future depends on how flight control systems continue to develop. With advancing technology, they are expected to become more efficient, more integrated, and may even be replaced by new types of control systems.
