If you ever begin flying as a hobby, one of the first publications you will read is the Airplane Flying Handbook. This surprisingly clear-cut instruction manual is a detailed step-by-step guide for getting from the ground to the air and back again.
Included is a break-down of the parts of an airplane and their uses. Many times it explains two critical airplane components that any pilot needs to be familiar with; the ailerons and the flaps. These components are control surfaces that allow for the aircraft to do all the things airplanes need to do; turn, slow-down, take-off, and land. They are completely separate components of an airplane’s wing, but when looked at by a passenger, they can appear to be one and the same.
What is the difference between flaps and ailerons? Flaps are retractable ‘extensions’ of the wing, that change the angle of the airfoil, allowing for a slower stall speed. Ailerons are wing components controlled directly by the yoke or control stick and lift or lower alternatively to cause the airplane to bank either left or right.
In this article, we’ll look more closely at what distinguishes flaps and ailerons. We’ll also take a look at some of the other critical airplane components necessary for flight.
Table of Contents
Wing flaps – How do they function and what is their purpose?
Wing flaps are mechanical ‘extensions’ that are attached to the trailing edge of an airplane wing, between the ailerons and the fuselage. They are used to generate lift, slow down the aircraft, and lower the stalling speed of the aircraft.
All of these functions are due to the flap changing the camber or curve of the wing/airfoil. This disruption of the normal airflow allows for different flying characteristics in all aspects of flight.
A pilot must make an individual determination every time they use flaps based on wind speed, aircraft weight, and runway length.
Here are some breakdowns of why flaps are used in different phases of flight:
Takeoff
Flaps are commonly used by airliners during takeoff to shorten the distance they must roll on the runway. They are activated by a separate electronic control within the cockpit. The added lift flaps provide means an airplane can ‘lift-off’ the runway sooner and at a slower speed, but the tradeoff is a less aggressive angle of take-off. This may be a factor if there are obstructions (such as skyscrapers or mountains) that need to be cleared.
Small planes in general aviation may also elect to take-off using flaps when using a particularly short runway.
Another common use is on soft or uneven ground. The flaps provide more lift, which takes the pressure off of the tires and provides a smoother acceleration down the runway.
Maneuvering
Some gliders and fighter jets use flaps when maneuvering. This is generally not done by airliners. Gliders use them when maneuvering to lower the stall speed and use the rising thermal air more efficiently. A negative flap setting can also be used to reduce trim drag.
Fighter jets can use flaps in mid-flight to increase lift and therefore make tighter turns (tighter turns general mean higher stall speeds).
Landing
Pilots elect to use flaps to land most of the time. Airliners deploy flaps miles out of the airport. Smaller planes generally won’t deploy them until they’re approaching the end of their landing pattern.
Lowering flaps while landing allows the pilot to pitch the aircraft down further without increasing airspeed. This provides a better view of the runway, and more importantly, allows for a steeper landing angle without gathering speed.
It is not necessary to use flaps. In some instances, such as particularly strong wind gusts, flaps are not recommended.
Landing roll
Once the plane has touched down, the flaps can be used as air brakes to decrease the length of roll distance on a runway. This may be necessary on a short runway.
Ailerons – A closer look
Also located on the wing’s trailing edge, ailerons are placed just outside the flaps. Ailerons are the flight controls that allow the airplane to bank, or roll on the longitudinal axis.
They move in the opposite direction from each other. Ailerons are generally connected by cables, bellcranks, pulleys, and/or push-pull tubes to a yoke or control stick.
They work like this:
The pilot moves the yoke to the left (picture turning a car steering wheel to the left), causing the left aileron to deflect upward, and the right aileron to deflect downwards.
The resulting drag on the left wing will lower it and the resulting lift on the right wing will raise it.
In this manner, the plane banks along its longitudinal axis. Banking, in coordination with rudder-steering, is required for smooth, balanced turns in an airplane. Once the desired bank angle is achieved, the pilot evens out the controls and, assuming all other controls are utilized properly, the airplane will stay in the bank angle it was put in.
Flaperons?
We’ve discussed flaps and ailerons, but there is such a thing as flaperons. Flaperons look and act like conventional ailerons, however, they are capable of lowering simultaneously to perform the duties of flaps.
These are generally seen on older small planes such as WWII fighters and on airliners as additions, located between the flaps and ailerons.
What are slats and how are they different than flaps?
Slats are another aerodynamic surface located on the wing, but unlike flaps and ailerons, they are on the leading edge. Like flaps, slats allow for a higher angle of attack (angle of the wing in relation to relative wind) without increasing speed. They are mostly found on airliners and are used in conjunction with flaps to increase the size of the wing.
What does coordinated flight mean?
Coordinated flight simply means using all of the airplane’s control surfaces to fly in a specific direction without ‘slipping’ or ‘side-streaming’.
In order to conduct coordinated flight, the pilot must use ailerons to bank the aircraft, the elevator to increase and decrease pitch angle, and the rudder, to turn the plane along the vertical axis in conjunction with one another.
As an example, here are the basic procedures for making a right turn in an airplane:
Step 1
The bank angle must be set using the ailerons as we discussed before.
The pilot must turn the control wheel to the right to enter into a right bank. This lowers the left aileron, raising the wing and lifts the right aileron, lowering the wing.
If the pilot were to leave the wheel turned without doing anything else, the plane would continue to bank until it was no longer creating lift, and then it would stall and fall out of the air.
Step 2
To compensate, the pilot turns the wheel to the desired bank, and then straightens out the wheel to the position it was in straight and level flight.
Step 3
Simultaneously to banking, the pilot must apply rudder movement using his feet. For a right turn, the right rudder is used, using the right foot. When the pilot pushes on the right rudder pedal, it moves the rudder to the right, causing a drag on the right side and pushing the aircraft to turn right.
Step 4
The final two controls necessary in an even turn are throttle and elevator.
The elevator is perpendicular to the rudder. When the plane enters a turn, the nose tends to dip down, meaning the pilot must pull back on the yoke. Pulling back on the yoke lowers the elevator, creating more lift which raises the nose.
Step 5
Finally, the throttle must be applied to compensate for the extra drag of the elevator and the reduced lift the wings have from flying at an angle.
All of that to make a small turn!
It might sound complicated, but it is all done as one fluid motion, and pilots actually learn it within their first few hours of flight lessons.
Summary
Flaps and ailerons are located right next to one another on most airplane wings, but they serve completely different functions.
Flaps are used to extend the wing camber, allowing for greater lift and lower stall speeds. The functions of this allow pilots to take off in shorter distances, land at steeper angles without increasing airspeed, and land on shorter runways. They are controlled by a lever or button located with an airplane’s cockpit.
Ailerons are used specifically to roll an airplane along the longitudinal axis. They work by alternatively creating lift and drag on opposing wings. Unlike flaps, they are controlled by the control wheel or ‘yoke’. When the pilot turns the yoke to the left, the left aileron goes down to create lift while the right simultaneously goes up to create drag, thus banking the airplane.
Controlled flight is only possible by coordinating the rudder, ailerons, elevator, and thrust with one another. All of these elements are needed to make even a small turn!
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